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Three-Dimensional Femorotibial Kinematic Analysis Using Single Plane Fluoroscopy in the Dog

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Title:
Three-Dimensional Femorotibial Kinematic Analysis Using Single Plane Fluoroscopy in the Dog
Creator:
Jones, Stephen Christopher
Place of Publication:
[Gainesville, Fla.]
Florida
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University of Florida
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english
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1 online resource (111 p.)

Thesis/Dissertation Information

Degree:
Master's ( M.S.)
Degree Grantor:
University of Florida
Degree Disciplines:
Veterinary Medical Sciences
Veterinary Medicine
Committee Chair:
KIM,STANLEY E
Committee Co-Chair:
POZZI,ANTONIO
Committee Members:
BANKS,SCOTT ARTHUR
CONRAD,BRYAN
LEWIS,DANIEL D
Graduation Date:
8/9/2014

Subjects

Subjects / Keywords:
Bones ( jstor )
Dogs ( jstor )
Fluoroscopy ( jstor )
Geometric planes ( jstor )
Kidnapping ( jstor )
Kinematics ( jstor )
Ligaments ( jstor )
Stifle joints ( jstor )
Three dimensional modeling ( jstor )
Tibia ( jstor )
Veterinary Medicine -- Dissertations, Academic -- UF
activity -- canine -- daily -- dog -- fluoroscopy -- kinematics -- non-invasive -- single-plane -- stifle
City of Hollywood ( local )
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bibliography ( marcgt )
theses ( marcgt )
government publication (state, provincial, terriorial, dependent) ( marcgt )
born-digital ( sobekcm )
Electronic Thesis or Dissertation
Veterinary Medical Sciences thesis, M.S.

Notes

Abstract:
The ability to quantify three-dimensional (3D) joint kinematics with accuracy and precision in-vivo is vital to gaining an understanding of the pathomechanics of joint disorders. The objectives of this study were to investigate the accuracy and precision of single-plane fluoroscopy in quantifying stifle kinematics of dogs, and to use this measurement modality to characterize high precision, 3D in-vivo stifle kinematics in healthy dogs during different activities. The accuracy and precision of the 3D-to-2D model registration technique was assessed in both normal and tibial plateau leveling osteotomy (TPLO) treated cadaveric stifles. Metallic beads were implanted in the femora and tibiae of both limbs; a TPLO was performed on the left tibia, no surgery was performed on the right stifle. Biplanar fluoroscopy was simulated by obtaining orthogonal fluoroscopic images of each stifle at 5 flexion-angles to simulate a normal gait cycle. Joint kinematics were measured with a single plane 3D-to-2D model registration technique and with modified-radiostereometric analysis (RSA). The single-plane technique was performed by shape-matching CT-generated 3D femoral and tibial bone models to lateral-view (2D) fluoroscopic images. RSA was performed by tracking the implanted beads in orthogonal fluoroscopic images. Accuracy of the single-planar model registration technique was assessed by comparison to biplanar RSA results. Following this cadaveric validation, the 3D-to-2D model registration technique was applied to 6 orthopedically normal Labrador retriever dogs performing common daily activities including walking, trotting, sitting and stair-ascent. For the ex-vivo validation, mean absolute differences between the single-planar model-registration technique and RSA were less than 1.28 mm and 1.05 mm for all translations, and 1.58 degrees and 1.08 degrees for all rotations, for the normal and TPLO-treated stifle respectively. For the in vivo stifle kinematics, increasing stifle flexion angle was associated with tibial internal rotation, abduction and cranial translation for all 4 activities. The exact relationship between flexion angle and these movements varied both within and between activities. We validated the accuracy and precision of a single-plane fluoroscopic 3D-to-2D model-registration technique in normal- and TPLO-treated dog stifles. We further documented that normal dog stifle kinematics are complex with movement being under precise active control, which is activity dependent. ( en )
General Note:
In the series University of Florida Digital Collections.
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Includes vita.
Bibliography:
Includes bibliographical references.
Source of Description:
Description based on online resource; title from PDF title page.
Source of Description:
This bibliographic record is available under the Creative Commons CC0 public domain dedication. The University of Florida Libraries, as creator of this bibliographic record, has waived all rights to it worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law.
Thesis:
Thesis (M.S.)--University of Florida, 2014.
Local:
Adviser: KIM,STANLEY E.
Local:
Co-adviser: POZZI,ANTONIO.
Statement of Responsibility:
by Stephen Christopher Jones.

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Source Institution:
UFRGP
Rights Management:
Copyright Jones, Stephen Christopher. Permission granted to the University of Florida to digitize, archive and distribute this item for non-profit research and educational purposes. Any reuse of this item in excess of fair use or other copyright exemptions requires permission of the copyright holder.
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LD1780 2014 ( lcc )

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1 THREE DIMENSIONAL FEMOROTIBIAL KINEMATIC ANALYSIS USING SINGLE PLANE FLUOROSCOPY IN THE DOG By STEPHEN CHRISTOPHER JONES A THESIS PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE UNIVERSITY OF FLORIDA 2014

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2 © 2014 Stephen Christopher Jones

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3 To Mam, Dad, Peter, Leonard, John, Andrew, Laura and Ashley

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4 ACKNOWLEDGMENTS I thank my amazing parents Laurence and Bridgeen, my brothers Peter, Leonard, John and Andrew, and my sister Laura for all their love and support through all my educational and life endeavors. I want to thank Ashley, my beautiful and loving girlfriend who has supported me through all the highs and lows of this work. My upmost gratitude goes to my mentor Dr . Stanley Kim who conceived, and was the driving force behind this study. Without his expert mentorship and invaluable insight, this project would not have been possible. Special thanks go to Dr . Scott Banks, Dr . Dan Lewis, Dr . Antonio Pozzi, Dr . Bryan Conrad and Abdullah Abbasi for their guidance and assistance throughout this study. This research was funded by an Intramural Faculty Research Grant, College of Veterinary Medicine, University of Florida and by the Hohn Johnson Research Award from the Veterinary Orthopedic Society.

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5 TABLE OF CONTENTS page ACKNOWLEDGMENTS ................................ ................................ ................................ .. 4 ! LIST OF TABLES ................................ ................................ ................................ ............ 7 ! LIST OF FIGURE S ................................ ................................ ................................ .......... 8 ! LIST OF ABBREVIATIONS ................................ ................................ ........................... 10 ! ABSTRACT ................................ ................................ ................................ ................... 11 CHAPTER 1 AN INTRODUCTION TO STIFLE KINEMATICS ................................ .................... 13 ! Overview ................................ ................................ ................................ ................. 13 ! Anatomy ................................ ................................ ................................ .................. 13 ! Ex Vivo Kinematic Investigations in the Dog ................................ ........................... 15 ! In Vivo Kinematic Investigations in the Dog ................................ ............................ 17 ! Optical Motion Capture ................................ ................................ ..................... 17 ! Model Based Fluoroscopic Image Registration ................................ ................ 19 ! Single plane fluoroscopy ................................ ................................ ............ 20 ! Biplanar fluoroscopy ................................ ................................ .................. 21 ! Radioste reometric Analysis ................................ ................................ .............. 22 ! Kinematics of the Cranial Cruciate Ligament Deficient Dog Stifle .......................... 24 ! Cruciate Ligament Rupture: Prevalence and Etiology ................................ ...... 24 ! Ex Vivo Kinematics ................................ ................................ ........................... 25 ! In Vivo Kinematics ................................ ................................ ............................ 25 ! Treatment ................................ ................................ ................................ ......... 26 ! Summary ................................ ................................ ................................ ................ 27 ! 2 ACCURACY OF NONINVASIVE, SINGLE PLANE FLUOROSCOPIC ANALYSIS FOR MEASUREMENT OF THREE DIMENSIONAL FEMOROTIBIAL JOINT POSES IN DOGS ................................ ............................ 34 ! Introduction ................................ ................................ ................................ ............. 34 ! Materials and Methods ................................ ................................ ............................ 34 ! Specimen Preparation ................................ ................................ ...................... 34 ! Fluoroscopic Image Acquisition ................................ ................................ ........ 35 ! 3D Model Creation and Coordinate Assignation ................................ ............... 36 ! 3D to 2D Shape Matching ................................ ................................ ................ 38 ! Statistical Analysis ................................ ................................ ............................ 39 ! Results ................................ ................................ ................................ .................... 40 ! Discussion ................................ ................................ ................................ .............. 41 !

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6 3 ACCURACY OF NONI NVASIVE, SINGLE PLANE FLUOROSCOPIC ANALYSIS FOR MEASUREMENT OF THREE DIMENSIONAL FEMOROTIBIAL JOINT POSES IN DOGS TREATED BY TIBIAL PLATEAU LEVELING OSTEOTOMY ................................ ................................ ...................... 59 ! Introduction ................................ ................................ ................................ ............. 59 ! Materials and Methods ................................ ................................ ............................ 61 ! Specimen Preparation ................................ ................................ ...................... 61 ! Fluorosc opic Image Acquisition ................................ ................................ ........ 62 ! 3D Model Creation and Coordinate Assignation ................................ ............... 62 ! 3D to 2D Shape Matching ................................ ................................ ................ 64 ! Statistical Analysis ................................ ................................ ............................ 65 ! Results ................................ ................................ ................................ .................... 66 ! Discussion ................................ ................................ ................................ .............. 67 ! 4 IN VIVO THREE DIMENSIONAL KNEE KINEMATICS DURING DAILY ACTIVITIES IN DOGS ................................ ................................ ............................ 82 ! Introduction ................................ ................................ ................................ ............. 82 ! Materials and Methods ................................ ................................ ............................ 83 ! 3D Mod el Creation and Coordinate Assignation ................................ ............... 83 ! Fluoroscopic Image Acquisition ................................ ................................ ........ 84 ! 3D to 2D Shape Matching ................................ ................................ ................ 85 ! Statistical Analysis ................................ ................................ ............................ 86 ! Results ................................ ................................ ................................ .................... 86 ! Discussion ................................ ................................ ................................ .............. 89 ! 5 CONCLUSION ................................ ................................ ................................ ........ 98 ! LIST OF REFERENCES ................................ ................................ ............................. 102 ! BIOGRAPHICAL SKETCH ................................ ................................ .......................... 111 !

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7 LIST OF TABLES Table page 1 1 A summary of femoral and tibial absolute precision results reported by knee fluoro scopy studies in humans ................................ ................................ ........... 29 ! 2 1 Comparison of the mean ± SD absolute differences, 95% CIs, and RMS errors obtained by use of singl e plane fluoroscopic analysis versus a modified RSA technique ................................ ................................ ..................... 57 ! 2 2 Intraobserver and interobserver variation (mean SDs) of DOF measurements obtained via single plane fluoroscopic analysis of the femorotibial joint by 2 observers. ................................ ................................ ................................ ........... 57 ! 2 3 Mean absolute differ ences between results of single plane fluoroscopic analysis and a modified RSA for DOF measurements of the femorotibial joint over 3 trials. ................................ ................................ ................................ ........ 58 ! 2 4 Mean absolute differences between results of single plane fluoroscopic analysis and RSA for DOF measurements of the femorotibial joint obtained by 2 observers. ................................ ................................ ................................ ... 58 ! 3 1 Comparison of the mean ± SD absolute differences, 95% CIs, and RMS errors obtained by use of single plane fluoroscopic analysis versus a modified RSA technique ................................ ................................ ..................... 80 ! 3 2 Mean absolute differences between results of single plane fluoroscopic analysis and a modified RSA of DOF measurements repeated over 3 trials, in the femorotibial joint treated by TPLO. ................................ ............................... 80 ! 3 3 Intraobserver and interobserver variation (mean SDs) of DOF measurements obtained by use of single plane fluoroscopic analysis of the femorotibial joint treated by TPLO by 2 observers. ................................ ................................ ........ 81 ! 3 4 Mean absolute differences between re sults of single plane fluoroscopic analysis and a modified RSA for DOF measurements of the femorotibial joint treated by TPLO by 2 observers. ................................ ................................ ........ 81 !

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8 LIST OF FIGURES Figure page 1 1 Frontal plane cross sectional ............................. 29 ! 1 2 Retroflective markers positioned for motion capt ure analysis of knee kinematics ................................ ................................ ................................ ........... 30 ! 1 3 Single plane fluoroscopy used to measure femorotibial kinematics associated with a unicondylar knee replacement ................................ ................................ . 31 ! 1 4 Single plane flu oroscopy used to measure femorotibia l kinematics in normal patients ................................ ................................ ................................ ............... 32 ! 1 5 Biplanar fluoroscopy for measurement of stifle kinemat ics in the dog using RSA ................................ ................................ ................................ .................... 33 ! 2 1 Photograph of a cadaveric canine hindquarter specimen position ed within the C arm fluoroscope ................................ ................................ .............................. 46 ! 2 2 Femoral and tibial models used for single plane flu oroscopic analysis and RSA ................................ ................................ ................................ .................... 47 ! 2 3 Local coordinate systems assigned to CT generated 3D bone models .............. 48 ! 2 4 Representative digital images of a canine femur and tibia obtained by use of shape matching software used for modified RSA ................................ ............... 49 ! 2 5 Representative digital images of a canine femur and tibia shaped matched to fluoroscopic images ................................ ................................ ............................ 50 ! 2 6 Bland Altman plots of the agreement between measurements of translations made in 3 trials by use of modified RSA and t he mean of these 3 measurements ................................ ................................ ................................ .... 51 ! 2 7 Bland Altman plots of the agreement between measurements of rotations made in 3 trials by use of a modified RSA and t he mean o f these 3 measurements ................................ ................................ ................................ .... 52 ! 2 8 Bland Altman plots of the agreement between single plane fluoroscopic analysis and a modi fied RSA for three translations ................................ ............ 53 ! 2 9 Bland Altman plots of the agreement between single plane fluoroscopic analysis and a modified RSA fo r three rotations ................................ ................. 54 ! 2 10 Bland Altman plots of the agreement between single plane fluoroscopic analysis and a modified RSA for b oth observers ................................ ................ 55 !

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9 2 11 Bland Altman plots of the agreement between single plane fluoroscopic analysis and a modified RSA for both observers . ................................ ............... 56 ! 3 1 Digital 3D femoral and h ybrid implant tibia bone models ................................ .... 71 ! 3 2 Representative digital images of CT derived canine femur and tibial beaded models used for a modified RSA ................................ ................................ ........ 72 ! 3 3 Representative digital images of femoral and hybrid tibial bone models matched up to s ingle plane fluoroscopic images ................................ ................ 73 ! 3 4 Bland Altman plots of the agreement between measurements made in 3 trials by use of modified RSA and the mean of these 3 measurements for translations ................................ ................................ ................................ ......... 74 ! 3 5 Bland Altman plots of the agreement between measurements made in 3 trials by use of modified RSA and the mean of these 3 measu rements for rotations.. ................................ ................................ ................................ ............ 75 ! 3 6 Bland Altman plots indicating the agreement between single plane fluoroscopic analysis and a modif ied RSA technique for translations ................. 76 ! 3 7 Bland Altman plots of the agreement between single plane fluoroscopic analysis and a modif ied RSA technique for rotations ................................ ......... 77 ! 3 8 Bland Altman plots of the agreement between single plane fluoroscopic analysis and a modified R SA technique for both observers ............................... 78 ! 3 9 Bland Altman plots of the agreement between single plane fluoroscopic analysis and a modified R SA technique for both observers . .............................. 79 ! 4 1 Dog pictured pe rforming different activities ................................ ........................ 93 ! 4 2 Representative shape matched fluoroscopic image of a dog stifle at the trot.. ... 94 ! 4 3 Averaged plots of stifle flexion angle versus axial tibi al alignment for all activities ................................ ................................ ................................ .............. 9 5 ! 4 4 Averaged plot of flexion versus axial ali gnment for all dogs at the trot ............... 96 ! 4 5 Averaged plots of stifle flexion angle versus coronal angulation for all four activities. ................................ ................................ ................................ ............. 97 !

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10 LIST OF ABBREVIATIONS 3D Three Dimensional 2D Two Dimensional ACL Anterior Cruciate Ligament CAD Computer Aided Design CdCL Caudal Cruciate Ligament CrCL Cranial Cruciate L igament CT Computed Tomographic DOF Degree Of Freedom MRI Magnetic Resonance Imaging RSA Radiostereometric Analysis TPLO Tibial Plateau Leveling Osteotomy

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11 Abstract of Thesis Presented to the Graduate School of the University of Florida in Partial Fulfillment of the Requirements for the Degree of Master of Science THREE DIMENSIONAL FEMOROTIBIAL KINEMATIC ANALYSIS USING SINGLE PLANE FLUOROS COPY IN THE DOG By Stephen C. Jones August 2014 Chair: Stanley E. Kim Major: Veterinary Medical Sciences The ability to quantify three dimensional (3D) joint kinematics with accuracy and precision in vivo is vital to gaining an understanding of the pathomechanics of joint disorders. The objectives of this study were to investigate the accuracy and precision of single plane fluoroscopy in quantifying stifle kinematics of dogs, and to use this measurement mo dality to characterize high precision, 3D in vivo stifle kinematics in healthy dogs during different activities. The accuracy and precision of the 3D to 2D model registration technique was assessed in both normal and tibial plateau leveling osteotomy (TPL O) treated cadaveric stifles. Metallic beads were implanted in the femora and tibiae of both limbs; a TPLO was performed on the left tibia while no surgery was performed on the right stifle. Biplanar fluoroscopy was simulated by obtaining orthogonal fluoro scopic images of each stifle at 5 flexion angles to simulate a normal gait cycle. Joint kinematics were measured with a single plane 3D to 2D model registration technique and with modified radiostereometric analysis (RSA). The single plane technique was pe rformed by shape matching CT generated 3D femoral and tibial bone models to lateral view (2D) fluoroscopic images. RSA was performed by tracking the implanted beads in orthogonal

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12 fluoroscopic images. Accuracy of the single planar model registration techniq ue was assessed by comparison to biplanar RSA results. Following this cadaveric validation, the 3D to 2D model registration technique was applied to 6 orthopedically normal Labrador retriever dogs performing common daily activities including walking, trott ing, sitting and stair ascen t. For the ex vivo validation, mean absolute differences between the single planar model registration technique and RSA were less than 1.28 mm and 1.05 mm for all translations, and 1.58¼ and 1.08¼ for all rotations, for the nor mal and TPLO treated stifle respectively. For the in vivo stifle kinematics, i ncreasing stifle flexion angle was associated with tibial internal rotation, abduction and cranial translation for all 4 activities. The exact relationship between flexion angle and these movements varied both within and between activities. We validated the accuracy and precision of a single plane fluoroscopic 3D to 2D model registration technique in normal and TPLO treated dog stifles. We further documented that normal dog stifle kinematics are complex with movement being under precise active control , which is activity dependent.

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13 CHAPTER 1 AN INTRODUCTION TO STIFLE KINEMATICS Overview Joint k inematics is the study of the motion of bones, wi thout regards to forces or mass. Interest in the motion of the human knee has a long history with early knee kinematic 1 The a bility to quantify joint kinematics with precision in vivo is vital to gaining an understanding of musculoskeletal pathomechanics and to evaluate the effect of treatment on joint function. Historically, stifle kinematics in the dog were measured in the sag ittal plane, where large flexion extension excursions could be quantified . 2,3 This approach however underestimates the complexity of femorotibial movement and reduces stifle kinematics to that of a simple hinge joint. Educational and technological advances have enabled us to study stifle kinematics in much greater detail and have exponentially improved our understanding of the complexity of femorotibial kinematics . Anatomy The stifle is a complex diarthrodial joint, w ith motions occurring in all three planes. 4 Stifle kinematics can refer to both femorotibial and patellofemoral kinematics; however, most motion is associated wi th the for mer and is the basis of our discussions and investigations here . The complex motion of the femorotibial joint is largely a function of the elaborate anatomic composition. Stifle kinematics are influenced by the delicate interplay between the distal femur, the proximal tibia, the lateral and medial menisci and the joint capsule, along with 15 different ligaments and 16 different muscles. 4

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14 Like most species, dogs display anat omical adaptations in response to the biomechanical loads encountered, which directly affect stifle kinematics. Adaptations of the cortical bone , which decrease in thickness from the diaphysis to the metaphysis, allow shock absorption through deformation d uring weight bearing . Furthermore, there is an increase in osseous diameter at the femorotibial surface , increas ing surface area to aid in reduction of peak vertical force within the stifle during ambulation and other activities. Despite these anatomicall y adv antageous morphologies , the femorotibial articular surface is incongruent with round, asymmetrical femoral condyles 5 articulating with a relatively flat to convex tibial plateau, which has a caudo distal orientation in the dog. 6 Due to the osseous incongruence of the femorotibial joint, stifle stability is highly dependent on the soft tissue constraints . The CrCL is considered to be the primary stabilizer of the stifle, limiting hyperextension, cranial translation and internal rotation of the tibia. 7 The CdCL functions to limit caudal tibial translation and secondarily helps to limit both internal and external tibial rotation. 7 The incongruency between the femorotibial articulation is largely negated by the lateral and medial menisci (Figure 1 1). The menisci are crescent shaped fibrocartilage discs that function as secondary stabilizers of the stifle and ensure uniform load transmission between the round femoral condyles and the relatively flat, sloped tibial plateau. 8 Clearly, the anatomy of the stifle joint is very complex. Unlike most other diarthrodial joints, the stifle is unique in that joint stability is highly dependent on the soft tissue constraints rather than bone congruen cy, leaving these soft tissues vulnerable to large and often excessive strain s and loads.

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15 Ex Vivo Kinematic Investigations in the Dog Injuries to the soft tissues supporting the stifle joint are frequently encountered in veterinary practice. C ranial cruciate ligament rupture is one of the most common causes of pelvic limb lameness in dog s 9 and has been the focus of numerous kinematic studies over the years. Much of our early understanding of stifle kinematics has thus come from ex vivo studies of the function of the C r CL and other stifle ligaments , and how these supporting structures relate to stifle kinematics. 7,10,11 Cadaveric studies area also useful in that they often allow for histologic and mechanical analysis of ligamen ts. Arnoczky and Marshall performed one of the first kinematic studies in the dog stifle. 7 In this study, metallic pins were placed at the points of origin and insertion of CrCL fibers and radiographs of the stifle were acquired over a range of motion, utilizing the distance between the markers as a function of ligament length. This study showed that the CrCL is composed of both craniomedial and caudolateral components which demonstrated reciprocal loosening and tightening as the stifle moved through a range of motion. The caudolateral band was found to be taut in extension and loose in flexion whereas the craniomedial band remained tensioned in extension and flexion. In agreement with what had previously been shown with the human ACL 12 , this study demonstrated that the CrCL in the dog functions to limit cranial tibial translation. More precisely, the craniomedial component of the CrCL, being taut in both flexion and extension was found to be the primary restraint against cranial tibial translation. In further agreement w ith that found in the human ACL 12 , the CrCL was also found to prevent internal tibial rotation and stifle hyperextension. Similar to the CrCL, the CdCL was also found to have both cranial and caudal components. While the indi vidual function of each component

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16 was not fully elucidated, the entire CdCL was found to be the primary restraint against caudal tibial translation. 7 A later study by Vasseur et al. looked at the function of the lateral collateral ligaments and how these structures affected frontal and transverse p lane stifle kinematics. 10 The length of these ligaments were measured in similar fashion, tracking ligament implanted lead markers with serial radiographs as the stifle moved through a range of motion. The medial collateral ligament was found to be taut throughout the full range of motion whereas the lateral collateral ligament was taut in extension on ly, becoming lax during flexion. This study demonstrated that both collateral ligaments are taut during extension, which results in tight control of tibial abduction/adduction and internal/external rotation when the stifle is in extension. Progressive rela xation of the lateral collateral ligament resulted in internal tibial rotation as the stifle flexion angle increased; continued internal tibial rotation was thought to be limited by the CrCL. This ated in human knee kinematics studies, where the tibia internally rotates with progressive flexion. 13 17 Monahan et al . furthered these previous veterinary studies by measuring the strain patterns of the CrCL, the CdCL, the medial and lateral collateral ligaments in vivo using mercury gauges. 18 These investigators found that valgus loading of the stifle lead to tibial internal rotation, with the degree of internal rotation increasing as the flexion angle increased, corroborating prev ious findings of Vasseur et al . 10 The study by Monahan et al . showed that internal and extern al tibial rotation is limited both by the collateral and cruciate ligaments. They confirmed that with increasing flexion angle and the associated

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17 internal tibial rotation, the CrCL assumes a greater role in limiting further internal rotation of the tibia. 18 These early studies clearly showed that stifle kine m atics are much more complex tha of the 3D features of stifle kinematics in the dog. These studies however were limited in their cadaveric nature. Isolated cadaveric stifle investigations typically limit the evaluations to a single joint, and negate the effects that muscular pull, cadence, velocity and body stance can have on the kinematics of that joint in vivo . A classic example of where cadaveric kinematic results do not c onsistently translate to the in vivo setting is illustrated by reviewing research on the human knee. Multiple cadaveric studies demonstrate the screw home mechanism, as described above. 13 17 This finding however is often not identified in 3D in vivo kinematic studies 19 , can be suppressed with external rotation of the foot, 20 and appears to be highly dependent on the activity being performed. 21 The realization of said limitations of cadaveric studies is slowly shifting the paradigm of kinematic investigations, in both human and veterinary research, to the in vivo dynamic setting. In Vivo Kinematic Investigations in the Dog Optical M otion Cap ture Some of the earliest in vivo kinematic measurement studies in both humans and dogs were conducted using optical motion capture technology. This technique involves tracking the position of surface mounted markers using motion sensor cameras. Markers a re attached to anatomical landmarks in order to outline specific bones and thus calculate the relative movement between these two bodies (Figure 1 2). The earliest form of this technology involved manually tracking assigned markers from a

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18 sequence of still analogue video images. 22 Modern motion capture systems typically track the motion of skin mounted markers using specialized high speed tracking video cameras. Unfortunately motion capture technology has inherent inaccuracy in its methodology, regardless of the marker type used. Placing markers on the skin to overlie specific anatomic structures makes a rigid body assumption, that marker motion precisely reflects that of the underlying skeletal structure. This assumption has been shown to be pro blematic, with numerous human and veterinary studies demonstrating considerable discrepancy between motion of the skin mounted markers and that of the underlying bone. 23 26 Studies quantifying the magnitude of this soft tissue artifact have shown that markers around the stifle can move relative to their assigned landmarks by up to 3 cm in humans and 1.2 cm in dogs. 23,25 A further complication encountered with this technique, unique to quadrupedal motion, is the inability to see medially b ased markers during ambulation. 27 Visualization of laterally based markers only, restricts the ability to measure kinematics in 3D and usually limits measurement of flexion extension angles only. Optical motion capture has been utilized in numerous veterinary studies investigating kinem atics of both the healthy 2,3,27 36 and pathologic 34,37,38 dog stifle. The vast majority of these studies evaluated stifle flexion extension angle only, due to the limited ability to accurately measure out of sagittal plane rotational and translational movements. In these studies, the stifle was found to have t wo peaks of maximal extension during the gait cycle; one during the swing phase and one during the stance phase of gait. 2,32,33 It was found that the maximal stifle extension and flexion at th e trot

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19 was approximately 150¼ and 90 , respectively. 28,33 The point of maximum stifle extension was further found to correspond with the onset of stance phase. 33 More recent work in dogs evaluated the use of a joint coordinate system with optical motion capture for measuring stifle kinematics in 3D. 27,39 This involves the assignation of a local coordinate system to both the femur and tibia, based on an initial static trial where all markers are visible; 39 computational models are then used to mathematically reconstruct any markers that are obscured during ambulation. 27 They found that using this system, in contrast to previous motion capture studies, permitted the measurem ent of coronal and transverse plane angulations. 27 While this rep resents a significant advancement in the ability to measure dog stifle kinematics in 3D using optical motion capture methodology, these studies did not perform an accuracy error analysis and are still prone to soft tissue artifact. Based on inaccuracies i n human studies using similar methodology, questions regarding the precision for measuring out of sagittal plane rotations remains. Model Based Fluoroscopic Image Registration Dynamic fluoroscopic imaging has become one of the most commonly used kinematic measurement techniques in humans. The subject is imaged while performing are then measured by aligning CT or MRI generated 3D bone models to the corresponding bone silhouettes on the 2D fluoroscopic images, to quantify the pose (translation and rotation) parameters. Fluoroscopic analysis has many advantages: the bones are visualized and tracked directly, eliminating the skin and soft tissue artifact encountered with some of the other techniques, as described above; 25,40 the

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20 methodology involved is minimally invasive, utilizes anatomically based coordinate systems and can be used to measure dynamic daily activities in vivo. 41 The ac curacy and precision of model registration using single and biplanar fluoroscopy has been evaluated in multiple investigations. Studies that utilized artificial bones and those that employed bone embedded markers in their methodology tended to demonstrate increased accuracy and precision levels when compared to shape matching natural bones without markers ( Table 1 1). Accuracy and repeatability results obtained from studies that shape matched to natural bones are obviously more representative of what can be done in the in vivo scenario. Investigations of femorotibial kinematics utilizing single plane fluoroscopy have demonstrated an absolute precision of less than 1.2 mm for in plane translations and 1.3¼ for all rotations. 41 Single plane fluoroscopy Single plane fluoroscopy and model registration involves lateral view imaging of as an activity is performed. Most of the early work utilizing this technique involved measuring knee kinematics in humans following total knee arthroplasty (TKA). 42 45 Manufacturer supplied 3D computer aided design (CAD) models of the metallic implants were shape matched to precisely overly the corresponding i mplants on lateral view fluoroscopic images (Figure 1 3). Total knee arthroplasty implants have very well defined geometry and this makes shape matching the CAD models of the implant to the corresponding implant outline on fluoroscopic images intuitive and accurate. 42 Researchers gradually moved to fluoroscopic kinematic analysis of the normal human knee. 46 49 As there are no CAD models available of the (CT) bone density data 46 , with similar accuracy to that reported using implant CAD

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21 models (Figure 1 4). 41 To try and negate the necessity for a CT scan and the associated radiation exposure, a more recent investigation showed that magnetic resonance image (MRI) derived bone models can be used with similar accuracy to that attained with CT derived bone models. 50 One major limitation of single plane fluoroscopy is reduced accuracy for out of plane translational measurements. Movement of the joint perpendicular to the fluoroscope manifests as changes in the size of the bone silhouette on the fluoroscopic image, which can be subtle and difficult to detect. Banks and Hodge showed that bone translations perpendicular to the image plane had standard errors ten times greater than translations parallel to the image plane. 42 Similar findings have been documented in multiple single plane fluoroscopic studies. 41,44,46,51,52 Despite the vast literature on the measurement of human knee (and other joint ) kinematics using a mod el registration technique and single plane fluoroscopy, to date, there are no published kinematic studies in dogs conducted using this methodology. Biplanar fluoroscopy Kinematic measurement using model registration and biplanar fluoroscopy involves imag ing the joint of interest with two simultaneously operating orthogonally positioned fluoroscopes (Figure 1 5). The ability to measure from orthogonal angles increases the measurement accuracy and precision for out of plane translations and rotations. 53 56 One previous study documented the use of a model registration technique and biplanar fluoroscopy for measuring femorotibial kinematics in the dog. 57 While a detailed description of the kinematics was not provided in that study, they documented the feasibility and accuracy of a biplanar shape matching technique in the dog stifle. Despite the increased accuracy attained with biplanar fluoroscopy over single plane

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22 fluoroscopy, large set up costs, limited availability, increased radiation exposure and a reduced field of view for imaging dynamic activities, limit the applicability of this technique in veterinary medicine. Radiost ereometric Analysis Radiostereometric analysis (RSA) is another kinematic analytic technique in which biplanar (stereo) radiography is used to track the relative movements of two bones or implants, in a highly accurate and precise manner. Originally descr ibed by Selvik et al. 58 with an in vivo accuracy of less than 250 m for translations and less than 0.5¼ for rotations. 59,60 Radiostereometric analysis involves tracking surgically implanted radiodense tantalum metallic markers in stereo radiographic images. The originally described RSA technique involved tracking marker beads in statically a cquired orthogonal film radiographs. A disadvantage of this method was the requirement for a lot of user interaction. 61 Consequently a faster, user friendly digital tracking system was later developed, with no differences documented in rotational or translational accurac y when compared with the manual RSA. 60 More recently, fluoroscopy has been used with RSA to track implanted beads in dynamic in vivo studies . 62 67 The accuracy of RSA when kinematics are measured dynamically using fluoroscopy has been shown to comparable to the traditional RSA methodology. 68 Despite the widespread application of RSA in the human medical field, use of RSA in animals is sparse. published in vivo studies using RSA in animals. The earliest stud y investigated the effects of porous coating on osteointegration in total knee arthroplasty in sheep. 69 Later,

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23 studies by Allen et al. assessed the feasibilit y of RSA for assessing implant migration in dogs with total hip arthroplasty 70 and with total knee arthroplasty 71 ,with satisfactory results documented. Radiostereometric analysis princip les were also used by Tashman et al. in normal and CrCL transected research dogs to assess the acute and chronic effects of CrCL deficiency on stifle kinematics. 66,67 While the primary objectives of this study was to assess the kinematic control, prior to CrCL transection. Unfortunately, the limited field of view afforded by two orthogonal fluoroscopes imaging simultaneously (Figure 1 5) did not allow capture of complete gait cycl es; only stifle kinematics immediately prior to and following paw strike of dogs at the walk were captured and analyzed. In the control (normal) dogs, the stifle was found to be actively extending in the late swing phase with this extension progressing in to the early stance phase, where maximum extension reached approximately 150¼. Although not specifically correlated, graphs in this paper indicate that the tibia was both adducting and externally rotating as the stifle extended. Tashman et al. evaluated the accuracy and precision of dynamic RSA in the dog stifle in vivo , using high speed biplanar radiography. 66 They documented an average precision of 0.064 mm for all translations and 0.31¼ for all rotations. 66 The results of this stu dy indicate that RSA is both a viable and precise method for measuring stifle kinematics in the dog dynamically in vivo . Although considered the most accurate and precise in vivo kinematic measurement modality available, RSA requires bone implantation of m etallic marker beads. Implantation involves an anesthetic episode and

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24 a surgical procedure, clearly reducing the applicability of RSA for everyday kinematic measurements in a clinical setting. Kinematics of the Cranial Cruciate Ligament Deficient Dog Stifl e Cruciate Ligament Rupture: Prevalence and Etiology Cranial cruciate ligament insufficiency is one of the most common causes of hind limb lameness in the dog. 9,72 Loss of integrity of the CrCL is a debilitating condition with affected dogs exhibiting lameness, muscle atrophy and invariably develop progress ive stifle osteoarthritis. 73 Estimates suggest that 100,000 people ruptured their ACL in the USA in 2007. 74 Although this is a large number, the prevalence of CrCL rupture in dogs appears to be much higher, with one large number retrospective study showing a 2.55% incidence of Cr CL disease in dogs . 75 Additionally, prevalence or reported prevalence of C rCL disease in dogs has more than doubled over the past three decades. 75 In contrast to the scenario seen in humans where sports related injuries account for 65% of ACL ruptures requiring surgery 76 , CrCL rupture usually occurs under normal physiologic loads of everyday activities in the dog as a result of progressive midbody ligament failure. 77,78 Although non contact injuries account for up to 72% of ACL ruptures in people 79 , the vast majority of these are associated with excessive loading of the ACL. 80 Injuries usually invo lve acceleration or deceleration motions with the knee near or at full extension, most often when combined with an internal moment and/or a valgus load exerted on the knee. 80 Due to these differences in disease etiology and presentation, the kinematic risk factors for and effects of ACL rupture in people cannot r eliably be extrapolated to explain CrCL disease in the dog.

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25 Ex Vivo Kinematics A number of ex and in vivo studies have been conducted to investigate the kinematic effects of CrCL insufficiency in the dog. In one of the earliest ex vivo studies, Arnoczky and Marshall found that transection of the CrCL resulted in a 150% increase in internal tibial rotation and an 8% increase in maximal extension angle. 7 They further found the normal stifle exhibited no cranial tibial translation; this value increased by an average of 9.5 mm after CrCL transection i n the medium sized dog cadavers (15 20 kg) used in their study. 7 More recently, Pozzi et al. investigated the effects of CrCL deficiency on stifle kinematics, articular contact area and contact pressures in canine cadaveric specimens. 81 It was found that CrCL deficiency shifts contact points to less frequently loaded areas of the tibial plateau, potentially contributing to cartilage pathology and osteoarthritis instigation. 81 Although these studies introduced important concepts such as the kinematic changes after CrCL injury, they also outlined the limitations of ex vivo models and the n eed for accurate 3D in vivo studies. In Vivo Kinematics Korvick et al. were the first group to investigate 3D dog stifle kinematics in vivo. 82 They measured dogs walking and trotting over ground before and after transection of the CrCL, to study the function of the CrCL. Kinematic curves for the walk and the trot in normal stifles were found to be very similar, with larger peaks noted for flexion, abduction and internal rotation during the trot versus the walk. For the intact and CrCL deficient stifle, increased flexion was accompanied by internal tibial rotation and tibial abduction. Following CrCL transection, dogs walked with the stifle in 5 14¼ more flexion. The tibia was more cranially and medially translated while also being more internally rotated in the CrCL deficient dogs. 82 This was the first study demonstrating the true 3D

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26 nature of normal stifle kinematics in vivo. This group further highlighted that stifle kinematics are affected in all 6 DOF post CrCL loss. 82 While providing invaluable femorotibial kinematic data, the study was not without limitations. The implemented methodolog y required multiple surgical procedures and involved the use of percutaneous pins, which may have influenced joint kinematics. Tashman et al. furthered these findings by measuring the acute and chronic effects of CrCL transection on femorotibial kinematic s. 66,67 As mentioned above, kinematics were measured using biplanar fluoroscopy and RSA principles. In 82 , the CrCL deficient dog carried the stifle in more flexion, by ~9 ¼ on average. Cranial cruciate ligament loss also resulted in an increase in cranial and medial tibial translation. The range of coronal plane angu lation doubled in the CrCL deficient dogs with the CrCL deficient stifles carried in greater adduction by 82 , Tashman did not find increased internal tibial rotation post CrCL transection. Although conducted with highly precise methodology 66 , this study was limited by the fact that only a s mall po r tion of the gait cycle was captured and that a surgical procedure to implant the marker beads for RSA was required. Treatment A previous study suggested that conservatively managed CrCL deficient dogs can have a satisfactory outcome. 83 Surgical intervention, however, is still considered by many to afford the best clinical outcomes. 84 Despite the numerous surgical procedures described for CrCL insufficiency in dogs, no single procedure has demonstrated clear superiority with regards to clinical ou tcomes. 84,85 This lack of consensus on the best tr eatment option for these dogs suggests that our understanding of the CrCL disease

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27 process, the effects of CrCL deficiency on femorotibial kinematics, and whether our surgical interventions restore normal femorotibial kinematics, are not fully understood. The overall economic impact for treating CrCL rupture in the USA in 2003 was estimated at over $1.3 billion. 86 In spite of the patient morbidity and the huge costs associated with the management of CrCL insufficiency, to date there are still no 3D studies assessing stifle kinematics of at risk breeds, to help provide some insight into the kinematic mechanisms of C rCL rupture. With the high frequency of CrCL insufficiency seen in dogs, there is a clear need to understand the effects of this disease on stifle kinematics. We furthermore need to assess the kinematic effects of the numerous surgeries described for stabi lizing the CrCL deficient stifle. The ability to restore normal kinematics to a CrCL deficient stifle is paramount to restoring normal physiologic load transmission to the articular cartilage, thereby removing one of the major instigators of cartilage wear and subsequent osteoarthritis 87 that is seen with many of the commonly performed surgical procedures. 88 93 Summary Recent advancements in joint kinematic research have resulted in a vast improvement in our understanding of stifle kinematics in the dog. Originally described to function as a hinge joint, stifle motion is now known to be much more complex with rotations and translations occurring in all three planes. Despite this increased understanding, a well defined quantitative description of normal stifle kinematics in the dog is lacking. While providing vital baseline data on CrCL deficient stifles, the studies by Korvick 82 and Tashman 67 did not provide a detailed description of normal stifle kinematics. These studies were further limited by the fact that they only st udied straight line ambulation and that they involved invasive

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28 methodology. It has been well documented in the human knee that femorotibial kinematics vary considerably between different activities. 21,94 The majority of published stifle kinematic studies in the dog involved femorotibial assessment during walking or tr otting. More recently, other activities such as swimming 34 , stair ascent and stair descent 95 have been described. While broadening our knowledg e of kinematics during different activities, the aforementioned swimming and stair activity investigations only assessed femorotibial flexion extension, and thus did not give a thorough description of stifle kinematics. The ability to quantify normal motio n during daily activities is critical to our understanding of the kinematic effects of different pathologies affecting the stifle. Furthermore, kinematics measured over a range of normal daily activities will help provide a baseline outcome measure for any stabilization procedures performed on the stifle. There clearly are a multitude of modalities available for quantifying joint kinematics. Despite the tremendous advancements in this measurement technology, many modalities suffer from drawbacks such as i nherent inaccuracy, invasiveness, lack of availability, and or the inability to measure dynamic activities. There is a clear need to define a technique which can be easily implemented to measure femorotibial kinematics in the dog with a high level of accur acy and precision, in a minimally invasive manner during a range of different activities.

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29 Table 1 1. A summary of f emoral and tibial absolute precision results reported by knee fluoro scopy studies in humans. 41 References Fluoroscopy Method Knee Type Models Matched In Plane Translation Out Plane Translation All Rotations Fregly 41 Single plane Natural Bones 0.42 5.6 1.3 Kanisawa 51 Single plane Natural Bones 1.2 4.0 0.8 Komistek 46 Single plane Natural Bones 0.45 ... 0.66 Banks 42 Single plane Artificial Implants 0.21 3.9 1.3 Hoff 52 Single plane Artificial Implants 0.46 2.2 0.35 Mahfouz 44 Single plane Artificial Implants 0.09 1.4 0.40 Tashman 66 Bi plane Artificial Markers 0.06 0.06 0.31 You 57 Bi plane Artificial Bones 0.23 0.23 1.2 Kaptein 96 Bi plane Artificial Markers 0.05 0.08 0.07 Kaptein 96 Bi plane Artificial Implants 0.06 0.14 0.17 Translations are measured in mm and rotations are measured in degrees . Figure 1 1. incongruity between the round femoral condyles and the relatively flat tibial plateau. The wedge shaped menisci function to fill the incongruent spaces

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30 abaxially. ( Peter Muir . Advances in the Canine Cranial Cruciate Ligament. Hoboken, NJ: Wiley Blackwel l , 2010 ). 8 Figure 1 2. Retroflective markers positioned for motion capture analysis of knee kinematics. Markers are positioned for a point cluster technique to help reduce error associated with soft tissue art efact. ( Source: Koh JSB, Nagai T, Motojima S, et al. Concepts and measurement of in vivo tibiofemoral kinematics. Oper Tech Orthop 2005;15:43 48). 15

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31 Figure 1 3. Single plane fluoroscopy used to measure femorotibial kinematics associated with a unicondylar knee replacement. Three dimensional models of the distal femur and proximal tibia/fibula, with manufacture supplied implant CAD models are shape matched to precisely overly the corresponding structures on the fluoroscopic image. (Source: Banks SA, Fregly BJ, Boniforti F, et al. Comparing in vivo kinematics of unicondylar and bi unicondylar knee replacements. Knee Surg Sports Traumatol Arthrosc 2005;13:551 556). 97

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32 Figure 1 4. Single plane fluoroscopy used to measur e femorotibial kinematics in normal patients. Computed tomography derived bone models of the distal femur and proximal tibia and fibula are shape matched to precisely overly the corresponding bones on the fluoroscopic image. (Source: Moro oka T A, Hamai S, Miura H, et al. Can magnetic resonance imaging derived bone models be used for accurate motion measurement with single plane three dimensional shape registration? J Orthop Res 2007;25:867 872). 50

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33 Figure 1 5. Biplanar fluoroscopy for measurement of stifle kinemat ics in the dog using RSA. A) A dog walks on a treadmill while being imaged by two (biplanar) fluoroscopes . B) An overhead schematic of the biplanar radiographic system. The joint of interest can only imaged where the two x ray beams intersect, as in dicated by the hatch line area . (Source: Tashman S, Anderst W. In vivo measurement of dynamic joint motion using high speed biplane radiography and CT: application to canine ACL deficiency. J Biomech Eng 2003;125:238 245 ). 66

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34 CHAPTER 2 ACCURACY OF NONINVASIVE, SINGLE PLANE FLUOROSCOPIC ANALYSIS FOR MEASUREMENT OF THREE DIMENSIONAL FEMOROTIBIAL JOINT POSES IN DOGS Introduction The accuracy of measuring femorotibial joint motion by use of single plane fluoroscopy in dogs cannot be extrapo lated from human studies due to differences in osseous morphology, size, and cadence. Reporting the feasibility and accuracy of single plane fluoroscopy for the stifle joint of dogs is required to conduct valid in vivo dynamic studies that use this methodo logy. The purpose of the study reported here was to determine the accuracy of a digital bone model based, single plane fluoroscopic technique for measuring 3D kinematics of normal canine stifle joints, with a biplanar marker based digitally modified RSA te chnique used as a reference for measuring femorotibial poses during simulated pelvic limb ambulation in a cadaver specimen. We hypothesized that single plane fluoroscopic analysis of dog stifle joints would offer a high degree of accuracy for rotations and translations in the sagittal plane (flexion extension, craniocaudal translation, and proximodistal translation), with poorer accuracy for rotations and translations out of the sagittal plane (mediolateral translation, abduction adduction, and internal ext ernal rotation). We further hypothesized that this technique would have a high level of inter and intraobserver repeatability. Materials and Methods Specimen P reparation The pelvis and intact normal pelvic limbs were collected by disarticulation of the v ertebral column at the lumbosacral joint from a 25 kg skeletally mature dog that was

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35 euthanized for reasons unrelated to the study. A CT scan a of both pelvic limbs from the hips to the tarsocrural joint was obtained. Metal marker beads of 2 mm diameter wer e then implanted into the cortices of the distal femur and proximal tibia of both limbs. The metal beads served as radiopaque markers for determining the precise position and orientation of the femur and tibia relative to each other by use of a digital mod ification to the originally described RSA. 58 A minimum of 4 beads per bone was used to satisfy the requirement of at least 3 markers; beads were positioned in each bone such that the beads would not overlap on mediolateral and cranioc audal view fluoroscopic images. No problems with identifying the beads were encountered in any of the fluoroscopic views. A TPLO was performed in the left limb for analyzing hybrid implant bone model based shape matching techniques; the results of that stu dy are discussed below . Following marker bead implantation, a second CT scan was obtained in similar fashion. Fluoroscopic Image A cquisition The specimen was mounted in a custom designed jig that allowed unconstrained passive movement of the hip, stifle, and hock joints (Figure 2 1); the specimen was positioned centrally within the field of view of the fluoroscope with a source to detector distance of 1,100 mm. Optical geometric features of a ceiling mounted fluoroscopic system b were determined by use of a calibration object with known spatial positions of metal beads. 42 This object measured 160 X 160 X 160 mm and contained 35 radiopaque metal beads; a CT scan of the calibration object allowed accurate determination of these metal bead loca tions. A simple validation was conducted to assess for potential calibration errors introduced with C arm rotation between a Toshiba Aquilon 8, Toshiba American Medical Systems Inc, Tustin, Calif. b Toshiba Infinix i flat panel C arm fluoroscope, Toshiba American Medical Systems Inc, Tustin, Calif.

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36 orthogonal image acquisitions. Fluoroscopic images of the calibration device in the craniocaudal orientation and then in the mediolat eral orientation were obtained. These sequential images were completed 6 times with all craniocaudal and mediolateral images, and assessed for variation in marker bead positioning in the images, with none detected. The x ray source was configured to supply a 76 kV beam with a 20 mA beam current, by use of a 1 shot fluoroscopy acquisition program. The flat panel detector had a field of view of 41 X 30 cm; image resolution was 1,024 X 1,024 pixels. By use of a goniometer, the right stifle joint was sequential ly positioned at 5 flexion angles, ranging from 150¡ to 110¡, to simulate a normal gait cycle range of motion. With the left limb manually moved out of the field of view, sequential mediolateral and craniocaudal view fluoroscopic images of the right stifle joint were obtained for each pose, while ensuring the specimen did not move between orthogonal image acquisitions. Images were acquired through 5 gait cycles. 3D Model Creation and Coordinate A ssignation Three dimensional bone models were created from CT scan digital imaging and communication in medicine images by use of an open source 3D segmentation software program. c This semiautomatic application uses bone contour edges to create surface models of the bones. 98 For the single plane fluoroscopic analysis, bone models of the femur and tibia were created from the first CT scan, which was free from any metal artifact (Figure 2 2). For RSA, marker based models were created from the second CT scan. Femoral and tibial 3D models used for RSA did not include the bone around the implanted metallic beads, and only contained the implante d beads in these regions. The c ITK SNAP, version 2.2, ITK SNAP.org, P hiladelphia, Pa. Available at: www.itksnap.o rg . Accessed Feb 10, 2013.

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37 3D bone models were imported into a reverse engineering software program. d Radiostereometric analysis marker models were aligned with the corresponding beadless bone models, and coordinate systems were assigned simultaneously to both models. This eliminated variability in the comparative measurements that may have occurred from use of different coordinate systems for each corresponding 3D model. Coordinate systems were assigned to the femurs and tibiae on the basis of local ana tomic landmarks as described. 66 By use of a best fit function in the software program d , spheres were contoured around both femoral condyles and the femoral head with the center point of each structure interactively identified. Femoral coordinates were applied so that the mediolateral axis (z axis) passed through the center of the lateral and medial femoral condyles with the femoral origin located at the midpoint between the center of the condyles on the mediolateral axis. The proximodistal axis (y axis) passed proximally, perpendicular to the mediolateral axis in a plane common to the center o f both femoral condyles and the femoral head (Figure 2 3) . Tibial coordinates were applied so that the mediolateral axis passed from the outermost edge of the medial and lateral tibial condyles; the tibial point of origin was set midway between these 2 poi nts on the mediolateral axis. The proximodistal axis passed from distal to proximal, perpendicular to this mediolateral axis in a plane common to this axis and the midpoint of the distal tibia. The craniocaudal axes (x axes) for the femur and tibia were cr eated from the cross product of the mediolateral and proximodistal axes, creating a Cartesian coordinate system. d Geomagic Studio, Geomagic Inc, Research Triangle Park, NC.

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38 3D to 2D Shape M atching Two dimensional fluoroscopic images and 3D bone models were imported into a custom written open source shape matching software program. e For RSA, 3D models of implanted beads were superimposed over the mediolateral and craniocaudal fluoroscopic images simultaneously and manually manipulated to overlie the beads in the orthogonal fluoroscopic images (Figure 2 4). This proc ess was repeated 3 times for all images to assess repeatability of the modified RSA technique. For the single plane fluoroscopic analysis, 3D bone models of the femur and tibia were superimposed over the lateral fluoroscopic images only and manually manipu lated to precisely match the silhouette of their respective bones (Figure 2 5). Frames were analyzed in a random fashion so that the shape matching from one frame could not bias the next corresponding frame in that gait cycle. All frames were analyzed 3 ti mes by the primary observer (SCJ) to assess for intraobserver repeatability. A second observer (GT) completed the process once for all 5 cycles, to assess for interobserver variability. Interobserver variability was assessed by comparing the first 5 cycle values measured the first time by the primary observer, with the 5 cycle values measured by the second observer. Both observers underwent training in the shape matching procedure before study commencement; this involved tutoring from an engineer experience d with the fluor oscopic analysis technique . Three dimensional position and orientation of each bone model was determined from the shape matching software; these data were then e JointTrack, Department of Mechanical and Aer ospace Engineering, College of Engineering, University of Florida, Fla. Available at: ufdc.ufl.edu/UFE0 021784/00001. Accessed Feb 1 0, 2013.

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39 imported into a custom written transformation matrix decomposition program, f whi ch transformed the data into clinically relevant femorotibial poses in 6 DOF. 99 Statistical A nalysis A statistical software package was used for all analyses. g Rotations (flexion extension, abduction adduction, and internal external) and translations (craniocaudal, mediolateral, and proximodistal) calculated by use of RSA and single plane fluoroscopic analysis were compared. The accuracy of each DOF was defined by the mean absolute difference and RMS errors between RSA and single plane fluoroscopic analysis. Intraobserver repeatability was assessed by comparing the 3 trials completed by the primary observer. Standard deviations were determined for each DOF from each fluoroscopic frame from the 3 times they were analy zed. A single repeatability measure was determined by calculating the mean SD for each DOF (75 frames). 66 Intraobserver variation was further assessed by use of a 1 way repeated measures ANOVA for the absolute difference between the single plan e fluoroscopic analysis and RSA for all 5 cycles that were completed 3 times by the primary observer. Interobserver repeatability was similarly assessed by determining the SD for each DOF in each fluoroscopic frame measured by both observers, with overall repeatability described as the mean SD for each DOF. Interobserver agreement was also assessed by means of a paired t test on the absolute differences between the single plane fluoroscopic analysis and RSA for each DOF. The agreement between the single pla ne fluoroscopic analysis and RSA for both intra and interobserver analysis was further described by the limits of agreement f Matlab, MathWorks, Natick, Mass. g SigmaPlot, version 12, Systat Software Inc, San Jose, Calif.

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40 approach, as described by Bland and Altman. 100 Agreement between the measurements, repeated 3 times on all biplanar images by use of the modified RSA, was evaluated with Bland Altman plots . For all statistical analyses, values of P < 0.05 were consid ered significant. Results Agreement between the repeated biplanar images by use of the modified RSA was very high, as demonstrated by narrow 95% limits of agreement in all 6 DOF on Bland Altman plots ( Figures 2 6 and 2 7). The absolute value of the differ ences of the means for single plane fluoroscopic analysis and RSA were determined (Table 1). Mean absolute differences between the techniques were small at 1.28 mm for all translations, and 1.58¡ for all rotations . The RMS errors between the single plane fluoroscopic analysis and RSA were 1.42 mm for all translations, and 2.01¡ for all rotations. For intraobserver variability, mean SDs were 0.52 mm for all translations, and 1.36¡ for all rotations (Table 2) . Significant differences were found in the absolute mean difference for proximodistal ( P = 0.001), mediolateral ( P = 0.001), abduction adduction ( P = 0.03), and internal external ( P = 0.04) measurements over the 3 times all kinematics were measured (Table 3). For interobserver repeatability, mean SDs were 0.52 mm for all translations, and 0.91¡ for all rotations. The absolute differences between the single plane fluoroscopic analysis and RSA techniques were significantly different between the 2 observe rs for abduction adduction ( P = 0.02) and internal external rotation ( P = 0.03; Table 4 ). Bland Altman plots revealed narrow 95% limits of agreement for all 6 DOF within (Figures 2 8 and 2 9) and between (Figures 2 10 and 2 11) observers.

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41 Discussion Resul ts suggested that single plane fluoroscopic analysis is a highly accurate method for measuring stifle joint kinematics in dogs in all 6 DOF. The largest absolute mean difference between RSA and single plane fluoroscopy was not > 1.28 mm for translations an d 1.58¡ for rotations. The results were in accordance with similar studies of the human knee, in which single plane fluoroscopic analysis resulted in mean errors of 1.2 mm for sagittal plane translations and 1.3¡ for all rotations. 41 Intuitively, motion of objects parallel to the flat panel detector will be seen as changes in position of that object in the image, whereas motion perpendicular to the detector will be seen primarily as changes in silhouette shape or size, which are more subtle and difficult to identify. 42 For instance, with lateral images, changes in mediolateral transla tion are seen as changes in bone silhouette size, whereas changes in abduction adduction and internal external rotations are seen as change in bone silhouette shape. Consistent with the hypothesis of greatest accuracy being found in the sagittal plane, the largest errors for rotations were found with abduction adduction and internal external rotations. The proximodistal translation results did not support the hypothesis that accuracy would be greatest in the sagittal plane. A systematic bias in the proximo distal translations measured by use of bone models was found, compared with the biplanar bead based measurements. The source of this bias, which makes the bones appear slightly farther from the x ray source, results from the graphic method used to superimp ose the bones on the fluoroscopic image. The bones are projected as solid objects, not as radiolucent objects, and thus they always will appear slightly larger than a true radiographic view in which the edges are slightly attenuated to make the object appe ar slightly smaller. Correction for this size discrepancy during the shape matching

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42 process results in femoral and tibial origins being distracted by approximately 1 mm, giving the bias. This bias was consistently present and was clearly evident in the Bla nd Altman plots, where differences between the fluoroscopic analysis technique and RSA were not centered about 0, unlike the 5 other DOF (Figures 2 8 and 2 10). The mediolateral alignment of the normal stifle joint is highly constrained in dogs. 66,67,82 The s hape matching software has a free view function that allows the operator to view and manipulate the femoral and tibial bone models together in 3D from any perspective (Figure 2 5). Seeing the bone models together, particularly from a digital craniocaudal view, allows the operator to estimate the relative positions of the femur and the tibia for mediolateral alignment. Thus, the high degree of accuracy in the mediolateral translation was suspected that a mediolateral translation of < 1 mm would result in subtle changes in bone silhouette size that are not easily detectable on mediolateral views. Hence, caution is advised i n the interpretation of the apparently high accuracy for quantifying mediolateral alignment with single plane fluoroscopy. Intraobserver repeatability was assessed by the primary observer performing shape matching analysis on all 5 cycles 3 times. Signifi cant differences in the mean absolute error were found for 4 variables (proximodistal, mediolateral, abduction adduction, and internal external), but the magnitude of difference that was detected was < 0.70 mm for translations and 0.96¡ for rotations and w as not considered a clinically relevant source of error. Three of the 4 variables with significant differences in the magnitude of error were out of sagittal plane rotations (abduction adduction and internal external) and translations (mediolateral), consi stent with previous findings that

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43 measurements made out of the sagittal plane are less repeatable than those made in plane. 42 Interobserver repeatability for single plane fluoroscopic analysis was high, with no significant differences obse rved in the magnitude of error between observers for 4 of the 6 DOF. Significant differences between observers were found for abduction adduction and internal external rotations. These variables may have been associated with poorer repeatability because th ese rotations do not occur in the sagittal plane. 42 Despite the detection of significant differences in the mean absolute er rors, the actual magnitude of the discrepancies between the 2 observers was extremely small (0.90¡ and 0.75¡ for ab duction adduction and internal external, respectively) and would not be considered to be a clinically relevant source of error in future clinical studies. The main limitation of this study was that images were acquired under static conditions, which may n ot directly replicate the image quality acquired in a dynamic setting with live dogs. The static setup in this study did not reproduce potential motion artifact that occurs with dynamic image acquisition, which can affect the accuracy of this fluoroscopic analysis technique. 101 Fluoroscopic systems used in dynamic musculoskeletal studies must be able to generate a sufficiently fast frame rate and a short enough exposure time to avoid motion artifact while capturing enough data to analyze the gait in its entirety. 101 The system is capable of generating 30 exposures/s with an exposure time of 1 millisecon d; pilot dynamic trials with live dogs performed in trotting was excellent and comparable to the images acquired in this validation study. In the present study, the ord er in which the fluoroscopic images were shape matched to the bone models was random so that the preceding image did not influence the shape

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44 matching of the following fluoroscopic image. A previous study 102 found that dynamic trials had the same or better mean accuracy than static trials, likely due to operator knowledge of bone position in the previous frame aiding the shape matching process. Thus, dynamic data collected in live subjects by use of single plane fluoroscopy may indeed have similar or better accuracy than the accuracy reported here. Limb overlap was avoided by manually moving the contralateral limb out of the ra diographic field of view. Limb overlap on the fluoroscopic images would be unavoidable in a dynamic setting and could negatively affect the shape matching process. Finally, the results may not be applicable to all dogs, given the anatomic variations among dogs. The cadaveric specimen used in the present study was a 25 kg non chondrodystrophic mixed breed dog. Potential variations in the accuracy of this technique may be introduced with dogs of different sizes, with anatomic anomalies, or radiographically ev ident disease such as osteoarthritis. There was a distinct learning curve associated with the shape matching process. Both observers underwent appropriate training before commencing the study. No statistical improvement in accuracy was detected among the 3 trials completed by the primary observer; however, both observers found that shape matching became easier and less time consuming as more experience was gained. The accuracy of results for future studies will be dependent on the training of those perform ing the analysis and their attention to detail with the shape matching of the models to the corresponding bones on the fluoroscopic images. Results of the present study indicated that 3D femorotibial poses of dogs can be measured with a high level of accu racy by use of noninvasive single plane fluoroscopic

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45 analysis. High interobserver and intraobserver repeatability was evident. This method of quantifying femorotibial kinematics could be a useful tool to investigate kinematics in normal and abnormal stifle joints during a variety of dynamic motions encountered during daily activities in clinical subjects. In addition, single plane fluoroscopic analysis could be used to assess the efficacy of surgical procedures performed to improve kinematics of diseased st ifle joints.

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46 Figure 2 1. Photograph of a cadaveric canine hindquarter specimen positioned within the C arm fluoroscope. The jig configuration allowed unrestrained passive movement of the hip, stifle, and hock joints (photo courtesy of author) .

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47 Figure 2 2. Femoral and tibial models used for single plane fluoroscopic analysis and RSA. A) Complete bone models create d from initial CT scan data. B) B eaded models created from CT data obtained following bead implantation fo r use with the RSA technique (image courtesy of author) .

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48 Figure 2 3. Local coordinate sys tems assigned to CT generated 3 D bone models. A) F emoral bone model. B) Tibial bone model . Femorotibial kinematics were determined by the relative rotations and translations between these bone fixed local coordinate systems (image courtesy of author) .

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49 Figure 2 4. Representative digital images of a canine femur and tibia obtained by use of shape matching software used for modified RSA . A) The CT derived beaded models are matched to implanted m etal be ads in the craniocaudal view fluoroscopic image . B) Models matched to the lateral view fluoroscopic image (image courtesy of author) .

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50 Figure 2 5. Representative digital images of a canine femur and tibia shaped matched to fluoroscopic images. A ) Mediolateral fluoroscopic image. B ) Femoral and tibial bone models manipulated into a different perspective, compared with image A ) , by use of a free view function. Manipulation of the viewing angle with the free view function does not affect the position of the bone models in the fluoroscopic imag e (image courtesy of author) .

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51 Figure 2 6. Bland Altman plots of the agreement between measurem ents of translations made in 3 trials by use of modified RSA and the mean of these 3 measurements . Plots determining A) craniocaudal , B) proximodistal , and C) mediolateral translations of the femorotibial joint are shown . The solid line represents the mean difference between the measurements; the dashed lines represent limits of agreement, between which 95% of difference s between the measurements are expected.

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52 Figure 2 7. Bland Altman plots of the agreement between measurements of rotations made in 3 trials by use of a modified RSA and t he mean of these 3 measurements. Plots determining A) flexion extension , B) abducti on adduction , C) and internal external rotations of the femorotibial joint are shown . The solid line represents the mean difference between the measurements; the dashed lines represent limits of agreement, between which 95% of differences between the measurements are expected.

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53 Figure 2 8. Bland Altman plots of the agreement between single plane fluoroscopic analysis and a modified RSA for three translations. Plots determining A) craniocaudal A), B) proximodistal , and C) mediolateral translations of t he femorotibial joint are shown . The solid line represents the mean difference between the 2 techniques. The dashed lines represent limits of agreement, between which 95% of differences between the 2 techniques are expected. Notice how differences between the techniques are not centered around 0 for proximodistal translations, due to systematic bias in this DOF.

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54 Figure 2 9. Bland Altman plots of the agreement between single plane fluoroscopic analysis and a modified RSA for three rotations. Plots determi ning A) flexion extension , B) abduction adduction , and C) intern al external rotations of the femorotibial joint are shown . The solid line represents the mean difference between the 2 techniques. The dashed lines represent limits of agreement, between which 95% of differences between the 2 techniques are expected.

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55 Figure 2 10. Bland Altman plots of the agreement between single plane fluoroscopic analysis and a modified RSA for both observers. Plots determining A) craniocaudal , B) proximodistal , and C) med iolateral translations of the femorotibial joint for 2 observers are shown . The solid line represents the mean difference between the techniques for the 2 observers. The dashed lines represent limits of agreement, between which 95% of differences between t he 2 techniques are expected. Notice how differences between the techniques are not centered around 0 for proximodistal translations, due to systematic bias in this direction.

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56 Figure 2 11. Bland Altman plots of the agreement between single plane fluoros copic analysis and a modified RSA for both observers. Plots determining A) flexion extension , B) abduction adduction , and C) internal external rotations of the femorotibial joint for each observer are shown . The solid line represents the mean difference be tween the techniques for the 2 observers. The dashed lines represent limits of agreement, between which 95% of differences between the 2 techniques are expected.

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57 Table 2 1. Comparison of the mean ± SD absolute differences, 95% CIs, and RMS errors obtained by use of single plane fluoroscopic analysis versus a modified RSA technique . Evaluation of 6 DOF for all fluoroscopic images, each assessed 3 times, in the right pelvic limb of a dog cadaver is presented. DOF Difference (mean ± SD) 95% CI RMS er ror Craniocaudal (mm) 0.60 ± 0.51 0.48 0.72 0.79 Proximodistal (mm) 1.28 ± 0.60 1.14 1.42 1.42 Mediolateral (mm) 0.64 ± 0.58 0.51 0.77 0.91 Flexion Extension (¡) 0.63 ± 0.56 0.50 0.76 0.84 Abduction Adduction (¡) 1.49 ± 1.26 1.20 1.78 2.00 Internal External (¡) 1.58 ± 1.16 1.31 1.85 2.01 Table 2 2. Intraobserver and interobserver variation (mean SDs) of DOF measurements obtained via single plane fluoroscopic analysis of the femorotibial joint by 2 observers. Translations (mm) Degrees (¼) Craniocaudal Proximodistal Mediolateral Flexion Extension Abduction Adduction Internal External Intraobserver variability 0.25 0.32 0.52 0.52 1.19 1.36 Interobserver variability 0.27 0.46 0.52 0.78 0.91 0.82 Intraobserver data represent analysis completed 3 times on all fluoroscopic images by the primary observer. Interobserver data represent analysis completed on all fluoroscopic images by both observers.

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58 Table 2 3. Mean absolute differences between results of single plane fluoroscopic analysis and a modified RSA for DOF measurements of the femorotibial joint over 3 trials. Translations (mm) Rotations (¼) Trial Craniocaudal Proximodistal Mediolateral Flexion Extension Abduction Adduction Internal External 1 0.74 a 1.01 a 0.95 a 0.81 a 1.94 a 1.93 a 2 0.50 a 1.25 b 0.59 b 0.52 a 1.55 a,b 1.65 a,b 3 0.55 a 1.58 b 0.38 b 0.55 a 0.98 b 1.15 b a,b Within a column, values with different superscript letters are significantly ( P < 0.05) different. Each analysis was repeated 3 times. Table 2 4.Mean absolute differences between results of single plane fluoroscopic analysis and RSA for DOF measurements of the femorotibial joint obtained by 2 observers. Translations (mm) Degrees (¼) Observer Craniocaudal Proximodistal Mediolateral Flexion Extension Abduction Adduction Internal External 1 0.74 a 1.01 a 0.95 a 0.81 a 1.94 a 1.93 a 2 0.46 a 1.06 a 0.75 a 1.03 a 1.04 b 1.18 b See Table 3 for key.

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59 CHAPTER 3 ACCURACY OF NONINVASIVE, SINGLE PLANE FLUOROSCOPIC ANALYSIS FOR MEASUREMENT OF THREE DIMENSIONAL FEMOROTIBIAL JOINT POSES IN DOGS TREATED BY TIBIAL PLATEAU LEVELING OSTEOTOMY Introduction Tibial plateau leveling osteotomy has become one of the most commonly performed surgical procedures to treat cranial cruciate ligament insufficiency in dogs. 103 By reducing the caudodistally angulated slope of the tibial plateau, TPLO is purported t o neutralize the cranially directed shear force across the stifle joint generated during weight bearing, thereby eliminating cranial tibial subluxation. 104 Clinical outcomes are reported to be good to excellent in approximately 90% of cases, yet little is known about in vivo biomechanics in stifle joints treated by TPLO. Several cadaveric studies 105 107 support the proposed mechanism behind the procedure, in which cranial tibial subluxation was consistently eliminated in cranial cruciate ligament deficient stifle joints treated by TPLO; however, a recent clinical radiographic study 108 found one third of dogs had persistent cranial tibial subluxation during standing after surgery. The effect of TPLO during dynamic activities remains unknown. Given that cranial tibial sublu xation of TPLO treated stifle joints can persist during static weight bearing, 108 it is possible that craniocaudal instability is also present during ambulation. In addition, TPLO was originally developed only to address instability in the sagittal plane 104 ; it is unknown how this procedure affects other stifle joint rotations and translations. Abnormal joint kinematics may be responsible for the progression of osteoarthritis seen in stifle joints treated by TPLO. 92,93 A better understanding of the in vivo effects of TPLO on joint stability may enable re finement of

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60 the clinical techniques and recommendations for dogs with cranial cruciate ligament insufficiency. The ability to detect subtle kinematic abnormalities requires precise methods for tracking joint motion. Hybrid implant bone modeling involves t he creation of a 3D model incorporating both bone and implant geometry. 97 Single plane fluoroscopy performed by use of CT derived bone models has been used to accurately quantify joint kinematics during dynamic activities in v arious joints of humans. 46,97,109 The principal advantage of this technique over other kinematic analysis methods includes the use of readily accessible equipment and the lack of requirement to surgically place bone markers. However, the accuracy of this kinematic analysis technique in TPLO treated dogs cannot b e extrapolated from human studies due to differences in osseous morphology and implant geometry; validation of single plane fluoroscopy for TPLO treated dogs is therefore required to conduct in vivo dynamic studies that use this methodology. Radiostereomet ric analysis is accepted as the gold standard method for tracking bone motion, 58 with an error accuracy of 0.06 mm for translations and 0.31¡ for rotations described in dogs. 66 The purpose of the study r eported here was to determine the accuracy of a digital hybrid implant bone model based single plane fluoroscopic technique for measuring 3D femorotibial poses in a TPLO treated canine stifle joint. We hypothesized that single plane fluoroscopic analysis w ould offer a high degree of accuracy for rotations and translations in the sagittal plane (flexion extension, craniocaudal, and proximodistal), with reduced accuracy for rotations and translations out of the sagittal plane (mediolateral, abduction adductio n, and internal external), and that this technique would have a high level of inter and intraobserver repeatability.

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61 Materials and Methods Specimen P reparation The pelvis and intact normal pelvic limbs were collected by disarticulation at the lumbosacral joint from a 25 kg skeletally mature dog that was euthanized for reasons unrelated to the study. A CT scan a of both pelvic limbs, from the hips to the tarsocrural joint was obtained. Radiopaque marker beads of 2 mm diameter were implanted into the cortice s of the left femur and tibia for determining the precise position and orientation of the femur and tibia relative to each other, by use of a digital modification to the originally described RSA. 58 The left cranial cruciate ligament w as transected via a medial stifle joint arthrotomy, and a TPLO was performed by a board certified surgeon (SEK), as described. 104 The osteotomy was stabilized with a precontoured, locking 3.5 mm TPLO plate b by use of 3.5 mm locking screws in the plateau segment and 3.5 mm cortical screws in the distal tibial segment. By use of a 3D laser scanner, c a digital 3D model of the plate and locking screws was created by scanning an identical plate locking screw construct as used in the specimen. Exact anatomic positioning of the marker beads was not required; beads were positioned such that most markers wou ld not overlap or be obscured by metallic TPLO implants on orthogonal fluoroscopic images. Following marker bead implantation and TPLO, a second CT scan was obtained in similar fashion. a Toshiba Aquilon 8, Toshiba American Medical Systems Inc, Tustin, Calif. b Standard 3.5 mm Synthes locking TPLO plate, Synthes, Paoli, Pa. c 3D Scanner HD, NextEngine, Santa Monica, Calif.

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62 Fluoroscopic Image A cquisition The specimen was mounted to a custom d esigned jig that allowed unconstrained passive movement of the hip, stifle, and hock joints; the specimen was positioned with the left stifle joint centered within the field of view of the fluoroscope with a source to detector distance of 1,100 mm. Optical geometry of a ceiling mounted fluoroscopic system d was determined by use of a calibration object with known spatial positions of metal beads. 42 This object measured 160 X 160 X 160 mm and contained 35 radiopaque metal beads; a CT scan of the calibration object allowed accurate determination of these metal bead locations. The x ray source was configured to supply a 76 kV beam with a 20 mA beam current by use of a 1 shot fluoroscopy acquisition program. The flat panel detector had a field of view of 40 X 30 cm; image resolution was 1,024 X 1,024 pixels. By use of a goniometer, the left stifle joint was sequentially positioned at 5 flexion angles, ranging from 150¡ to 110¡ of extension, to simulate a normal gait cycle range of motion. With the right limb manually moved out of the field of view, mediolateral and craniocaudal projection fluoroscopic images of the left stifle joint were obtained for each pose, while ensuring the specimen did not move between orthogonal image acquisitions. Images w ere acquired through 5 individual gait cycles. 3D Model Creation and Coordinate A ssignatio n Three dimensional bone models were created from CT scan digital imaging and communication in medicine images by use of an open source 3D segmentation software prog ram. e This semiautomatic application uses bone contour edges to create surface d Toshiba Infinix i flat panel C arm fluoroscope, Toshiba American Medical Systems Inc, Tustin, Calif. e ITK SNAP, version 2.2 , ITK SNAP.org, P hiladelphia, Pa. Available at: www.itksnap.org. Accessed Feb 10, 2013.

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63 models of the bones. 98 For single plane fluor oscopic analysis of the stifle joint, the femoral bone model was created from the first CT scan, which was free from any metal artifact (Figure 3 1). A reverse engineering software program f was used to construct a hybrid tibial bone model by amalgamating s can data from the first and second CT scans, as well as the laser scanned TPLO plate screw construct. The initial CT scan was used to create a tibial model free from artifact associated with the metallic implants. Data from the second CT scan were used to ascertain the precise position of the implanted plate screw construct on the tibia. The laser scanned TPLO plate screw construct was then superimposed over this tibial model. For RSA, marker based models were created from the second CT scan. Femoral and ti bial 3D models used for RSA did not include the bone, bone plate, or screws around the implanted metallic beads and only contained the implanted beads in these regions (Figure 3 2). The RSA marker models were aligned with the corresponding hybrid bone mod els and coordinate systems were applied simultaneously to both models. This eliminated variability in the comparative measurements that may have occurred from use of different coordinate systems for each 3D model. Femoral coordinates were applied so that t he mediolateral axis passed through the center of the lateral and medial femoral condyles with the femoral origin located at the midpoint between the centers of the condyles, on this axis. The proximodistal axis passed proximally, perpendicular to the medi olateral axis at the origin, in a plane common to the center of both femoral condyles and the femoral head. Tibial coordinates were applied so that the mediolateral axis passed from the outermost edge of the lateral and medial tibial condyles; the tibial f Geomagic Studio, Geomagic Inc, Research Triangle Park, NC.

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64 p oint of origin was set midway between these 2 points on the mediolateral axis. The proximodistal axis passed from distal to proximal, perpendicular to the tibial origin in a plane common to the mediolateral axis and the midpoint of the distal portion of th e tibia. The craniocaudal axes for the femur and tibia were created from the cross product of the mediolateral and proximodistal axes, creating a Cartesian coordinate system. 3D to 2D Shape M atching Two dimensional fluoroscopic images and 3D bone and hybr id models were imported into a custom written open source shape matching software program. g For the biplanar RSA, 3D models of implanted beads were superimposed over the mediolateral and craniocaudal projection fluoroscopic images simultaneously and manual ly manipulated to overlie the beads in the orthogonal fluoroscopic images (Figure 3 2). This process was repeated 3 times for all images to assess for repeatability of the modified RSA technique. For the single plane fluoroscopic analysis, the femoral and hybrid tibial 3D models were superimposed over the mediolateral fluoroscopic images and manually manipulated to match the silhouette of the respective bones and metallic implants (Figure 3 3). Each individual fluoroscopic frame was analyzed in a random fashion so that the shape matching from one frame could not bias the next corresponding frame in that gait cycle. All frames were analyzed 3 times by the primary observer (SCJ) to assess intraobs erver repeatability. A second observer (GT) completed the process once for all 5 gait cycles, to assess interobserver variability. Interobserver variability was assessed by comparing the 5 cycles completed the first time by the primary observer with the 5 cycles completed by the second observer. Both g JointTrack, Department of Mechanical and Aerospace Engineering, College of Engineering, University of Florida, Fla. Available at: ufdc.ufl.edu/UFE0021784/00001. Accessed Feb 10, 2013.

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65 observers underwent training in the shape matching procedure before study commencement; this involved tutoring from an engineer experienced with the fluoroscopic analysis technique (SAB). Three dimensional posi tion and orientation of each bone model was determined from the shape matching software; these data were then imported into a custom written transformation matrix decomposition program h , which transformed the data into clinically relevant femorotibial pose s in 6 DOF. 99 Statistical A nalysis A statistical software package was used for all analyses. i Rotations (flexion extension, abduction adduction, and internal external) and translations (craniocaudal, mediolateral, and proximodistal) calculated by use of RSA and single plane fluoroscopic analysis were compared. The accuracy for each DOF was defined by the mean absolute difference and RMS errors between RSA and single plane fluoroscopic analysis. Intraobserver repeata bility was assessed by comparing the 3 trials completed by the primary observer. Standard deviations were determined for each DOF, from each fluoroscopic frame over the 3 times they were analyzed. A single repeatability measure was determined by calculatin g the mean SD for each DOF (75 frames). 66 Intraobserver variation was further assessed by use of a 1 way repeated measures ANOVA for the absolute difference between results of the fluoroscopic analysis and RSA for all 5 cycles that were complet ed 3 times. Interobserver agreement was assessed by use of a paired t test performed on the absolute difference between the single plane fluoroscopic analysis and RSA for each DOF. Similarly, repeatability was assessed by determining h Matlab, MathWorks, Natick, Mass. i SigmaPlot, version 12, Systat Software Inc, San Jose, Calif.

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66 the SD for each DOF in each fluoroscopic frame measured by both observers, with overall repeatability described with the mean SD for each DOF. The agreement between the fluoroscopic analysis and RSA for both intra and interobserver analysis was further described by the limits of agreement approach, as described by Bland and Altman. 100 Agreement between the measurements, repeated 3 times on all biplanar images by use of the modified RSA, was evaluated by use of Bland Altman plots. For all statistical analyses, values of P < 0. 05 were considered significant. Results Agreement between the repeated biplanar images by use of the modified RSA was ver y high, as demonstrated by narrow 95% limits of agreement in all 6 DOF on Bland Altman plots ( Figures 3 4 and 3 5). The absolute value of the differences of the means for single plane fluoroscopic analysis and RSA were determined (Table 3 1). Mean absolute differences between the 2 techniques were 1.05 mm for all translations, and 1.08¡ for all rotations. The RMS errors between the single plane fluoroscopic analysis and RSA were 1.23 mm all translations, and 1.44¡ for all rotations. For intraobserver repeatability, no significant differences were found between RSA and fluoroscopic analysis in the absolute mean differences in any of the 6 DOF measurements, over the 3 times kinematics were measured (Table 3 2). Intraobserver mean SDs were 0.59 mm for all translations and 0.93¡ for all rotations (Table 3 3). For interobserver repeatability, mean SDs were 0.56 mm for all translations and 0.84¡ for all rotations. The absolute differences between results of the fluoroscopic analysis and RSA for both observers revealed a significant ( P = 0.044) difference only for mediolateral translation (Table 3 4). Bland Altman plots revealed narrow 95% limits

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67 of agreements for all 6 DOF within (Figures 3 6 and 3 7) and between (Figures 3 8 and 3 9) observers. Discu ssion Consistent with the primary hypothesis, results indicated that single plane fluoroscopic analysis with hybrid implant bone models was a highly accurate method for measuring 3D femorotibial joint kinematics in stifle joints treated by TPLO. The largest mean difference between RSA and single plane fluoroscopy was 1.05 mm for translations and 1.08¡ for rotations. The results were in accordance with similar human kinematic studi es 41,42 that used a single plane fluoroscopic technique, in which normal knees and knees modified with metallic implants had reported mean errors of Results of the init ial study in normal dog stifles indicated that single plane fluoroscopic analysis of a normal limb by use of CT derived bone models has a high order of accuracy. Results of the study reported here suggest that accuracy was higher with hybrid implant bone m odels, compared with bone only models. Greater accuracy was found for all 6 DOF, compared with accuracy attained by use of this single plane fluoroscopy technique in a normal canine pelvic limb. The TPLO treated tibia had more marker beads and wider bead d ispersion, compared with the normal tibia. This was conducted to avoid metal overlap between the TPLO plate and the beads on the fluoroscopic images. Both of these factors may have nominally increased the accuracy of the modified RSA. The mean absolute dif ference between results of RSA and single plane fluoroscopic analysis for TPLO treated stifle joints was smaller than the values obtained from normal stifle joints by 0.26, 0.23, and 0.16 mm for craniocaudal,

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68 proximodistal, and mediolateral translations, r espectively, and 0.07¡, 0.64¡, and 0.50¡ for flexion extension, abduction adduction, and internal external rotations, respectively. Of particular note was the increased accuracy attained with abduction adduction and internal external rotations. These rotat ions are out of the sagittal plane. Lateral projection single plane fluoroscopy has excellent accuracy for motions in the sagittal plane with reduced accuracy for out of plane rotations and translations. 42 We suspect that the well defined geometry of the metallic implants in the TPLO treated stifle joint made the shape matching process more accurate. The laser scanned plate and locking screws in the hybrid model was of particular benefit in orientating the model for abduction adduction and internal external rotations, which were more subtle and difficult to detect on the lateral view fluoroscopic images of normal bones. In contrast to the normal limb, in which significant differences in the mean absolute error between RSA and single plane f luoroscopic analysis were found in 4 of the 6 DOF, no significant differences were found for any of the 6 DOF in the TPLO treated stifle joint over the 3 times they were measured. The improved repeatability of this technique is again attributed to the impr oved accuracy attained when the TPLO plate and locking screw construct was used in the hybrid model for the shape matching process. Interobserver repeatability for single plane fluoroscopic analysis was also high, with no significant differences observed i n the magnitude of error between 2 observers for 5 of the 6 DOF. A significant difference in errors between observers was found for mediolateral translations. Motion in this plane is perpendicular to the radiographic beam, making assessment of this variabl e difficult by use of the single plane fluoroscopy method. The mediolateral alignment of the stifle joint is highly constrained in dogs and

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69 could be estimated during the shape matching process by use of the free view feature in the shape matching software. g The free view function allows the operator to view and manipulate the femoral and tibial bone models from any perspective; major discrepancies in the mediolateral alignment between femur and tibia could be visu alized and corrected for as described above . The accuracy in the mediolateral translations was recommend the use of this technique for assessing mediolateral stifle joint translations. During 3D model creation, it was p ossible to preserve the tibial plateau in the hybrid tibial model. This aided shape matching, particularly in relation to proximodistal translations and abduction adduction rotations. Because of CT metal artifact, the position of the TPLO plate and screws dictate the regions of bone that can be reconstructed into the 3D model. It must be noted that the application of a more proximal TPLO plate may preclude the ability to reconstruct the tibial plateau, which could potentially affect the ability to define th e exact relationship of the femoral and tibial articulating surfaces. A TPLO plate and locking screws, identical to the implanted construct, were laser scanned and incorporated into the hybrid tibial 3D model. Cortical screws were not included in this scan ned model due to the directional variability encountered during screw placement. A TPLO performed by use of only cortical screws would therefore preclude the ability to incorporate screws in the laser scanned model, likely with an associated reduction in a ccuracy. Improperly placed locking screws would not identically match a corresponding laser scanned locking screw construct and is a limitation to this technique.

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70 The limitations of this fluoroscopic analysis technique have been thoroughly described above . In brief, images were obtained under static conditions, which may not reliably replicate dynamic in vivo image quality. Furthermore, limb overlap, which is inevitable in dynamic trails and could affect the accuracy of this technique, was avoided in the p resent study. Fluoroscopic images were analyzed in random fashion; however, a previous dynamic trial revealed that similar or improved accuracy may be attainable when performed in vivo due to operator knowledge of bone position and orientation in the previ ous frame. 102 The shape matching technique involves a distinct learning curve; the accuracy of future studies will be depe ndent on the training of the individual and the attention to detail with the shape matching process. Contrary to our hypothesis of greatest accuracy in the sagittal plane, inaccuracy of proximodistal translations was more than twice that of the other trans lations. We ascribe this apparent reduced accuracy for the proximodistal parameter to the graphic method used to superimpose the bones on the fluoroscopic image. Finally, potential variations in the accuracy of this technique may be associated with dogs of different sizes, anatomic anomalies, or radiographically evident disease such as osteoarthritis. Single plane fluoroscopic analysis by use of bone and hybrid implant bone models had excellent accuracy for measuring 3D femorotibial poses in dogs following TPLO. This technique may allow for noninvasive, accurate quantification of femorotibial kinematics in clinical subjects that have undergone TPLO to treat cranial cruciate ligament insufficiency.

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71 Figure 3 1 . Digital 3D femoral and hybrid implant tibia bo ne models. A) Femoral model created from initial CT scan data of a cadaveric hin dquarter specimen from a dog. B) D igital 3D hybrid implant tibial model constructed from pre and post TPLO CT scans and laser scanned TPLO implants (image courtesy of author) .

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72 Figure 3 2. Re presentative digital images of CT derived canine femur and tibia l beaded models used for a modified RSA . The CT models are matched by use of implanted metal beads that appear b lue and orange . A) C raniocaudal fluoroscopic image. B) M ediolat eral fluoroscopic image e (image courtesy of author) .

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73 Figure 3 3. Re presentative digital images of femo r al and hybrid tibia l bone models matched up to single plane fluoroscopic images . The femoral model was derived from the first CT scan; t he tibial model was derived from a combination of the first and second CT scans, as well as a laser scan of an identical TPLO plate screw construct. The femoral and tibial models are matched to the silhouette of the bones and TPLO implants on the lateral v iew fluoroscopic image . A) Use of edge detection mode for shape matching. B) Use of 3D mode for shape matching (image courtesy of author) .

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74 Figure 3 4. Bland Altman plots of the agreement between measureme nts made in 3 trials by use of modified RSA and t he mean of these 3 measurements for translations. Plots determining A) craniocaudal, B) proximodistal, and C) mediolateral translations of the femorotibial joint treated by TPLO are shown . The solid line represents the mean difference between the measureme nts; the dashed lines represent limits of agreement, between which 95% of differences between the measurements are expected.

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75 Figure 3 5. Bland Altman plots of the agreement between measurements made in 3 trials by use of modified RSA and t he mean of t hese 3 measurements for rotations. Plots determining A) flexion extension , B) abduction adduction , and C) internal external rotations of the femorotibial joint treated by TPLO are shown. The solid line represents the mean difference between the measurement s; the dashed lines represent limits of agreement, between which 95% of differences between the measurements are expected.

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76 Figure 3 6. Bland Altman plots indicating the agreement between single plane fluoroscopic analysis and a modified RSA technique f or translations. Plots determining A) craniocaudal , B) proximodistal , and C) mediolateral translations of the femorotibial joint treated by TPLO are shown . The solid line represents the mean difference between the 2 techniques. The dashed lines represent l imits of agreement, between which 95% of differences between the 2 methods are expected.

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77 Figure 3 7. Bland Altman plots of the agreement between single plane fluoroscopic analysis and a modified RSA technique for rotations. Plots determining A) flexion extension , B) abduction adduction , and C) internal external rotations of the femorotibial joint treated by TPLO are shown . The solid line represents the mean difference between the 2 techniques. The dashed lines represent limits of agreement, betwe en which 95% of differences between the 2 methods are expected.

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78 Figure 3 8. Bland Altman plots of the agreement between single plane fluoroscopic analysis and a modified RSA technique for both observers. Plots determining A) craniocaudal , B) proximo dist al , and C) mediolateral translations of the femorotibial joint treated by TPLO for 2 observers are shown . The solid line represents the mean difference between the techniques for the 2 observers. The dashed lines represent limits of agreement, between whic h 95% of differences between the 2 techniques are expected.

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79 Figure 3 9. Bland Altman plots of the agreement between single plane fluoroscopic analysis and a modified RSA technique for both observers. Plots determining A) flexion extension , B) abd uction adduction , and C) internal external rotations of the femorotibial joint treated by TPLO for 2 observers are shown . The solid line represents the mean difference between the techniques for the 2 observers. The dashed lines represent limits of agreement, bet ween which 95% of differences between the 2 techniques are expected.

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80 Table 3 1. Comparison of the mean ± SD absolute differences, 95% CIs, and RMS errors obtained by use of single plane fluoroscopic analysis versus a modified RSA technique . Evaluation of 6 DOF for all fluoroscopic images, each assessed 3 times in the femorotibial joint treated by TPLO is presented . DOF Difference (Mean ± SD) 95% CI RMS error Craniocaudal (mm) 0.34 ± 0.32 0.30 0.38 0.39 Proximodistal (mm) 1.05 ± 0.64 0.91 1.19 1.23 Mediolateral (mm) 0.48 ± 0.39 0.39 0.57 0.62 Flexion extension (¡) 0.56 ± 0.37 0.48 0.64 0.67 Abduction adduction (¡) 0.85 ± 0.86 0.66 1.04 1.20 Internal external (¡) 1.08 ± 0.97 0.86 1.30 1.44 Table 3 2.Mean absolute differences between results of single plane fluoroscopic analysis and a modified RSA of DOF measurements repeated over 3 trials, in the femorotibial joint treated by TPLO. Translations (mm) Rotations (¼) Trial Craniocaudal Proximodistal Mediolateral Flexion Extension Abduction Adduction Internal External 1 0.31 1.30 0.41 0.56 0.95 1.39 2 0.41 0.99 0.49 0.57 0.66 1.00 3 0.29 0.85 0.53 0.56 0.93 0.84

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81 Table 3 3. Intraobserver and interobserver variation (mean SDs) of DOF measurements obtained by use of single plane fluoroscopic analysis of the femorotibial joint treated by TPLO by 2 observers. Translations (mm) Rotations (¼) Variable Craniocaudal Proximodistal Mediolateral Flexion Extension Abduction Adduction Internal External Intraobserver 0.33 0.59 0.41 0.31 0.91 0.93 Interobserver 0.38 0.46 0.56 0.37 0.61 0.84 Interobserver data represents analysis completed 3 times on all fluoroscopic images by the primary observer. Intraobserver data represents analysis completed on all fluoroscopic images by both observers. Table 3 4.Mean absolute differences between results of single plane fluoroscopic analysis and a modified RSA for DOF measurements of the femorotibial joint treated by TPLO by 2 observers. Translations (mm) Rotations (¼) Observer Craniocaudal Proximodistal Mediolateral Flexion Extension Abduction Adduction Internal External 1 0.31 a 1.30 a 0.41 a 0.56 a 0.95 a 1.39 a 2 0.51 a 1.08 a 0.69 b 0.36 a 0.99 a 1.17 a a,b Within a column, values without the same superscript letter grouping are significantly ( P < 0.05) different.

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82 CHAPTER 4 IN VIVO THREE DIMENSIONAL KNEE KINEMATICS DURING DAILY ACTIVITIES IN DOGS Introduction Understanding stifle kinematics in the dog is of considerable interest for both human and veterinary orthopedist s . The dog stifle is morphologically similar to the human knee, thus the dog has been frequently used as an experimental model to study knee injuries in people. 110 The CrCL deficient dog mo del, known as the Pond Nuki Model, reliably causes joint degeneration, and is commonly utilized to investigate the intrinsic relationship between abnormal kinematics and the development of osteoarthritis. 111,112 The dog stifle has been also used to study posterolateral injuries, 113 meniscectomy, 114 meniscal repair techniques 115 and meniscal regeneration. 116 Additionally, one of the leading causes of pelvic limb lameness in dogs is naturally occurring CrCL degeneration, which is estimated to cost US pet owner $1.3 billion annually. 86 Comparative anatomical s tudies have presented both differences and similarities between the human and dog knee. 110 Defining normal kinematic parameters over a range of different daily activities is required to r ecognize pathologic patterns of motion as well as establish optimal treatment goals for joint disorders; unfortunately, there is little detailed information on such baseline values for the dog stifle. High precision 3D in vivo stifle kinematics in normal dogs has been described in two experimental studies. 67,82 These investigations were limited by the fact that the primary focus was to assess abnormal motion associated with CrCL deficiency, and normal kinematic patterns were not thoroughly described. One of these studies also adopted invasive methodology to track kinematics, which may have influenced natura l gait patterns. 82 Additionally, the analyses were

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83 restricted to straight line ambulation. The objective of the c urrent study was to characterize high precision, 3D in vivo stifle kinematics in healthy dogs during different activities using a non invasive 3D to 2D model registration technique. Materials and Methods Six client owned, adult Labrador retrievers with a mean age of 4 years (range 1 7 years) and mean weight of 28 kg (26 32 kg) were studied. The study was approved consent was obtained. No discernable abnorm alities were det ected on orthop edic examination, as conducted by a board certified veterinary surgeon (S.E.K.). 3D Model Creation and Coordinate A ssignation Computed tomographic (CT) scans a of the pelvic limbs were obtained. CT scans used a 512x512 image matrix, a 0.35 x 0.35 pixel dim, and 1 mm slice thickness over the full length of the femur and tibia . The scans confirmed absence of pelvic limb orthopedic disease in all dogs. The cortical bone margins were segmented using a n open source 3D segmentation software progra m b as described above. These point clouds were converted into polygonal surface models with a reve rse engineering software program. c Anatomic coordinate systems were applied to each model as described above and previously for the dog. !! In brie f, the mediolateral (Z) axis of the femur was defined by a line passing through the center of two spheres fitted to each femoral condyle; for the tibia, the mediolateral axis was defined by a line passing a Toshiba Aquilon 8, Toshiba American Medical Systems Inc, Tustin, Calif. b ITK SNAP, version 2.2 , ITK SNAP.org, P hiladelphia, Pa. Available at: www.it ksnap.org. Accessed June 20, 2013. c Geomagic Studio, Geomagic Inc, Research Triangle Park, NC.

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84 through the most abaxial points of the medial and l ateral tibial condyles. The proximodistal (Y) axes were defined by lines perpendicular to the mediolateral axes in the plane intersecting the femoral head center and talocrural center for the femur and tibia, respectively. The c r anio caudal (X) axes were formed from the cross product of the first two. The center of the CrCL origin and insertion were used as the specific points to define joint translations, as previously described. 66 Fluoroscopic Image A cquisition All dogs were habituated to treadmill ambulation, stair ascent and stand to sit activities with biweekly training sessions for 1 month prior to data collection. All dogs acclimated well to the daily activities tested, and were subjectively assessed as performing the mot ions in a non stressful manner by the time of data collection. Continuous mediolateral view fluoroscopic images of the stifles were acquired during treadmill walk, treadmill trot, stand to sit, and stair ascent activities using a ceiling mounted fluoroscop ic syste m with the flat panel detector d (Figure 4 1). Prior to fluoroscopic image acquisition, o ptical geometry (principal point and principal distance) of the fluoroscopy system was determined using fluoroscopic images of a calibration target as described above. "# For data collection, images were obtained using a pulse rate of 30 frames/s, pulse width of 1 ms , and an image area of 410 x 300 mm, giving a 0.20 mm x 0.20 mm pixel resolution . T he x ray source was configured to supply a 72 kV b eam with a 50 mA beam current; slight adjustments to these parameters were made between dogs to obtain optimal cortical bone definition. d Toshiba Infinix i flat panel C arm fluoroscope, Toshiba American Medical Systems Inc, Tustin, Calif.

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85 Dog s walked on a treadmill at a velocity of 1.1 m/s (2.5 mph) and trotted at a velocity of 2 m/s (4.5 mph); consistent with that previously reported . 67 For the walk and trot, fluoroscopic imaging was o btained for 10 full gait cycles. A full gait cycle was paw strike paw strike To determine the phase of the gait cycle on the fluoroscopic images, high speed video recordings e were captured at 60 frames/sec, with a shutter speed of 1/1000 s , and were visually synchronized frame by frame with fluoroscopic images during these activities . Custom made stairs, consisting of 3 steps with a rise height and run length of 25 cm and 26 cm respectively were utilized for the stair ascen t activity. Due to the limited fluoroscopic field of view, acquisition of a complete gait cycle during stair ascent was not possible. Stairs were positioned so that the stance phase of stair ascent kinematics could be captured within the fluoroscopic fiel d of view. The stand to sit activity involved instructing the dog to sit on command with the pelvic limbs positioned within the fluoroscopic field of view. Thus, stair ascent measured femorotibial kinematics from flexion to full extension while the stand to sit activity measured femorotibial kinematics from extension to full flexion. Each subject commenced the stair ascent and stand to sit activities at slightly different flexion angles; thus, a maximum stifle flexion angle and maximum stifle extension ang le, common to all subjects were selected as starting points for stair ascent and stand to sit activities, respectively. 3D to 2D Shape M atching The 3D position s of the femur and tibia/fibula were determined using the 3D 2D shape matching technique describ ed above and previously. #$%"$%"# As described in e Canon Vixia HF G10, Melville, NY

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86 C hapter 2, the accuracy of this technique in dogs was found to be within 1.3 mm for translations and 1.6 for rotations. The CT bone models were projected onto the fluoroscopic images and manually aligned to the bone projections using open source shape matching software f (Figure 4 2). Three dimensional femorotibial kinematics were determined from the 3D position of each bone model using cardan angles , as previously described. 99 Statistical A nalysis Each gait cycle was time normalized using spline interpolation at 1% intervals from 0 100%. Time normalization allowed averaging of the data across multiple cycles for individual dogs, despite differences in cadence between tri als and between dogs. Of the ten gait cycles captured for the walk and trot, the three cycles that subjectively were best captured in the field of view, were chosen for analysis. Due to difficulty in obtaining adequately positioned stifle fluoroscopic imag es, only two stand to sit and one stair ascent activities were analyzed in each dog . The kinematics for these two activities were similarly interpolated, using a common starting stifle flexion angle in all dogs. One way ANOVA and Tukey post hoc tests ( p < 0.05) were used to examine differences among overall results. Pearson correlations were used to assess for any coupling in motion for selected kinematic parameters. Results Average flexion patterns for both the walk and trot treadmill gait were similar. A biphasic flexion extension pattern was observed, where the stifle extended during the first 10% of stance phase; for the remainder of stance phase there was slight flexion f JointTrack, Department of Mechanical and Aerospace Engineering, College of Engineering, University of Florida, Fla. Available at: ufdc.ufl.edu/UFE0021784/00001. Accessed Feb 10, 2013.

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87 followed by slight extension. Swing phase was characterized by large flexion follo wed by large extension, with the extension continuing into early stance phase. Trotting encompassed a wider range of flexion extension motion when compared to walking by 18 (P < 0.05). The stifle flexed to an average of 30 during sitting, and extended to an average of 145 during stair ascent, linearly over time, for the portion of these activities captured by fluoroscopy. Maximum stifle extension did not differ between the walk and trot (P = 0.98). Maximum extension during stair ascent was less compared to the walk and trot by an average of 6¼ (P < 0.05). Increasing flexion was associated with increased internal tibial rotation for all activities (P <0.01, r =0.83); the exact relationship between axial rotational alignment and flexion angle varied both within and between activities (Figure 4 3). During the walk and trot, external rotation of the internally rotated tibia occurred at paw strike and during early stance phase; neutral alignment was sustained for the remainder of stance phase. During the swin g phase, the tibia rotated from 1 of external rotation to 8 of internal rotation, and from 4 of external rotation to 11 of internal rotation for the walk and trot, respectively. The tibia then began externally rotating at the end of active extension of the swing phase. Overall, axial rotational range of motion was greater during the trot than at walk (P <0.01). Offset, which was defined as significant differences in secondary displacements of the stifle observed at identical flexion angles within and be tween activities, 117 was evident for axial rotational alignment during walking and trotting. For instance, at a stifle flexion angle of 120 for the trot, there was external tibial rotation of 2 during early swing phase, and internal tibial rotatio n of 11 during early stance phase (P = 0.03) (Figure 4 4). Coupling between internal external rotation and flexion

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88 extension for stair ascent (r = 0.83) resembled the pattern that was observed during early swing phase of trot (r = 0.96) During deep flexio n of sitting, internal rotation was coupled with flexion (r = 0.95), but axial rotational alignment was still within the range observed during other activities despite the deeper flexion found during the sit activity. Increased flexion was correlated with mildly increased abduction angulation for all activities (Figure 4 5). Abduction was closely correlated with flexion angle for both the walk and trot (r = 0.91, 0.87 respectively). During the trot, a mildly abducted tibia gradually adducted over the durat ion of stance phase; during walking the joint was in neutral coronal plane alignment at pawstrike, but became mildly adducted over stance phase. During swing phase, the tibia angulated from 4 of adduction to 1 and 4 of abduction for the walk and trot, r espectively. Adduction coincided with active extension during swing phase. Overall, coronal angulation range of motion was not different between activities. Offset was also evident for coronal angulation during walking and trotting; for instance, at a stif le flexion angle of 120 for the trot, there was abduction of 2 during early swing phase, and adduction of 2 during late swing phase (P= 0.04). Coronal angulation alignment during stifle extension for stair ascent resembled the pattern observed during wa lking. During deep flexion of sitting, mild abduction was coupled with flexion, but coronal angulation alignment was within the range observed during other activities that had greater stifle extension. Cranial tibial translation was nominal, and was corre lated with increasing stifle flexion angle when assessed over all activities. At maximal extension of the trot and walk, the tibial origin was 13 mm cranial to the femoral origin. The tibial translated cranially by 2 mm during peak flexion of the swing pha se for walking and trotting.

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89 Deeper flexion caused by sitting induced the greatest cranial tibial translation, where the tibia origin was 18 mm cranial to the femoral origin in full flexion. Offset was also evident for cranio caudal translations during the trot, but not the walk. For instance during the trot at a stifle flexion angle of 130¼, the tibial origin was 13 mm cranial to the femoral origin during early stance swing phase, and 14.9 mm cranial to the femoral origin during early late swing phase (P = 0.04 ) . Discussion Using single plane fluoroscopy, we demonstrated that normal in vivo femorotibial joint kinematics in dogs are complex, where 3D joint alignment is dependent on the type of activity performed. Our study highlighted that an envelope of mot ion exists in all three planes for the canine femorotibial joint, and that a wide range of joint poses were evident during the daily activities that were assessed. Similar to what has been observed in the human knee, 19,21 there appears to be tight active control of 3D stifle alignment in the dog, within the boundaries set by passive ligamentous constraints. A strong positive correlation between internal tibial rotation and stifle flexion was present during all activities. The coupled motion between axial rotation and flexion can be explained primarily by the passive restraints including the cruciate and collateral ligaments, as well as articular surface geometry. Cadaver studies have shown that the magnitude of normal rota tional laxity increases with flexion, when the caudolateral band of the CrCL is not completely taught and the lateral collateral ligament becomes lax. 7,10 In addition, articular surface geometry is asymmetric, where the lateral tibial condyle has a smaller radius of curvature than the medial side. All of these factors combined likely contribute to the lateral tibial condyle translating further cranially than the medial

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90 mechanism, was originally recognized in the human knee under pa ssive conditions . 13 Similar geometric features of both the dog and human knee, such as asymmetry between the medial and lateral tibial condyles, explain the coupled motion between 19 We found internal tibial rotation was tightly coupled to increased flexion for all activities, th Axial rotational alignment was significantly different at equivalent flexion angles between certain activities, revealing offset during in vivo dynamic activities for the dog stifle. We suspect this difference is the result of varying muscle activity over the entire gait cycle. For instance, internal rotators of the tibia such as the popliteus, gracilis, semimembranosus, and sartorius muscles are also flexors of the st ifle, and are likely to be predominately contracting during early to mid swing when there is active stifle that the deep flexion with sitting would create marked internal tibi al rotation; however, the tibia remained in relatively neutral axial rotational alignment. Equivalent tibial rotational poses during deeper flexion while sitting might also be explained by differences in muscle activation and initial posture. Our study hig hlights the need for studies that define the contributions of muscle activity to rotational stifle alignment in dogs. Coronal plane angulation was more tightly constrained than axial rotation, where the stifle did not angulate by more than 4 in abduction and adduction. This is consistent with anatomic studies that demonstrate the important contributions of the collateral

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91 ligaments to stifle stability in the dog. 10 Despite the limited range of motion, we still observed a significant coupling between increased flexion and tibial abduction . The to involve angulation of the stifle in the coronal plane. Increased abduction with flexion may be predominately caused by the normal caudal sagittal slope of the tibial plateau in the dog, which is much steeper than the slope present in humans: with the ti bia internally rotated upon flexion, the lateral femoral condyle is positioned on the more distal, caudal aspect of the lateral tibial condyle, whereas the medial femoral condyle is articulating on the more proximal, cranial aspect of the medial tibial con dyle. Similar to axial rotational alignment, significantly different poses also occurred between various activities with stifle adduction/abduction, suggesting that a large degree of active muscular control is also present in the coronal plane. We identif ied changes in cranial tibial translation caused by two distinct processes. First, there was a significant correlation between increasing flexion angle and cranial tibial translation across all activities. Concurrent gliding and rolling of the femoral cond yles on the tibial plateau with flexion resulted in relative caudal translation of the femoral origin with respect to the tibial origin. This should not to be interpreted as increasing tension on the CrCL, as it is well established that a large portion of the CrCL is lax in flexion; 7 rather, the ch ange in cranio caudal alignment measured during flexion was dependent on the assigned location of the femoral and tibial origins. Second, a mild but significant offset in cranio caudal alignment was found during trotting. A change of up to 1. 9 mm was ident ified at equivalent flexion angles but differing phases within a gait cycle. The significant offset suggests that the normal CrCL is under enough tension

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92 during trotting to allow slight elongation. We were unable to estimate the magnitude of load in the Cr CL, but future high precision kinematic studies may provide further insight into the pathomechanics of naturally occurring fatigue failure of the CrCL in the dog. There are several limitations to our study. Data were obtained using single plane fluoroscop ic imaging, which is less accurate for measuring out of sagittal plane motions than biplanar systems. 42 This limitation precluded the ability to accurately assess medio lateral translations in the current study. Furthermore, the flat panel detector has a defined field of view, which only allowed us to capture the stance portion of stair ascent. Treadmill kinematics has been shown to be different to that over ground in dogs 29 ; thus our kinematic findings may vary slightly from what occurs in normally ambulating dogs over ground. La stly, our results may not be representative of gait patterns in other dog breeds due to variations in size, conformation and cadence. Femorotibial kinematics in dogs involves complex 3D motion during normal daily activities. Stifle movements occur within an envelope of motion which vary according to the activity performed and are heavily influenced by the combination of active and passive forces acting across the joint. Our kinematic data establishes a reference standard outcome measure that can be used as a comparison for future studies on both pathologic and normal canine stifle motion.

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93 Figure 4 1. Dog pictured performing different activities. A) Dog walking with the C arm positioned to acquire lateral v iew fluoroscopic stifle images . B) Stairs positioned to captur e stance phase of stair ascent . C) Dog positioned after co mpleting stand to sit exercise (image courtesy of author) .

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94 Figure 4 2. Representative shape matched fluoroscopic image of a dog stifle at the trot. Three dimensional bo ne models from 5 different phases of the gait are included to demonstrate capture of the complete gait cycle on the flat panel detector (image courtesy of author) .

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95 Figure 4 3. Averaged plots of stifle flexion angle versus axial tibial alignment for all activities. Increased flexion was associated with internal tibial rotation for all activities. Note that despite the deep flexion seen with the sit activity, the tibia maintains a relatively neutral axial alignment.

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96 Figure 4 4. Averaged plot of fle xion versus axial alignment for all dogs at the trot. Axial tibial rotation was compared at four separate flexion angles (gray circles), using a paired t test. At all four flexion angles measured, a significant difference or offset in axial alignment was f ound.

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97 Figure 4 5. Averaged plots of stifle flexion angle versus coronal angulation for all four activities. Increased flexion was associated with abduction for all activities. Note that despite the deep flexion seen with the sit activity, the tibia maintains a relatively neutral coronal angulation.

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98 CHAPTER 5 CONCLUSION Interest in the study of joint kinematics has a long history, with some human kinematic observations dating back to the early 19 th century. 1 Chapter 1 provided an overview of some of the primary kinematic measurement techniques that have been used, and are available, for the measurement of femorotibial kinema tics in the dog. Each of the kinematic modalities has associated advantages and disadvantages. Many of the described techniques suffer from limitations such as inherent inaccuracy, invasiveness and or a lack of availability, which preclude their common use in the veterinary clinical setting. We also discussed the absence, to date, of a described measurement technique that can track femorotibial kinematics in a minimally invasive yet highly accurate and precise manner in dogs. Chapter 1 further detailed th e kinematic consequences of CrCL deficiency in dogs. It was discussed that despite the high prevalence of this debilitating disease, there remains a paucity of kinematic data to help explain the pathomechanics leading to rupture of the CrCL. Despite the mu ltitude of surgical interventions described for the CrCL deficiency in dogs, studies have not been conducted in vivo to assess the 3D kinematic effects of any of these procedures. We performed ex vivo studies to validate the accuracy and precision of sing le plane fluoroscopic analysis, for measuring 3D femorotibial kinematics in a normal and a TPLO treated dog stifle. Accuracy of kinematics measured using single plane fluoroscopy and a 3D to 2D model registration technique was compared with results obtaine d by use of a modified RSA.

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99 In C hapter 2, we documented that single plane fluoroscopy could accurately and precisely measure kinematics of . Mean absolute differences between the biplanar RSA and the 3D to 2D model registra tion technique were small at 1.28 mm and 1.58¼ for all translations and rotations, respectively . Intra and interobserver repeatability was strong with maximum mean translational and rotational standard deviations of 0.52 mm and 1.36 , respectively . This accuracy and repeatability compares favorably with that demonstrated in human knee kinematics, and validates the use of this methodology for assessing normal stifle kinematic measurement in vivo. 41 The TPLO is one of the most commonly performed surge ries to help stabilize the CrCL deficient dog stifle. 103 Despite the widespread popularity of the TPLO, little is known about the 3D femor otibial kinematics in vivo. In C hapter 3, we validated the use of single plane fluoroscopy with 3D to 2D model registration, as a hi ghly accurate and precise technique for measuring femorotibial kinematics in a TPLO treated cadaveric stifle. Accuracy was shown to be in the order of 1.05 mm and 1.08¼ for all translations and rotations, respectively . Intra and interobserver mean standar d deviations did not exceed 0.59 mm for all translations and 0.93 for all rotations. The high level of accuracy and precision demonstrated, make this technique very suitable for measuring TPLO treated stifle kinematics in vivo, in a minimally invasive man ner. In C hapter 4, we measured in vivo femorotibial kinematics in six client owned, normal Labrador retrievers using the single plane fluoros copic methodology validated in C hapter 2. Kinematics were measured in each dogs while performing walk, trot, stair ascent and sit activities. Three dimensional joint alignment was found to be highly

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100 dependent on the type of activity performed. Increasing stifle flexion angle was shown to be associated with tibial internal rotation, abduction and cranial translation fo r all four activities . The exact relationship between flexion angle and these movements varied both within and between activities. It was further found that significant differences in cranial tibial translation, axial and coronal rotation were found at the same flexion angle during different phases of the walk and trot gait cycles. Our findings highlight the complexity and variability of femorotibial kinematics in dogs during different daily activities. We have shown that a 3D envelope of motion exists in t he normal dog stifle joint, and that joint poses within this envelope are under precise control for each individual activity performed. These data establish a baseline of normal stifle kinematics in the dog during daily activities. The kinematics documente d may be used as a reference standard outcome measure for future studies evaluating normal and pathologic dog stifles. While a very useful kinematic measurement modality, single plane fluoroscopy with 3D to 2D model registration is not without its limita tions. Primary amongst these limitations is the inability to accurately measure out of plane translations. It is well known that dog femorotibial motion occurs in 6 DOF; 67,82 despite this fact, accurate assessment of medio lateral translations utilizing single plane fluoroscopy is not possible. Another major limitation to this technique is the requirement for manual matching of 3D bone models to the fluoroscopic bone outlines. This process requires a high level of user training and attention to detail. Automated shape matching has been described in human kinematic measurement 49,56,118 and permits the assessment of larger amounts of kinematic data with less user intervention when compared with the

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101 techniques assessed in our investigations here . Accuracy and precision validation of automated shape matching algorithms however, are required before these techniques can be utilized to evaluate into kinematics in dog stifles. The results presented here demonstrate the utility of single plane fluoroscopy in measuring femorotibial kinematics, in both normal and TPLO treated dog stif les. This technique now permits comprehensive, accurate evaluations of stifle kinematics under a variety of different conditions in the clinical setting. Perhaps, of the plethora of interesting studies that this technique enables , the most interesting stud y lies in the evaluation of potential kinematic risk factors for CrCL rupture. Considering the high frequency of pathology and surgical interventions associated with the stifle joint in the dog , the ability to accurately assess kinematics in vivo is paramo unt to help define the pathomechanics of disease and effects of various treatment modalities for these conditions.

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102 LIST OF REFERENCES 1. Pinskerova V, Maquet PGJ, Freeman MAR. Annotation: writin gs on the knee between 1836 and 1917. J Bone Joint Surg Br 2000;82 B:1100 1102. 2. DeCamp CE, Soutas Little RW, Hauptman J, et al. Kinematic gait analysis of the trot in healthy greyhounds. Am J Vet Res 1993;54:627 634. 3. Hottinger HA, DeCamp CE, Olivier NB, et al. Noninvasive kinematic analysis of the walk in healthy large breed dogs. Am J Vet Res 1996;57:381 388. 4. Carpenter DH, Cooper RC. Mini review of canine stifle joint anatomy. Anat Histol Embryol 2000;29:321 329. 5. Evans HE, de Lahunta A. The ske leton, arthrology, the muscular system. In Evans HE, ed. Miller's Anatomy of the Dog, 4 th ed. Philadelphia, PA: WB Saunders Co, 2012;80 280. 6. Guerrero TG, Geyer H, Hassig M, et al. Effect of conformation of the distal portion of the femur and proximal portion of the tibia on the pathogenesis of cranial cruciate ligament disease in dogs. Am J Vet Res 2007;68:1332 1337. 7. Arnoczky SP, Marshall JL. The cruciate ligaments of the canine stifle: an anatomical and functional analysis. Am J Vet Res 1977;38:180 7 1814. 8. Pozzi A, Kim SE. Biomechanics of the normal and cranial cruciate ligament deficient stifle. In: Muir P, ed. Advances in the Canine Cranial Cruciate Ligament. Hoboken, NJ: Wiley Blackwel l , 2010;38. 9. Johnson JM, Johnson AL. Cranial cruciate lig ament rupture. Pathogenesis, diagnosis, and postoperative rehabilitation. Vet Clin North AM Small Anim Pract 1993;23:717 733. 10. Vasseur PB, Arnoczky SP. Collateral ligaments of the canine stifle joint: anatomic and functional analysis. Am J Vet Res 1981 ;42:1133 1137 11. Vasseur PB, Pool RR, Arnoczky SP, et al. Correlative biomechanical and histologic study of the cranial cruciate ligament in dogs. Am J Vet Res 1985;46:1842 1854. 12. Furman W, Marshall, Girgis FG. The anterior cruciate ligament. A functio nal analysis based on postmortem studies. J Bone Joint Surg Am 1976;58:179 185. joint. Acta Orthop Scand 1966;37:97 106. 14. Iwaki H, Pinskerova V. Tibiofemoral movement 1: the shapes and rela tive movements of the femur and tibia in the unloaded cadaver knee. J Bone Joint Surg Br 2000;82 B:1189 1195

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103 15. Koh JSB, Nagai T, Motojima S, et al. Concepts and measurement of in vivo tibiofemoral kinematics. Oper Tech Orthop 2005;15:43 48. 16. Moglo KE, Shirazi Adl A. Cruciate coupling and screw home mechanism in passive knee joint during extension flexion. J Biomech 2005;38:1075 1083. 17. Grood ES, Stowers SF, Noyes FR. Limits of movement in the human knee. Effect of sectioning the posterior cruciate li gament and posterolateral structures. J Bone Joint Surg Am 1988;70 A:88 97. 18. Monahan JJ, Grigg P, Pappas AM, et al. In vivo strain patterns in the four major canine knee ligaments. J Orthop Res 1984;2:408 418. 19. Lafortune MA, Cavanagh PR, Sommer HJ, e t al. Three dimensional kinematics of the human knee during walking. J Biomech 1992;25:347 357. 20. Karrholm J, Brandsson S, Freeman MAR. Tibiofemoral movement 4: changes of axial tibial rotation caused by forced rotation at the weight bearing knee studied by RSA. J Bone Joint Surg Br 2000;82 B:1201 1203. 21. Moro oka T A, Hamai S, Miura H, et al. Dynamic activity dependence of in vivo normal knee kinematics. J Orthop Res 2008;26:428 434. 22. Gillette RL, Angle TC. Recent developments in canine locomotor an alysis: a review. Vet J 2008;178:165 176. 23. Schwencke M, Smolders LA, Bergknut N, et al. Soft tissue artifact in canine kinematic gait analysis. Vet Surg 2012;41:829 837. 24. Torres BT, Whitlock D, Reynolds LR, et al. The effect of marker location variab ility on noninvasive canine stifle kinematics. Vet Surg 2011;40:715 719. 25. Akbarshahi M, Schache AG, Fernandez JW, et al. Non invasive assessment of soft tissue artifact and its effect on knee joint kinematics during functional activity. J Biomech 2010;4 3:1292 1301. 26. Tsai TY, Lu TW, Kuo MY, et al. Effects of soft tissue artifacts on the calculated kinematics and kinetics of the knee during stair ascent. J Biomech 2011;44:1182 1188 27. Fu Y C, Torres BT, Budsberg SC. Evaluation of a three dimensional ki nematic model for canine gait analysis. Am J Vet Res 2010;71:1118 1122. 28. Owen MR, Richards J, Clements DN, et al. Kinematics of the elbow and stifle joints in greyhounds during treadmill trotting An investigation of familiarisation. Vet Comp Orthop Trau matol 2004;17:141 145 29. Torres BT, Moens NMM, Al Nadaf S, et al. Comparison of overground and treadmill based gaits of dogs. Am J Vet Res 2013;74:535 541.

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104 30. Ragetly CA, Griffon DJ, Hsu MKI, et al. Kinetic and kinematic analysis of the right hind limb d uring trotting on a treadmill in Labrador Retrievers presumed predisposed or not predisposed to cranial cruciate ligament disease. Am J Vet Res 2012;73:1171 1177. 31. Holler PJ, Brazda V, Dal Bianco B, et al. Kinematic motion analysis of the joints of the forelimbs and hind limbs of dogs during walking exercise regimens. Am J Vet Res 2010;71:734 740. 32. Kim J, Rietdyk S, Breur GJ. Comparison of two dimensional and three dimensional systems for kinematic analysis of the sagittal motion of canine hind limbs during walking. Am J Vet Res 2008;69:1116 1122. 33. Clements DN, Owen MR, Carmichael S, et al. Kinematic analysis of the gait of 10 labrador retrievers during treadmill locomotion. Vet Rec 2005;156:478 481. 34. Marsolais GS, McLean S, Derrick T, et al. Kin ematic analysis of the hind limb during swimming and walking in healthy dogs and dogs with surgically corrected cranial cruciate ligament rupture. J Am Vet Med Assoc 2003;222:739 743. 35. Allen K, Decamp CE, Braden TD, et al. Kinematic Gait Analysis of the Trot in Healthy Mixed Breed Dogs. Vet Comp Orthop Traumatol 1994;7:17 22. 36. Schaefer SL, DeCamp CE, Hauptman JG, et al. Kinematic gait analysis of hind limb symmetry in dogs at the trot. Am J Vet Res 1998;59:680 685. 37. Decamp CE, Riggs CM, Olivier NB, et al. Kinematic evaluation of gait in dogs with cranial cruciate ligament rupture. Am J Vet Res 1996;57:120 126. 38. Lee JY, Kim G, Kim J H, et al. Kinematic gait analysis of the hind limb after tibial plateau levelling osteotomy and cranial tibial wedge osteotomy in ten dogs. J Vet Med A Physiol Pathol Clin Med 2007;54:579 584. 39. Torres BT, Punke JP, Fu Y C, et al. Comparison of canine stifle kinematic data collected with three different targeting models. Vet Surg 2010;39:504 512. 40. Garling EH, Kapte in BL, Mertens B, et al. Soft tissue artefact assessment during step up using fluoroscopy and skin mounted markers. J Biomech 2007;40:S18 S24. 41. Fregly BJ, Rahman HA, Banks SA. Theoretical accuracy of model based shape matching for measuring natural knee kinematics with single plane fluoroscopy. J Biomech Eng 2005;127:692 699. 42. Banks SA, Hodge WA. Accurate measurement of three dimensional knee replacement kinematics using single plane fluoroscopy. IEEE Trans Biomed Eng 1996;43:638 649.

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105 43. Banks SA, Ma rkovich GD, Hodge WA. In vivo kinematics of cruciate retaining and substituting knee arthroplasties. J Arthroplasty 1997;12:297 304. 44. Mahfouz MR, Hoff WA, Komistek RD, et al. A robust method for registration of three dimensional knee implant models to two dimensional fluoroscopy images. IEEE Trans Med Imaging 2003;22:1561 1574. 45. Sarojak M, Hoff W, Komistek R, et al. An interactive system for kinematic analysis of artificial joint implants. Biomed Sci Instrum 1999;35:9 14. 46. Komistek RD, Dennis DA, Mahfouz M. In vivo fluoroscopic analysis of the normal human knee. Clin Orthop Relat Res 2003;410:69 81. 47. Lu T W, Tsai T Y, Kuo M Y, et al. In vivo three dimensional kinematics of the normal knee during active extension under unloaded and loaded conditi ons using single plane fluoroscopy. Med Eng Phys 2008;30:1004 1012. 48. Tsai T Y, Lu T W, Chen C M, et al. A volumetric model based 2D to 3D registration method for measuring kinematics of natural knees with single plane fluoroscopy. Med Phys 2010;37:1273 1284. 49. Tanifuji O, Sato T, Kobayashi K, et al. Three dimensional in vivo motion analysis of normal knees using single plane fluoroscopy. J Orthop Sci 2011;16:710 718. 50. Moro oka T A, Hamai S, Miura H, et al. Can magnetic resonance imaging derived bone models be used for accurate motion measurement with single plane three dimensional shape registration? J Orthop Res 2007;25:867 872. 51. Kanisawa I, Banks AZ, Banks SA, et al. Weight bearing knee kinematics in subjects with two types of anterior cruciate ligament reconstructions. Knee Surg Sports Traumatol Arthrosc 2003;11:16 22. 52. Hoff WA, Komistek RD, Dennis DA, et al. Three dimensional determination of femoral tibial contact positions under in vivo conditions using fluoroscopy. Clin Biomech 1998;13:45 5 472. 53. Li G, Wuerz TH, DeFrate LE. Feasibility of using orthogonal fluoroscopic images to measure in vivo joint kinematics. J Biomech Eng T Asme 2004;126:314 318. 54. Li G, Van de Velde SK, Bingham JT. Validation of a non invasive fluoroscopic imaging technique for the measurement of dynamic knee joint motion. J Biomech 2008;41:1616 1622. 55. Hanson GR, Suggs JF, Freiberg AA, et al. Investigation of in vivo 6DOF total knee arthoplasty kinematics using a dual orthogonal fluoroscopic system. J Orthop Res 2006;24:974 981

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106 56. Bingham J, Li G. An Optimized Image Matching Method for Determining In Vivo TKA Kinematics with a Dual Orthogonal Fluoroscopic Imaging System. J Biomech Eng 2006;128:588 595. 57. You BM, Siy P, Anderst W, et al. In vivo measurement of 3 D skeletal kinematics from sequences of biplane radiographs: application to knee kinematics. IEEE Trans Med Imaging 2001;20:514 525. 58. Selvik G. Roentgen stereophotogrammetry. A method for the study of the kinematics of the skeletal system. Acta Orthop Scand Suppl 1989;232:1 51. 59. KŠrrholm J. Roentgen Stereophotogrammetry Review of Orthopedic Applications. Acta Orthop Scand 1989;60:491 503. 60. Valstar ER, Vrooman HA, Toksvig Larsen S, et al. Digital automated RSA compared to manually operated RSA. J Biomech 2000;33:1593 1599. 61. Valstar ER, Nelissen RGHH, Reiber JHC, et al. The use of roentgen stereophotogrammetry to study micromotion of orthopaedic implants. ISPRS J Photogramm Remote Sens 2002;56:376 389. 62. Muhit AA, Pickering MR, Ward T, et al. A comparison of the 3D kinematic measurements obtained by single plane 2D 3D image registration and RSA. Conf Proc IEEE Eng Med Biol Soc 2010;2010:6288 6291. 63. Massimini DF, Warner JJP, Li G. Non invasive determination of coupled motion of the scapula a nd humerus An in vitro validation. J Biomech 2011;44:408 412. 64. Zhu Z, Massimini DF, Wang G, et al. The accuracy and repeatability of an automatic 2D 3D fluoroscopic image model registration technique for determining shoulder joint kinematics. Med Eng Ph ys 2012;34:1303 1309. 65. Bey MJ, Zauel R, Brock SK, et al. Validation of a new model based tracking technique for measuring three dimensional, in vivo glenohumeral joint kinematics. J Biomech Eng 2006;128:604 609. 66. Tashman S, Anderst W. In vivo measure ment of dynamic joint motion using high speed biplane radiography and CT: application to canine ACL deficiency. J Biomech Eng 2003;125:238 245. 67. Tashman S, Anderst W, Kolowich P, et al. Kinematics of the ACL deficient canine knee during gait: serial cha nges over two years. J Orthop Res 2004;22:931 941. 68. Kedgley AE, Birmingham T, Jenkyn TR. Comparative accuracy of radiostereometric and optical tracking systems. J Biomech 2009;42:1350 1354.

PAGE 107

107 69. Bellemans J. Osseointegration in porous coated knee arthro plasty. The influence of component coating type in sheep. Acta Orthop Scand Suppl 1999;288:1 35. 70. Allen MJ, Hartmann SM, Sacks JM, et al. Technical feasibility and precision of radiostereometric analysis as an outcome measure in canine cemented total hi p replacement. J Orthop Sci 2004;9:66 75. 71. Allen MJ, Leone KA, Dunbar MJ, et al. Tibial Component Fixation with a Peri Apatite Coating Evaluation by Radiostereometric Analysis in a Canine Total Knee Arthroplasty Model. J Arthroplasty 2012;27:1138 1148. 72. Johnson JA, Austin C, Breur GJ. Incidence of canine appendicular musculoskeletal disorders in 16 veterinary teaching hospitals from 1980 through 1989. Vet Comp Orthop Traumatol 1994;7:56 69. 73. Innes JF, Costello M, Barr FJ, et al. Radiographic progre ssion of osteoarthritis of the canine stifle joint: a prospective study. Vet Radiol Ultrasound 2004;45:143 148. 74. Prodromos CC, Han Y, Rogowski J, et al. A meta analysis of the incidence of anterior cruciate ligament tears as a function of gender, sport, and a knee injury reduction regimen. Arthroscopy 2007;23:1320 1325. 75. Witsberger TH, Villamil JA, Schultz LG, et al. Prevalence of and risk factors for hip dysplasia and cranial cruciate ligament deficiency in dogs. J Am Vet Med Assoc 2008;232:1818 1824 . 76. Gianotti SM, Marshall SW, Hume PA, et al. Incidence of anterior cruciate ligament injury and other knee ligament injuries: a national population based study. J Sci Med Sport 2009;12:622 627. 77. Comerford EJ, Smith K, Hayashi K. Update on the aetiopathogenesis of canine cranial cruciate ligament disease. Vet Comp Orthop Traumatol 2011;24:91 98. 78. Hayashi K, Manley PA, Muir P. Cranial cruciate ligament pathophysiology in dogs with cruciate disease: a review. J Am Anim Hosp Assoc 2004;40:385 39 0. 79. Boden BP, Dean GS, Feagin JA, et al. Mechanisms of anterior cruciate ligament injury. Orthopedics 2000;23:573 578. 80. Shimokochi Y, Shultz SJ. Mechanisms of noncontact anterior cruciate ligament injury. J Athl Train 2008;43:396 408. 81. Pozzi A, Ki m SE, Conrad BP, et al. Ex vivo pathomechanics of the canine Pond Nuki model. PLoS One 2013;8:e81383. 82. Korvick DL, Pijanowski GJ, Schaeffer DJ. Three dimensional kinematics of the intact and cranial cruciate ligament deficient stifle of dogs. J Biomech 1994;27:77 87.

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108 83. Vasseur PB. Clinical results following nonoperative management for rupture of the cranial cruciate ligament in dogs. Vet Surg 1984;13:243 246. 84. Jerram RM, Walker AM. Cranial cruciate ligament injury in the dog: pathophysiology, diagno sis and treatment. N Z Vet J 2003;51:149 158. 85. Moore KW, Read RA. Cranial cruciate ligament rupture in the dog a retrospective study comparing surgical techniques. Aust Vet J 1995;72:281 285. 86. Wilke VL, Robinson DA, Evans RB, et al. Estimate of the a nnual economic impact of treatment of cranial cruciate ligament injury in dogs in the United States. J Am Vet Med Assoc 2005;227:1604 1607. 87. Andriacchi TP, MŸndermann A, Smith RL, et al. A framework for the in vivo pathomechanics of osteoarthritis at th e knee. Ann Biomed Eng 2004;32:447 457. 88. Boyd DJ, Miller CW, Etue SM, et al. Radiographic and functional evaluation of dogs at least 1 year after tibial plateau leveling osteotomy. Can Vet J 2007;48:392 396. 89. Rayward RM, Thomson DG, Davies JV, et al. Progression of osteoarthritis following TPLO surgery: a prospective radiographic study of 40 dogs. J Small Anim Pract 2004;45:92 97. 90. GuŽnŽgo L, Zahra A, MadelŽnat A, et al. Cranial cruciate ligament rupture in large and giant dogs. A retrospective eva luation of a modified lateral extracapsular stabilization. Vet Comp Orthop Traumatol 2007;20:43 50. 91. Cook JL, Luther JK, Beetem J, et al. Clinical comparison of a novel extracapsular stabilization procedure and tibial plateau leveling osteotomy for trea tment of cranial cruciate ligament deficiency in dogs. Vet Surg 2010;39:315 323. 92. Hurley CR, Hammer DL, Shott S. Progression of radiographic evidence of osteoarthritis following tibial plateau leveling osteotomy in dogs with cranial cruciate ligament ru pture: 295 cases. J Am Vet Med Assoc 2007;230:1674 1679. 93. Lazar TP, Berry CR, Dehaan JJ, et al. Long term radiographic comparison of tibial plateau leveling osteotomy versus extracapsular stabilization for cranial cruciate ligament rupture in the dog. V et Surg 2005;34:133 141. 94. Jevsevar DS, Riley PO, Hodge WA, et al. Knee kinematics and kinetics during locomotor activities of daily living in subjects with knee arthroplasty and in healthy control subjects. Phys Ther 1993;73:229 239. 95. Richards J, Hol ler P, Bockstahler B, et al. A comparison of human and canine kinematics during level walking, stair ascent, and stair descent. Wien TierŠrztl Monatsschr 2010;97:92 100.

PAGE 109

109 96. Kaptein BL, Valstar ER, Stoel BC, et al. A new model based RSA method validated us ing CAD models and models from reversed engineering. J Biomech 2003;36:873 882. 97. Banks SA, Fregly BJ, Boniforti F, et al. Comparing in vivo kinematics of unicondylar and bi unicondylar knee replacements. Knee Surg Sports Traumatol Arthrosc 2005;13:551 5 56. 98. Yushkevich PA, Piven J, Hazlett HC, et al. User guided 3D active contour segmentation of anatomical structures: significantly improved efficiency and reliability. Neuroimage 2006;31:1116 1128. 99. Tupling SJ, Pierrynowski MR. Use of cardan angles t o locate rigid bodies in three dimensional space. Med Biol Eng Comput 1987;25:527 532. 100. Altman DG, Bland JM. Measurement in medicine: the analysis of method comparison studies. Statistician 1983;32:307 317 on invasive fluoroscopic imaging 2008;41:3290 3291. 102. Acker S, Li R, Murray H, et al. Accuracy of single plane fluoroscopy in determining relative position and orientation of total knee replacement components. J Biomech 2011;44:784 787. 103. Conzemius MG, Evans RB, Besancon MF, et al. Effect of surgical technique on limb function after surgery for rupture of the cranial cruciate ligament in dogs. J Am Vet Med Assoc 2005;226:232 236. 104. Slocum B, Slocum TD. Tibial plateau leveling osteotomy for repair of cranial cruciate ligament rupture in the canine. Vet Clin North Am Small Anim Pract 1993;23:777 795. 105. Warzee CC, Dejardin LM, Arnoczky SP, et al. Effect of tibial plateau leveli ng on cranial and caudal tibial thrusts in canine cranial cruciate deficient stifles: an in vitro experimental study. Vet Surg 2001;30:278 286. 106. Reif U, Hulse DA, Hauptman JG. Effect of tibial plateau leveling on stability of the canine cranial cruciat e deficient stifle joint: an in vitro study. Vet Surg 2002;31:147 154. 107. Kim SE, Pozzi A, Banks SA, et al. Effect of tibial plateau leveling osteotomy on femorotibial contact mechanics and stifle kinematics. Vet Surg 2009;38:23 32. 108. Kim SE, Lewis DD , Pozzi A. Effect of tibial plateau leveling osteotomy on femorotibial subluxation: in vivo analysis during standing. Vet Surg 2012;41:465 470.

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110 109. Matsuki K, Matsuki KO, Yamaguchi S, et al. Dynamic in vivo glenohumeral kinematics during scapular plane ab duction in healthy shoulders. J Orthop Sports Phys Ther 2012;42:96 104. 110. Proffen BL, McElfresh M, Fleming BC, et al. A comparative anatomical study of the human knee and six animal species. Knee 2012;19:493 499. 111. Pond MJ, Nuki G. Experimentally ind uced osteoarthritis in the dog. Ann Rheum Dis 1973;32:387 388. 112. Brandt KD, Myers SL, Burr D, et al. Osteoarthritic changes in canine articular cartilage, subchondral bone, and synovium fifty four months after transection of the anterior cruciate ligame nt. Arthritis Rheum 1991;34:1560 1570. 113. Griffith CJ, Wijdicks CA, Goerke U, et al. Outcomes of untreated posterolateral knee injuries: an in vivo canine model. Knee Surg Sports Traumatol Arthrosc 2011;19:1192 1197. 114. Cox JS, Nye CE, Schaefer WW, et al. The degenerative effects of partial and total resection of the medial meniscus in dogs' knees. Clin Orthop Relat Res 1975;109:178 183. 115. Arnoczky SP, Warren RF, Spivak JM. Meniscal repair using an exogenous fibrin clot an experimental study in dog s. J Bone Joint Surg Am 1988;70:1209 1217. 116. Cook JL, Fox DB, Malaviya P, et al. Evaluation of small intestinal submucosa grafts for meniscal regeneration in a clinically relevant posterior meniscectomy model in dogs. J Knee Surg 2006;19:159 167. 117. D yrby CO, Andriacchi TP. Secondary motions of the knee during weight bearing and non weight bearing activities. J Orthop Res 2004;22:794 800. 118. Torry MR, Shelburne KB, Peterson DS, et al. Knee Kinematic Profiles during Drop Landings: A biplane fluoroscop y study. Med Sci Sports Exerc 2011;43:533 541.

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111 BIOGRAPHICAL SKETCH Stephen C. Jones grew up in Carrickmacross, a small town in Co. Monaghan , Ireland. His interest in veterinary surgery stems from his upbringing with racing greyhounds and time spent with his uncle Brian, who is a veterinarian with a special interest in orthopedic surgery. Stephen graduated from University College Dublin with a Bachelor of Veterinary Medicine degree in 20 09. He then completed a clinical internship in small animal medicine and surgery at Hollywood Animal Hospital, Hollywood, Florida between 2009 and 2010. After completing this internship, Stephen remained at Hollywood Animal Hospital where he completed a sp ecialty small animal surgery internship between 2010 and 2011. On completion of these internships, Stephen moved to Gainesville, Florida where he began a residency in small animal surgery, at the ng this surgical residency, Stephen also attained a Master of Science degree, graduating in the summer of 2014. Stephen is scheduled to finish his surgical residency and become board eligible in 2015.