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Effects of balance training on gait parameters in patients with chronic ankle instability: a randomized controlled trial

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Effects of balance training on gait parameters in patients with chronic ankle instability: a randomized controlled trial
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  Clinical Rehabilitation  2009;  23:  609–621 Effects of balance training on gait parameters in patientswith chronic ankle instability: a randomized controlled trial Patrick O McKeon  Department of Rehabilitation Sciences, University of Kentucky, Lexington, KY, USA, Gabriele Paolini  Vicon, Oxford, UK,  Christopher D Ingersoll  Department of Human Services,  D Casey Kerrigan  Departmentof Physical Medicine and Rehabilitation,  Ethan N Saliba  Department of Human Services,  Bradford C Bennett  Department ofOrthopedics and  Jay Hertel  Department of Human Services, University of Virginia, Charlottesville, VA, USAReceived 3rd October 2008; returned for revisions 29th November 2008; revised manuscript accepted 17th December 2008. Objective : To examine the effects of a four-week balance training programme onankle kinematics during walking and jogging in those with chronic ankle instability.A secondary objective was to evaluate the effect of balance training on themechanical properties of the lateral ligaments in those with chronic ankle instability. Design : Randomized controlled trial. Setting : Laboratory. Subjects/patients : Twenty-nine participants (12 males, 17 females) with self-reported chronic ankle instability were randomly assigned to a balance training groupor a control group. Intervention : Four weeks of supervised rehabilitation that emphasized dynamicbalance stabilization in single-limb stance. The control group received no intervention. Main outcome measures : Kinematic measures of rearfoot inversion/eversion, shankrotation, and the coupling relationship between these two segments throughout thegait cycle during walking and jogging on a treadmill. Instrumented ankle arthrometermeasures were taken to assess anterior drawer and inversion talar tilt laxity andstiffness. Results : No significant alterations in the inversion/eversion or shank rotationkinematics were found during walking and jogging after balance training. There was,however, a significant decrease in the shank/rearfoot coupling variability duringwalking as measured by deviation phase after balance training (balance trainingposttest: 13.1   6.2  , balance training pretest: 16.2   3.3  ,  P  ¼ 0.03), indicatingimproved shank/rearfoot coupling stability. The control group did not significantlychange. (posttest: 16.30   4.4  , pretest: 18.6   7.1  ,  P  4 0.05) There were nosignificant changes in laxity measures for either group. Conclusions : Balance training significantly altered the relationship between shankrotation and rearfoot inversion/eversion in those with chronic ankle instability. Address for correspondence: Patrick O McKeon, Division of Athletic Training, University of Kentucky, College of HealthSciences, Wethington Building, Room 206C, 900 SouthLimestone, Lexington, KY 40536-0200, USA.e-mail: Patrick.McKeon@uky.edu   SAGE Publications 2009Los Angeles, London, New Delhi and Singapore 10.1177/0269215509102954  Introduction Ankle sprains are among the most common inju-ries in the physically active population. 1 The mostcommon predisposing factor to suffering an anklesprain is a previous history of ankle sprain. 2 Thesubjective feeling of the ankle ‘giving way’ after aninitial ankle sprain and repetitive bouts of instabil-ity resulting in numerous ankle sprains hasbeen termed chronic ankle instability. 3 Chronicankle instability has been linked to many differentcontributing factors including altered gait mecha-nics. 3–5 Ankle sprains have been proposed to ariseduring the transition from an unloaded to aloaded condition at initial ground contact. 6 Themechanism of recurrent sprain typically resultsfrom a hypersupinated rearfoot on an externallyrotated lower leg shortly after initial contact. 3,6 It has been proposed that damage to the lateralligaments after suffering a sprain may result in thisaltered positioning of the rearfoot in the transitionbetween the swing and stance phase contact duringwalking and running. 7 Altered gait mechanics during walking andrunning have been reported in individuals withchronic ankle instability. 5,8,9 Individuals withchronic ankle instability have demonstratedincreased inversion kinematics and kinetics incomparison to healthy controls. 5,8,9 Specifically,these altered mechanics may be related to an asyn-chronous coupling between motion of the rearfootand shank. 10 The coupling of rearfoot eversionand tibial rotation in the stance phase has beeninvestigated as it relates to healthy subjects 11–13 and those with overuse knee injuries. 10,14 A change in the coupling relationship of therearfoot and shank may be due to an alterationof a functional level of variability in the compo-nents controlling the motions of the two seg-ments. 15,16 In a recent study 4 performed in ourlaboratory examining the rearfoot/shank couplingat heel strike, individuals with chronic ankleinstability demonstrated an altered coupling rela-tionship at the last 10% of the gait cycle just priorto heel strike during walking and jogging.Individuals with chronic ankle instability werealso more inverted than healthy controls through-out the entire gait cycle. In jogging, this alterationwas most apparent just prior to heel strike.This altered positioning may be related to anincreased predisposition to suffering anklesprain. 4,17 It has also been proposed that mechanicalchanges of the lateral ligaments of the ankle dueto ankle sprain may play a role in altered footposition prior to initial foot contact. 6,17,18 Thesealterations have been demonstrated with cadavermodels, however there is currently no evidence tosupport this  in vivo . 6,7 Ankle arthrometry has beendemonstrated to be a valid and reliable diagnostictool for the assessment of ligamentous laxity asso-ciated with mechanical ankle instability. 19,20 Individuals with chronic ankle instability havedemonstrated greater anterior displacement andinversion talar tilt than healthy controls. 19,20 These alterations have been proposed to relate toa greater predisposition to ankle sprains.Balance training has been purported to bean effective modality in reducing the episodesof inversion (‘giving way’) in individuals withchronic ankle instability. 21 In a concurrent studyusing the same subjects as this study, 22 we reportedsignificant improvements in postural control andself-reported function in individuals with chronicankle instability after four weeks of balance train-ing. The primary purpose of this study was toexamine the effects of the four-week dynamic bal-ance training programme on ankle kinematicsduring walking and jogging. We hypothesizedthat after balance training, the training groupwould demonstrate a change in ankle kinematicsand the joint coupling relationship between theshank and the rearfoot compared with those whodid not undergo balance training. As a secondarypurpose, we examined measures of ligamentouslaxity and stiffness with an ankle arthrometer. Wehypothesized that balance training would have noeffect on measures of laxity and stiffness related tothe anterior drawer or the talar tilt. Methods Study design This study was a randomized controlled trial inwhich individuals with self-reported chronicankle instability were randomly assigned toone of two groups: a balance training group or acontrol group. The balance training group610  PO McKeon  et al.  underwent 12 supervised balance training sessionsover a four-week period while the control groupmaintained the same level of activity prior to studyenrolment for the duration of four weeks.Measures of self-reported ankle function, walkingand jogging gait, and ankle laxity were assessedbefore and after the four-week interventionperiod in both groups. Subjects Thirty-one physically active individuals (12males, 19 females) with a self-reported history of chronic ankle instability were recruited to partici-pate in the study. Physically active was defined asparticipating in some form of physical activity forat least 20 minutes per day, three days per week.Inclusion criteria was a history of more than oneankle sprain and residual symptoms as quantifiedby four or more ‘yes’ responses on the AnkleInstability Instrument 23,24 and self-reported symp-toms of disability due to ankle sprains qualified bya score of 90% or less on the Foot and AnkleDisability Index and Foot and Ankle DisabilityIndex Sport surveys. 25 None of the subjects hadhistory of lower extremity injury, including anklesprain within the past six weeks, history of lowerextremity surgery, balance disorders, neuropa-thies, diabetes or other conditions known toaffect balance. If a subject reported bilateralankle instability, the self-reported worse limbwas used for analysis and training. Prior to testing,all subjects signed an informed consent formapproved by the institutional review board.Prior to the initial baseline testing session,subjects were randomly assigned to one of twogroups: balance training group or the controlgroup. The randomization sequence was generatedbyanindependentinvestigatorwhopreparedsealedenvelopes of group membership prior to studyenrolment. A separate investigator interviewedpotential subjects and determined who qualified toparticipate. Upon qualification, the interviewinginvestigator would open a sealed envelope to deter-minetowhichgroupthesubjectwouldbeallocated.The allocationofgroupmembership wasconcealedto the interviewing investigator and the subject.AflowdiagrambasedontheCONSORTstatementshows the inclusion and exclusion of subjectsthrough the entire study (Figure 1).There were two testing sessions separated byfive weeks in which subjects were evaluated onthe gait and arthrometry outcome measuresdescribed below. The balance training group wastested prior to the initiation of the balance trainingprogramme and within one week after completionof the programme. The control group was initiallyevaluated, then maintained their usual level of physical activity for four weeks, and was evaluatedagain at week 5. Based on the nature of the study,subjects were not blinded to group membership.In addition, the evaluators were not blinded togroup membership. Gait analysis Kinematic data were collected using a10-camera motion analysis system (VICONMotion Systems, Inc., Lake Forest, CA, USA)with a sampling rate of 240Hz. 5 This system hasbeen demonstrated to have a spatial error of 0.42mm and a mean error of angle reproductionof 0.16  . The treadmill was customized with anindwelling forceplate (AMTI, Watertown, MA,USA) directly underneath the belt to quantifyinstantaneous heel strike. Vertical ground reactionforces were sampled at 30Hz with a threshold of 10–20% body weight to determine initial contactand toe-off during walking and jogging.Retroreflective markers were attached to sub- jects via double-sided tape on specific landmarkson the pelvis, thigh, shank and foot in accordancewith the placements established by Pohl  et al  . 13 Two static trials were taken in order to calibratethe markers and provide a reference for walkingand jogging trial analysis. Subjects walked bare-foot at a self-selected pace for 5 minutes to accom-modate to treadmill walking. Subjects walked and jogged barefoot on a treadmill at speeds of 1.32m/s and 2.64m/s, respectively. 17 Five 15-second trialsof walking and jogging at each speed werecollected.For each trial of walking and jogging, kinematicdata from all gait cycles within each trial wereaveraged and resampled to 100 points based onforceplate data which provided informationfor the relevant events of initial contact andtoe-off. 4,26 This resampling to 100 data pointsthen represented 100% of a stride cycle for eachlimb. Kinematic data from the 15-second walking Ankle instability and balance training  611  and jogging trials were averaged and 95%confidence intervals for each of the 100 datapoints were calculated for pretest and posttestmeasures for the balance training and controlgroups. Inversion angular and shank rotationvelocities were calculated from their respectivethree-dimensional kinematic positional data. Forwalking trials, the first 60% of the gait cycle wasdefined as stance phase and the last 40% wasdefined as swing. 27 For jogging, the stance phaseof the gait cycle was defined as the first 40% andthe swing phase the last 60%. 28 Assessed for eligibility ( n = 59) Excluded ( n = 28) Not meeting inclusion criteria ( n = 25) Refused to participate ( n = 3) Other reasons ( n = 0) Analysed ( n = 15)Excluded from analysis ( n  =1)Reasons for exclusion: Technical issues with data capture and analysis from walking and jogging trials Lost to follow-up ( n = 0) Discontinued intervention ( n = 1)Reason for discontinuation: One subject sustained an injury during an outside event which excluded the subject from participation Allocated to intervention ( n = 17) Received allocated intervention ( n = 17) Did not receive allocated intervention ( n = 0) Lost to follow-up ( n = 0) Discontinued intervention ( n = 0)Allocated to control ( n = 15) Received allocated intervention ( n = 0) Did not receive allocated intervention ( n = 15) Analysed ( n = 13) Excluded from analysis ( n = 2) Reasons for exclusion: Technical issues with data capture and analysis from jogging trials Randomallocation Analysis Follow-up Enrolment Figure 1  CONSORT Flow diagram. 612  PO McKeon  et al.  In order to assess the coupling relationshipbetween the rearfoot and shank, continuous rela-tive phase measures between the shank and rear-footwere calculated across all 100 points within theof the gait cycle in accordance to previously estab-lished methods. 4,15 The closer the relative phaseangle is to 0  , the more the two segments arecoupled as they have similar spatial and temporalvalues in phase space. 15,29 The closer the relativephase angle is to 180  , the less the two segmentsare coupled as they are moving asynchronously orin opposite directions in phase space. 15,29 A posi-tive relative phase angle indicates that the distalsegment is moving faster in phase space than theproximal. A negative relative phase angle indicatesthat the proximal is moving faster than the distal.The mean absolute relative phase was calculatedto compare the overall coupling relationshipbetween the shank and rearfoot throughout theentire time window. 4,29 This measure provides asingle measure which represents the average cou-pling relationship across the entire gait cyclebetween the rearfoot and shank. The deviationphase was also calculated, 4,29,30 which allowedfor the assessment of variability within the cou-pling relationship between the shank and rearfootthroughout the entire time window. A lower devia-tion phase indicated a greater amount of stabilityof the coupling relationship between the shankand rearfoot. The mean of the five trials for eachmeasure was used for statistical analysis. Instrumented arthrometry Instrumented measurement of ankle–subtalar joint stability was performed using a portableankle arthrometer (Blue Bay Research Inc.,Navarre, FL, USA). 19 Subjects underwent threetrials of instrumented arthrometry for anteriorlaxity and three trials for inversion rotation inaccordance to a previously established protocol. 19 Dependent variables included anterior laxity(mm), anterior stiffness (N/mm), inversion laxity(  ), and inversion stiffness (N  mm/  ). Balance training programme The progressive balance training programmewas designed to challenge a subject’s ability tomaintain single-limb stance while performing var-ious balance activities. Each subject participated in12 supervised sessions, which lasted approximately20 minutes. 22 During each session, subjects per-formed single-limb dynamic balance activitiesdesigned to challenge recovery of single-limb bal-ance efficiently after landing from a hop and toeffectively develop spontaneous strategies to exe-cute movement goals. 22 As a subject developedproficiency within the programme, the task andenvironmental constraints placed on the sensori-motor system were progressively increased. Eachactivity contained seven levels of difficultythrough which the subjects advanced. Thesenovel activities were intended to promote therestoration of functional variability within thesensorimotor system. Activities include: (1) hopto stabilization, (2) hop to stabilization andreach, (3) unanticipated hop to stabilization, (4)progressive single-limb stance balance activitieswith eyes open, and (5) progressive single-limbstance activities with eyes closed. 22 Statistical analysis The independent variables were group (balancetraining, control) and test (pretest, posttest). Therewere three variables of interest throughout the100-point window in both the walking and joggingconditions: degrees of rearfoot inversion/eversion,shank rotation, and the continuous relative phaseangle for the coupling relationship between rear-foot inversion/eversion and shank rotation.For each of these measures, the entire gait cyclewas considered. 27 In order to determine poten-tially meaningful differences, the means and asso-ciated 95% confidence intervals for each of the100 data points were calculated across the entiregait cycle for group (balance training, control) andtime (pretest, posttest). Throughout the entire gaitcycle, windows were identified where the confi-dence interval bands for the two groups and thepre- and posttest measures did not cross eachother. Mean differences between groups werethen calculated at the intervals identified as beingdifferent. Microsoft Excel 2003 (MicrosoftCorporation, Redmond, WA, USA) was used forgraphing all means and confidence intervals.The mean absolute relative phase and deviationphase for each group were also calculated for pre-test and posttest for walking and jogging. Themean absolute relative phase and the deviation Ankle instability and balance training  613
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