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Structural and Functional Adaptations of Ankle Stability Do Not Affect Symptomatic Response and Clinical Outcome

Permanent Link: http://ufdc.ufl.edu/UFE0021408/00001

Material Information

Title: Structural and Functional Adaptations of Ankle Stability Do Not Affect Symptomatic Response and Clinical Outcome
Physical Description: 1 online resource (96 p.)
Language: english
Creator: Wikstrom, Erik A
Publisher: University of Florida
Place of Publication: Gainesville, Fla.
Publication Date: 2007

Subjects

Subjects / Keywords: adaptations, ankle, balance, disability, instability
Applied Physiology and Kinesiology -- Dissertations, Academic -- UF
Genre: Health and Human Performance thesis, Ph.D.
bibliography   ( marcgt )
theses   ( marcgt )
government publication (state, provincial, terriorial, dependent)   ( marcgt )
born-digital   ( sobekcm )
Electronic Thesis or Dissertation

Notes

Abstract: Lateral ankle sprains are the most common orthopedic injury in the United States. More than 70% of people who sprain their ankle will have a recurrent episode and about 50% will develop ankle instability. This disability decreases quality of life by limiting the activities that individuals can perform comfortably and with confidence. However, it is unclear why some people can inherently compensate or cope (copers) and others cannot (non-copers). This investigation explored structural and functional adaptations among copers and non-copers to determine how those adaptations might influence symptomatic response and performance based clinical tests. Specifically, we examined the structural (fibula position relative to the tibia and ligament stiffness) as well as functional adaptations (static and dynamic postural control) among the two patient populations and a control group. A total of 72 subjects were recruited (24 in each patient group and 24 healthy controls) and underwent a series of lateral radiographic (x-ray) images and a ligament stiffness test of both the right and left ankle followed by a static and dynamic balance test. The results indicated that non-copers had significantly increased disability as shown by the FADI, FADI Sport, and SRQAF. Similarly, both copers and non-copers had increased ligament stiffness when compared to healthy controls. In addition, differences in static and dynamic postural stability were revealed. However, the secondary variables examined in this investigation appear to have little influence on the primary outcome variables. However, none of the performance based clinical tests or secondary variables related to the inclusionary criteria or self-report symptoms of disability, which indicates the need to reexamine the variables that we have based our ankle instability research on.
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 Erik A Wikstrom.
Thesis: Thesis (Ph.D.)--University of Florida, 2007.
Local: Adviser: Borsa, Paul A.
Local: Co-adviser: Tillman, Mark D.
Electronic Access: RESTRICTED TO UF STUDENTS, STAFF, FACULTY, AND ON-CAMPUS USE UNTIL 2017-08-31

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Source Institution: UFRGP
Rights Management: Applicable rights reserved.
Classification: lcc - LD1780 2007
System ID: UFE0021408:00001

Permanent Link: http://ufdc.ufl.edu/UFE0021408/00001

Material Information

Title: Structural and Functional Adaptations of Ankle Stability Do Not Affect Symptomatic Response and Clinical Outcome
Physical Description: 1 online resource (96 p.)
Language: english
Creator: Wikstrom, Erik A
Publisher: University of Florida
Place of Publication: Gainesville, Fla.
Publication Date: 2007

Subjects

Subjects / Keywords: adaptations, ankle, balance, disability, instability
Applied Physiology and Kinesiology -- Dissertations, Academic -- UF
Genre: Health and Human Performance thesis, Ph.D.
bibliography   ( marcgt )
theses   ( marcgt )
government publication (state, provincial, terriorial, dependent)   ( marcgt )
born-digital   ( sobekcm )
Electronic Thesis or Dissertation

Notes

Abstract: Lateral ankle sprains are the most common orthopedic injury in the United States. More than 70% of people who sprain their ankle will have a recurrent episode and about 50% will develop ankle instability. This disability decreases quality of life by limiting the activities that individuals can perform comfortably and with confidence. However, it is unclear why some people can inherently compensate or cope (copers) and others cannot (non-copers). This investigation explored structural and functional adaptations among copers and non-copers to determine how those adaptations might influence symptomatic response and performance based clinical tests. Specifically, we examined the structural (fibula position relative to the tibia and ligament stiffness) as well as functional adaptations (static and dynamic postural control) among the two patient populations and a control group. A total of 72 subjects were recruited (24 in each patient group and 24 healthy controls) and underwent a series of lateral radiographic (x-ray) images and a ligament stiffness test of both the right and left ankle followed by a static and dynamic balance test. The results indicated that non-copers had significantly increased disability as shown by the FADI, FADI Sport, and SRQAF. Similarly, both copers and non-copers had increased ligament stiffness when compared to healthy controls. In addition, differences in static and dynamic postural stability were revealed. However, the secondary variables examined in this investigation appear to have little influence on the primary outcome variables. However, none of the performance based clinical tests or secondary variables related to the inclusionary criteria or self-report symptoms of disability, which indicates the need to reexamine the variables that we have based our ankle instability research on.
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 Erik A Wikstrom.
Thesis: Thesis (Ph.D.)--University of Florida, 2007.
Local: Adviser: Borsa, Paul A.
Local: Co-adviser: Tillman, Mark D.
Electronic Access: RESTRICTED TO UF STUDENTS, STAFF, FACULTY, AND ON-CAMPUS USE UNTIL 2017-08-31

Record Information

Source Institution: UFRGP
Rights Management: Applicable rights reserved.
Classification: lcc - LD1780 2007
System ID: UFE0021408:00001


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STRUCTURAL AND FUNCTI ONAL ADAPTATIONS OF ANKLE STABILITY DO NOT AFFECT SYMPTOMATIC RESPONSE AND CLINICAL OUTCOME By ERIK A. WIKSTROM A DISSERTATION PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLOR IDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY UNIVERSITY OF FLORIDA 2007 1

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2007 Erik A. Wikstrom 2

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To my family, friends and most importantly my beautiful wife April who has encouraged my pursuit of scholarship 3

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ACKNOWLEDGMENTS Completing this dissertation has been one of the most challenging and rewarding endeavors of my academic career, and I could not ha ve done so without the help and support of a great many people. My committee, Dr. Paul Bors a, Dr. Mark Tillman, Dr. Terese Chmielewski, and Dr. James Cauraugh deserve a great deal of thanks. They encouraged me, supported my ideas, but most importantly guided me throughout the research and disse rtation process. In addition to my committee, several other people were very helpful during this time. Jason Clark volunteered to help co llect and enter data; a nd Joan Street and her staff at the X-Ray Division of the Student Health Ca re Center assisted in data co llection; and most importantly, Keith Naugle, a first class research assistan t, and an even better friend and colleague. 4

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TABLE OF CONTENTS page ACKNOWLEDGMENTS...............................................................................................................4 LIST OF TABLES................................................................................................................. ..........8 LIST OF FIGURES.........................................................................................................................9 ABSTRACT...................................................................................................................................10 CHAPTERS 1 INTRODUCTION................................................................................................................. .12 Background and Significance.................................................................................................12 Specific Aims..........................................................................................................................13 Primary Aim.................................................................................................................... 13 Secondary Aims...............................................................................................................14 Tertiary Aims...................................................................................................................14 2 LITERATURE REVIEW.......................................................................................................16 Introduction................................................................................................................... ..........16 Epidemiology................................................................................................................... .......16 Ankle Instability.............................................................................................................. .......17 Structural Adaptations.....................................................................................................18 Functional Adaptations....................................................................................................21 The Coping Mechanism..........................................................................................................2 2 Outcomes................................................................................................................................24 Summary.................................................................................................................................26 3 MATERIALS AND ANALYTIC PLAN...............................................................................30 Experimental Design............................................................................................................ ..30 Subjects............................................................................................................................30 Power Analysis................................................................................................................3 1 Primary outcomes.....................................................................................................31 Secondary outcomes.................................................................................................31 Data Management............................................................................................................32 Methods for Primary and Secondary Aims............................................................................32 Primary Outcome Measures............................................................................................32 Self-Report measures...............................................................................................32 Performance based clinical tests..............................................................................34 Secondary Outcome Measures........................................................................................35 Structural adaptations...............................................................................................36 Functional adaptations..............................................................................................37 5

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Analytic Plan..........................................................................................................................39 Primary Outcomes...........................................................................................................40 Secondary Outcomes.......................................................................................................40 Tertiary Outcomes...........................................................................................................41 4 RESULTS...................................................................................................................... .........44 Demographics.........................................................................................................................44 Primary Outcomes............................................................................................................... ...44 Self-Report Questionnaires.............................................................................................44 Performance Based Clinical Tests...................................................................................44 Secondary Outcomes............................................................................................................. .45 Structural Adaptations.....................................................................................................45 Functional Adaptations....................................................................................................45 Effect on Primary Outcomes...........................................................................................46 Tertiary Outcomes..................................................................................................................47 Reliability........................................................................................................................47 Correlations.....................................................................................................................47 Predictions.......................................................................................................................47 5 DISCUSSION................................................................................................................... ......59 Summary of Findings............................................................................................................ .59 Demographics.........................................................................................................................59 Primary Outcomes............................................................................................................... ...60 Self-Report Questionnaires.............................................................................................60 Reports of function/disability...................................................................................60 Fear of reinjury.........................................................................................................61 Reliability.................................................................................................................63 Performance Based Clinical Tests...................................................................................63 Test results................................................................................................................63 Failed trials...............................................................................................................65 Subjective feelings...................................................................................................66 Reliability.................................................................................................................67 Secondary Outcomes............................................................................................................. .68 Structural Adaptations.....................................................................................................68 Joint stiffness...........................................................................................................68 Fibula position..........................................................................................................69 Reliability.................................................................................................................71 Functional Adaptations....................................................................................................71 Static postural control...............................................................................................71 Dynamic postural control.........................................................................................73 Tertiary Outcomes..................................................................................................................75 Correlations.....................................................................................................................75 Predictions.......................................................................................................................77 Conclusions.............................................................................................................................77 6

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APPENDICES A MODIFIED HUBBARD AND KAMINSKI QUESTIONNAIRE........................................80 B ANKLE JOINT FUNCTIONAL ASSESSMENT TOOL......................................................81 C FUNCTIONAL ANKLE DISABILI TY INDEX AND FUNCTIONAL ANKLE DISABILITY INDEX SPORT...............................................................................................82 D SELF REPORT QUESTIONNAIRE OF ANKLE FUNCTION............................................83 E TAMPA SCALE FOR KINESIOPHOBIA............................................................................84 F METHODOLOGY CHANGE................................................................................................85 LIST OF REFERENCES...............................................................................................................87 BIOGRAPHICAL SKETCH.........................................................................................................96 7

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LIST OF TABLES Table page 4-1 Group demographics..........................................................................................................49 4-2 Group demographics of the reliability subset....................................................................50 4-3 ICC values for selected primary and secondary outcomes................................................51 4-4 Variable correlation results................................................................................................52 4-5 Regression analyses for primar y and secondary outcomes................................................53 8

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LIST OF FIGURES Figure page 1-1. Experimental paradigm......................................................................................................15 2-1. Joint stability......................................................................................................................28 2-2. The potential mechanisms fo r altered fibular position......................................................29 3-1. Performance based clinical tests........................................................................................42 3-2. Side lying position for joint stiffness measurements.........................................................42 3-3. Fibula position measurement.............................................................................................43 3-4. Single leg hop stabilization maneuver...............................................................................43 4-1. Self-report questionnaires group main effect.....................................................................54 4-2. Self-report questionnaire s limb main effect.......................................................................54 4-3. Performance based clinical test scores (mean SD).........................................................55 4-4. Number of failed performance based c linical test trials (mean SD)...............................55 4-5. Frequency analysis of subjectiv e feelings of instability....................................................56 4-6. Stiffness group main effect (mean SD)..........................................................................56 4-7. Fibula position variables (mean SD)..............................................................................57 4-8. Static postural control group by limb interactions (mean SD).......................................57 4-9. Static postural control limb main effect (mean SD).......................................................58 4-10. Normalized DPSI scores (mean SD)..............................................................................58 5-1. Study comparison of clinical test group means.................................................................79 5-2. Study comparison of AP and ML mean sway group means..............................................79 9

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Abstract of Dissertation Pres ented to the Graduate School of the University of Florida in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy STRUCTURAL AND FUNCTI ONAL ADAPTATIONS TO ANKLE STABILITY DO NOT AFFECT SYMPTOMATIC RESPONSE AND CLINICAL OUTCOME By Erik A. Wikstrom August 2007 Chair: Paul Borsa Co-chair: Mark Tillman Major: Health and Human Performance Lateral ankle sprains are the most common ort hopedic injury in the United States. More than 70% of people who sprain their ankle will have a recurrent episode and about 50% will develop ankle instability. This disability decreases quality of life by limiting the activities that individuals can perform comforta bly and with confidence. Howe ver, it is unclear why some people can inherently compensate or cope (c opers) and others cannot (non-copers). This investigation explored structural and functional adaptations among copers and non-copers to determine how those adaptations might influenc e symptomatic response and performance based clinical tests. Specifically, we examined the st ructural (fibula position re lative to the tibia and ligament stiffness) as well as functional adap tations (static and dynami c postural control) among the two patient populations and a control group. A tota l of 72 subjects were recruited (24 in each patient group and 24 healthy controls) and underw ent a series of lateral radiographic (x-ray) images and a joint stiffness test of both the ri ght and left ankle followed by a static and dynamic balance test. The results indi cated that non-copers had signifi cantly increased disability as shown by the FADI, FADI Sport, and SRQAF. Similarly, both copers and non-copers had increased joint stiffness when comp ared to healthy controls. In a ddition, differences in static and 10

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dynamic postural stability were revealed. Howeve r, the secondary variables examined in this investigation appear to have litt le influence on the primary outcome variables. However, none of the performance based clinical test s or secondary variables related to the inclusionary criteria or self-report symptoms of disability, which indicates the need to reexamine the variables that we have based our ankle in stability research on. 11

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CHAPTER 1 INTRODUCTION Background and Significance Lateral ankle sprains are a co mmon injury with an incredib le incidence of 25,000 daily in the US1,2 and a recurrence rate greater than 70%.3 Treatment costs have been shown to exceed 3 billion dollars on an annual basis4 and 40-75%3 develop chronic ankle instability. Chronic ankle instability has been defined as ligamentous laxity, altered propriocep tion, altered muscular function, and complaints of the ankle giving way, but most importantly has been shown to lead to a recurring cycle of instabil ity and microtrauma to the joint.5,6 The development of ankle instability in such a large percentage of individua ls is alarming given that ankle instability is a known risk factor for secondary os teoarthritis; recurrent sprains compromise the repair of the articular surface of the talus a nd increase the risk of progressi ve degeneration of the joint.7,8 Despite the impairments illustrated, the remaini ng 25-60% can maintain high level activities (jumping, cutting), experiencing neither instability nor loss of function despite a previous history of lateral ankle sprain(s ). This group is thought to be si milar to the small percentage of individuals who can maintain high-level activities after ACL injury,9-12 because they have an intrinsic or rapidly developed c oping mechanism that is thought to limit the structural and/or functional adaptations caused by trauma. Several investigators have iden tified structural an d functional differences between healthy and chronic ankle instability subjects (non-c opers). Structurally, a mal-positioned fibula13-18 may limit accessory motions causing a cascade of events such as: altered jo int arthrokinematics, abnormal physiologic motions, distorted state of ligamentous structur es, and altered joint function.19 While speculative, the seriousness of mechanical adaptations warrants further investigation. A functional adaptati on may be impaired postural control20 which may manifest 12

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itself as impaired proprioception, movement patterns, muscle activation, and balance.21-25 Since it is hypothesized that c opers function as if their ligaments were not damaged, it is thought that copers will not suffer postural control impairment s, which previous research has shown does occur in individuals with a nkle instability (non-copers).26 These speculated adaptations may decrease the bodys dependence on the use of muscular stability and peripheral receptors about the ankl e, possibly predisposing those individuals to increased risk of reinjury. While application of this theory to the ankle is new, previous investigations support the idea that these adaptations can be limited by a coping mechanism.25-27 Therefore, this investigation as sessed subjective and objective clinical outcomes and measures in two patient populations (copers, non -copers) and compared that data to a healthy control group. The secondary objective was to de termine how structural and functional adaptations (i.e. fibula position, ligament stiffness, dynamic postural control and st atic postural contro l) might influence self-reported symptoms and performance based clinical test scores. Our findings will help elucidate the mechanisms of ankle instability following a lateral ankle sprain and may lead to effective early interventions that will prevent ankle instability (Figure 1-1). Specific Aims Primary Aim To determine symptomatic responses and perfor mance based clinical test scores of two patient populations (copers, non-copers) as comp ared to a healthy control group based upon their current ankle instability status as determined by the inclusion criteria. Group differences among the symptomatic (self-reported pain and function) and performance based clinical tests of a single test session were examined to determine if ankle instability status affects disability. 13

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Primary Hypothesis Non-copers would be associated with incr eased symptoms and worse performance based clinical test scores (functional impairment) when compared to copers and healthy controls. Copers would be associated with symptoms and pe rformance based clinical test scores similar to those of the healthy controls. Secondary Aims To determine the magnitude of structural a nd functional adaptations secondary to ankle injury and instability. Group differences am ong fibular position, joint stiffness, dynamic postural control and static postural control we re examined. In addition, how the secondary outcome variables might influence symptomatic response and performance based clinical test scores among the experimental groups was also evaluated. Secondary Hypothesis Non-copers would be associated with a mal-positioned fibula (anteriorly positioned), decreased joint stiffness, worse dynamic postural control (increased scores), and an impaired postural control (increased sway) leading to in creased symptoms and functional impairment as compared to copers and healthy control subjects. Copers would be associated with fibula positioning, joint stiffness, dynamic postural control and static postural cont rol values similar to healthy controls. Tertiary Aims To determine the reliability of the primary and select secondary outcome variables, and to examine the relationships between the dependent variables. In additi on, we examined if our primary and/or secondary variables could be used as inclusionary cr iteria in future investigations. Intersession ICC values were calculated for reliab ility, and correlation values were determined to examine the strength of the relationships be tween the inclusionary criteria, primary and 14

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secondary outcome variables. Finally, independen t linear step-wise multiple regression analyses were conducted to determine if our dependent vari ables could be potential inclusionary criteria for future investigations. Tertiary Hypothesis Reliability of the selected va riables would range from good to excellent and subsets of the dependent variables would be highly correlated with each other. It is also hypothesized that the self-report questionnaires of ankle disability and static postural control variables could be used as future inclusionary criteria. Figure 1-1. This experimental paradigm indicat es how an individual with a coping mechanism can return to proper function w ithout the chance for reinjury. It also illustrates how there are several potential adaptations that may occur and are unknown at this time. 15

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CHAPTER 2 LITERATURE REVIEW Introduction The ankle uses both static and dynamic restraints to maintain joint stability.28 However, high joint forces imparted on the ankle during sports activitie s often exceed the physiologic limits of the static stabilizers.5,29 Due to the lack of bony congr uence and the inability of the static restraints to handle these forces, the ankle is forced to rely on dynamic restraining mechanisms (Figure 2-1). The sensorimotor system maintains joint stab ility through a complex relationship between the static and dynamic restraints, and these re straints are controlled by the peripheral mechanoreceptors.30,31 In addition, the effectiveness of dynamic restraints are dependent on the success of feedforward and feedback neuromuscular control via afferent information and efferent motor responses.30 Researchers suggest that increased muscular stiffness, a product of the efferent motor response during f unctional tasks, provides greater joint stability and protection against joint injury.31 Both preparatory and reactive activities of the lower extremity musculature help to regulate this stiffness,32 which is responsible for determining the load and actual stability of the joint.28 Epidemiology The ability to maintain dynamic joint stabilit y is extremely important as injuries to the ankle can occur in any activity of daily living an d athletic events because total body weight is transmitted in series through the joints of the lower extremity during simple ambulation. Injuries to the ankle joint are among the most common in athletics and are most prevalent in sports requiring cutting and jumping maneuvers such as volleyball, football, soccer and basketball.33-35 The majority of lateral ankle sp rains are non-contact in nature caused by sudden inversion forces 16

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that are often combined with plan tar flexion and result in the stretc hing or tearing of the peroneal muscles and/or the stabilizing ligaments. While considered relatively minor injuries, ankle sprains can result in a great deal of missed athle tic participation and cause a tremendous financial burden. Lateral ankle sprains oc cur at a rate of 5,000 a day in the United Kingdom1 and between 23,000 and 27,000 a day in the United States.1,2 Based on a 1983 investigation, it was estimated that moderate to severe ankle sprains in the Unit ed States alone cost approximately $2 billion in health care costs.36 Obsorne and Rizzo4 then accounted for inflat ion in 2003 and found this figure to equal $3.65 billion in health care costs. However, 55% of individuals suffering a lateral ankle sprain may not seek treatment from a health care professional37-38 thus the actual incidence of lateral ankle spra ins could be vastly underestimated. Ankle Instability Previous investigations have reported that recurrence rates for lateral ankle sprains have exceeded 70%.39 In addition, about 40-75% of individua ls suffering from a la teral ankle sprain will develop residual symptoms.3,40,41 Frequently, lateral ankle spra ins cause a loss of ankle joint stability, altered proprioception, altered muscular function and co mplaints of the ankle giving way.5 A combination of these symptoms operationally define ankle instability (AI): a) mechanical and b) functional.42 While two types of instability have been coined, these instabilities are most likely not mutually exclus ive but rather form a continuum of pathologic contributions.5 Previous researchers have found that functional and mechanical instability are associated with each other 42% and 36% of the time respectively.43 Additional research has shown that individuals reporting functional ankl e instability also demonstrate ligamentous laxity.44 17

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The causal factors of these adaptations are still unknown, but several theories have been proposed. For example, returning athletes to play as quickly as possible (potentially too quickly) overlooks symptoms such as ar thogenic muscle inhibition.45 By overlooking symptoms, the clinicians may be starting a vicious cycle of chronic injuries and/or permanent disability, including osteoarthritis. Osteoa rthritis (OA) is the most comm on joint disease and is among the most frequent and symptomatic health problems for active adults.46 While OA can occur in any joint, the ankle is extremely susceptible to de veloping secondary OA, caused by a history of joint injuries. The current evidence indicates that acute joint injury is chondrocyte destructive47, and that posttraumatic instability compromises the re pair of the articular surface and increases the risk of progressive degenera tion of articular cartilage.8 Structural Adaptations One detrimental effect of AI is that it can lead to abnormal ankle mechanics such as hypermobility or hypomobility.48 Previous investigations have reported increased laxity at both the talocrural and subtalar joints in individuals with AI49-51 while others have failed to reveal differences between groups.14,43,52 Methodological differences and lack of sufficient empirical data contribute to the controversy and apparent disinteres t by researchers. The vast majority of AI research has fo cused on functional deficiencies, such as proprioception, strength, and balance. This focus suggests that mechanical adaptations (i.e., malpositioned fibula) do not contribute to AI; howev er, to move through full physiologic motion, proper arthrokinematic motions are needed, of wh ich many are accessory motions that cannot be voluntarily produced.48 While still unknown, a mal-positioned fibula may limit accessory motions causing a cascade of ev ents such as: altered joint arthrokinematics, abnormal physiologic motions, distorted state of ligamen tous structures, and altered joint function.48 While speculative, the seriousness of mechani cal adaptations warrants further investigation. 18

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Mulligan53 first proposed that some individuals diagnosed with lateral ankle sprains experience an anterior positional fault of the distal fibula relative to the tibia. According to Mulligan,53 when the foot is inverted past its norm al range, the fibula is pulled forward on the tibia at the inferior tibiofibular joint, and causes a mal-positioned fibula at the joint. Since the original hypothesis, several st udies have examined mal-positi oned fibula in subjects with AI.13,14,16-18 Kavanagh16 began a series of investigations to determine if a greater range of anterior/posterior movement existed at the distal fibula compared to the uninjured ankle. The results illustrate a significantly greater amount of movement in one third of the subjects, which Kavanagh believed supported Mulligans hypothe sis of a mal-positioned fibula in some subjects.16 However, a sample of 6 acutely injured s ubjects is small, and only 2 of the six had greater movement per unit force. With only 2 subjects demonstrating increased movement it is impossible to generalize these results. Mavi et al.17 used a more objective form of measur ement (MRI) on eighteen subjects with recurrent ankle sprains and f ound a significant difference between the injured and control group males. The results show an anteriorly positioned fibula in the injured subjects with a mean distance for the male control group of 14.3 mm, and 11.8 mm for the injured group (a smaller distance indicates anterior pos ition, as shown in figure 2-2.17 A more direct measure was conducted by Ebraheim et al.54 who used CT scans on 20 cadaver lower limbs and noted a mean distance of 17.40 mm.54 The large difference in mean s illustrates the limitation of not controlling for the size of the tibia. The most recent investigation found significan t group differences between healthy and AI subjects.15 Specifically, 12 of 19 subjects had a more an teriorly positioned fibula in their injured ankle compared to the contralateral limb. These findings support the original hypothesis 19

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proposed by Mulligan, that some but not all individuals will develop an anteriorly positioned fibula.53 Adding to the controversy of mal-positione d fibula are the results of three recent investigations that reported posteriorly positioned fibulas.13,14,18 Eren et al.14 prospectively examined the position of the fibula after acute inversion ankle sprains with CAT scans and the axial malleolar index. The mean malleolar inde x of the injured group was +11.5, compared with +5.85 of the control group, indica ting statistical significance and posterior positioned fibula. However, Scranton et al.18 reported a posteriorly positioned fibula in subjects with unstable ankles and Berkowitz and Kim13 reported a posteriorly positione d fibula in subjects undergoing lateral ankle stabiliz ation procedures. The differences in the aforementioned studies an d the studies that have reported an anterior fibular position are in the measur ement techniques. Mavi et al.17 and Hubbard et al.15 examined the position of the fibula in direct relation to the tibia in the sagitt al plane. The distance between the anterior borders of the distal fibula and tibia were used. Berkowitz and Kim13, Eren et al.14, and Scranton et al.18 measured the relationship in a transverse plane at the talocrural joint. The major limitation of this measurement is that it is based on the position of the talus. Previous research has reported the talus to be ante riorly displaced after an ankle sprain,19,55 therefore masking an anteriorly positioned talus as a pos teriorly positioned fibula. The methodology of Mavi et al.17 and Hubbard et al.15 included measuring fibular pos ition in relation to the tibia without consideration of talar position, whic h may explain the different results. Two speculative hypotheses have been presented to explain mal-positioned fibula. Acutely, fibular position (posterior) may be ma intained by the effusion accompanying soft tissue injury.16 Although effusion dissipates rather quickly in most ankle sprains, in some it can persist 20

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for days to weeks despite treatment. Chronica lly, the anterior position may be maintained by changes in muscle tone mediated through the ga mma motorneuron system. The altered afferent input from musculotendinous and ligamentous mech anoreceptors may contribute as the input and may affect the gamma motor neuron output to th e peroneals or other musculature. Figure 2-3 illustrates the paradigm explaining the potential m echanisms for altered fibular position that may occur after lateral ankle sprain. However, it is still unknown if repetitive ankle sprains caused the anterior fibular position or if the position was a predispo sing factor to injury. Functional Adaptations Several researchers have examined functional adaptations in AI subjects as well. For example, AI patients have demonstrated signif icantly worse active joint reposition sense when compared to healthy controls. Similarly, EMG ac tivity and kinematic alterations have also been noted in AI subjects. Sp ecifically, Caulfied et al.22 indicated reduced preparatory muscle activity, while Brown et al.21 detected reduced reactive EM G and a trend towards reduced preparatory EMG activity during a jump landing. In addition, ki nematic analysis has also revealed that AI subjects have significantly more dorsiflexion before and after a single leg jump landing.23 Similarly, it was found that AI subjects ha ve altered ankle ossici lation while standing on their toes as compared to a healthy control group.56 However, strength deficits are not correlated with AI.57 Postural control in subjects with CAI has also been investigated extensively and alterations on both stable and unstable platforms have been found.43,51,58-60 While no bilateral differences were found in center of pressure measurements between healthy and unstable ankles of soccer players, the authors did find that when compar ed to a healthy refere nce group, the injured group had significantly greater center of pressure excursions.61 Researchers have speculated that neuromuscular deficits associat ed with ankle instability might be responsible for impairing 21

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postural stability.62-68 Most recently, dynamic postural stability deficits have been observed between healthy and AI groups.21,24,69,70 However, no relationship between static (COP) and dynamic (Star Excursion Balance Test and single leg hop stabilization test s) measurements of postural sway have been found.71 A possible reason for this can be found in the type of mechanoreceptor that these protocols stimulate. Ce nter of Pressure scores, measured in a static leg stance are dependent not only on visual and vestibular inform ation but information from the slow-adapting mechanoreceptors as well. Howeve r, dynamic joint stability tests are functional and stimulate the fast-adapting mechanoreceptors of the lower extremity, thus testing the sensitivity of different mechanore ceptors. Again, it is not known if AI causes these deficits or if AI is developed by the damage done dur ing the initial traumatic event. The Coping Mechanism Traditionally, the individuals with AI have b een compared to healthy subjects, with few investigations giving consideration to how well patients compensate after injury. Most authors would agree that measurable disturbances exist in the face of AI; however there is no consensus about why only some patients develop AI. The most relevant and important question is why the reinjury rate is 70% a nd why 40-75% develop AI.3,40,41 While no causal factor(s) for AI have been identified, the AI consortium has recently proposed that a small percentage (copers) do not develop AI because of an inherent or rapidl y developing mechanism. When using an ACL model, copers function as if th eir ligaments were not damaged. We anticipate that ankle copers will act similarly and their behaviors will clos ely resemble those of healthy subjects. In an ACL model, investigators have compared copers to non-copers during various tasks from quiet stance to walking and jogging. Th e results suggest that non-copers exhibited strategies during gait11,72 and stance9,73 that illustrate a potential c ontribution to knee instability. In addition, copers had significantly higher functional knee scores.9,11 This stiffening strategy 22

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is hypothesized to exist to reduce anterior tibial transl ation, but appears to be too extreme to maintain normal function.9 The authors speculated that a stiffening strategy of non-copers mentioned in previous studies11 would decrease joint integrity ove r long term use. In a recent review, clinicians and research ers were shown how and which patients (copers) would be better candidates for conservative non-operative re habilitation after an acute ACL rupture10 and that potential copers can enhance their copi ng mechanism with perturbation training.74,75 It is believed this model can and should be applied to the ankle and AI. The model suggests that after a lateral ankle sprain, so me individuals will develop a mechanism of compensation for the damaged ligaments (copers ) and thus be less likely to develop AI. Conversely, some individuals wont be able to co pe and were more likely to develop AI. While this idea is new to the ankle, previous reports support its basis, although unintentionally, and a recent investigation was the first to compare an AI group to a coper group.76 Specifically, individuals with a history of repetitive ankle sp rains that did not show signs of AI had no deficits in proprioception.25 In addition, no bilateral differences in center of pressure measurements between the uninvolved a nd contralateral unstable ankles were found in soccer players.61 Instead, when compared to a hea lthy reference group, the injured group had significantly greater cen ter of pressure excursions on both the involved and uninvolved limb. This investigation indicates that AI can affect the postural control system at a level high enough to affect both limbs27 suggesting that the postural contro l strategy has been changed. Most recently, Brown et al.76 noted altered landing kinematics and ground reaction force loading in the AI group when compared to a group of copers. The authors suggested that this most likely indicated a compensatory landing pa ttern. It is believed that th e non-copers will instinctively 23

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alter their postural control st rategy or have some other adaptation, which over time may alter their motor control and predispose th em to reinjury (Figure 1-1). Outcomes Despite the empirical evidence collected over the past 40+ years since Freeman42 first introduced AI, little has been done to improve the outcomes of those with AI. Ankle instability is still predominantly diagnosed subjectivel y and little is known about how to improve performance based clinical te sts and reduce symptoms. Evid ence suggests that bracing and balance training will improve balance but does not address quality of life. The examination of how outcomes (symptomatic response and performa nce based clinical tests) are affected by the observed adaptations seen will provide baseline data and hopefully infer new ways to improve the quality of life for those with AI. Performance based clinical tests assess multiple systems of the sensorimotor system, including neuromuscular control, joint stability, and muscular strength. These tests have a strong clinical relevance because of thei r use in the later phases of rehabi litation. Several investigators have examined the sensitivity of performa nce based clinical tests using a knee model77,78 but only recently have the same tasks been applied to the ankle.79-81 The most common are the single leg hop for distance, triple hop for dist ance, triple hop cross over test, timed hop, and shuttle run.80-85 The hop tests (single leg hop for distan ce, triple hop for distance, timed hop and cross over hop test) have been s hown to have good reliablility.83 However, despite the reliability, detecting group differences in pathol ogical populations has produced mixed results. For example, Nadler et al. failed to find group differences when using a shuttle run between healthy and those with a previous lower extremity injury.82 However, Itoh et al.86 indicated that a deficit in at least one of four functional te sts used (figure-8, side hop, up-down hop, and single hop for distance) could identify 82% of ACL deficient knees. A similar investigation used the 24

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same four functional tests and indi cated that 76% of the AI subject s reported feeling unstable in at least one the functional tests.78 In addition, the authors fou nd that the figure-8 and side hop test were able to detect group differences, and attributed the detection to the stressing of the lateral structures. If additional investigations can confirm the ability of these performance based clinical tests to detect group di fferences, then these tests would provide a timely and efficient tool to objectively evaluate intervention protoc ols designed to improve quality of life for those with AI. In addition to performance based clinical tests, subjective repor ts of function/disability are becoming critical measures for health care practitioners.87 These measures allow clinicians to assess changes in functional limitations and disab ilities after injury and clinical interventions. Many of theses subjective reports are general h ealth models and therefore have limitations when applied to an athletic populati on. Therefore, many researchers ha ve developed their own scales and questionnaires in an effort to minimize the limitations. For example, Hubbard and Kaminski developed a questionnaire that established the criteria for AI as each subject having subjective sensations of weakness, and episode s of giving way during daily activity.88 In addition, the Ankle Joint Functional Assessmen t Tool (AJFAT) has been used as a criterion for subject classification.70,89,90 In addition, the AJFAT questionnair e along with the number of ankle sprains were predictors of group membership (healthy and FA I) in a study conducted by Ross.90 The AJFAT and number of sprains combined illustra ted sensitivity and specificity probabilities of 96 and 100% respectively. Similarly, the Se lf-Report Questionnaire for Ankle Function was used to help identify functional deficits in subjects with AI.81,91 In all cases, the questionnaires were clinically useful as they successfully distinguished between groups of healthy subjects and those with functional deficits in prop rioception, and dynamic postural stability.24,70,88,91 25

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The most used self report questionnaire for the ankle is the Foot and Ankle Disability Index (FADI) and its sport counte rpart (FADI-sport). These reports have been shown to be reliable in detecting functional limitations in su bjects with AI, sensitive to differences between healthy subjects and subjects with AI, and responsive to improvements in function after rehabilitation in subjects with AI.92 But little other information is available to apply towards individuals wanting to impr ove their quality of life. In addition to using self report questionnaires of disability, a new questionnaire regarding patient fear of reinjury has been developed. Ps ychological responses always occur as a result of injury and may result in an increased fear or return to activity or a decrease in performance because of a fear of reinjury.93 Such a fear may be a driving force behind the potential functional (neuromuscular) adaptations that have been suggested to cause AI. The Tampa Scale for Kinesiophobia (TSK) was initially developed for patients with low back pain and has been examined multiple times within patients with chronic pain for musculoskeletal injuries.94 The TSK, a seventeen statement questionnaire as well as an abridged (11 statement) version have been shown to have a high internal consistenc y (r=0.76 and .79 respectiv ely), and are precise measures (SEM= 3.26 and 2.54 respectively) when dealing with chronic low back pain.95 In addition, the TSK, which is a 68 point scale questionnaire has indicated that a negative correlation was noted between knee-re lated quality of life and a fear of reinjury in patients after an ACL reconstruction.96 Summary After 40 years of research, the exact cause of AI is still unknown. We have identified numerous deficiencies and developed interven tions to minimize those deficiencies but the incidence and recurrence rate is still extremely high. It is hoped that by taking a new direction 26

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by examining copers and non-copers, we were able to shed new light on the cause(s) of AI and provide more information about how to impr ove function and reduce the symptoms of AI. 27

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Figure 2-1. Joint stability is the cumulative result of the sensorimotor system working effectively. More specifically, joint stabi lity is the result of the afferent information (dotted lines) from the somatosensory system (peripheral feedback), integrati on of feedback from the somatosensory (and other sensorimotor system components) and the efferent response (solid lines) regulated by an individuals neuromuscular control. 28

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Figure 2-2. The potential mechanisms for altere d fibular position that may occur after lateral ankle sprain according to Hubbard. 29

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CHAPTER 3 MATERIALS AND ANALYTIC PLAN Experimental Design This study was a single blind case control, among groups design that assessed subjective and objective outcomes thought to be caused by ankl e instability. Each su bject was required to attend a single test session where they complete d self-report questionnaire s and participated in clinical tests, diagnostic imaging and a postural stability test. Us ing the data and analytic plan outlined in the next sections enabled us to de termine the role that structural and functional adaptations play in ankle impairment and outcome The primary outcomes for this investigation were the (1) symptomatic response as reported by the patient using ankle stability questionnaires, and (2) performance based clinical test scores. Our secondary outcomes were the (1) structural adaptations due to injury (fibula position, joint stiffness), (2) functional adaptati on due to injury (dynamic postural control and static postural control), and (3) how these variables might influence the primary outcomes. Our tertiary out comes were the (1) reliability of the primary outcomes and selected secondary outcomes, and (2) relationships among our inclusion criteria and outcome variables. Subjects We examined structural and functional adap tations as well as symptomatic response and performance based clinical test scores in 72 subject s. Subjects were even ly split into two patient population groups (coper, non-coper) and a heal thy control group. This sample size was determined by a priori power analyses of the prim ary aims. Effects sizes were determined from control and experimental group means from previous research and the larger standard deviation between those groups for a more conservative esti mate. Alpha was set at .05 and Beta at .80 for all estimates. 30

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Power Analysis Primary outcomes Symptomatic response effect sizes were found to range from 1.02 (involved to contralateral limb on the Foot and Ankle Disa bility Index) to 1.59 (involved to matched control on the Foot and Ankl e Disability Index Sport).92 A total sample size of 24 subjects is needed to determine group differen ces based on the effect size of 1.02. Performance based clinical test effect sizes ranged from .08 (healthy to mildly unstable on a side hop test) to .87 (healthy to se verely unstable on a figure 8 hop test).79 Total sample size ranged from 2010 to 24 respectively. Secondary outcomes Fibular Position effect sizes ranged from .39 (involved to matched control) to .73 (involved to contralateral limb).15 Total sample size ranged from 96 to 36 total subjects respectively. No effect sizes for postural control strategy can be calculated as no si milar data have been collected. All subjects regardless of gr oup classification were between the ages of 18-35 and without history of head or acute lower extremity injury within the past three months. All coper and noncoper subjects had a history of at least one mode rate to severe ankle sp rain that required acute care such as immobilization, ice, etc. as dete rmined by the initial inclusion questionnaire (modified from Hubbard and Kaminski).88 Inclusion criteria for the cope r group requires that subjects re sumed all pre-injury activity without limitation for at least 12 months and sc ored higher than 24 on the Ankle Joint Functional Assessment Tool (AJFAT). Recruitment difficulti es allowed a few copers to experience a single reinjury but all pre-injury activ ity was resumed without limitation for at least 6 months from the recurrent episode and AJFAT scores were still hi gher than 24. This score was not arbitrarily chosen, but rather was based on pr evious studies that no ted clinical deficits being consistently present in subjects who score 24 or less70 (96% sensitive and 100% specific for FAI group membership).90 Non-copers were operationally defined as having chronic ankle instability. The 31

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modified Hubbard and Kaminiski88 questionnaire showed that noncopers had a history of at least one moderate to severe ankle sprain that required acute care such as immobilization, ice, etc. and had at least 1 recurrent sp rain within six months of testing as well as a score of 20 or less on the AJFAT. Subjects were recruited by flyers posted on campus as well as through classroom recruitment visits made by the primary investigator. Data Management The primary investigator screened all subjects and placed them into the coper, non-coper, or healthy control group. The research assist ant (blinded to the subjects patient category) generated a random four digit number for each su bject (to which the primary investigator was also blinded) prior to taking each subject thr ough the data collection procedure. The data collection procedure was conducted by the research assistant who was also responsible for data entry for all measurements with the exception of fibula position (compl eted by the research assistant and the primary investigator). The pr imary investigator measur ed fibula position after all other data were collected to minimize bias. Data analysis occurred after the primary investigator and research assistant cro ss referenced their subject lists. Methods for Primary and Secondary Aims Primary Outcome Measures Ankle symptoms and functional ability were evaluated using a combination of self-report and performance based clinical tests in both patient populations and the healthy control group. Self-Report measures Ankle instability Questionnaire A modification of the questionnaire developed by Hubbard and Kaminski88 was used to determine the subjects inst ability status. The modified questionnaire with inserted notes about how c opers and non-copers would have to answer to be included in the study can be seen in Appendix A. 32

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Ankle Joint Functional Assessment Tool (AJFAT) Subject classification was confirmed by the AJFAT (Appendix B). The validity and reliability of this ques tionnaire has not been studied. However, previous investigations have shown that a conservative score of 20 on the AJFAT was sensitive to group differences. Ross et al.70 used a cut off of 24 on the AJFAT but found that the mean score for those with ankle instability was 17.30 .8 which was similar to the average found by Rozzi et al.89 (17.11 .44) who also found that hea lthy controls averaged 22.92 .22. The AJFAT has a maximum value of 48 points and wa s scored for the involved limb relative to the uninvolved limb for the pati ent populations. For the heal thy control group, the dominant limb was scored relative to the non-dominant limb. Foot and Ankle Disability Indexand th e Foot and Ankle Disability Index Sport These questionnaires (Appendix C) have been shown to be reliable and precise ( r=.89, SEM= 2.61 and r=.84, SEM= 5.32 respectively) in detecting func tional limitations in subjects with ankle instability, sensitive to differences between healt hy subjects and subjects with ankle instability (p<.01 and p<.01 respectively), and responsive to improvements in function after rehabilitation (p<.01 and p<.01 respectively).92 The FADI has a total possible score of 104 and the FADI sport a total of 32 points. These scores were calculated separately and scored as a percentage for each limb for all subjects. The administration of this test was randomized for the first subject and counter balanced for all subsequent subjects. Self-Report Questionnaire for Ankle Function This questionnaire (Appe ndix D) has been shown to detect functional deficits in subjects with ankle instability (77.8.9), however no validity or reliability data have been established.81,91 A subjects function for each limb was scored out of 100 and administered as previously established. 33

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Tampa Scale for Kinesiophobia (TSK) This questionnaire (Appendix E) has not been used in subjects with AI but has been shown to be re liable, precise, and sensitive in other patient populations.93,94 A subjects fear of pain and reinjury were scored out of 68 and administered as previously established. Performance based clinical tests All tests were conducted with the subject in shoe s to allow the results to be more clinically relevant. After the completion of each test, the subjects were as ked, Did you feel stable during that activity? and gave a respons e of yes or no. The purpose of th is question is to determine if subjects perceived being unstable even if their objective clin ical outcome scores were not affected by ankle instability status.79 Each test was conducted twice with the best time or distance being recorded as the crit erion measure for each leg. If the subject fell or was unable to maintain balance upon landing, then the trial was discarded and repeated. The number of failed trials was recorded for each clinical test. A 30 second rest period was given between trials and a 1-minute rest was given between tests. The orde r of testing was randomized for the first subject and counter balanced for all subsequent subject s using a Latin Square Design. In addition, the order of limb testing was also randomized for the first subject and counter balanced for all subsequent subjects. Side to side hop test79 Participants were instructed to hop laterally 30cm and back for a total of 10 repetitions (Figure 3-1). Time was measured with a hand stopwatch to the nearest .01 second. No psychometric data (reliability and validity) have been reported for this clinical test; however it has been used successfully to detect differe nces between healthy and unstable ankle groups. Figure 8 hop test79 This test was conducted over a 5 me ter course outlined by cones (Figure 31). Participants were instructed to hop as quickly as possible twice through the course. Time was measured with a hand stop-watch to the nearest .01 second. No psychometric data 34

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(reliability and validity) has been reported for this clinical test; however this clinical test has detected group differences between healthy and unstable ankle patients. Triple crossover hop for distance81 Subjects stood on one limb w ith their non-stance limb flexed to 90 Participants were asked to hop three times from a start line in a zigzag fashion, crossing over a line that was 15cm wide (Figure 3-1). Ea ch subject started so that the first hop was towards the lateral side of the limb being tested. The distance from the start line to where the heel landed on the third hop was recorded to the n earest .01 meter. This f unctional test has been shown to be reliable in healthy subjects ( r=.96, SEM= 15.95).83 Single hop test79 Participants were instructed to hop forw ard as far as possible (Figure 3-1). The distance was recorded from the position of the to es on the starting line to the end of the jump (heel position) to the nearest .01 meter. This c linical test has been s hown to be both reliable ( r=.96) and precise (SEM= 4.56).83 Secondary Aims To determine the magnitude of structural and functional adaptations th at have occurred in patients with a history of ankle injury and instability we evaluated the differences in fibula position, ligament stiffness, dynamic postural stability and static pos tural control dur ing a single test session. We evaluated these variables to de termine their potential influence on symptomatic response and performance based clinical test scores among our two patient samples and a healthy control group. Secondary Outcome Measures Structural and functional adaptations include fibula position, joint stiffness, dynamic postural stability and static postural control. 35

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Structural adaptations After completing the self-repor t questionnaires and performa nce based clinical tests, subjects had their ankles tested for stiffness imme diately followed by a trip to the student health care center for a radiography session. Ligament Stiffness A LigMaster (Sport Tec h, Inc., Charlottesville, VA) was used to measure ligament stiffness. Subjects were placed in a side lying position so that the leg to be tested was slightly flexed at the knee ar ound a counter bearing and the h eel was fixed against another counter bearing (Figure 3-2).24 The tester applied a force to th e anterior tibia via an actuator, stressing the anterior talo-fi bular ligament. Force was app lied up to 150N and the two trial average of the slope of the curve (stiffness) was calculated. Figure 5 Fibula Position A Phillips Medio 30 CP-H with a 150 kV microprocessor-controlled highfrequency X-ray generator in conjunction with a Horizontal Diagnost Table System was used for all radiographic images. In addition, Kodak La nex Fine Screens combined with Kodak Regular Speed green spectrum film was used as the film /screen system employed for this study. All films were shot TableTop / 40 using Manual Technique form 3.2 MaS @ 64 kVp (avg male) to 2.5 MaS @ 62 kVp (avg female) by Joan Street, R.T. (R), (QM), ARRT, Manager of the Department of Radiology at the Student Health Care Center. Precau tions were taken in accordance with UF IRB (#2005-U-547, #561-2005) and HURRAC (approval on November 2, 2005), including mandatory pregnancy tests for all female participants. Subjects were positioned side ly ing on the treatment table. Steps were taken to maintain a neutral position of the hip and knee.15 The distance between the ante rior margin of the fibula and the anterior margin of the tibia were recorded in millimeters (Figure 3-3). In addition, these differences were normalized to each patient but because no established normalization procedure for this variable exists several possibilities were explored. Two techniques were chosen based 36

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on their potential clinical relevance. The first presents the distance betw een the anterior fibula margin and the anterior tibial marg in as a percentage of the tibial width. The second is a ratio of the calculated distance between the involved and uninvolved limb. All measurements were made by two clinicians (EW) and the re search assistant, both of whom were blinded of the subjects / images classification. The analys is procedure has been shown to have very high intratester (.98) and intertester (.98) reliability and sh own to be a precise measure (.64mm).15 Functional adaptations Next, subjects performed static and dynami c postural stability tests (see Appendix F for static methodology change rationale). First, su bjects completed three trials of a single leg hop stabilization test accordi ng to Wikstrom et al.97 and then completed tw o trials of a 30 second single leg static stance on a force plate according to Matsusaka et al.60 Because the time of day has been shown to influence both static and dynami c postural control, all subjects were tested during the same general time of day (early afternoon).98 If a subject fell or stepped down, the trial was discarded and repeated. The numbe r of failed trials dur ing the single leg hop stabilization test was record ed for each subject. Static Postural Control A Bertec tri-axial force plate (Bert ec Corporation, Columbus, Ohio) was used to evaluate static postural control (center of pressure measures) at a sampling rate of 200Hz. Center of pressure (COP) is ar guably the gold standard in stabilometry and can be defined as the point of application of the resultant ground reaction force.59 These measures indicate a change in the COP location on the force plate as a result of muscular responses an d gravity. Rectangular area (area A) and AP and ML range were calculated according to Matsusaka et al.60 Postural sway was calculated according to Ross and Guskiewicz and Michell et al.70,99 Path length and average path length velocity were calculated according to Paillard et al.100 The variation in COP location allows for the calculation of postura l sway and other vari ables mentioned above.26,58,66 37

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Data were exported as comma de limited (.CSV) files and were re duced using Microsoft Office Excel 2003 (Microsoft Corp., Redmond WA). Jump Protocol The jump protocol was performed as first described by Ross and Guskiewicz.101 Subjects stood 70 cm from the cente r of the force plate and jumped with both legs to touch an overhead marker placed at a position equivalent to 50% of each subjects maximum vertical leap before landing on a single leg on the force plate, as seen in Figure 3-4. Subjects were instructed to jump with their head up and hands in a posi tion to touch the designate d marker. Subjects were instructed to land on the test le g, stabilize as quickly as possible, and balance for 3 seconds with their hands on their hips, while looking straight ahead. If a subj ect lost balance and touched the floor with the contralateral limb, the trial was discarded and repeated. Likewise, if a short additional hop occurre d upon landing, the trial was discarded and repeated. The number of failed trials was recorded for each subject. A Bertec triaxial force plate (Bertec Corporation, Columbus, OH) was used to co llect the baseline and jump landing data at a rate of 200 Hz.69,70,97,101 The force plate data underwent an analog to digital conversion and was stored on a PC-type computer using the DAT APAC 2000 (Run Technologies, Laguna Hills, CA) analog data acquisition, processi ng, and analysis system. Data from three successful jump protocol trials were averag ed and further analyzed. Ground reaction force (GRF) data were exporte d into a QuickBasic subroutine (version 4.5, Microsoft Corporation, Redmond, WA). The s ubroutine calculated stability indices in the three principal directions (medial/lateral, ante rior/posterior, vertical) and the DPSI. These indices are created from the st andard deviation fluctuations around a zero point, rather than a group mean, and divided by the number of sample s within the collection time period. The medial/lateral stability index (MLSI) and anteri or/posterior stability index (APSI) assess the 38

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fluctuations from zero along the frontal (X) and sagittal (Y) axes of the force plate, respectively. The vertical stability index (VSI) assesses th e fluctuation from the subjects body weight equivalent to standardize the vertical GRF along the Z-axis of the force plate. This is done to normalize the vertical scores am ong individuals with different body weights (mass). The DPSI is a composite of the medial/lateral, anterior/poste rior, and vertical stability index and is sensitive to changes in all three directions.97 The indices were normalized by the energy di ssipated during the la ndings performed by each individual based on previous investigation.101 Moreover, three indices were normalized to relevant energy values (horiz ontal kinetic energy or vert ical potential energy). The anterior/posterior stability inde x is a measure of va riance of the ground reac tion force values in the anterior/posterior direction a nd is sensitive to the horizontal velocity and mass of the jumper. Thus, the anterior/posterior stability index was normalized to the horizontal kinetic energy (0.5 Mass Horizontal Velocity2), with horizontal velocity calculat ed as (0.7 m/ time from jump to landing in seconds). Alternatively, the vertical stability index was normalized to the potential energy (Mass Gravity Jump Height) dissipated during the landing becaus e the vertical stability index is a measure of variance in the vertical ground reaction force. Analytic Plan A series of analyses were needed to prope rly examine the data. Both univariate and multivariate ANOVAs (Wilks Lambda)102,103, a correlation analysis, a series of multiple regression analyses, and intraclass correlation coeffifiencts104 were conducted. For the purposes of this study, correlation coeffi cients were interpreted as fo llows: below 0.50 indicates poor validity, 0.50 to 0.75 indicates moderate to good validity, and above 0.75 indicates excellent validity.105 All reliability coefficients were inte rpreted as follows; below 0.69 was poor, 0.70 to 39

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0.79 was fair, 0.80 to 0.89 was good, and 0.90 to 1.00 was considered excellent.105 An alpha level of .05 was used for all statistical tests. Pa irwise comparisons (Fishers LSD) were made to further examine where main effects or interactions occurred when necessary and an a priori alpha level was set at .05 for all statistical tests. In addition, effect sizes were calculated according to Cohen106 and magnitude was interp reted according to Gansneder and Paker (small=.10-.24, medium=.25-.39, large>.40).107 Primary Outcomes Self report questionnaires were divided in 2 part s: ankle disability a nd fear of reinjury. Therefore two independent analyses were conducte d: a 3 (coper, non-coper, control) x 2 (right, left limb) MANOVA was conducted for the FA DI, FADI Sport, SRQAF while a one way ANOVA was run for the TSK. Additionally, two separate 3 (c oper, non-coper, control) x 2 (right, left limb) MANOVAs were performed to analyze the four performance based clinical tests (Sid e to side hop, Figure-8 hop, Triple crossover hop, Single ho p tests) and the number of tria ls failed when completing the clinical outcome tests. Secondary Outcomes A series of linear step-wise multiple regression analyses were performed to determine any potential influence that the s econdary outcome variables might have on the primary outcome variables. Probability of F to enter the equati on was set to <=0.05, while probability to remove was >=0.10. In addition, group differences among the structural adapta tion variables were analyzed using a 3 x 2 MANOVA for the fibular position variables and a 3 x 2 ANOVA for joint stiffness. Group differences among the functiona l adaptation variables were analyzed in a similar manner, with a separate 3 x 2 MAN OVA for dynamic and static postural control. 40

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Tertiary Outcomes ICC values were calculated for the primary out comes and selected secondary outcomes. In addition, a series of correlation analyses were conducted to determine the relationships between the secondary and primary outcomes. A series of linear step-wise multiple regression analyses were also run to determine which of the depende nt variables are most closely associated with ankle instability status and should be potenti ally used as future inclusion criteria. 41

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Figure 3-1. Performance based clin ical tests. A) Figure-8 hop te st, B) Side-hop test, C) Crossover hop test, D) Single leg hop test. Figure 3-2. Side lying position for joint stiffness measurements. 42

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Figure 3-3. The distance between the anterior marg in of the fibula (1) and the anterior margin of the tibia (2) will be recorded in milli meters for each radiographic image. Figure 3-4. Starting and finish ing position of the single leg hop stabi lization maneuver. 43

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CHAPTER 4 RESULTS Demographics All subjects read and signed the univers ity approved informed consent prior to participation in this investigation. A total of 72 subjects were collected with 24 in each group (healthy, coper, non-coper). In addition, groups were gender matche d (n= 12, n= 12) within each group. Sixty-seven of the sevent y two subjects were considered to be right limb dominant, and of the 48 previously injured subjects, 26 injured their dominant limb. Injury demographic data were significantly different among groups but anth ropometric data were not (Table 4-1). Primary Outcomes Self-Report Questionnaires The MANOVA for self reported ankle di sability revealed a group [F(6,272)=9.67, p<0.001] and limb [F(3,136)=4.56, p=0.004] main eff ect but failed to reveal a group x limb interaction [F(6,272)=1.83, p=0.094)]. Pairwise comparisons revealed that the FADI, FADI Sport, and SRQAF scores were significantly lo wer (worse) for the non-coper group compared to the coper and healthy control group (Figure 4-1) In addition, the FADI, FADI Sport, and SRQAF scores were significantly lower for the injured/dominant limb when compared to the uninjured side (Figure 4-2). However, the ANOVA for fear or reinjury did not indicate significant differences am ong groups [F(2,69)=.108, p=.898]. Performance Based Clinical Tests The performance based clinical test M ANOVA revealed no significant interaction [F(8,270)=.330, p=.954]. Similarly, no group [F (8,270)=.688, p=.702] or limb [F(4,135)=.485, p=.747] main effects (Figure 4-3) were rev ealed. The MANOVA performed to examine group differences in the number of failed trials also failed to reveal an interaction [F(8,270)=.709, 44

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p=.684], group [F(8,270)=1.59, p=.127] or limb [F( 4,135)=.441, p=.779] main effects (Figure 44). However, despite the lack of performance based clinical test deficits or increased failure rate, a frequency analysis revealed that there were a greater perc entage of non-copers who felt unstable on their injured limb in all but th e triple hop for distan ce (Figure 4-5). Secondary Outcomes Structural Adaptations A 3 x 2 ANOVA revealed a statistically si gnificant group main effect [F(2,138)=3.16, p=.045] but did not indicate a limb main effect [F(1,138)=.91, p=.342] or group x limb interaction [F(2,138)=1.30, p=.275] for ligament stiffn ess. Pairwise compar isons indicated that the healthy control group produced significantly lowe r ankle joint stiffness scores than the coper and non-coper groups (Figure 4-6). The MANOVA regarding positional faults at the ankle also failed to reveal a group x limb interaction [F(6,272)=1.23, p=.291], as we ll as group [F(6,272)=.486, p=.819] and limb [F(3,136)=.583, p=.627] main effects. This MANOVA tested for differences among the following variables: fibula position15, tibia width, and normalized fi bular position relative to the width of the tibia (Figure 4-7). Similarly, the 3 x 2 ANOVA performed to examine the second normalization procedure (side to side ratio) did not reveal significant group differences [F(2,69)=.033, p=.749] with the following means: non-copers (1.0042.37) copers (0.95.35), healthy controls (0.93.26). Howe ver, a frequency analysis rev ealed that more copers (n=8, 33%) and non-copers (n=9, 37%) had an anteriorly positioned fibula compared to the healthy reference group (n=3, 12.5%). Functional Adaptations All static postural stabilit y variables were analyzed using a 3 x 2 MANOVA. The MANOVA revealed a significant group x limb interaction [F(18,260)=2.09, p=.007], and limb 45

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main effect [F(9,130)=4.64, p<.001] but not a group main effect [F(18,260)=1.29, p=.19]. Subsequent ANOVA and pa irwise comparisons re vealed that the significant interactions occurred between the dominant and non-dominant limbs of the healthy control group (Figure 48). Specifically, the healthy control group dominant limb had significantly less AP range and area A than the healthy control group non-dominan t limb. Additional pairwise comparisons also revealed that the injured limb had significantly less area A and AP range when compared to the uninjured limb (Figure 4-9). All dynamic postural stability variables were analyzed using a 3 x 2 MANOVA. The MANOVA revealed a significant group [F(6,272)= 3.83, p<.001] main effect but not a limb [F(3,136)=.27, p=.85] main effect or group x limb interaction [F(6,272)=.121, p=.99]. Subsequent ANOVA revealed that the NAPSI, and NVSI variables had statistically significant differences (Figures 4-10). Further examinati on indicated that the healthy control group had significantly better (lower) NAPSI scores than both the copers and non-copers but had worse (higher) NVSI scores than the coper group. The number of failed jump protocol attempts was also recorded and a 3 x 2 ANOVA revealed no group [F(2,138)=.811, p=.446] or limb [F(1,138)=.366, p=.546] main effect or group x limb interaction [F(2,138)=.044, p=.957]. Effect on Primary Outcomes Independent step-wise multiple regression analyses were conducted in an attempt to identify any potential influence that the secondary outcome variables might have on the primary variables. Few of the secondary variables could significantly predict primary outcome variables. Two self-report questionnaires we re significantly predicted. Specifically, the SRQAF was predicted by the NDPSI [r=.233, r2=.055 (F=4.03, p=.048)], and the TSK was predicted by four secondary variables. In or der, the ML range [r=.316, r2=.10 (F=7.7, p=.007)], NVSI [r=.429, r2=.184 { r2 change =.085} (F=7.8, p=.001)], AP sway [r=.500, r2=.250 { r2 change =.065} 46

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(F=7.5, p<.001)], and the fibula position [r=.551, r2=.304 { r2 change =.054} (F=7.3, p=.001)]. Performance based clinical tests were also sign ificantly predicted. Specifically, the Figure 8 hop test was predicted by the AP range (static postural control) [r =.255, r2=.065 (F=4.87, p=.030)]. Similarly, the Triple hop [r =.306, r2=.093 (F=7.20, p=.009)] and single hop [r =.245, r2=.060 (F=4.45, p=.038)] for distance were predicted by the AP sway. Tertiary Outcomes Reliability A randomly selected group of 15 subjects (5 per group) returned 1 week later to be retested for the primary outcome variables as well. In add ition, intratester and intert ester reliability of the fibular position measurement was also calculate d. Group demographics for this subset of subjects (Table 4-2) were calculated and 6 of 11 ICC values showed good to excellent reliability ( 0.80) (Table 4-3). Correlations A Pearson Product Moment Correlation was run to examine the relationships between the primary (self-report questionnaires, clinical tests) and the se condary outcomes (functional and structural adaptations) as well as the inclusionary criteria. Significant correlations stronger than .500 are listed in Table 4-4. If a variable did not correlate with any othe r variable that strongly, the strongest correlation is listed. In total, 29 correlations demonstrated moderate to good strength, while 15 were excelle nt in strength at a signi ficance level of p=.001. Predictions An additional set of independent linear st ep-wise multiple regression analyses were conducted on the inclusionary criteria (depende nt) to determine if any of the primary or secondary outcome variables should be used as inclusionary criteria in future investigations. A 47

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total of 4 of the 5 inclusi onary criteria were significantly predicted with an R2 of greater than .20 (Table 4-5). 48

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Table 4-1. Group demographics. Means, standard deviation (SD), degrees of freedom (df), f, and p values. Variable Group Mean SD F(2,69) p Healthy 21.82.6 Coper 20.81.5 Age (years) Non-coper 21.72.8 1.3 0.27 Healthy 170.09.6 Coper 173.410.9 Height (cm) Non-coper 175.012.5 1.3 0.28 Healthy 73.115.8 Coper 78.327.3 Weight (kg) Non-coper 70.912.7 0.9 .41 Healthy 18.46.2 Coper 20.65.9 Jump Height (cm) Non-coper 21.56.6 1.5 0.22 Healthy 0.00.0 Coper* 7.76.6 # Days Immobilized Non-coper* 9.19.7 12.5 <.01 Healthy 0.00.0 Coper 0.30.5 # Times re-injured Non-coper* 2.51.6 50.2 <.01 Healthy 0.00.0 Coper (12) 0.00.0 # Times re-injured within past X months Non-coper (6)* 1.30.8 73.6 <.01 Healthy 0.00.0 Coper 0.30.5 # Episodes of giving way Non-coper* 5.14.6 27.9 <.01 Healthy 26.11.8 Coper* 24.91.0 AJFAT Non-coper* 17.91.9 173.5 <.01 Indicates a statistically significan t difference from the healthy group (p 0.05). Indicates a statistically significant diffe rence from the coper group (p 0.05). 49

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Table 4-2. Group demographics of the reliability subset. Means, standard deviation (SD), degrees of freedom (df), f, and p values. Variable Group Mean SD F(2,12) p Healthy 20.81.3 Coper 21.61.5 Age (years) Non-coper 22.82.6 1.4 .28 Healthy 167.27.9 Coper 177.09.6 Height (cm) Non-coper* 184.911.4 4.1 .04 Healthy 69.010 Coper 80.917.2 Weight (kg) Non-coper 79.511.1 1.2 .33 Healthy 33.212.2 Coper 43.213.8 Jump Height (cm) Non-coper 45.417.4 .97 .40 Healthy 00 Coper* 74.8 # Days Immobilized Non-coper 5.44.9 4.2 .04 Healthy 00 Coper .4.5 # Times re-injured Non-coper* 2.61.5 11.3 <.01 Healthy 00 Coper (12) 00 # Times re-injured within past X months Non-coper (6) 10 Healthy 00 Coper .2.4 # Episodes of giving way Non-coper 6.28.0 39.2 <.01 Healthy 27.83.0 Coper 25.41.3 AJFAT Non-coper* 16.61.5 39.2 <.01 Indicates a statistically significan t difference from the healthy group (p 0.05). Indicates a statistically significant diffe rence from the coper group (p 0.05). 50

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Table 4-3. ICC values for selected primary and secondary outcomes. Variable Mean 1 Mean 2 ICC FADI (%) 99.172.3 99.41.7 .887 FADI sport (%) 992.3 98.372.2 .194 SRQAF (%) 96.95.3 96.136.5 .727 TSK 304.8 28.65.1 .691 Side to side hop (sec) 9.7.7 9.3.2 .769 Figure-8 (sec) 12.4.9 11.9.9 .911 Triple hop for distance (m) 3.141.12 3.488.58 .639 Hop for distance (m) 1.17.39 1.26.30 .799 IntratesterKN 12.33.8 12.33.6 .883 IntratesterEW 12.53.8 12.43.9 .906 Intertester (original measures) 12.33.8 12.53.8 .972 Fibular position (mm) Intertester (follow up measures) 12.33.6 12.43.9 .989 51

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Table 4-4. Variable correlation results. Variable Correlated variables # days immobilized SRQAF -.423** # times reinjured # injured w/in .683** AJFAT -.690** # times reinjured w/in X months # injured .683** AJFAT -.694** FADI Sport -.517** SRQAF -.573** # of giving way episodes AJFAT -.592** N Fib pos (%) .497** AJFAT # injured -.690** # injured w/in -.694** # giving way -.592** SRQAF .555** FADI FADI Sport .805** SRQAF .670** FADI sport # injury w/in -.517** FADI .805** SRQAF .639** SRQAF # injury w/in -.573** AJFAT .555** FADI .670** FADI Sport .639** TSK NDPSI -.225 Side to side Figure 8 .633** Figure 8 Side to Side .633** Triple Hop -.667** Single Hop -.669** Triple hop Figure 8 -.667** Single Hop .704** Single hop Figure 8 -.669** Triple Hop .704** Stiffness Fibular Pos .202 Fibular position N Fib pos (%) .954** NAPSI .864** NDPSI .863** N fib pos % Fib pos .954** NAPSI .912** NDPSI .911** N fib pos ratio # giving way .497** Area A AP range .926** ML range .562** AP sway ML sway .417** ML sway ML range .800** AP range Area A .926** ML range Area A .562** ML sway .800** 52

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Table 4-4. Continued AP path length NVSI .629** ML path length .973** Path length .997** Path length vel .997** ML path length NVSI .577** AP path length .973** Path length .986** Path length vel .986** Path length NVSI .626** AP path length .997** ML path length .986** Path length vel 1.00** Path length velocity NVSI .626** AP path length .997** ML path length .986** Path length 1.00** NAPSI Fib pos .864** N Fib pos (%) .912** NDPSI 1.00** NVSI Fib pos -.258** NDPSI Fib Pos .863** N Fib pos (%) .911** APSI 1.00** *Correlation is significant at p=0.05. **Correlation is sign ificant at p=0.01. Table 4-5. Regression analyses for prim ary and secondary outcomes with R, R2, F and p values. Variable: Predicted by: R R2 (change) F (1,70) p Days immob SRQAF .423 .179 15.2 <.001 # injuries SRQAF .476 .227 20.5 <.001 # injured w/in SRQAF .573 .328 34.1 <.001 Figure 8 .622 .059 21.7 <.001 FADI sport .659 .048 17.4 <.001 # giving way N fib pos (ratio) .497 .247 22.9 <.001 SRQAF .592 .104 18.6 <.001 AJFAT SRQAF .555 .308 31.2 <.001 53

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80 85 90 95 100 105 110 Control CoperNon-coper* FADI FADI SPORT SRQAF Figure 4-1. Self-report questionn aires group main effect. Scores for ankle disability questionnaires are expressed as a percentage (mean SD). Indicates a statistically significant difference from the healthy and coper group (p 0.05) for all three variables. 80 85 90 95 100 105 Dom / Injured* Non-Dom / Uninjured FADI FADI SPORT SRQAF Figure 4-2. Self-report questionnaire s limb main effect. Scores for ankle disability questionnaires are expressed as a percentage (Mean SD). Indicates a statistically significant difference from the Non-Domi nant / Uninjured limb (p 0.05) for all three variables. 54

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0 2 4 6 8 10 12 14 16 Control Coper Non-coper Side to Side Figure 8 Triple Hop Single Hop Figure 4-3. Performance based clinical test scores (mean SD). Side to side and figure 8 values are reported in seconds, while triple hop and single hop valu es are reported in meters. 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 Control Coper Non-coper Side to Side Figure 8 Triple Hop Single Hop Figure 4-4. Number of failed perf ormance based clinical test tria ls (mean SD). Values are expressed as the number of failed trials for each performance based clinical test. 55

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0 1 2 3 4 5 6 7 8 9 10 DomNon-DomInjuredNon-injuredInjuredNon-injured Control Coper Non-coper Side to Side Figure 8 Triple Hop Single Hop Figure 4-5. Frequency analysis of subjective feelings of instability during the performance based clinical tests. Values are expressed as the number of subjects who felt unstable during each of the performa nce based clinical tests. 12 13 14 15 16 17 18 Control* Coper Non-coper Figure 4-6. Stiffness group main effect (mean SD ). Stiffness values are reported in N/mm. Indicates a statistically significant difference from the coper and non-coper group (p 0.05). 56

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0 5 10 15 20 25 30 35 40 45 Control Coper Non-coper Fibula Position Tibia Width (x.1) N Fibula Position (%) Figure 4-7. Fibula position variable s (mean SD). Fibula positi on is expressed in mm, while tibia width is expressed in cm. N. fibula position is expressed as a percentage of the tibia width. 0 20 40 60 80 100 120 140 DomNon-DomInjuredNon-injuredInjuredNon-injured Control* Coper Non-coper area A (x.01) AP range Figure 4-8. Static postural cont rol group by limb interactions (mean SD). Area A values are expressed in cm2 and AP range values are expressed in mm. Indicates a statistically significant difference between the dominant and the non-dominant limb (p 0.05) for both variables. 57

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0 20 40 60 80 100 120 Dom* Non-Dom area A (x.01) AP range Figure 4-9. Static postural control limb main effect (mean SD). Area A values are expressed in cm2 and AP range values are expressed in mm Indicates a stat istically significant difference between the dominant and the non-dominant limb (p 0.05) for both variables. 0 0.02 0.04 0.06 0.08 0.1 0.12 0.14 Control* Coper Non-coper NAPSI NVSI NDPSI Figure 4-10. Normalized DPSI scores (mean SD). Indicates a statistically significant difference from the coper (p 0.05) for the NAPSI score. Indicates a statistically significant difference from both groups (p 0.05) for the NVSI score. 58

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CHAPTER 5 DISCUSSION Summary of Findings The purpose of this investigation was to examine how the primary outcomes (symptomatic response and performance based clinical tests) were affected by a history of AI. In addition, group differences in the secondary outco mes (structural and functional adaptations to AI) were examined; as well as how the secondary outcomes relate to the primary outcomes. The primary hypothesis was partially supported by the increased symptomatic response (higher degree of self-reported disabil ity) of the non-coper group. However, no performance based clinical test differences were observed. Similarly, the secondary outcomes explained little of the variance in the primary outcomes indicating that there is only a weak relationship between the secondary and primary outcome variables. Demographics We found no differences in the standard dem ographic data but did find that ankle injury history demographics differed among groups. For example, copers and non-copers were immobilized for similar time periods suggesting th at the initial traumas we re equally graded for both groups. Additionally, non-copers had significan tly more recurrent sprains and episodes of giving way compared to the coper and healthy control group. Most importantly, the AJFAT (group validation tool) revealed group differences (healthy > c opers > non-copers), supporting our choice for inclusionary criteria and compleme nting previous investigations that used the AJFAT as inclusionary criteria.70,89,90 Furthermore, our reported group means (healthy 26.1, copers 24.9, non-copers 17.9) were similar to th ose reported previously (healthy 22.9, non-coper 17.1)89 and (non-coper 17.3).70 These results support the pos sibility that a compensatory 59

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mechanism may take place after an initial trauma to the lateral ankle ligaments. However, it is more likely that the increased disability (low er scores) are a result of multiple traumas. Primary Outcomes Self-Report Questionnaires Reports of function/disability In the current investigation, a ll three questionnaires of ankle disability indicated greater disability in the non-coper group compared to the coper and healthy control group. The calculated effect sizes (d values)106,107 indicate medium to large magnitudes (FADI=.32, FADI Sport=.31, SRQAF=.49) suggesting that the results are clin ically meaningful. The results of the current investigation (self-re ported disability and AJFAT scores) agree with previous investigations that have investigated copers (kne e model after ACL injury).9,11 In addition, the increased disability (lower scores) of the curren t investigation confirm the deficits observed in previous AI research.91,92 Hale and Hertel92 examined the FADI and FADI Sport and reported means for a subset of AI subjects (n=26) as 87% and 79% respec tively, while hea lthy controls reported near 100% function. Our non-coper means of 95% a nd 92% respectively were higher than Hale and Hertel92 but our healthy controls al so reported near 100% function. Similarly, Munn et al.81 reported a SRQAF mean of 78 fo r the involved limb of AI subjec ts which is also lower than our reported mean of 85. Yet despite our higher non-coper means, which may be the result of differences in inclusionary crit eria or AI severity, group differe nces were revealed. While, the inclusionary criteria were similar among the curre nt and previous investigations, neither Hale and Hertel92 or Munn et al.81 reported the mean number of r ecurrent sprains or giving way episodes making direct co mparisons difficult. 60

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The FADI, FADI Sport, and SRAQF also il lustrated a limb main effect (bilateral differences). Hale and Hertel92 indicated that the i nvolved limb of an AI group was significantly lower than the uninvolved limb for both the FADI and FADI Sport. However, no bilateral differences were found in the hea lthy control group. The results of the current investigation were similar to those of Hale and Hertel.92 Specifically, bilateral differe nces in non-copers (injured limb had greater disability) but not copers or healthy c ontrols were reveale d. The SRQAF results of the current investigation also revealed as ymmetric responses in non-copers. However, no previous investigation is available for comparison. We also found that copers reported greater di sability (although not sta tistically significant because of high variability) on the previously injured limb regardless of questionnaire (largest impairment generated by the SRQAF). Our results suggest that the self-r eport questionnaires are capable of detecting differences based on AI status as determined by the in clusionary criteria of this investigation. Furthermore, the SRQAF may be the most clinically useful at detecting impairments within a coper population however further research is needed to ascertain if bilateral differences exist in this population. Despite the lack of statistical differences in the current investiga tion, the reported coper deficits (group and limb) are present over a year from the time of initial trauma. This suggests that the initial trauma and/or subsequent clinic al treatments may be responsible for some degree of the subjective feelings of di sability reported by the non-copers. Further investigations are needed to determine the extent of disability that the initial trau ma causes and how that disability affects the development of ankle instability. Fear of reinjury Psychological responses always occur as a result of injury and may result in an increased fear of return to activity b ecause of a fear of reinjury.93 This unique perspective has been 61

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examined in patients with chronic musculoskeletal pain94 and after ACL reconstruction96 but the psychological response to AI has never been examined. The TSK is a fear of reinjury questionnaire and was given to healthy subjects to keep a standardized te sting protocol among all subjects. The results indicated no differences among groups which may be extremely interesting or indicate that the current fo rm of the TSK was not a valid tool for AI subjects. The lack of group differences may be the re sult of similar psychological responses among the coper and non-coper groups in regards to re-spraining their ankle. One possible reason for this phenomenon could be societys attitude that an ankle sprain is not a severe injury. For example, a physician is willing to accept 5, 10, maybe 20 recurrent ankle sprains before considering surgical intervention but a single knee or shoulder trauma (perhaps a single recurrence) warrants immediate surgical interv ention. However, our TSK means of 32 and 31 for copers and non-copers re spectively are almost twice as high as those reported by Kvist et al. (17)96 in patients who underwent ACL reconstruc tion. If our results were based on cultural attitudes, then our group means should be much lower than those of individuals who suffered an ACL injury. However, pain and fear are relative and the initial trauma suffered by subjects in the current investig ation may have been the worst traumatic injury suffered in their respective lives. While unlikely, it is possible that their limited experiences with pain and injury are the cause of such high TSK scores. It is also possible and more li kely that the TSK (in the curren t form) is not a valid scale for subjects with AI. The TSK was initially developed for patients with low back pain and is internally consistent and precise within that patient population.96 However, the terminology used in the TSK may have confused the subjects in th e current investigation. For example, medical condition (question five) is not normally associat ed with a lateral ankle sprain. Additionally, 62

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many questions referred to the worsening of pain, which copers did not have, and many noncopers only had pain during activity. This belief can be confirmed anecdotally, as many subjects needed assistance with question interpretation. Thus the subsequent responses may not have been valid. Future investigations should atte mpt to modify and validate the TSK for subjects with AI so that accurate information may be ga thered regarding the psychological response to injury between copers and non-copers. Reliability Test-retest reliability was consistent with prev ious research findings for all but one scale. The FADI was found to have good reliability in th e current investigation similar to the findings of Hale and Hertel.92 However, the FADI Sport had poor reliability (ICC=.194) in the current investigation despite similar group means and st andard deviations from day one to day two which contradicts previous repor ts of good reliability (r =.84).92 Our results indicate that the SRQAF had fair reliability but no comparisons to pr evious reports are possi ble. Our TSK results indicated poor reliability (r=.691) which is consistent with test retest reliability of the TSK in acute low back pain patients,108 however the reliability may impr ove once the scale is validated for subjects with ankle instability. Performance Based Clinical Tests Test results Performance based clinical tests assess multiple aspects of the sensorimotor system, and are clinically relevant because of their use in rehabilitation and return to play decisions. Numerous investigators have used performance ba sed clinical tests in order to determine group deficits in pathologic popul ations with varying results.77-82,85,86 For example, Demeritt et al. found no differences in three functio nal tests in AI subjects when compared to healthy controls.80 Similarly, Munn et al. found no differences in the triple crossover hop for distance or the timed 63

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shuttle run despite self-reported deficits in ankle function as measured by the SRQAF.81 These findings are identical (except for performance base d clinical tests used) to those of the current investigation. However, Docherty et al. recently found functional deficits with a side to side hop test and a figure 8 hop test.79 Functional impairment was belie ved to be caused by greater stress on the lateral structures imposed by these spec ific tasks. Group means from the current investigation are similar to thos e reported by Docherty et al.79 in two of three clinical tests used in both investigations (Figure 5-1). Several methodological differences may explain the contrary findings between the results of the current investigation and those of Docherty et al. The current i nvestigation tested all subjects in shoes, to allow for more clinically re levant outcomes, while Doch erty et al. tested all subjects bare foot. While sp eculative, it is possible that s hoes provided mechanical support effectively masking functional deficits. Eils et al. indicated that the passive stability of ankle braces are greatly dependent on being used with a shoe.109 Similarly, a review by Verhagen et al. found that low top shoes (similar to those worn by the subjects in the current inve stigation) did restrict mechanically impos ed ankle inversion stress.110 Future investigations are needed to determine if functional deficits can be masked by wearing shoes. It is also possible that our sm aller sample size (n=24) inhibi ted our ability to detect group differences compared to the previous investigat ion (n=42). This possibility is based on the low to small effect sizes for the performance base d clinical tests (Side to side=.08, Figure 8=.12, Triple hop=.07, Single hop=.07). Additionally, differe nt inclusionary criteria may have led to the contrary findings. While Docherty et al. di d include a wide range of AI severity based upon their eligibility criteria and assumptions, the number of sprains and recurre nt episodes were not reported and therefore, comparis ons must be made cautiously. 64

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Methodological differences ma y explain differences among studies, but it is entirely possible that researchers have been examining variables that are incapable of consistently detecting group differences. For example, the focus on the outcomes of performance based clinical tests (i.e. time, distance) in previous investigations has made it difficult to draw conclusions because of the multiple degr ees of freedom available to subjects.70,101 The capability of biological organisms to produce a variety of solutions to a pa rticular task (i.e. different strategies) offers flexibility and is a major source of variability in movement patterns.111 For example, a healthy person might have motor control pattern while a non-coper has pattern Patterns and will have different kinematics, kinetics muscle activity, etc. but both allow subjects to complete (have the same outcome) the required motor skill. Kowalk et al. demonstrated that the biomechanical parameters of an ACL reconstructed knee were altered when compared to their contralateral limb and a healthy control during stair climbing.112 More importantly, they indicated that these deficits were accommodated by increases in excursion, moment, and power at the contra lateral ankle. These findings suggest that performance based clinical test outcomes may not be affected despite alterations in performance characteristics. Future investigations are needed to examine diffe rences in performance characteristics and their impact on joint loads and forces placed upon the ankle after injury. Failed trials The number of failed trials for each performa nce based clinical test was collected and indicated no differences among grou ps. However, while not statis tically significa nt, it appears that healthy controls failed more side to si de hop tests than copers and non-copers. While surprising, no previous investigations are availa ble to compare our results to or to provide possible explanations. Docherty et al. indicated that 6% (n=10) of their subjects had at least 1 65

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unacceptable trial during the up/down or side to side hop test, but did not indicate which subjects (healthy or unstable) failed the trial. In contrast 55% (n=40) of our subjec ts had at least 1 failed trial during the side to side hop test and 9.7% (n =7) failed at least 1 figure 8 hop test trial. It is possible that healthy cont rol subjects, in an attempt to complete the task as fast as possible, failed several of the fi rst attempts. As a result, they may have slowed down in order to complete the task. While speculative as the sequence of failed and successful trials was not recorded, the subjective feeling of instability fe lt in higher numbers of the coper and non-coper groups does support this idea. Subjective feelings The importance of performance characteristics du ring a motor skill may be vital to future diagnosis but self-reported feelings of instability are still the primary method of diagnosing AI. Itoh et al.86 indicated that a deficit in at least one of four functiona l tests used (figure-8, side hop, up-down hop, and single hop for distance) could id entify 82% of ACL deficient knees. However, if performance based clinical test sc ores are the only source of information and the scores do not differ between groups or individuals clinicians may be placing their patients in danger. In an effort to determine if subjects per ceive instability even if their objective clinical outcome scores were not affected by AI status, Do cherty et al. asked the simple question of Do you feel stable? af ter each of the above mentioned tasks.79 The authors indicated that 76% of AI subjects reported feeling unstable in at least one of the performance ba sed clinical tests but may not have had functional deficits in the task in which they felt unstable.79 Similarly, 71% of non-copers in the current investigat ion also reported feeling unstable in at least one of the four performance based clinical tests but it is unknown if f unctional deficits existed. These results suggest that non-copers may have slowed/i nhibited themselves while completing the performance based clinical te sts to avoid injury or sens ations of instability. 66

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Reliability Limited psychometric data were previously av ailable for the perfor mance based clinical tests. Specifically, no data were available for the si de to side or figure 8 h op tests. The results of the current investigation indicate th at the side to side hop test has fair reliability (r =.77), while the figure 8 hop test had excellent reliability (r =.91). However, pr evious investigations indicate that the triple hop for distance and the single leg hop test have excelle nt reliable (r =.96).83 Yet the results of the current investigation indicate much lower ICC values for both tests. The triple hop for distance had poor reliability (r =.64), whil e the single leg hop for distance was just short of good reliability (r=.79). While differences in motor ability, lower ex tremity strength, and experience may have played a part in determining the group mean s and ICC values, neither previous or our investigation collected such information. More likely, the lower ICC values of the current investigation are the result of data re duction differences. Bolga and Keskula83 determined ICC values from a three trial average on day one a nd day two. However, the current investigation took the best score from a two tria l test on each day. It is also po ssible that our ICC values were affected by the apparent learning effect that took place as scores for all four performance based clinical tests improved during the second test session (Table 4.8). However, we are confident that fatigue as a result of testing order was not a factor because of the Latin square design used during the investigation. Future research should focus on es tablishing a standardized method of calculating and reporting ICC values for performance based clinical tests as well as determining how many practice trials are needed to remove a learning effect. 67

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Secondary Outcomes Structural Adaptations Joint Stiffness Few investigations have examined joint stiffness in an AI group.24 A previous investigation by Wikstrom et al revealed no differences between a healthy control group (11.8 1.9) and those with AI (12.8 3.8), which is contrary to the findings of the current investigation.24 The current findings of increased jo int stiffness in the coper and non-coper group compared to the healthy control group suggest that this structural adaptation occurs after the initial injury and is not related to AI. The exact reason for the increased stiffness in our study sample is unknown but believed to be caused by improper healing (i.e. fibrosis, residual edema) of the lateral ligaments. The increased stiffness seen in both the coper and non-coper group may be the result of improper acute treatment and/or long immobilization times (time of immobilization was the same for copers and non-copers). A systematic review indicated that functional treatments are more effective than immobilization for the acute care of lateral ankle sprains.115 This review is supported by a recent prospective investigation indi cating that ankle braces are more effective at decreasing pain and swelling than ace wraps (a form of immobilization).116 However, it is possible that increased joint stiffn ess is a positive adaptation, but fu ture investigations are needed to ascertain how and why this would be a positive adaptation. While few investigations have examined passive joint stiffness, ankle joint laxity has been well studied. Hubbard et al. noted that AI subjects had greate r displacement compared to their contralateral limb and a healthy control group.44 In another investiga tion, Hubbard et al. found increased ankle joint laxity in both the involved and uninvolve d limb of AI subjects when compared to healthy controls.55 Similarly, Hubbard et al. indi cated that both inversion and 68

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anterior laxity were significant predictors of AI status.113 Most recently, Hubbard compared the mechanical joint laxity of a coper and non-coper group.114 The results indicated that the noncoper group had significantly greater anterior laxity and inversi on rotation when compared to copers and healthy controls. Hubbard suggests that the increase d laxity may be why subjects develop AI. While speculative, it is possible that there is a very precise acute treatment needed for ankle sprains. Excessive immobilization may result in increased stiffness, while limited immobilization may result in increased laxity. Fibula position Altered distal fibular position relative to th e tibia is believed to limit accessory motions causing a cascade of events ultimately leading to ankle joint dysfunction (AI).48 However, limited research has been done in the area until very recently.13,14,16-18 Mavi et al.17 showed an anteriorly positioned fibula in the injured subjects with a mean distance for the male control group (n=75) of 14.3 mm, and 11.8 mm fo r the injured group (n=18) (a smaller distance indicates anterior po sition, as shown in Figure 3-3). Hubbard et al. also found significant differences between the involved ankle of an AI group (14.3.1) compared to the contralateral ankle (16.7.4) and to the matched limb of the control group (16.1.6).15 The group means of the current investig ation illustrate a much more anteriorly positioned fibula for the involved limb of the noncopers (12.4.8), uninvolved limb of the copers (13.2.6), and the matched limb of the healthy control group (12.9.8) when compared to the results of Hubbard et al. The lack of statistically significant differences may be the result of a smaller sample size (n=24) compared to Hubbard et al. (n=30)15 or the injury demographics of subjects used in the investigations. This is speculation as no previo us investigation regarding fibular position has reported injury demographic data. Our results do indicate that 41.6 %(n=10) of non-copers 69

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demonstrated and anteriorly positioned fibula rela tive to the tibia. This finding is similar to Hubbard et al.15 56.6%(n=17) and Kavanagh16 33% (n=2) and does s upport the original hypothesis proposed by Mulligan.53 However, 41.6% (n=10) of copers also had an anteriorly positioned fibula, suggesting that if a positional fault of the fibula occurs, it would do so after the initial trauma and would not be related to AI. Supporting this idea is th e recent investigation by Hubbard and Hertel, who found an anterior positione d fibula after sub-acute la teral ankle sprains. Specifically, the injured limb (14.2.4) was more anterior than the contralateral limb (17.0.2) and a matched control limb (16.8.3).117 In addition, they found a strong positive correlation between an anterior position of the fibula and the amount of swelling (measured by the figure-8 method), which supports one of two proposed mech anisms for positional fault (Figure 2.3). The lack of a standardized procedure to measure fibula position has always been a limitation. For example, Mavi et al.17 and Hubbard et al.15 examined the position of the fibula in direct relation to the tibia in the sagi ttal plane. However, Berkowitz and Kim13, Eren et al.14, and Scranton et al.18 measured the relationship in a transverse plane at the talocrural joint. As a result of these methodological differences two norm alization techniques we re developed in order to standardize the measurement technique. The first technique expresse d fibular position as a percentage of tibia width (tibia width did not differ among groups). The technique was chosen to reduce the possibility of masked positional faults due to differences in tibia size. The second technique created a ratio of symmetry between the limbs of each subject (healthy = nondominant: dominant, copers and non-copers= injured: un injured). Despite the novelty of these techniques and their potential clinical relevance, no differences were revealed. Although we failed to detect group differences, relatively little empirical data exists and the magnitude of a clinically meaningful difference remains unknown. Based on our group means and standard 70

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deviations, we believe that the first normalizatio n technique may be the mo st clinically useful because of its medium effect size (.36) as comp ared to the original calculation technique (.10) and the ratio normalization technique (.09). However future research is needed to further explore possible normalization techniques available for fibula position. Reliability Reliability characteristics of the original fibular position ca lculation ranged from good to excellent in the current investig ation. Specifically, test-retest reliability ranged from r =.88 .90 depending on the tester (KN or EW). Similarly, intertester reliability was found to be excellent (r = .97 .98) on two separate occasions. These valu es are consistent with previous reports of reliability regarding fibula positi on calculations by Hubbard et al.15 Hubbard et al. reported testretest reliability to be r =.98 while intrateste r reliability was r =.92. These findings support the previously established notion that sagittal measurements of the fibula position are reliable but validity parameters still n eed to be established. Functional Adaptations Static postural control Group x limb interactions were not relevant findings because the of the interaction location, between limbs of the healthy contro l group. However, the limb main effects did indicate that the previously injured limb had decreased area A and AP range during a single leg stance when compared to the uninjured limb. No previous investiga tion regarding AI has reported AP range, and no investigation has pe rformed bilateral comparisons of area A. Matsusaka et al. reported that th at AI subjects had a significantly larger rectangular area (16.0.4cm2) when compared to healthy controls (9.6.7cm2).60 These means are significantly smaller than those seen in the current investigation for bot h non-copers (26.1.1 cm2) and healthy controls (28.9.8 cm2). Methodological differences ex ist between the investigations 71

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and may explain the large differences between th e reported means. For example, Matsusaka et al. did not report the num ber of recurrent sprains or episode s of giving way but did require all subjects to have two recurrent sprains within six months of testing. In addition, Matsusaka et al. tested subjects bare foot and took a three tr ial average (as opposed to two in the current investigation). However, it is unknown how these methodological differences could create large differences in group means. Our results are contrary to other investigations that have illustrated impaired static postural control in subjects with AI.26,42,43,51,58 However, several studies have failed to reveal group differences.70,89,99 Ross and Guskiewicz and Michell et al. found no differences in AP or ML mean sway, but reported values similar to the findings of our investigation (Figure 5-2).70,99 Similarly, Rozzi et al. reported no static postural control differe nces, however it must be noted that they used a Biodex Stability System and not a force plate during their investigation.89 Although the values generated by the Biodex Stability System correlate well to data from static force plates, a direct comparison should be made with great caution.118 Despite the lack of group differences, the non-coper group presented lower group means in the rectangular area A, and AP range. Furtherm ore, it was noted that copers and non-copers presented lower group means with regards to AP sway, and overall path length when compared to the healthy controls. The d ecreased range and sway suggest th at those with AI or at least history of an ankle injury are either concerned or unable to ap proach their stability boundaries for some unknown reason. Ross and Guskiewicz70 proposed that AI subjects had higher dynamic postural stability scores because they allow themselves to approach their stability boundaries, which is contradi cted by our results. 72

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The results of the current investigation do appe ar to suggest that t hose with AI limit or have their postural sway limited as a result of injury. Recent research in nonlinear dynamics (a dynamical system that has a sensitive dependenc e on its initial conditions) also known as the chaos theory, has challenged the traditional pers pectives that associate high variability with decreased performance and pathology.119 The argument stems from the capability of biological organisms to produce a variety of solutions to a particular task (i.e. different landing strategies [degrees of freedom problem]).111 This variability is suggested as being the cornerstone of healthy and adaptable physiological systems.120 Other investigators, however, suggest that both an increase or decrease in vari ability may be the result of di sease depending on the specific dynamics being investigated.121 A recent review indicates the need for further research but strongly suggests that higher variability in postural control is a sign of a more stable individual.119 If this is the case, then it is possi ble that our non-coper group possess impaired static postural control, however further research is needed. In addition, the traditional postural sway variables may be inappropriate measures given the information from these recent investigations. It is entirely possible that we should be focusing on the complexity of postural sway and not the magnitude of sway. A more appropriate variable to study might be approximate entropy, which is a nonlinear dynamic approach for evaluating postural control.122124 Dynamic postural control Both the copers and non-copers had worse (higher) NAPSI scores when compared to the healthy control group. However, the healthy controls had significantly worse (higher) NVSI scores when compared to the coper group. This is contrary to Wikstrom et al. who indicated that the NAPSI scores of AI subjects di d not differ from healthy controls.103 However, the same jump landing protocol has identifie d sagittal plane (NAPSI equivalent) deficits using the time to 73

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stabilization measure in previous investigations.21,24,69,70,125 Furthermore, Wikstrom et al. revealed that AI subjects had worse (higher) NVSI and NDPSI scores than healthy controls.103 Ross and Guskiewicz speculated that the da mage caused by lateral ankle sprains and subsequent AI is responsible fo r the increased (worse) dynamic postu ral stability scores seen in their investigation.70 They theorized that peop le with AI take longer to decelerate their center of mass oscillations because they allow their center of mass to approach the limits of stability causing large external moments that act to dest abilize the body. If true the idea would explain the larger NAPSI scores seen in the current investigation. However, it is unknown if the increased NAPSI scores are caused by AI sympto ms (i.e. self-reported weakness) or because different landing strategies are used to improve stabilization time as suggested by Ross and Guskiewicz.70 Based on the results of our investigation, it appears that different landing strategies are used, however we dont know if the different strategies are the result of changes in motor programming after injury. Previously Caulfield and Garrett noted that subjects with unilateral AI possessed different biomechanical parameters during a jump landing task (both groups completed the motor skill).23 Similarly, previous investigations regarding limb dominance showed no bilateral deficits in dynamic postural stability.70,126 However, differences in kinematic and kinetic variables were revealed suggesting multiple motor control strategies in a healthy population.70 The current investigation illustrates that re gardless of group, subjects were able to successfully complete the jump landing task (with similar failure rates) despite different dynamic postural stability scores. Thes e results support the idea that different motor control programs exist in subjects with a history of ankle sprains. Further supporting this idea is the fact that we 74

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may not be able to state whether one group had significantly worse dynamic postural stability because of the recent research in nonlinear dynamics discussed earlier. Tertiary Outcomes Correlations Correlation analyses indicated that subsets of highly related variables exist within our data set. Specifically, the data can be separated into four subset s: 1) injury demographic data (including the AJFAT) and the self-report questionna ires of ankle disabil ity, 2) the performance based clinical tests, 3) fibula position and dynamic postural stability variables, and 4) static postural control variables. These subsets also represent our MANOVA st atistic groups, which supports the use of the MANOVA (highly correl ated variables make a MANOVA appropriate) in our statistical an alysis of the data.102 Subset one suggests that there is a direct link between the nu mber of sprains and episodes of giving way and an increase in disability (Tab le 4.4). Further investig ation of the specific disabilities reported and their relati on with the inclusionary criteria of this investigation may lead to more appropriate testing methods and protocols. Subset two (performance based clinical tests) was expected, as all clinical test s are related to the subjects moto r ability/abilities. However, because of the lack of relationships with the inclusionary criteria and self-reported disability, these tasks may not be appropriate to use on subjects with a histor y of ankle sprains (i.e. copers or non-copers). Subset three (fibular position and dynamic postu ral stability) was an unexpected result. Specifically, it was unexpected to have both sets of variables fall within the same subset. However, the lack of relationships between the in clusionary criteria and self-reported disability to the variables in subset three suggest that these variables may not be appropriate to consider when attempting to minimize symptomatic response to injury. Yet strong relationships between 75

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these two sets of variables suggest that as the position of the fibula becomes more posterior, dynamic postural stability sc ores increase. Further research is needed to explore this relationship and determine the significance of these results. The correlation between fibular position and dynamic postural stability may aff ect the biomechanical parameters of jump landing and/or the force that the lower extremity (specifically th e lower leg) can produce. McKinely and Pedotti reported that greater preparatory muscle activ ity provides a better dynamic defense mechanism, thus minimizing dynamic postural stability scores.128 In addition, previous investigations have indicated that dynamic control of the ankle re sults from an interaction between central programming and peripheral feedback129 but to our knowledge no investigation has examined how bony alignment may affect force production in the lower leg. Subset four (static postural co ntrol variables) was an expect ed result because all of the variables were derived from the same ground reac tion force data. However, much like subset two and three, there was no relati onship to the inclusionary crit eria, which suggests that these variables provide limited information regarding a nkle instability status. Similarly, the lack of significant relationships with th e self-report questionnaires of di sability implies that static postural control variables will not aid clinicians in their quest to improve symptomatic response to ankle injury and instability. The TSK and joint stiffness did not correlate st rongly to any other vari able. This suggests that neither of these variables give a unique pers pective that may be beneficial or that these variables should not be included in future i nvestigations. The TSK, does give a unique perspective but the strongest correlation was with the NDPSI (-.225). Unfortunately this relationship indicates that as f ear of injury increases, dynamic postural stability scores also decrease (improve) which implies that subjects focu s more on the landing, perhaps in an effort to 76

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reduce the risk of injury. It was anticipated that joint stiffness would relate to other structural adaptation variables, yet only a ve ry weak relationship was displaye d. The reason for this is still not understood but could have something to do w ith the inconsistent reporting of mechanical instabilities in subjects with ankle instability. Predictions As Table 4.5 suggests, few of the primary or secondary outcome variables used in this investigation should be considered for use as inclusionary criteria in future investigations. The figure 8 hop test, FADI Sport, and normalized fi bula position (ratio) all predicted one of five inclusionary criteria. Furthermore, only th e normalized fibula positi on (ratio) predicted an inclusionary criteria with any strength (r2 change = .247). However, the SRQAF predicted all five of the current investigations inclusionary criteria. In addition, two of t hose predictions explained more than 30% of the variance (# of times injured with the past 12/6 months, and AJFAT). To the best of our knowledge no previous investigation has examin ed if their selected outcome variables could predict th eir inclusionary criteria, but th e results of our investigation suggest that the SRQAF could be used as incl usionary criteria for fu ture investigations. Conclusions Based on the results of our investigation, it is apparent that symptomatic response of ankle disability is increased in non-c opers (those with ankle instability ) based on the consistent group differences across three different self-report qu estionnaires. Furthermore, performance based clinical tests and the number of failed performance based clinical test trials do not differ based on ankle instability status despite larger numbers of copers and non-copers feeling unstable while completing the tests when compared to healthy controls. Ligament stiffness does differ among the groups and appears to occur as a result of the initial trauma (increased stiffness in copers a nd non-copers). A positional fault (fibula position) 77

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does not differ across groups but appears to occu r in some but not all individuals who have suffered an initial trauma (based on the frequency of an anteriorly positio ned fibula in copers and non-copers). Limited and mixed findings in stat ic and dynamic postural st ability in conjunction with recent nonlinear dynamics insights suggest that further research is needed before a conclusion can be drawn about th e current variables being used and the results those variables have given. Symptomatic response and injury demographic data are strongly correlated. Furthermore, the SRQAF should be considered as an inclusionary criterion for future investigations because of its ability to predict ankl e instability status. None of the c linical tests or s econdary variables correlated to the inclusionary criteria or self-report symptoms of disability. 78

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0 2 4 6 8 10 12 14 16 HealthyNoncoper HealthyNoncoper HealthyNoncoper Side to SideFigure 8Single Hop Docherty et al. Wikstrom et al. Figure 5-1. Study comparison of clinical test group means.79 Side to side and figure 8 values are expressed in seconds, while single hop values are expressed in meters. 0 0.2 0.4 0.6 0.8 1 1.2 1.4 HealthyNon-coperHealthyNon-coper AP Sway ML Sway Ross and Guskiewicz Michell et al Wikstrom et al Figure 5-2. Study comparison of AP and ML mean sway group means.70,99 Values are expressed in cm. 79

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APPENDIX A MODIFIED HUBBARD AND KAMINSKI QUESTIONNAIRE 80

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APPENDIX B ANKLE JOINT FUNCTIONAL ASSESSMENT TOOL 81

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APPENDIX C FUNCTIONAL ANKLE DISA BILITY INDEX AND FUNCTI ONAL ANKLE DISABILITY INDEX SPORT 82

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APPENDIX D SELF REPORT QUESTIONNAIRE OF ANKLE FUNCTION 83

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APPENDIX E TAMPA SCALE FOR KINESIOPHOBIA 84

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APPENDIX F METHODOLOGY CHANGE As suggested at the proposalA functional adaptation may be th e alteration of the postural control strategy.1 Since it was hypothesized that c opers function as if their ligaments were not damaged, it was thought that copers will maintain proper postural control strategies (i.e., ankle strategy), which previous research has shown does not occur in individuals with ankle instability (non-copers).1 The planned methodology was: First subjects will complete tw o trials of a 30 second single leg static stance on a force plate according to Karlsson and Persson, and Karlsson and Lanshammer.2,3 The strategy will be calculated based on the vertical, anterior /posterior (A/P), and medial/lateral (M/L) ground reaction force (GRF) measured at a frequency of 25-Hz.3 Data will be exported as a comma delimited (.CSV) files and be reduced using QuickBasic subroutines (version 4.5, Microsof t Corporation, Redmond, WA). The subroutine will be used to calculate the postural control strategy used by th e subjects. This will be determined using the formulas introduced by Karlsson.2,3 The extent to which the s ubject acted as an inverted pendulum will be quantified. However, the formulas provided did not function as indicated. The formulas were checked for errors numerous times and modifications were made to correct the formula. However after multiple attempts to correct the formula and multiple failed attempts to contact the authors, an alternative approach4 to calculating the static pos tural control st rategy using only force plate data was adopted for this investigatio n with the approval of the Chair and Co-chair. At this time, the methodology was changed to the following: First, subjects will complete two trials of a 30 second single le g static stance on a force plate according to Karlsson and Persson, and Karlsson and Lanshammer.2,3 However, calculation of th e static postural control was conducted according to Colobert et al.4 Static Postural Control StrategyA Bertec tri-axial force plate (Bertec Corporation, Columbus, Ohio) was used to help analyze th e static postural cont rol strategy of the s ubjects. The postural control strategy was based on the use of a double i nverted pendulum model and is proposed to be more robust than previous techniques.4 The model is based on the vertical, anterior/posterior (A/P), and medial/lateral (M/L) ground reactio n forces (GRF) and some anthropometric data4 sampled at a frequency of 25-Hz.2,3 Data were exported as co mma delimited (.CSV) files and were reduced using a custom made Matlab (The MathWorks, Natick, Massachusetts) program in the Laboratoire de Physiologie et Biomcanique de lExercise Musculaire in Rennes, France. The program implemented two operations: calc ulation of hip and ankle angles and an optimization of the position of the Center of Mass.4 From this information a strategy index ( = 1 / 2) was generated based on the covariance between hip and a nkle angles to quantify the postural control strategy used by the subjects. A larger indicates a hip strategy while a lower indicates an ankle strategy.4 However, Armel Crtual (corresponding autho r) who agreed to help with data reduction (because of the optimization process) encountered difficulties with his formulas algorithm. Specifically, their formula was designed for bipe dal stance and the algorithm was not appropriate 85

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for a unipedal stance (and the increased ML fo rce production). Armel continues to design an algorithm that will work for a si ngle limb stance with the data I provided and his own pilot work. When completed we will be able to use the algorithm in the future (time of the future is TBD). However, time constraints did not allow me to wait on Armel and with th e approval of my Chair and Co-chair, new static postural control vari ables were selected for use in the current investigation. These va riables and the methodology to reduce them can be seen in Chapter 3. 1. Pinstaar A, Brynhildsen J, Troop H. Po stural corrections after standardized perturbations of single limb stance; effect of training and orthotic devices in patients with ankle instability. Br J Sports Med 1996;30: 151-155. 2. Karlsson A, Persson T. The ankle strategy for postural controla comparison between a model-based and a marker based method. Comp Meth Prog Biomech 1997; 52: 165173. 3. Karlsson A, Lanshammar H. Analysis of pos tural sway strategies using an inverted pendulum model and force plate data. Gait Posture 1997; 5: 198-203. 4. Colobert B, Crtual A, Allard P, Delamarc he P. Force-plate based computation of ankle and hip strategies from doubl e-inverted pendulum model. Clin Biomech 2006; 21: 427-434. 86

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LIST OF REFERENCES 1. Kannus P, Renstrom P. Treatment for acute te ars of the lateral ligaments of the ankle: operation, cast, or early controlled mobilization. J Bone Joint Surg 1991: 73; 305-312. 2. Baumhauer J, Alosa D, Renstrom A, Trev ino S, Beynnon B. A prospective study of ankle injury risk factors. Am J Sport Med 1995; 23: 546-570. 3. Gerber J, Williams G, Scoville C, Arciero R, Taylor D. Persistent disability associated with ankle sprains: a prospective exam ination of an athletic population. Foot Ankle Int 1998: 19; 653-660. 4. Osborne M, Rizzo T. Prevention and trea tment of ankle sprain in athletes. Sports Med 2003; 15: 1145-1150. 5. Hertel J. Functional anatomy, pathomechanics, and pathophysiology of lateral ankle instability. J Athl Train 2002; 37: 364-375. 6. Nitz A, Dobner J, Kersey D. Nerve injuries and grades II and III ankles sprains. Am J Sport Med 1985: 13; 177-182. 7. Harrington K. Degenerative ar thritis of the ankle seconda ry to longstanding lateral ligament instability. J Bone Jt Surg Am 1979; 61: 354-361. 8. Marsh J, Buckwalter J, Gelberman R, Dirschl D, Olson S, et al. Articular fractures: does an anatomic reduction really change the result? J Bone Joint Surg 2002; 84-A: 1259-1271. 9. Chmielewski T, Ramsey D, Synder-Mackler L. Evidence for differential control of tibial position in perturbed unilateral stan ce after acute ACL rupture. J Orthop Res 2005; 23: 54-60. 10. Lewek M, Chmielewski T, Risberg M, Snde r-Mackler L. Dynamic knee stability after anterior cruciate ligament rupture. Exerc Sport Sci Rev 2003; 31: 195-200. 11. Rudolph K, Eastlack M, Axe M, Snyder-Mac kler L. 1998 Basmajian student award paper. Movement patterns after anterior cruciate ligament injury: a comparison of patients who compensate well for the injury and those who require operative stabilization. J Electromyo Kines 1998; 8: 349-362. 12. Rudolph K, Axe M, Buchanan T, Scholz J, Snyd er-Mackler L. Dynamic stability in the anterior cruciate ligament deficient knee. Knee Surg Sport Traumatol Arthosc 2001; 9: 62-71. 13. Berkowitz C, Kim D. Fibular position in relation to lateral ankle instability. Foot Ankle Int 2004; 25: 318-321. 87

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14. Eren O, Kucukkaya M, Kabukcuoglu Y and Ku zgun U. The role of a posteriorly positioned fibula in ankle sprain. Am J Sport Med 2003; 31: 995-998. 15. Hubbard T, Hertel J, Sherbondy P. Fibular pos ition in those with self-reported chronic ankle instability. J Orthop Sport Phys Ther 2006; 36: 3-9. 16. Kavanagh J. Is there a positional fault at the inferior tibiofibular joint patients with acute or chronic ankle sprains compared to normals? Man Ther. 1999; 4: 19-24. 17. Mavi A, Yildirim H, Gunes H, Pestamalci T and Gumusburun E. The fibular incisura of the tibia with recurrent sprained ankle on magnetic resonance imagining. Saudi Med J. 2002; 23: 845-849. 18. Scranton P, McDermott J, Rogers J. The re lationship between chronic ankle instability and variations in mortise anatomy and impingement spurs. Foot Ankle Int 2000; 21: 657-664. 19. Denegar C, Miller S. Can chronic ankl e instability be prevented? Rethinking management of lateral ankle sprains. J Athl Train 2002; 37: 430-435. 20. Pinstaar A, Brynhildsen J, Troop H. Postural corrections after standardized perturbations of single limb stance; effect of training and orthotic devices in patients with ankle instability. Br J Sports Med 1996;30: 151-155. 21. Brown C, Ross S, Mynark R, Guskiewicz K. Assessing functional ankle instability with joint position sense, time to st abilization, and electromyography. J Sport Reabil 2004; 13: 122-134. 22. Caulfield B, Crammond T, OSullivan A, Reynol ds S, Ward T. Altered ankle muscle activation during jump landing in participants with functional instability of the ankle joint. J Sport Rehabil 2004; 13: 189-200. 23. Caulfield B, Garrett M. Functi onal instability of the ankle: Differences in patterns of ankle and knee movement prior to and post landing in a single leg jump. Int J Sport Med. 2002; 23: 64-68. 24. Wikstrom E, Tillman M, and Borsa P. Detection of Dynamic Stability Deficits In Subjects With Functional Ankle instability. Med Sci Sport Exer 2005; 37: 169-175. 25. Willems T, Witvrouw E, Verstuyft J, Vaes P, De Clercq D. Proprioception and muscle strength in subjects with a history of ankles and chronic instability. J Athl Train 2002; 37: 487-493. 26. Troop H, Odenrick P. Postural c ontrol in single limb stance. J Orthop Res 1988; 6: 833-839. 27. Riemann B. Is there a link between chronic ankle instability and postural stability? J Athl Train 2002; 37: 386-393. 88

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BIOGRAPHICAL SKETCH I was born in Jacksonville, FL, on October 16, 1978, to Raymond and Geraldine Wikstrom. Growing up, my younger sister and I we re exposed to a variety of cultural and educational experiences. As a result, my passion for sports and love of science and medicine merged during a sports medicine class in high school. I went on to earn my BS from Roanoke College (Salem, VA) in sports medicine/athletic training. After graduating in 2001, I enrolled in the University of Florida graduate athletic trai ning program, where I earned my MS in Exercise and Sports Science with a specialization in athlet ic training in 2003. I stayed at the University of Florida to complete my PhD and in the proce ss was hired on as the program director of the undergraduate athletic traini ng education program. 96