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Intraoperative Measurement of Shoulder Joint Contact Forces during Reverse Total Shoulder Arthroplasty

Permanent Link: http://ufdc.ufl.edu/UFE0045566/00001

Material Information

Title: Intraoperative Measurement of Shoulder Joint Contact Forces during Reverse Total Shoulder Arthroplasty
Physical Description: 1 online resource (43 p.)
Language: english
Creator: Chang, Chih Chiang
Publisher: University of Florida
Place of Publication: Gainesville, Fla.
Publication Date: 2013

Subjects

Subjects / Keywords: arthroplasty -- calibration -- in-vivo -- intraoperative -- rtsa -- shoulder
Mechanical and Aerospace Engineering -- Dissertations, Academic -- UF
Genre: Mechanical Engineering thesis, M.S.
bibliography   ( marcgt )
theses   ( marcgt )
government publication (state, provincial, terriorial, dependent)   ( marcgt )
born-digital   ( sobekcm )
Electronic Thesis or Dissertation

Notes

Abstract: The knowledge of glenohumeral joint contact force is crucial for reverse total shoulder arthroplasty (RTSA) surgery. It affects the stability of humerus during motions and the complication rate after the RTSA surgery. An instrumented implant was developed to measure three components of joint contact forces by four strain gauges. The accuracy of the instrumented implant is decided by the structure and the calibration method. Aims of this study were to develop a simple but accurate calibration method, to find a mathematical method for calculating forces from strain measurements, and to validate the intraoperative contact forces measurement was in a reliable range. Simple but accurate calibration method can be achieved by applying forces on 12 different poses of the calibration jig, which provided 12 sets of three linearly independent combinations of force components. The matrix method was used for force calculation from strain measurements, and most of the average measuring errors can be possibly kept below 6% of the calibration range. The instrumented implants were used in 3 patients in RTSA surgery, and strain data was measured during four passive motions. Joint reaction forces exhibited characteristic patterns that were consistent between three patients, and remained below 300 N for every passive motion. Highest joint reaction force was found in 277 N during flexion. These first shown intraoperative measurements of glenohumeral joint contact forces are continuing with a goal of 20 total patients.
General Note: In the series University of Florida Digital Collections.
General Note: 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.
Statement of Responsibility: by Chih Chiang Chang.
Thesis: Thesis (M.S.)--University of Florida, 2013.
Local: Adviser: Banks, Scott Arthur.

Record Information

Source Institution: UFRGP
Rights Management: Applicable rights reserved.
Classification: lcc - LD1780 2013
System ID: UFE0045566:00001

Permanent Link: http://ufdc.ufl.edu/UFE0045566/00001

Material Information

Title: Intraoperative Measurement of Shoulder Joint Contact Forces during Reverse Total Shoulder Arthroplasty
Physical Description: 1 online resource (43 p.)
Language: english
Creator: Chang, Chih Chiang
Publisher: University of Florida
Place of Publication: Gainesville, Fla.
Publication Date: 2013

Subjects

Subjects / Keywords: arthroplasty -- calibration -- in-vivo -- intraoperative -- rtsa -- shoulder
Mechanical and Aerospace Engineering -- Dissertations, Academic -- UF
Genre: Mechanical Engineering thesis, M.S.
bibliography   ( marcgt )
theses   ( marcgt )
government publication (state, provincial, terriorial, dependent)   ( marcgt )
born-digital   ( sobekcm )
Electronic Thesis or Dissertation

Notes

Abstract: The knowledge of glenohumeral joint contact force is crucial for reverse total shoulder arthroplasty (RTSA) surgery. It affects the stability of humerus during motions and the complication rate after the RTSA surgery. An instrumented implant was developed to measure three components of joint contact forces by four strain gauges. The accuracy of the instrumented implant is decided by the structure and the calibration method. Aims of this study were to develop a simple but accurate calibration method, to find a mathematical method for calculating forces from strain measurements, and to validate the intraoperative contact forces measurement was in a reliable range. Simple but accurate calibration method can be achieved by applying forces on 12 different poses of the calibration jig, which provided 12 sets of three linearly independent combinations of force components. The matrix method was used for force calculation from strain measurements, and most of the average measuring errors can be possibly kept below 6% of the calibration range. The instrumented implants were used in 3 patients in RTSA surgery, and strain data was measured during four passive motions. Joint reaction forces exhibited characteristic patterns that were consistent between three patients, and remained below 300 N for every passive motion. Highest joint reaction force was found in 277 N during flexion. These first shown intraoperative measurements of glenohumeral joint contact forces are continuing with a goal of 20 total patients.
General Note: In the series University of Florida Digital Collections.
General Note: 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.
Statement of Responsibility: by Chih Chiang Chang.
Thesis: Thesis (M.S.)--University of Florida, 2013.
Local: Adviser: Banks, Scott Arthur.

Record Information

Source Institution: UFRGP
Rights Management: Applicable rights reserved.
Classification: lcc - LD1780 2013
System ID: UFE0045566:00001


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1 INTRAOPERATIVE MEASUREMENT OF SHOULDER JOINT CONTACT FORCES DURING REVERSE TOTAL SHOULDER ARTHROPLASTY By CHIH CHIANG CHANG 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 2013

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2 2013 Chih Chiang Chang

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3 To my Professors, Dr. Scott A. Banks and Dr. Masaru Higa, who has been my best support in this research and my graduate study

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4 ACKNOWLEDGMENTS I am grateful to the many people who have supported me as I worked on this thesis and helped me grow especially my advisor Dr. Scott Arthur Banks, who got me excited about orthopaedic biomechanics and whose professions on both clinic s and engineer ing inspired me to develop an extreme interest in doing research in o rthopaedic engineering. him for trusting me to work on this project and guiding and develop ing my skills. This thesis research work would not have been possible without his mentoring and his guidance and encouragement I would like to express m y gratitude to Dr. Masaru Higa, at University of Hyogo in Japa n for trusting me to work on this project with him I would not be able to accomplish t h e se tasks in this research w ithout his time and effort on training me I thank for h is mentoring and valuable advice gain research experiences by working with him. I would like then to thank Dr. Thomas Wright for also trusting in my abilities to accomplish the task of running the measurement in operation room. I would like to also thank Aimee Struk for her efforts and helps on every measurement task in the hospital. I al so want to thank Dr. Bryan Conrad for his training of use of the MTS machine and providing me all the instruments I needed for the calibration. Especially, I would like to thank David Walker for his helps on the data collecting both in operation room and calibration ; and I would also like to thank Ira Hill for giving me valuable advices on programming anytime. Fina l ly, I would like to express my deepest gratitude to my parents for their encouragement in all my endeavors. I would not have been able to go for my dream without the ir fully support

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5 TABLE OF CONTENTS page ACKNOWLEDGMENTS ................................ ................................ ................................ .. 4 LIST OF TABLES ................................ ................................ ................................ ............ 6 LIST OF FIGURES ................................ ................................ ................................ .......... 7 ABSTRACT ................................ ................................ ................................ ..................... 9 CHAPTER 1 INTRODUCTION ................................ ................................ ................................ .... 11 Reverse Total Shoulder Arthroplasty ................................ ................................ ...... 11 Soft tissue Tension Measurement ................................ ................................ .......... 11 2 MATERIALS AND METHODS ................................ ................................ ................ 14 Inst rumented Implant ................................ ................................ .............................. 14 Calibration ................................ ................................ ................................ ............... 15 Intraoperative Measurements ................................ ................................ ................. 16 3 C AlIBRATION R ESULTS ................................ ................................ ........................ 19 Linearity of the Strain Measurement ................................ ................................ ....... 19 Linear Calibration ................................ ................................ ................................ .... 21 Calibratio n and Measuring Error ................................ ................................ ............. 25 4 IN VIVO MEASUREMENT OF SHOULDER JOINT CONTACT FORCES ............. 26 External Rotation ................................ ................................ ................................ .... 27 Flexion ................................ ................................ ................................ .................... 29 Scaption ................................ ................................ ................................ .................. 31 Abduction ................................ ................................ ................................ ................ 33 5 CONCLUSION ................................ ................................ ................................ ........ 35 APPENDIX A LINEARITY OF THE STRAIN MEASUREMENT ................................ .................... 37 B CONSTANTS IN CALIBRATION MATRICES ................................ ......................... 40 LIST OF REFERENCES ................................ ................................ ............................... 41 BIOGRAPHICAL SKETCH ................................ ................................ ............................ 43

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6 LIST OF TABLES Table page 2 1 The different angle position combinations for the B matrix calculations ............. 16 3 1 The calibration errors of each calibration matrix ................................ ................. 25 4 1 The highest forces during each passive motion for each patient ( units in Newton) ................................ ................................ ................................ .............. 26 4 2 The highest forces during each passive motion in each patient ( units in percentage of bodyweight) ................................ ................................ ................. 26

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7 LIST OF FIGURES Figure page 1 1 Rotator Cuff Tears and Reve rse Total Shoulder Arthroplasty ............................. 13 1 2 Shoulder Joint Dislocation after RTSA surgery ................................ ................... 13 2 1 The Custom Designed Instrumented Implant ................................ ..................... 18 2 2 The Calibration Jig ................................ ................................ .............................. 18 3 1 Linear strain measurement during calibration ................................ ..................... 19 3 2 Strain measurement during calibration showed nonlinearity in some sensors in patient #11 ................................ ................................ ................................ ...... 20 3 3 Strain measurement during calibration showed nonlinearity in some sensors in patient #12 ................................ ................................ ................................ ...... 20 3 4 Strain measurement during calibration showed nonlinearity in some sensors in patient #13 ................................ ................................ ................................ ...... 21 3 5 Linear res ponse of the strain measurement according to corresponding applied forces during calibration in patient #11 ................................ .................. 22 3 6 Linear res ponse of the strain measurement according to corresponding applied forces during calibration in patient #12 ................................ .................. 23 3 7 Linear res ponse of the strain measurement according to corresponding applied forces during calibration in patient #13 ................................ .................. 24 4 1 In vivo measurement of external rotation for patient #11 ................................ .... 27 4 2 In vivo measurement of external rotation for patient #12 ................................ .... 28 4 3 In vivo measurement of external rotation for patient #13 ................................ .... 28 4 4 In vivo measurement of flexion for patient #11 ................................ ................... 29 4 5 In vivo measurement of flexion for patient #12 ................................ ................... 30 4 6 In vivo measurement of flexion for patient #13 ................................ ................... 30 4 7 In vivo measurement of scaption for patient #11 ................................ ................ 3 1 4 8 In vivo measurement of scaption for patient #12 ................................ ................ 32

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8 4 9 In vivo measurement of scaption for patient #13 ................................ ................ 32 4 10 In vivo measurement of abduction for patient #11 ................................ .............. 33 4 11 In vivo measurement of abduction for patient #12 ................................ .............. 34 4 12 In vivo measurement of abduction for pa tient #13 ................................ .............. 34

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9 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 INTRAOPERATIVE MEASUREMENT OF SHOULDER JOINT CONTACT FORCE S DURING REVERSE TOTAL SHOULDER ARTHROPLASTY By Chih Chiang Chang May 2013 Chair: Scott Arthur Banks Major: Mechanical Engineering The knowledge of glenohumeral joint contact force is crucial for reverse total shoulder arthroplasty (RTSA) surgery. It affects the stability of humerus during motions and the complication rate after the RTSA s urgery. A n instrumented implant was developed to measure three components of joint contact forces by four strain gauges. The accuracy of the instrumented implant is decided by the structure and the calibration met hod Aims of this study were to develop a simple but accurate calibration method to find a mathema tical method for calculating forces from strain measurements and to validate the intraoperative contact forces measurement was in a reliable range Simple but accurate calibration method can be achieved by applying forces on 12 different poses of the calibration jig, which provided 12 sets of three linear ly independent combinations of force components The matrix method was used for force calcul ation from strain measurements, and most of the average measuring errors can be pos s ibl y kept below 6% of the calibration range. The instrumented implants were us ed in 3 patients in RTSA surgery and strain data was measured during four passive motions. J oint reaction forces exhibited characteristic patterns that were consistent between three patients and remained below 300 N for every passive motion. Highest joint

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10 reaction force w as found in 277 N during flexion T hese first shown intraoperative measurement s of glenohumeral joint contact forces are continuing with a goal of 20 total patients.

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11 CHAPTER 1 INTRODUCTION Reverse Total Shoulder Arthroplasty In 2004, the U.S. Food and Drug Administration (FDA) released the reverse total shoulder arthroplasty (RTSA ) to be used in specific clinical situations. The RTSA is a non anatomic shoulder replacement, designed to provide a fixed fulcrum allowing the deltoid to elevate the arm. Recently, RTSA s are being increasingly recommended for patients who need a revision after previous surgery, or who suffer from massive rotator cuff tears ( Figure 1 1 A,B ) [ 1 2 3,4]. While the early outcomes of RTSA surgery are promising for improvements in range of motion and pai n relief, the complicat ion rate of RTSA is still high [5] A significant early complication of RTSA is disloc ation, occurring in up to 7.5% [6] of patients undergoing RTSA. It can occur due to multiple factors including scapula notching, neurological injur y, periprosthetic fracture, baseplate failure, and acr omion fracture [ 7 ] Adequate tension of the deltoid is critical to prevent fracture s and insure prosthesis stability. If the deltoid is insufficient ly tension ed it can lead to prosthesis dislocation ( Figure 1 2 ) ; if the deltoid is over tensioned, it can result in an acromial fr acture or neurovascular injury [8,9,10] Soft tissue Tension Measurement RTSA prosthes e s. By using a sensor instrumen ted femoral head, Tanino et al [11] have recently obtained the intraoperative soft tissue tension of the hip. The researchers were able to intraoperativel y quantify soft tissue tension and direction around the hip joint during

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12 passive flexion and extension. The research team noted that intraoperative force direction changed significantly through the measured range of motion. Bergmann et al have measured th e glenohumeral joint contact forces of a patient 7 months after total shoulder arthroplasty by a telemetric instrumented implant [12] but no equivalent recordings have been performed for RTSA implants where the joint reaction forces are very likely differ ent A key goal of this research is to provide intraoperative joint reaction force measurements in shoulders during RTSA surgery. V arious implants for measuring joint load and soft tissue tension have been reporte d [13,14,15] For multi component force sensors, intraoperative measurement s of each component of force are calculated from strain gauge signals using a calibration matrix method [16] The calibration matrix method allows accurate force components to be determined from se nsors with non precisely positioned strain gauges, and was originally developed for three force components sensors [17,18] There are two goals of this study: the first is to obtain objective data on the soft tissue tension of shoulder joint during RTSA by using a custom designed instrumented implant; the second is to validate the calibration matrix method for computing joint reaction forces from strain ga u ge readings

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13 Figure 1 1 Rotator Cuff Tears and Reverse Total Shoulder Arthroplasty. A) Rotator Cuff Tears (Source: www.Healingartsce.com) B) Reverse Total Shoulder Arthroplasty (Source: www.Schulter.de/Endoprothetik) Figure 1 2. Shoulder Joint Dislocation after RTSA surgery. (Source: Emilie Cheung,

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14 CHAPTER 2 MATERIALS AND METHODS Instrumented Implant There are several requirements for force instrumented implants [19] : The force sensing implant should be designed according to the size of the standard RTSA prosthesis. The sensor must be compatible with the standard RTSA prosthes e s should not affect their function and its use should not significantly change the surgical procedure. The force sensing implant must be sterilized befor e intraoperative use, and must not expose the patient to materials or interfaces that are not biocompatible All three components of the shoulder joint reaction force should be measured with good accuracy. Strain gauges must be placed in an area of the imp lant where the entire joint load is transferred A custom designed instrumented implant was designed to fulfill these requirements (Figure 2 1 A,B ) The implant was fabricated from 304 stainless steel and outfitted with four strain gauges ( 120 ohm uni axial foil gauge, QFLG 2 11 1LJB Tokyo Sokki Kenkyujo Co.,Ltd. Japan) The sensor was designed to fit with in the modular glenosphere of a commercially available and FDA approved RTSA system ( Equinoxe Reverse Total Shoulder Exactech Inc., Gainesville, FL ). The f our strain gauges are aligned with the implant post and glued in place ( Figure 2 1 C ) The strain gages are self temperature compensated for 304 stainless steel over the temperature range including 20 C (room temperature) to 3 7 C (body temperature). Data acquisition was performed using USB based data acquiisiotn hardware ( NI 9219 DAQ National Instruments, Austin, TX) and LabVIEW software (National Instruments) Calculation of the force components was performed with customized software.

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15 Calibration To achieve measurements with good accuracy, the setup of the calibration should be similar to the in vivo situation. Therefore, the force sensing implant is fixed on a custom jig, and a trial glenosphere is threaded on the stem of the implant. A polyethylene liner i s arranged between load cell and the glenosphere (Figure 2 2 A ) and c alibration is performed by applying three linear ly independent combinations of force components ( Figure 2 2 A,B ) A total of t welve different loading conditions are used for calibration ( Figure 2 2 C ). F orces are applied at the same point, but the loading orienta t ion is changed by manipulating the calibration jig. For example, when force applied at and the force vector is The applied calibration forces were 10N, 20N, 40N, 70N, 100N, 200N, and 400N i n accordance with ASTM E4 08 The relation between the applied forces and the signal s from the four strain gauge s can be written : ( 1 ) W here matrix is the calibration matrix, which can be calculated as the pseudoinverse: ( 2 ) To calculate Eq (2), f our groups of different loading conditions are used for the calculation of the calibration matrix (Table 2 1) All of the constants in these calibration matrices are shown in Appendix B.

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16 Table 2 1. The different angle position combinations for the B matrix calculations Group Differ angle position combinations Number of angle positions =30, 150, 30, 150 4 =45, 135, 45, 135 4 =60, 120, 60, 120 4 =30, 150, 30, 150, 45, 135, 45, 135, 60, 120, 60, 120 12 Calibration accuracy is quantified in terms of a verage r elative e rrors or residuals, of the load components from all calibration measurements : ( 3 ) w here is the known applied force component (i.e. when = 10N, 20N, 40N, 70N, 100N, 200N, and 400N ) is the calculated force component : ( 4 ) and is the calibration range of component Bergmann et al. [16] classified Intraoperative Measurements The instrumented implants were us ed in 3 patients (p#11, p#12, and p#13) during RTSA surgery and were removed immediately after the intraoperative measurements. Four passive motions external rotation, flexion, scaption, and abduction were tested while recording the strain measurements. Additional patient

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17 st udies are continuing with a goal of 20 total patients with intraoperative measurement of shoulder joint reaction forces

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18 Figure 2 1 The Custom Designed Instrumented Implant A) The medial lateral view of the implant. B) The anterior posterior view of the implant C) The f our strain gauges are aligned with the implant post and glued in place. Figure 2 2. The Calibration Jig ; A) is rotated 30 degrees about X axis, B) is rotated 30 degrees about Z axis, C) can be used for 12 different loading conditions

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19 CHAPTER 3 C ALIBRATION RESULTS Linearity of the Strain Measurement The force strain response was linear for most stain gauges and for most sensor orientations (Figure 3 1 Tables 3 1, 3 2, 3 3, Appendix A ). However, each sensor exhibited instances of individual gauges at specific orientations where the force strain response was nonlinear (Figures 3 2, 3 3, 3 4). Figure 3 1 Linear strain measurement during calibrat ion (X axis: Applied force (N); Y Axis: Strain ( ) )

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20 Figure 3 2 Strain measurement during calibration showed nonlinearity in some sensors in patient #11 (X axis: Appl ied force (N); Y Axis: Strain ( ) ) Figure 3 3 Strain measurement during calibration showed nonlinearity in some sensors in patient #12 (X axis: Appl ied force (N); Y Axis: Strain ( ) )

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21 Figure 3 4 Strain measurement during calibration showed nonlinearity in some sensors in patient #13 (X axis: Appl ied force (N); Y Axis: Strain ( ) ) Linear Calibration A highly linear response for and ( >0.99) was noted between calculated and applied forces (Figure 3 5, 3 6, 3 7) However, a high coefficient of determination ( ) does not necessarily indicate good measur ement accuracy [12], because occasional high errors will only decrease slightly. The r elative e rrors of load components from each calibration measurement : ( 5 ) where the definition of and is the same as in Eq. (3); we re c omput ed by (Table 2 1)

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22 Figure 3 5 Linear response of the strain measurement according to corresponding applied forces during calibration in patient #11 (X axis: Applied force (N); Left vertical axis: Calculated force (N); Right vertical axis: the relative errors (%) )

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23 Figure 3 6 Linear res ponse of the strain measurement according to corresponding applied forces during calibration in patient #12 (X axis: Applied force (N); Left vertical axis: Calculated force (N); Right vertical axis: the relative errors (%) )

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24 Figure 3 7 Linear res ponse of the strain measurement according to corresponding applied forces du ring calibration in patient #13 (X axis: Applied force (N); Left vertical axis: Calculated force (N); Right vertical axis: the relative errors (%) )

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25 Calibration and M easuring Error Using different combinations of applied force (Table 2 1) affect ed the calibration residual error s (Table s 3 1 ) In general, calibration performed with a total of four different loading orientations resulted in smaller average residual errors than calibrations using the entire set of twelve loading orientations. Table 3 1. The calibration errors of each calibration matrix Patient number Calibration matrix Patient #11 5.228 2.537 4.000 2.975 1.904 2.743 2.309 2.478 2.403 3.933 2.717 3.393 Patient #12 3.694 3.759 6.032 2.439 4.314 3.420 2.335 4.323 4.981 3.497 4.161 6.625 Patient #13 2.585 2.179 6.602 2.916 2.283 3.957 2.197 1.902 3.361 2.751 2.320 4.663

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26 CHAPTER 4 IN VIVO MEASUREMENT OF SHOULDER JOINT CONTACT FORCES Intraoperative joint reaction forces were calculated from the intraoperative strain measurements and the sensor calibration matrix as described previously in Eq (4 ) : ( 6 ) where is the intraoperative measurement of strain, is the linear sensor calibration matrix, and is the computed joint reaction force vector. Intraoperative joint reaction force components were computed using matrix (Table 2 1) The maximum joint force components during passive arm mot ions are shown in Table 4 1 and 4 2 Table 4 1. The highest forces during each passive motion for each patient ( units in Newton) P atient #11 P atient #12 P atient #13 Starting position 100 70 125 175 10 45 40 65 10 70 25 75 External Rotation 154 70 170 223 20 69 53 76 15 88 38 91 Flexion 195 90 228 277 22 69 89 90 52 90 70 122 Scaption 114 104 160 209 18 63 60 86 10 94 55 97 Abduction 148 109 170 220 30 56 57 77 89 89 90 130 Note: units in Newton (N) Table 4 2. The highest forces during each passive motion in each patient ( units in percentage of bodyweight ) P atient #11 P atient #12 P atient #13 Starting position 13 9 16 22 1 6 5 8 1 9 3 9 External Rotation 19 9 21 28 3 9 7 10 2 11 5 11 Flexion 24 11 29 35 3 9 11 11 7 11 9 15 Scaption 14 13 20 26 2 8 8 11 1 12 7 12 Abduction 19 14 21 28 4 7 7 10 11 11 11 16 Note: units in percentage of bodyweight (BW%)

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27 External Rotation Durin g passive external/internal rotation, the surgeon moved the arms of the patients from 0 to 90 external rotation while supporting the arm against gravity. Maximum joint reaction forces were 223 N in patient #11 (Figure 4 1), 76 N in patient #12 (Figure 4 2), and 91 N in patient #13 (Figure 4 3). In patient #13 the z component of force was transiently negative indicating the joint was under tension. This is not physically possible, and must result from measurement noise or calibration errors. Figure 4 1 In vivo measurement of external rotation for p atient # 11 ( Upper: Calculated In traoperative Joint Contact Forces; Lower: Strain measurement )

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28 Figure 4 2 In vivo measurement of external rotation for p atient # 12 ( Upper: Calculated Intraoperative Joint Contact Forces; Lower: Strain measurement ) Figure 4 3 In vivo measurement of external rotation for p atient # 13 ( Upper: Calculated Intraoperative Joint Contact Forces; Lower: Strain measuremen t)

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29 Flexion During the passive flexion motion, the surgeon raised the patients arms up to 90 while supporting them against gravity. The maximum ca l culated joint reaction forces were 277 N in patient #11 (Figure 4 4), 90 N in patient #12 (Figure 4 5), and 122 N in patient# 13 (Figure 4 6). These values are higher than for external rotation, indicating a larger component of arm weight acting at the joint. Figure 4 4 In vivo measur ement of flexion for p atient # 11 ( Upper: Calculated Intraoperative Joint Contact Forces; Lower: Strain measurement )

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30 Figure 4 5 In vivo measurement of flexion for p atient # 12 ( Upper: Calculated Intraoperative Joint Contact Forces; Lower: Strain measurement ) Figure 4 6 In vivo measurement of flexion for p atient # 13 ( Upper: Calculated Intraoperative Joint Contact Forces; Lower: Strain measurement )

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31 Scaption P assive scaption motion was performed from the arm at the side to 90, and maximum joint reaction forces were 209 N in patient #11 (Figure 4 7), 86 N in patient #12 (Figure 4 8), and 97 N in patient# 13 (Figure 4 9). Figure 4 7 In vivo measurement of scaption for p atient # 11 ( Upper: Calculated Intraoperative Joint Contact Forces; Lower: Strain measurement )

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32 Figure 4 8 In vivo measurement of scaption for p atient # 12 ( Upper: Calculated Intraoperative Joint Contact Forces; Lower: Strain measurement ) Figure 4 9 In vivo measurement of scaption for p atient # 13 ( Upper: Calculated Intraoperative Joint Contact Forces; Lower: Strain measurement )

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33 Abduction P assive abducti o n of the arm was performed from 0 to 90 with the arm in a plane parallel to the ground M aximum joint reaction forces were 220 N in patient #11 (Figure 4 10), 77 N in patient #12 (Figure 4 11), and 130 N in patient# 13 (Figure 4 12). Figure 4 10 In vivo measurement of abduction for p atie nt # 11 ( Upper: Calculated Intraoperative Joint Contact Forces; Lower: Strain measurement )

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34 Figure 4 11 In vivo measurement of abduction for p atient # 12 ( Upper: Calculated Intraoperative Joint Contact Forces; Lower: Strain measurement ) Figure 4 12 In vivo measurement of abduction for p atient # 13 ( Upper: Calculated Intraoperative Joint Contact Forces; Lower: Strain measurement )

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35 CHAPTER 5 CONCLUSION Understanding the soft tissue tension during Reverse Total Shoulder Arthroplasty (RTSA) is critical to the success of the surgery. The studies discussed in Chapter 3 and Chapter 4 aimed to provide the intraoperative force measurement during passive motions These results were validated by the calibration described in Chapter 3 which provide s an accurate method to calculate the joint reaction force vector from the intraoperative strain measurement s In Chapter 3, it was found that the strain measurement of e ach sensor of each implant is close to linear with respect to the applied forces. According to the linearity of the strain measurement, the calibration matrix method is then applied to calculate the forces from strain measurements. The average relative err ors between the applied forces and the forces recalculated using the calibration matrix are less than 6%. D ifferent calibration errors were found by applying different sets of loading conditions and calculating the calibration matrix. This might because of experimental issues, including inaccurate machining of the custom calibration jig or slightly different load application conditions during calibration. Nevertheless, th e s e result s provide satisfactory demonstration of the calibration matrix method for cal culating the intraoperative joint reaction forces from sensor strain measurement s In Chapter 4, it was found that intraoperative joint reaction forces exhibited characteristic patterns that were consistent between three patients. However, the absolute lev el of force was quite different between the patients indicating different levels of soft tissue tension in each shoulder (or unaccounted differences in the sensors used).

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36 In conclusion, a reliable calibration method has been developed for the intraoperative shoulder joint contact force measurement during RTSA. Further refinements in the calibration procedure, primarily more accurate fixturing, may result in more accurate c a libration and joint force measurements.

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37 APPENDIX A LINEARITY OF THE STRAIN MEASUREMENT Strain Measurements of calibration for each sensor from each implant: Implant for Patient 11:

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38 Implant for patient 12:

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39 Implant for patient 1 3 :

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40 APPENDIX B CONSTANTS IN CALIBRATION MATRICES

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41 LIST OF REFERENCES [ 1 ] Edwards TB, Indications for reverse total shoulder arthroplasty in rotator cuff disease. Clin Orthop Relat Res. 2010; 468:1526 1533 [ 2 ] Boileau P, Sinnerton RJ, Chuinard C, Walch G. Arthroplasty of the shoulder. J Bone Joint Surg Br. 2006; 88(5):562 575 [3] Hatzidakis AM, Norris TR, Boileau P. Reverse shoulder arthroplasty indications, technique, and results. Tech Shoulder Elbow Surg. 2005; 6(3):135 149 [4] Leung B, Horodyski MB, Struk A, Wright T. Rotator cuff tear arthropathy: hemiarthroplasty or reverse total shoulder Arthroplasty? Open Meeting o the American Shoulder and Elbow Surgeons. San Diego, CA; Feb. 19, 2011 [5] Nam D, Kepler CK, Neviaser AS, Jones KJ, Wright TM, Craig EV, Warren RF. Reverse total shoulder arthroplasty: current concepts, results, and component wear analysis. J Bone Joint Surg Am. 2010; 92:23 35 [6] Wall B, Nove DP, Edwards TB, Walch G. Reverse total shoulder Arthroplasty: a review of results according to etiology. J Bone Joint Surg Am. 2007; 89:1476 1485 [7] Cheung E, Willis M, Walker M, Clark R, Frankle MA. Complications in reverse total shoulder arthroplasty. J Am Acad Orthop Surg. 2011; 19(7):439 49. [8] Edwards TB, Williams MD, Labriola JE et al. Subscapularis insufficiency and the risk of shoulder dislocation after reverse shoulder arthroplasty. J Shoulder Elbow Surg. 2009 Mar 10. [9] McFarland EG, Sanguanjit S, Tasaki A, Keyurapan E, Fishman EK, Fayad LM. The reverse shoulder prosthesis: a review of imaging features and complications. Skeletal Radiol. 2006; 35:488 496. [10] Sanchez Sotelo J. Reverse total shoulder arthroplasty. Clin Anat. 2008; 22(2): 172 82 [11] Tanino H, Higa M, Ito H, Sato T, Matsuno T, Banks SA. Intraoperative soft tissue tension measurements during total hip Arthroplasty. In review, Clin Biomech 2010. [12] Bergmann G, Graichen F, Bender A, Kaab M, Rohlmann A, Westerhoff P. In vivo glenoh umeral contact forces measurements in the first patient 7 months postoperatively. J. Biomech.2007; 40:2139 2149. [13] Carlson KL. Human hip joint mechanics an investigation into the effects of femoral head endoprosthetic replacement using in vitro and in vivo pressure data. PH.D. Thesis, Department of Mechanical Engineering, M.I.T., Boston, MA. 1993.

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42 [14] Taylor SJG, Meswania JM, Rodrguez Arias J, Calle R, Bayley IL, Blunn GW. An instrumented implant and calibration technique for measurement of glenohume ral joint forces In vivo. Proceedings of the 14th Conference of the European Society on Biomechanics, S Hertogenbosch, The Netherlands. 2004. [15] D'Lima DD, Patil S, Steklov N, Colwell, Jr. CM, In vitro and in vivo measurement of dynamic soft tissue balan cing during total knee arthroplasty with an instrumented tibial prosthesis. Trans. Annu. Meet. Orthop. Res. Soc. 2004; 29. [16] Bergmann G, Graichen F, Rohlmann A, Westerhoff P, Heinlein B, Bender A, Ehrig R. Design and calibration of load sensing ortho paedic implants. J. Biomech. Eng., 130 (2008), p. 021009 [17] Bergmann G. Ein Dreikomponenten Kraftaufnehmer und Seine Anwendung fr die Messung von Gelenkkrften am Tier. Ph.D. thesis, Technische Universitt Berlin, Germany.1981. [18] Bergmann G, Siraky J Rohlmann A, and Klbel R. 1982. Measurement of spatial Method. Proceedings of the Ninth World Congress IMEKO, Berlin, Germany. 1982; pp. 395 404. [19] Westerhoff P, Graichen F, Bender A, Rohlmann A, Bergmann G. An instrumented impl ant for in vivo measurement of contact forces and contact moments in the shoulder joint. Med Eng Phys. 2009; 31:207 213

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43 BIOGRAPHICAL SKETCH Chih Chiang Chang was born in Taiwan in 1986. Chih Chiang attended National Tsing Hua University where he received his B.Sc. in p ower m echanical e ngineering in 2008. He received h is Master of Science degree in m echanical e ngineering from the University of Florida in May 2013. He majored in the study of orthopaedic biomechanics for his graduate study.