Assessing recovery and establishing prognosis following total knee arthroplasty
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Assessing recovery and establishing prognosis following total knee arthroplasty

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    Assessing recovery and establishing prognosis following total knee arthroplasty Assessing recovery and establishing prognosis following total knee arthroplasty Document Transcript

    • Research Report Assessing Recovery and EstablishingDM Kennedy, BScPT, MSc, is Man- Prognosis Following Total Kneeager of Program Development, Hol-land Orthopaedic & Arthritic Cen- Arthroplastytre, Sunnybrook Health SciencesCentre, 43 Wellesley St E, Toronto, Deborah M Kennedy, Paul W Stratford, Daniel L Riddle, Steven E Hanna,Ontario, Canada M4Y 1H1. She also Jeffrey D Gollishis Instructor, Department of Physi-cal Therapy, University of Toronto,and Part-time Assistant Clinical Pro- Background and Purposefessor, School of Rehabilitation Sci- Information about expected rate of change after arthroplasty is critical for makingence, McMaster University, Hamil-ton, Ontario, Canada. Address all prognostic decisions related to rehabilitation. The goals of this study were: (1) tocorrespondence to Ms Kennedy at: describe the pattern of change in lower-extremity functional status of patients overd.kennedy@utoronto.ca. a 1-year period after total knee arthroplasty (TKA) and (2) to describe the effect ofPW Stratford, PT, MSc, is Profes- preoperative functional status on change over time.sor, School of Rehabilitation Sci-ence, and Associate Member, De- Subjectspartment of Clinical Epidemiology Eighty-four patients (44 female, 40 male) with osteoarthritis, mean age of 66 yearsand Biostatistics, McMaster Uni-versity, and Scientific Affiliate, De- (SD 9), participated.partment of Surgery, SunnybrookHealth Sciences Centre. MethodsDL Riddle, PT, PhD, FAPTA, is Otto Repeated measurements for the Lower Extremity Functional Scale (LEFS) and theD Payton Professor, Department Six-Minute Walk Test (6MWT) were taken over a 1-year period. Data were plotted toof Physical Therapy, Virginia Com- examine the pattern of change over time. Different models of recovery were ex-monwealth University, Medical plored using nonlinear mixed-effects modeling that accounted for preoperative statusCollege of Virginia Campus, Rich-mond, Va. and gender.SE Hanna, PhD, is Associate Pro- Resultsfessor, Department of Clinical Ep-idemiology and Biostatistics and Growth curves were generated that depict the rate and amount of change in LEFSSchool of Rehabilitation Science, scores and 6MWT distances up to 1 year following TKA. The curves account forMcMaster University. preoperative status and gender differences across participants.JD Gollish, BASc, MD, FRCSC, isMedical Director, Holland Ortho- Discussion and Conclusionpaedic & Arthritic Centre, Sunny- The greatest improvement occurred in the first 12 weeks after TKA. Slower improve-brook Health Sciences Centre, andAssistant Professor, Department of ment continued to occur from 12 weeks to 26 weeks after TKA, and little improve-Surgery, Faculty of Medicine, Uni- ment occurred beyond 26 weeks after TKA. The findings can be used by physicalversity of Toronto. therapists to make prognostic judgments related to the expected rate of improvement[Kennedy DM, Stratford PW, Rid- following TKA and the total amount of improvement that may be expected.dle DL, et al. Assessing recoveryand establishing prognosis follow-ing total knee arthroplasty. PhysTher. 2008;88:22–32.]© 2008 American Physical TherapyAssociation Post a Rapid Response or find The Bottom Line: www.ptjournal.org22 f Physical Therapy Volume 88 Number 1 January 2008
    • Recovery and Prognosis Following Total Knee ArthroplastyK nee osteoarthritis (OA) is one of The expected rate of change in func- WOMAC and LEFS, site of arthroplasty the most frequent causes of dis- tional status following surgery is of was not a predictor and preoperative ability.1 For patients with end- significant interest to both research- levels of function were met and ex-stage OA, which is characterized by ers and clinicians. Researchers can ceeded much earlier (1–3 weeks) thansevere pain and poor functional sta- apply this information to schedule what was observed for the perfor-tus, total knee arthroplasty (TKA) is optimal outcome assessment points mance measures (6 –9 weeks post-recognized as a highly beneficial and in a randomized trial, and clinicians operatively). A ceiling effect aroundcost-effective treatment.2– 4 Despite can use this knowledge to bench- 9 to 10 weeks was observed with re-the benefits and the rise in utilization mark progress and to make prognos- spect to the TUG, indicating that thisof this procedure,5 questions remain tic decisions related to rehabilitation measure is not useful for detectingunanswered, particularly in the area needs. Studies investigating exercise- improvement beyond 3 months. A lim-of rehabilitation services. The Na- based interventions have often as- itation of these studies was the inabil-tional Institutes of Health consensus sessed outcome up to 1 year after ity to predict when patients hadstatement on total knee replacement arthroplasty.16 –18 Long-term follow-up reached their maximal functional lev-indicates that the use of rehabilita- is essential for some interventions spe- els as measured via self-report or gaittion services is one of the most un- cific to arthroplasty to prevent prob- performance. We found no other stud-derstudied aspects of the periopera- lems such as prosthetic failure. How- ies that determined the specific timetive management of this population.6 ever, extended follow-up times are point of maximal functional return fol- likely not necessary for interventions lowing knee arthroplasty.One issue that clinicians face when that lead to rapid changes in a patient’streating patients with TKA is the de- status over a relatively short period of The purpose of this study, therefore,cision as to which outcome mea- time. In a study examining the first 4 was to build on the existing worksures to use for assessment of func- months of recovery in patients fol- by profiling the change in lower-tional recovery. A growing body of lowing hip and knee replacement, extremity functional status of partic-literature indicates that self-report Kennedy et al12 found that the greatest ipants during the first year followingmeasures of function provide differ- period of postoperative change oc- primary TKA using the 6MWT andent information than physical perfor- curred in the first 9 weeks. the LEFS. Although the WOMAC ismance measures in people with OA one of the leading outcome mea-or arthroplasty.7–11 Physical perfor- Numerous studies7,12,19 –26 have ex- sures for people with arthroplasty,mance and self-report measures may amined recovery patterns after TKA the LEFS has demonstrated cross-assess different aspects of physical with differing periods of follow-up. sectional and longitudinal validityfunction.12 In the arthroplasty litera- Several authors19,21,23 provided graph- equal to or better than that of theture, many studies have used only ical representations of recovery for WOMAC physical function sub-self-report measures, with the Medi- the WOMAC and SF-36 but did not scale.27 Clinicians find the LEFS easycal Outcomes Study 36-Item Short- include performance measures. The to administer in busy clinic settings,Form Health Survey questionnaire study by Mizner et al24 provided recov- and data are published on its score(SF-36) and the Western Ontario and ery curves for quadriceps femoris mus- interpretation to a greater extentMcMaster Universities Osteoarthritis cle strength (force-generating capac- than for the WOMAC.28 –30 OurIndex (WOMAC) cited most fre- ity), knee range of motion, the TUG, a choice to report LEFS scores alsoquently.13 Although performance- timed stair-climbing test, SF-36 sum- was influenced by the growing bodybased measures appear to provide mary scores, and the Knee Outcome of evidence indicating that themore information about actual phys- Survey–Activities of Daily Living Scale WOMAC lacks factorial validity.31–34ical ability, consensus is still needed at 1, 2, 3, and 6 month postoperative We chose the 6MWT because it ison what activities should be in- time points. Two studies12,22 exam- recognized as a useful measure ofcluded for patients with hip or knee ined recovery in the first 4 months functional status and exercise capac-OA.14 Previously, Kennedy et al15 in- after total hip and knee arthroplasty ity in elderly adults.35–38 Speed andvestigated the measurement proper- using hierarchical linear modeling to distance abilities are both importantties of the Six-Minute Walk Test illustrate trajectories of change. Signif- considerations for community mobil-(6MWT), the Timed “Up & Go” Test icant differences in the patterns and ity in older adults. Older adults need(TUG), a fast self-paced walk test, predictors of recovery were found to be able to walk, on average, 300 mand a stair performance measure in when comparing the WOMAC and the during the performance of instru-subjects with arthroplasty. Lower Extremity Functional Scale mental activities of daily living.39 (LEFS) with the TUG, a timed stair test, and the 6MWT. In the case of theJanuary 2008 Volume 88 Number 1 Physical Therapy f 23
    • Recovery and Prognosis Following Total Knee ArthroplastyThe specific study goals of this study Mr Smith likely to reach his maxi- participated in a progressive pro-were: (1) to describe the pattern of mum functional level? gram of range of motion, strengthen-change in lower-extremity func- ing exercises, proprioceptive exer-tional status as measured by the LEFS Method cises, and functional training. At theand 6MWT of participants over a All data were collected as part of a time of this study, the majority of1-year period after TKA and (2) to larger observational study conducted the patients were transferred fromexplore the effect of preoperative at a tertiary care orthopedic facility the acute care floor on the fourth orfunctional status on the pattern of in Toronto, Canada, from Novem- fifth postoperative day to the on-sitechange. Clinicians need prognostic ber 2001 to February 2004. Desig- short-term rehabilitation unit to con-evidence to educate their patients nated a Centre of Excellence for tinue the aforementioned programabout expected time to reach their hip and knee replacement, the facil- for a maximum length of stay of 7maximal recovery. Having this knowl- ity is one of the largest-volume ar- days. All patients were dischargededge allows patients and their family throplasty sites in the country. Pa- with a home exercise program, andmembers to judge progress over time tients were recruited prospectively some patients received additionaland have realistic expectations.40 We either at point of consultation with physical therapy treatment in theprovide a brief illustration using a hy- the orthopedic surgeon or at the community.pothetical clinical vignette to illustrate preadmission visit prior to surgery.how the study results can be applied Only those patients with follow-up Subjectsto assist clinicians in making prognos- for the first year postoperatively Preoperatively, 88 patients con-tic decisions when treating patients were eligible for this study. During sented to participate in the study;following TKA. the larger study, there were periods however, only 84 patients contrib- of interruption of recruitment and uted LEFS and 6MWT data follow-Clinical Practice Vignette tracking, such as with the outbreak ing arthroplasty. Table 1 provides aMr Smith, a 67-year-old with a long- of severe acute respiratory syndrome summary of the participants’ char-standing history of OA of the right in Toronto from April to June 2003. acteristics. Female participants hadknee, is referred for rehabilitation 2 At the height of the outbreak, thou- a greater body mass indexweeks after a right TKA. As part of sands of people were quarantined, and (t82 2.05, P2 .042); male partici-the initial assessment, you adminis- there were significant restrictions on pants had higher LEFS scorester the LEFS and the 6MWT and ob- patient-related activities in hospitals (t82 3.02, P2 .003) and walkedtain values of 28 LEFS points and for several months. None of the pa- greater distances in 6 minutes261 m, respectively. These values are tients took part in other interventional (t82 5.28, P2 .001).substantially lower than Mr Smith’s studies. However, the current samplepreoperative values of 40 points overlaps samples described in earlier Designfor the LEFS and 507 m of the 6MWT. publications, which used data from We applied a prospective study de-Mr Smith mentions that he has a va- the same observational study.10,12,15,22 sign with repeated measurementscation cruise scheduled in 8 weeks over a period of approximately 1and asks what his function is likely to Participant eligibility criteria in- year following arthroplasty. To pro-be at that time. He also wonders cluded the following: diagnosis of vide an accurate model of changewhat his maximum functional status OA, scheduled for primary TKA; suf- over time, participants’ follow-upis likely to be and when he will reach ficient language skills to communi- measurements were not standard-this level of functioning. Questions cate in written and spoken English; ized to be at the same time pointsarising from the assessment include and absence of neurological, cardiac, during the first 4 postoperativethe following: (1) How much change or psychiatric disorders or other months, the period of greatestis required in these measures to be medical conditions that would signif- change.7,12 When measurementsreasonably certain that a true change icantly compromise physical func- take place at the same spaced timehas occurred? (2) What factors tion. Ethics approval for the study points, the shape of the curve is dic-should be considered in scheduling was received from the institution’s tated by the choice of time points.the next assessment, and when research ethics review board, and all Three assessments were plannedshould it occur? (3) What is Mr participating patients provided writ- during this time frame, and subse-Smith’s lower-extremity functional ten informed consent. Patients re- quently participants were assessedstatus likely to be in 8 weeks? (4) ceived standardized inpatient treat- at points corresponding to the nextWhat is Mr Smith’s maximum func- ment following a primary total knee surgeon follow-up appointments,tional status likely to be? (5) When is care pathway. All patients were per- which typically might fall at 6 or 9 mitted to be full weight bearing and months and then 12 months postop-24 f Physical Therapy Volume 88 Number 1 January 2008
    • Recovery and Prognosis Following Total Knee Arthroplastyeratively. As noted earlier, this sched- Table 1.uling of assessments facilitated ob- Preoperative Descriptive Statistics Expressed as Quartile Values (25th, 50th, 75th)taining good estimates of the rate of Measure Female Malechange as well as the limit values or Participants Participantspoint of maximal return. (n 44) (n 40) Age (y) 60, 64, 71 61, 67, 74Measures 2 Body mass index (kg/m ) 29, 32, 34 27, 29, 32Previous work7,8,10 has suggestedthat self-report and performance- Prearthroplasty Lower Extremity 21, 27, 38 26, 38, 45 Functional Scale scorebased measures capture different,but related, aspects of lower- Prearthroplasty Six-Minute Walk 312, 353, 416 397, 501, 552extremity functional status. Accord- Test distance (m)ingly, we chose 2 measures of lower-extremity functional status—one aself-report measure and the other a ized 6MWT has become a popular if a patient following arthroplastyperformance-based measure. measure of lower-extremity func- missed an appointment due to a tional limitation for patients with OA change in his or her schedule; how-LEFS. Conceived by Binkley and col- of the lower extremity and those ever, it would be a problem if theleagues,28 the LEFS is a 20-item self- progressing to arthroplasty.7,8,15,47,48 patient missed the appointment be-report measure of lower-extremity Participants were instructed to cover cause of poor functioning due to anfunctional status. It includes items as much distance as possible during increase in pain. Therefore, we alsothat assess the disablement concepts the 6-minute time frame. The test examined the pattern of missing dataof functional limitation (activity lim- was conducted on a measured 46-m across the time points.itation) and disability (participation uncarpeted rectangular indoor cir-restriction).41,42 Each item is scored cuit. The course was marked off in Based on the plotted data, we devel-on a 5-point scale (0 – 4). Accord- meters, and the distance traveled by oped and tested several nonlinearingly, total LEFS scores can vary from each participant was measured to models of change that related the0 to 80 points, with higher scores the nearest meter. Standardized en- dependent variable of functional sta-being associated with greater levels couragement—“You are doing well, tus— either LEFS scores or 6MWTof functional status. Considerable keep up the good work”—was pro- distances—to the independent vari-support for this measure’s reliability, vided at 60-second intervals.49 The able of number of weeks after arthro-validity, and ability to detect change outcome was the distance walked in plasty.50 The equation for our non-exists both for general lower- 6 minutes. A previous investigation linear change model (model 1) was:extremity conditions43– 45 and spe- with a similar group of subjects dem-cific to patients with OA progressing onstrated the reliability and validity Functional status (LEFS or 6MWT)to knee or hip arthroplasty.27,29,46 of data for this measure (intraclassThe test-retest reliability estimate correlation coefficient .94 for test- limit (y0 limit)(intraclass correlation coefficient, retest reliability, SEM 26.3 m, and e( e(lnchange rate) weeks),type 2,1) for the LEFS derived from a MDC90 61.34 m).15sample of patients following arthro-plasty was .85, the standard error of Data Analysis where the functional status variablemeasurement (SEM) was 3.7 LEFS Before beginning the modeling, we is the LEFS or 6MWT value, e is thepoints, and the minimal detectable plotted the data to gain an impres- base of natural logarithms (approxi-change at the 90% confidence level sion of the pattern of change over mately 2.71828), weeks is the num-(MDC90) was estimated to be 9 LEFS time. Although one of the benefits of ber of weeks after arthroplasty; y0 ispoints.28 In patients undergoing using mixed-effects modeling is that the parameter that represents theknee or hip arthroplasty, the LEFS it does not require the number and y-intercept value; limit is the param-has been shown to detect change as timing of observations to be the eter that represents the asymptote orwell as or better than the WOMAC same across all participants, missing maximum LEFS or 6MWT value, andphysical function subscale.27,46 data are still important. Bias will re- lnchange rate is the natural log of sult if the cause of the missing data the change rate (“change rate” re-6MWT. Originally conceived as an points is related to the outcome fers to the rate of improvement atoutcome measure for people with that would have been observed. For which patients approach their max-respiratory problems, the standard- example, it would not be a problem imum functional status). We esti-January 2008 Volume 88 Number 1 Physical Therapy f 25
    • Recovery and Prognosis Following Total Knee ArthroplastyTable 2. All knee prostheses were posteriorSummary of Nonlinear Analysis Without Covariates stabilized, with the majority ce- mented. At our institution, the peri- Female Male Participants Participants operative management and rehabili- (n 44) (n 40) tation protocols are not influenced Lower Extremity Functional Scale analysis by prosthesis selection or method of fixation. Postoperatively, one partic- Parameters of average changea ipant developed a documented deep Limit (SE) 54.0 (2.3) 60.4 (2.3) vein thrombosis. None of the partic- Y-intercept (SE) 10.4 (2.6) 19.0 (2.7) ipants required revision surgery Change rate (SE) 1.7 (0.1) 1.8 (0.1) within the 1-year follow-up period. Standard deviation of individual differences Sixty-seven of the 84 participants from average composing the study sample were Limit 12.1 11.6 assessed within 17 days of arthro- Y-intercept 7.9 10.2 plasty. Of these 67 participants, 66 Within-patient variation 7.6 6.7 completed the LEFS and 44 per- formed the 6MWT during this 17-day 6-Minute Walk Test analysis period. The mean ( SD) preopera- Parameters of average change tive LEFS score for those participants Limit (SE) 467.3 (15.4) 577.7 (18.2) who contributed LEFS data within 17 Y-intercept (SE) 154.7 (22.2) 185.7 (22.9) days of arthroplasty was 32.3 points (SD 12.1) compared with 33.1 Change rate (SE) 2.0 (0.1) 1.7 (0.1) points (SD 14.4) for those partici- Standard deviation of individual differences pants who were not assessed within from average this period (t82 0.22, P2 .83). Sim- Limit 84.7 94.6 ilarly, the mean preoperative dis- Y-intercept 84.5 68.7 tance for those participants who Within-patient variation 40.7 48.8 contributed 6MWT data within 17a days of arthroplasty was 428.4 m Parameters of average change fixed effects. Some parameters (ie, change rate) have only fixedeffects, indicating that there are no significant individual differences. SE standard error. (SD 114.8) compared with 393.4 m (SD 105.8) for participants who did not contribute 6MWT data within this period (t82 1.46, P2 .15). Fi-mated the parameters using the rate coefficients. Finally, because nally, the mean LEFS score assessednonlinear mixed-effects modeling previous work has shown that func- within 17 days of arthroplasty waspackage in S-Plus.50 A mixed-effects tional status levels differ by gen- 26.0 points (SD 10.7) for the partic-approach indicates that some param- der,22,51 we created separate models ipants who contributed 6MWT dataeters have both fixed and random for female and male participants. during this period compared witheffects. The fixed effects describe 16.7 points (SD 10.2) for the partic-the average change in the popula- Results ipants who were assessed duringtion (in this case, the sample of All participants completed baseline this interval but not able to contrib-participants who underwent TKA), preoperative assessments and had a ute 6MWT data (t64 3.45, P2 .001).and the random effects describe minimum of 2 visits postoperatively. Post-arthroplasty assessments follow-the individual differences among To summarize, 31 participants were ing the 3-week mark yielded approx-participants. We explored dif- assessed 3 times, 18 were assessed 4 imately equal representation of LEFSferent models, and our final model times, 9 were assessed 5 times, and 2 and 6MWT data points.specified the limit, y-intercept, and had 6 visits, with the rest of the sam-change rate parameters as fixed ef- ple having 2 visits. Supplemental Table 2 reports the fixed-effects pa-fects and the limit and y-intercept as Figures 1 and 2 (available online rameter values and the variation inrandom effects. Next, we examined only at www.ptjournal.org) provide random-effects parameter values forthe effect of including preoperative spaghetti plots showing the data the LEFS and 6MWT obtained fromLEFS scores and 6MWT distances points and change profiles for each model 1. Also reported in Table 2 areon the limit, y-intercept, and change participant. the standard deviations of individual26 f Physical Therapy Volume 88 Number 1 January 2008
    • Recovery and Prognosis Following Total Knee Arthroplastydifferences from the estimated aver- Aage parameter values. For example, 80the standard deviation of individual 70differences from the average LEFSlimit value for the female partici- Predicted LEFS Score 60pants was 12.1. Accordingly, 68%of the female participants displayed 50limit values from 42 to 66 LEFS 40points. The curves shown in Figure 1were generated by substituting the 30 Male Participantsparameter estimates reported in Female ParticipantsTable 2 into model 1. This figure 20shows that most of the change oc- 10curred in the first 16 weeks afterarthroplasty. 0 0 4 8 12 16 20 24 28 32 36 40 44 48 52Our exploration of the effect preop- Weeks After Arthroplastyerative functional status scores had Bon limit values, y-intercept, and 700change rate coefficients revealedthat limit values only were signifi- 600 Predicted 6MWT Distance (m)cantly affected. This finding indi-cates that preoperative levels of 500function help to predict the maximalfunctional status that patients attain 400postoperatively. Better preoperative Male Participants 300scores will be associated with pa- Female Participantstients attaining higher maximum 200postoperative levels of function. Ac-cordingly, our revised model (model 1002) was as follows: 0Functional status (LEFS or 6MWT) 0 4 8 12 16 20 24 28 32 36 40 44 48 52 Weeks After Arthroplasty (limit preoperative function) Figure 1. (A) Change in Lower Extremity Functional Scale (LEFS) scores over time. (B) Change in (y0 limit 6-Minute Walk Test (6MWT) distances over time. preoperative function) 2A represents LEFS scores for male over a 1-year period for patients who e( e(lnchange rate) weeks), participants with a preoperative underwent TKA and received stan- LEFS score of 45 points (ie, third dardized inpatient physical therapywhere is the regression coefficient quartile value reported in Tab. 1). care for 1 to 2 weeks (acute andassociated with preoperative func- The 16-week value of 61 points on subacute short-term rehabilitation).tional status level. Gender- and this curve was obtained by substitut- The subsequent discussion will firstmeasure-specific coefficients are re- ing the coefficient values reported in provide a synthesis of our findingsported in Table 3. Figures 2 and 3 Table 3 into model 2 and applying a and then illustrate applications ofdisplay the change curves for the preoperative value of 45 points. this information by referring to theLEFS and 6MWT adjusted for preop- Again, these figures show that most vignette introduced early in thiserative scores. The 3 curves pre- of the change occurred within the article.sented in each figure depict the first 16 weeks after arthroplasty.gender- and measure-specific change To our knowledge, this is the firstcurves based on the preoperative Discussion study to sample patients at differentquartile values reported in Table 1. Our goal was to describe the change time points over a 1-year period afterFor example, the top curve in Figure in lower-extremity functional status TKA and to apply a nonlinear mixed-January 2008 Volume 88 Number 1 Physical Therapy f 27
    • Recovery and Prognosis Following Total Knee ArthroplastyTable 3. 6MWT distances were influencedSummary of Nonlinear Analysis With Preoperative Score as a Covariate only by their respective preoperative values. Accordingly, it is important Female Male Participants Participants that clinicians take the preoperative (n 44) (n 40) value into account when making a Lower Extremity Functional Scale analysis prognosis concerning a patient’s fi- nal level of lower-extremity func- Parameters of average change tional status. Limit (SE)a 38.1 (5.3) 42.2 (5.6) Preoperative ( ) (SE) 0.50 (0.1) 0.50 (0.1) As illustrated in the section on re- Y-intercept (SE) 10.3 (2.6) 19.0 (2.7) sponses to the clinical practice vi- gnette, we believe that graphical rep- Change rate (SE) 1.7 (0.1) 1.8 (0.1) resentations of recovery can be very Standard deviation of individual differences useful in assisting clinicians to from average benchmark recovery. The graphs Limit 10.4 9.8 can be used to compare measured Y-intercept 7.5 10.0 scores obtained on patients with the predicted scores to monitor progress Within-patient variation 7.7 6.7 and guide treatment decisions. Nor- 6-Minute Walk Test analysis mative scores for the measures in Parameters of average change similar populations also are available Limit (SE) 277.2 (55.0) 326.2 (56.9) to enable further benchmarking.52,53 Preoperative ( ) (SE) 0.6 (0.1) 0.5 (0.1) The recovery curves in our study also facilitate determination of the Y-intercept (SE) 154.7 (22.2) 188.6 (22.8) critical time points for measuring Change rate (SE) 2.0 (0.1) 1.7 (0.1) change. For example, if researchers Standard deviation of individual differences were interested in determining the from average effect of interventions on improving Limit 64.0 71.2 the rate of recovery and the maxi- mum level of function attained, they Y-intercept 83.7 71.5 could apply these graphs to assist in Within-patient variation 41.1 48.5 their decision making. More studiesa SE standard error. are needed to determine the effect of various postoperative physical therapy interventions on recovery. Frequently cited assessment points are 3, 6, and 12 months after arthro-effects analysis to model change. we applied a nonlinear mixed-effects plasty13; however, based on the in-Previously, members of our team analysis. The current study’s results formation from the current study, tohave applied hierarchical linear over the initial 16 weeks after TKA assess the effect of interventions, itmodeling and a second-degree poly- compare favorably with those mod- would be important to assess pa-nomial to model LEFS scores and eled using a second-degree poly- tients more frequently in the first 36MWT distances over the first 16 nomial in patients who similarly re- months. In addition, because most ofweeks after arthroplasty.12,22,30 Par- ceived a mixed-effects model of the recovery has occurred by 6ticipants’ LEFS scores and 6MWT physical therapy intervention with months, researchers might decide todistances increased rapidly over unknown parameters including out- not assess individuals beyond thisthis period, and a second-degree patient treatment and natural point to avoid unnecessary costs.polynomial fit the data well within recovery.22,30this interval. However, a second-degree polynomial specifies a parab- Our study also explored the effect ofola that clearly does not represent preoperative LEFS scores and 6-MWTthe change pattern of LEFS scores distances as potential predictors ofor 6MWT distances over a 1-year y-intercept, change rate, and limitperiod, and it is for this reason that values. Maximal LEFS scores and28 f Physical Therapy Volume 88 Number 1 January 2008
    • Recovery and Prognosis Following Total Knee ArthroplastyResponses to the Clinical Practice AVignette 80How confident can the clinician 70be in the measured values of 28points on the LEFS and 261 m 60on the 6MWT, and how much Predicted LEFS Scorechange is required in these mea- 50 Preop LEFS 45sures to be reasonably certain 40 Preop LEFS 38that a true change has occurred? Preop LEFS 26To answer these questions, the re- 30sults from 2 other studies that 20examined the reliability of data forthe LEFS29 and 6MWT,15 whose 10estimates are reported in theMethod section, are used. For exam- 0 0 4 8 12 16 20 24 28 32 36 40 44 48 52ple, the 90% confidence level (ie, 1 Weeks After ArthroplastySEM 1.65) for an estimate of the“true score” is 6.1 points for the BLEFS and 43.4 m for the 6MWT. We 70can say with 90% confidence thatMr Smith’s true LEFS score is likely to 60fall between 21.9 and 34.1 points Predicted LEFS Score 50and that his true 6MWT distance islikely to lie between 222.9 and 304.4 40m. To identify the minimal detect- Preop LEFS 38able change (MDC), the confidence 30 Preop LEFS 27values reported are multiplied by Preop LEFS 21the square root of 2. For example, 2090% of patients who are truly stable 10will display random fluctuations,when assessed on multiple occa- 0sions, of less than 9 points on the 0 4 8 12 16 20 24 28 32 36 40 44 48 52LEFS and 61.3 m on the 6MWT. Ac- Weeks After Arthroplastycordingly, a change of 9 points ormore on the LEFS and of 61.3 m or Figure 2.more on the 6MWT is interpreted (A) Change in Lower Extremity Functional Scale (LEFS) scores for male participants, adjusted for preoperative (preop) LEFS scores. (B) Change in LEFS scores for femaleas evidence of a true change. Esti- participants, adjusted for preoperative LEFS scores.mates obtained from this approachoften are referred to as MDC withthe confidence value subscripted(eg, MDC90).54 a change of 9 points. This informa- week is required for an expected tion is coupled with the curve for change of 61.3 m.What factors should the clinician patients with a preoperative LEFSconsider in scheduling the next value of 38 (ie, the curve closest to What is Mr Smith’s lower-assessment, and when should it Mr Smith’s value). Referring to the extremity functional status likelyoccur? Clearly, many factors, in- middle curve presented in Figure 2A, to be in 8 weeks? To answer thiscluding feasibility, influence the it appears that a change of 9 LEFS question, the clinician can inspectchoice of reassessment interval. Two points occurs between 2 and 4 the predicted functional status val-factors specific to the context of this weeks postoperatively. Accordingly, ues for 10 weeks after TKA (the firstarticle are MDC and the interval over the interval between assessments for assessment occurred at the 2-weekwhich a typical patient is likely to this specific instance is approxi- mark). For a person with Mr Smith’sachieve a change equal to the MDC. mately 2 weeks. Applying the same preoperative values, the expectedMr Smith’s 2-week postoperative approach to 6MWT distance, it ap- LEFS and 6MWT scores are approxi-LEFS value was 28, and the MDC90 is pears that a minimum interval of 1 mately 52 points and 520 m, respec-January 2008 Volume 88 Number 1 Physical Therapy f 29
    • Recovery and Prognosis Following Total Knee Arthroplasty A What is Mr Smith’s maximum 700 functional status level likely to be? Recalling that a patient’s pre-Predicted 6MWT Distance (m) 600 operative level of function is a deter- minant of his or her postoperative 500 maximal function level, Figures 2A 400 and 3A are referenced to answer this Preop 552 m question. Because Mr Smith had a 300 Preop 501 m preoperative score of 40 points on Preop 397 m the LEFS, the middle curve is se- 200 lected, and this would lead to a pre- 100 diction that Mr Smith would have a terminal LEFS score of just over 60 0 points. In terms of the 6MWT, using 0 4 8 12 16 20 24 28 32 36 40 44 48 52 a similar approach, the maximal dis- Weeks After Arthroplasty tance that Mr Smith would be able to cover would be around 600 m. B 600 When is Mr Smith likely to reach his maximum functional level? Predicted 6MWT Distance (m) 500 In both the case of the LEFS and 6MWT, Mr Smith would reach his 400 maximum functional level sometime between 6 and 7 months. Preop 416 m 300 Preop 353 m Preop 312 m Study Limitations 200 One limitation is that all participants in the change study were able to 100 complete the LEFS and 6MWT pre- operatively. Accordingly, the gener- alizability of our findings are re- 0 0 4 8 12 16 20 24 28 32 36 40 44 48 52 stricted to patients who are able to complete these tests preoperatively Weeks After Arthroplasty and who have preoperative charac-Figure 3. teristics similar to those reported in(A) Change in 6-Minute Walk Test (6MWT) distances for male participants, adjusted for Table 1. A second limitation is thatpreoperative (preop) 6MWT distances. (B) Change in 6MWT distances for female fewer participants provided 6MWTparticipants, adjusted for preoperative (preop) 6MWT distances. data than LEFS data within a few weeks of arthroplasty. Our analysis showed that participants who weretively. Although the meaning of ing up or down 10 stairs or lifting an assessed within 17 days of arthro-520 m is straightforward, the inter- object such as a bag of groceries plasty and who did not contributepretation of an LEFS score of 52 from the floor; and (3) “no difficulty” 6MWT data during this period hadpoints is not intuitively obvious, and sitting for 1 hour, putting on shoes significantly lower LEFS scores at thisthe clinician will need to translate or socks, or walking short distances. time point. A consequence of thisthis number into a narrative. Based These data will likely assist the clini- missing value pattern is that the pre-on information provided in a previ- cian in advising Mr Smith on what he dicted 6MWT distances over the firstous article,30 a person with an LEFS can expect regarding his mobility, several weeks after arthroplasty arescore of approximately 52 points which will likely assist Mr Smith in not applicable to the entire sample,will have: (1) “moderate difficulty” deciding whether he should con- but rather are restricted to those par-with heavy activities around the sider rescheduling his trip. ticipants who were capable of per-house, recreational activities, walk- forming the 6MWT within this timeing a mile, or standing for 1 hour; frame. This could have resulted in(2) “a little bit of difficulty” with go- overestimation of the predicted30 f Physical Therapy Volume 88 Number 1 January 2008
    • Recovery and Prognosis Following Total Knee Arthroplastyscores for the 6MWT during this Neil Reid for data collection, project man- 14 Terwee CB, Mokkink LB, Steultjens MP, agement, and clerical support. Dekker J. Performance-based methods fortime frame. measuring the physical function of pa- This article was received February 11, 2007, tients with osteoarthritis of the hip or and was accepted August 20, 2007. knee: a systematic review of measurementAlthough mixed-effects modeling properties. Rheumatology (Oxford). 2006;will stabilize the estimates of pa- DOI: 10.2522/ptj.20070051 45:890 –902.tients who have limited data by an- 15 Kennedy DM, Stratford PW, Wessel J, et al. Assessing stability and change of four per-choring them to the group average, formance measures: a longitudinal studyit should be noted that 66% of the evaluating outcome following total hip References and knee arthroplasty. BMC Musculoske-participants in this study were as- let Disord. 2005;6:3. 1 Peat G. Knee pain and osteoarthritis insessed only 2 or 3 times. More than older adults: a review of community bur- 16 Avramidis K, Strike PW, Taylor PN, Swain50% of the participants were not as- den and current use of primary health ID. Effectiveness of electric stimulation of care. Ann Rheum Dis. 2001;60:91–97. the vastus medialis muscle in the rehabil-sessed for both LEFS and 6MWT near itation of patients after total knee arthro- 2 Caracciolo B, Giaquinto S. Determinants ofto or at the end of the study termi- the subjective functional outcome of total plasty. Arch Phys Med Rehabil. 2003; joint arthroplasty. Arch Gerontol Geriatr. 84:1850 –1853.nation. Finally, it was not possible to 2005;41:169 –176. 17 Beaupre LA, Davies DM, Jones CA, Cinatsdescribe with accuracy the patients JG. Exercise combined with continuous 3 Hartley RC, Barton-Hanson NG, Finley R,who were potentially eligible for the Parkinson RW. Early patient outcomes af- passive motion or slider board therapy ter primary and revision total knee arthro- compared with exercise only: a random-study due to study interruptions ized controlled trial of patients following plasty. J Bone Joint Surg Br. 2002;84:such as the outbreak of severe acute 994 –999. total knee arthroplasty. Phys Ther. 2001;81:1029 –1037.respiratory syndrome. 4 Lavernia CJ, Guzman JF, Gachupin-Garcia A. Cost effectiveness and quality of life in 18 Kramer JF, Speechley M, Bourne R, Rora- knee arthroplasty. Clin Orthop. 1997;(345): beck C. Comparison of clinic-and home-Conclusion 134 –139. based rehabilitation programs after total knee arthroplasty. Clin Orthop. 2003;Our findings demonstrated that the 5 Kurtz S, Mowat F, Ong K, et al. Prevalence 410:225–234.greatest improvement for the LEFS of primary and revision total hip and knee arthroplasty in the United States from 19 Fitzgerald JD, Orav EJ, Lee TH, et al. Pa-and 6MWT occurred in the first 12 1990 through 2002. J Bone Joint Surg Am. tient quality of life during the 12 months 2005;87:1487–1497. following joint replacement surgery.weeks after TKA. Improvement con- Arthritis Rheum. 2004;51:100 –109.tinued to occur from 12 to 26 weeks 6 NIH consensus statement on total knee re- placement, December 8 –10, 2003. J Bone 20 Fortin PR, Clarke AE, Joseph L, et al. Out-after TKA, although at a slower rater, Joint Surg Am. 2004;86:1328 –1335. comes of total hip and knee replace- ment: preoperative functional status pre-and little improvement occurred be- 7 Parent E, Moffet H. Comparative respon- dicts outcomes at six months after surgery.yond 26 weeks after TKA. The maxi- siveness of locomotor tests and question- Arthritis Rheum. 1999;42:1722–1728. naires used to follow early recovery aftermum scores obtained on the LEFS and total knee arthroplasty. Arch Phys Med Re- 21 Fortin PR, Penrod JR, Clarke AE, et al. Tim- habil. 2002;83:70 – 80. ing of total joint replacement affects clin-6MWT were influenced by their re- ical outcomes among patients with osteo-spective preoperative scores. Clini- 8 Maly MR, Costigan PA, Olney SJ. Determi- arthritis of the hip or knee. Arthritis nants of self-report outcome measures in Rheum. 2002;46:3327–3330.cians can use the recovery curves to people with knee osteoarthritis. Arch Phys Med Rehabil. 2006;87:96 –104. 22 Kennedy DM, Hanna SE, Stratford PW,make prognoses concerning the rate et al. Preoperative function and genderof improvement in functional status 9 Stratford PW, Kennedy DM. Performance predict pattern of functional recovery af- measures were necessary to obtain a com- ter hip and knee arthroplasty. J Arthro-after TKA and the expected time- plete picture of osteoarthritic patients. plasty. 2006;21:559 –566.specific and maximal functional status J Clin Epidemiol. 2006;59:160 –167. 23 Lingard EA, Katz JN, Wright EA, Sledge CB.scores. This information is critical to 10 Stratford PW, Kennedy DM, Woodhouse Predicting the outcome of total knee ar- LJ. Performance measures provide assess- throplasty. J Bone Joint Surg Am. 2004;identifying rehabilitation needs and as- ments of pain and function in patients 86:2179 –2186.sisting patients to set realistic goals with advanced osteoarthritis of the hip or knee. Phys Ther. 2006;86:1489 –1496. 24 Mizner RL, Petterson SC, Snyder-Macklerand plan their lives accordingly. L. Quadriceps strength and the time 11 Terwee CB, van der Slikke RMA, van Lum- course of functional recovery after total mel RC, et al. Self-reported physical func- knee arthroplasty. J Orthop Sports Phys tioning was more influenced by pain than Ther. 2005;35:424 – 436.Ms Kennedy and Dr Gollish provided con- performance-based physical functioning in knee-osteoarthritis patients. J Clin Epi- 25 Mizner RL, Petterson SC, Stevens JE, et al.cept/idea/research design and fund procure- Preoperative quadriceps strength pre-ment. Ms Kennedy, Mr Stratford, Dr Riddle, demiol. 2006;59:724 –731. dicts functional ability one year after totaland Dr Hanna provided writing. Ms Kennedy 12 Kennedy DM, Stratford PW, Hanna SE, et al. knee arthroplasty. J Rheumatol. 2005;32:and Mr Stratford provided data collec- Modeling early recovery of physical function 1533–1539. following hip and knee arthroplasty. BMCtion and project management. Mr Stratford Musculoskelet Disord. 2006;7:100. 26 Aarons H, Hall G, Hughes S, Salmon P.and Dr Hanna provided data analysis. Dr Short-term recovery from hip and knee ar- 13 Ethgen O, Bruyere O, Richy F, et al. throplasty. J Bone Joint Surg Br. 1996;Gollish provided subjects and institutional Health-related quality of life in total hip 78:555–558.liaisons. Ms Kennedy provided facilities/ and total knee arthroplasty: a qualitative and systematic review of the literature. 27 Stratford PW, Kennedy DM, Hanna SE.equipment. Mr Stratford, Dr Riddle, Condition-specific Western Ontario Mc-Dr Hanna, and Dr Gollish provided consul- J Bone Joint Surg Am. 2004;86:963–974. Master Osteoarthritis Index was not supe-tation (including review of manuscript be- rior to region-specific Lower Extremityfore submission). The authors acknowledge Functional Scale at detecting change. J Clin Epidemiol. 2004;57:1025–1032.January 2008 Volume 88 Number 1 Physical Therapy f 31
    • Recovery and Prognosis Following Total Knee Arthroplasty28 Binkley JM, Stratford PW, Lott SA, Riddle 36 Bean JF, Kiely DK, Leveille SG, et al. The 46 Pankaj J, Kramer JF, Birmingham T. Com- DL; for the North American Orthopaedic 6-minute walk test in mobility-limited el- parison of the Western Ontario and Mc- Rehabilitation Research Network. The ders: what is being measured? J Gerontol Master Universities Osteoarthritis Index Lower Extremity Functional Scale (LEFS): A Biol Sci Med Sci. 2002;57:M751–M756. (WOMAC) and the Lower Extremity Func- scale development, measurement proper- tional Scale (LEFS) questionnaires in pa- 37 Enright PL, McBurnie MA, Bittner V, et al. ties, and clinical application. Phys Ther. tients awaiting or having undergone total The 6-min walk test: a quick measure of 1999;79:371–383. knee arthroplasty. Physiother Can. 2005; functional status in elderly adults. Chest. 57:208 –216.29 Stratford PW, Binkley JM, Watson J, Heath- 2003;123:387–398. Jones T. Validation of the LEFS on patients 47 Kreibich DN, Vaz M, Bourne RB, et al. 38 Harada ND, Chiu V, Stewart AL. Mobility- with total joint arthroplasty. Physiother What is the best way of assessing outcome related function in older adults: assess- Can. 2000;52:97–105. after total knee replacement? Clin Orthop ment with a 6-minute walk test. Arch Phys Relat Res. 1996;(331):221–225.30 Stratford PW, Hart DL, Binkley JM, et al. In- Med Rehabil. 1999;80:837– 841. terpreting lower extremity functional status 48 Ouellet D, Moffet H. Locomotor deficits be- 39 Shumway-Cook A, Patla AE, Stewart A, scores. Physiother Can. 2005;57:154 –162. fore and two months after knee arthroplas- et al. Environmental demands associated ty. Arthritis Rheum. 2002;47:484 – 493.31 Faucher M, Poiraudeau S, Lefevre-Colau with community mobility in older adults MM, et al. Algo-functional assessment of with and without mobility. Phys Ther. 49 Guyatt GH, Pugsley SO, Sullivan MJ, et al. knee osteoarthritis: comparison of the 2002;82:670 – 681. Effect of encouragement on walking test test-retest reliability and construct validity performance. Thorax. 1984;39:818 – 822. 40 Rosenbaum PL, Walter SD, Hanna SE, et al. of the WOMAC and Lequesne indexes. Os- Prognosis for gross motor function in ce- 50 Pinheiro JC, Bates DM. Mixed Effects Mod- teoarthritis Cartilage. 2002;10:602– 610. rebral palsy: creation of motor develop- els in S and S-Plus. New York, NY:32 Guermazi M, Poiraudeau S, Yahia M, et al. ment curves. JAMA. 2002;288:1357–1363. Springer Verlag New York; 2000. Translation, adaptation and validation of 41 Jette AM. Toward a common language for 51 Kennedy DM, Stratford PW, Pagura SMC, the Western Ontario and McMaster Uni- function, disability, and health. Phys Ther. et al. Comparison of gender and group dif- versities Osteoarthritis Index (WOMAC) 2006;86:726 –734. ferences in self-report and physical perfor- for an Arab population: the Sfax modified mance measures in total hip and knee ar- WOMAC. Osteoarthritis Cartilage. 2004; 42 Nagi SZ. A study in the evaluation of disabil- throplasty candidates. J Arthroplasty. 12:459 – 468. ity and rehabilitation potential: concepts, 2002;17:70 –77. methods, and procedures. Am J Public33 Kennedy DM, Stratford PW, Pagura SMC, Health Nations Health. 1964:1568 –1579. 52 Lieberman JR, Hawker G, Wright JG. Hip et al. Exploring the factorial validity and function in patients 55 years old: popu- clinical interpretability of the Western On- 43 Alcock GK, Stratford PW. Validation of the lation reference values. J Arthroplasty. tario and McMaster Universities Osteoar- Lower Extremity Functional Scale on ath- 2001;16:901–904. thritis Index (WOMAC). Physiother Can. letic subjects with ankle sprains. Phys- 2003;55:160 –168. iother Can. 2002;54:233–240. 53 Steffen TM, Hacker TA, Mollinger L. Age- and gender-related test performance in34 Thumboo J, Chew LH, Soh CH. Validation 44 Riddle DL, Pulisic M, Sparrow K. Impact of community-dwelling elderly people: Six- of the Western Ontario and McMaster Uni- demographic and impairment-related vari- Minute Walk Test, Berg Balance Scale, versity osteoarthritis index in Asians with ables on disability associated with plantar Timed “Up & Go” Test, and gait speeds. osteoarthritis in Singapore. Osteoarthritis fasciitis. Foot Ankle Int. 2004;25:311–317. Phys Ther. 2002;82:128 –137. Cartilage. 2001;9:440 – 446. 45 Watson CJ, Propps M, Ratner J, et al. Reli- 54 Beaton DE, Bombardier C, Katz JN, Wright35 Bautmans I, Lambert M, Mets T. The six- ability and responsiveness of the lower ex- JG. A taxonomy for responsiveness. J Clin minute walk test in community dwelling tremity functional scale and the anterior Epidemiol. 2001;54:1204 –1217. elderly: influence of health status. BMC knee pain scale in patients with anterior Geriatr. 2004;4:6. knee pain. J Orthop Sports Phys Ther. 2005;35:136 –146.32 f Physical Therapy Volume 88 Number 1 January 2008