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Research Report                    Determinants of Function After                    Total Knee Arthroplasty              ...
T         he utilization rates of elective total knee arthro-               This meta-analysis showed that 89.3% of patien...
Table 1.                                                                        after TKA, accounting for 15% of thePartic...
English. Exclusion criteria included hemiarthroplasties        3 health care professionals (a physical therapist and 2and ...
Table 2.Preoperative and 6-Month Health Statusa                                            Preoperative Health Status     ...
living arrangements), and (3) perioperative variables         Sixty-seven percent of the patients (n 183) did not have(the...
Table 3.Unadjusted Regression Coefficients Relating Preoperative Variables to 6-Month Physical Function for Both the Weste...
Table 4.                                                        Multiple Linear Regression: Western Ontario and McMaster U...
6-month score approximately 12 points higher than that          reported that exercise programs can produce pain reliefof ...
appropriate, given the objective of our study and sup-                       6 Kirwan JR, Currey HL, Freeman MA, et al. Ov...
25 Kantz ME, Harris WJ, Levitsky K, et al. Methods for assessing                 36 Rodgers JA, Garvin KL, Walker CW, et a...
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Determinants of function knee arthroplasty


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  1. 1. Research Report Determinants of Function After Total Knee Arthroplasty Background and Purpose. Decreasing hospital stays for patients with total knee arthroplasties (TKAs) have a direct effect on rehabilitation. The identification of modifiable determinants of postsurgical func- tional status would help physical therapists plan for discharge from hospitals. The purpose of this study was to identify preoperative determinants of functional status after a TKA. Participants. Using a community-based, prospective cohort study, data were collected from 276 patients who received a primary TKA in a Canadian health care region. Data were collected in the month before surgery and 6 months after surgery. Methods. Function was measured using the function subscale of a disease-specific measure—the Western Ontario and McMaster Universities (WOMAC) Osteoarthritis Index—and a generic health status measure—the Medical Outcomes Study 36-Item Short- Form Health Survey (SF-36). Independent variables examined included demographic variables (eg, age, sex), medical variables (eg, diagnosis, number of comorbid conditions, ambulatory status), surgi- cal variables (eg, type of implant, number of complications), and knee range of motion. Results. At 6 months after surgery, the average WOMAC physical function score was 70.5 (SD 18.2) and the average SF-36 physical function score was 44.8 (SD 25.3). Using multiple regression analyses, baseline function, walking device, walking dis- tance, and comorbid conditions predicted 6-month function (WOMAC: R2 .20; SF-36 physical function: R2 .27). Discussion and Conclusions. Patients who have lower preoperative function may require more intensive physical therapy intervention because they are less likely to achieve similar functional outcomes similar to those of patients who have less preoperative dysfunction. [Jones CA, Voak- lander DC, Suarez-Almazor ME. Determinants of function after total knee arthroplasty. Phys Ther. 2003;83:696 –706.] Key Words: Determinant, Function, Total knee arthroplasty. C Allyson Jones, Donald C Voaklander, Maria E Suarez-Almazor 696 Physical Therapy . Volume 83 . Number 8 . August 2003
  2. 2. T he utilization rates of elective total knee arthro- This meta-analysis showed that 89.3% of patients plasties (TKAs) are steadily increasing with an reported good to excellent results at an average aging population.1 Moreover, the trend toward follow-up period of 4.1 years. The mean improvement in earlier hospital discharge after TKA has meant range of motion in those studies in which preoperativethat patients are returning home during a more acute and postoperative range of motion of the knee wasphase of recovery. These 2 factors have had direct measured was 8 degrees.4implications for the rehabilitation of patients with TKA. Although the improvements following TKA can be dra-Elective TKA is, more often than not, the last effort in matic, the gains are typically less than the changesmanaging joint pain and dysfunction caused by arthritis. reported by patients who have had a total hip arthro-Extensive evidence indicates that the majority of patients plasty.5,9 –11 Long-term “technical failures” requiring revi-who have had a TKA report improvement in pain and sion of the prosthesis (eg, loosening, fracture, or infec-function.2– 4 Eighty-five percent to 90% of patients with tion) are low (less than 10% over 10 years),4,12 yet theTKA report pain relief after surgery, and 70% to 80% lack of improvement is usually related to continuingreport functional improvement.4,5 The greatest amount pain and poor function. Approximately 15% to 30% ofof improvement is seen within 3 to 6 months after patients receiving TKA report little or no improvementsurgery, with more gradual improvements occurring up after surgery or are unsatisfied with the results after a fewto 2 years after surgery.6 – 8 A meta-analysis of 130 studies4 months.5,13,14indicated that these favorable results continue over time.CA Jones, PT, PhD, is Postdoctoral Fellow, Faculty of Pharmacy and Pharmaceutical Sciences, University of Alberta, Dentistry/Pharmacy Building,Room 2137, Edmonton, Alberta, Canada T6G 2N8 ( Address all correspondence to Dr Jones.DC Voaklander, PhD, is Associate Professor in Community Health, University of Northern British Columbia, Prince George, British Columbia,Canada.ME Suarez-Almazor, MD, PhD, is Associate Professor in Medicine, Baylor College of Medicine, Houston, Tex.All authors provided concept/research design, writing, and data collection. Dr Jones provided data analysis. Dr Voaklander and Dr Suarez-Almazorprovided project management, fund procurement, institutional liaisons, and consultation (including review of manuscript before submission). DrSuarez-Almazor provided facilities/equipment and clerical support. The authors thank Dr Karen Kelly and Sue Barrett for their assistancethroughout the study, as well as Lauren Beaupre and Dr DWC Johnston for their clinical expertise. They also are grateful to Dr Lynn Redfern and ´Gordon Kramer for instigation of this project.Ethics approval was obtained from the Health Research Ethics Board (University of Alberta Sciences Faculties, Capital Health Authority, and theCaritas Health Group).This research was supported by grants from the Capital Health Authority Research and Grant Fund and the Edmonton Orthopaedic ResearchTrust. Dr Suarez-Almazor was supported by The Arthritis Society of Canada and the Alberta Heritage Foundation for Medical Research. Dr Joneswas supported, in part, by the Canadian Physiotherapy Foundation, the Royal Canadian Legion, and the Alberta Heritage Foundation for MedicalResearch.This article was received July 5, 2002, and was accepted March 24, 2003.Physical Therapy . Volume 83 . Number 8 . August 2003 Jones et al . 697
  3. 3. Table 1. after TKA, accounting for 15% of theParticipant Characteristics variance. To date, no clear predictors of functional recovery have been con- Characteristic n % X SD sistently reported in the literature. Demographics (n 276) Age (y) 69.2 9.2 Given the shortened length of stay in Female 162 59 acute care hospitals for patients with Living alone 67 24 TKA, we believe that it is important Medical status for the physical therapist to identify Osteoarthritis (n 273) 257 94 those patient-related factors that will Previous arthroplasty (n 276) 68 25 Comorbid conditions (n 276) 3.5 2.0 affect functional independence. If Body mass index (kg/m2) (n 276) 31.6 5.9 modifiable determinants of function Preoperative walking distance (n 253) could then be identified, patients Indoors 19 7 who require additional interventions 1 block 67 27 during their recovery could be readily 1–5 blocks 124 49 identified. The primary objective of 6–10 blocks 22 9 our study was to identify those demo- Unlimited 21 8 graphic, medical, and clinical factors Preoperative assistive walking devices (n 256) available to physical therapists that None 158 62 Cane 86 33 predict function at 6 months after Walker 12 5 surgery. A 6-month follow-up time Preoperative knee range of motion (°) (n 259) 106 15 was selected because studies6 – 8 have shown that the greatest change in Surgical Implant fixation (n 272) pain and function occurs during the Cementless 44 16 first 3 to 6 months after surgery. Hybrid 156 57 Moreover, we contend that short- Cemented 72 27 term evaluation can provide useful In-hospital complications (n 272) information on patient recovery and None 183 67 may highlight the need for further Health services utilization (n 276) therapy to augment recovery. This Hospital length of stay (d) 6.8 2 study was part of a larger study that Discharge directly home (n 272) 156 57 examined the effect of waiting times Rehabilitation facility length of stay (d) 9.3 3.3 Community therapy 129 47 for hip and knee arthroplasties on the subsequent health-related quality of life (HRQL) after this surgery.5,17For the physical therapist, rehabilitation of patients with MethodTKA is often a challenge. One of the primary issues intreating patients with TKA is identifying those patients Participantswho may require extensive rehabilitation. For those Our study was a prospective, longitudinal study of anhigh-risk patients, early rehabilitation is thought to pro- inception cohort of surgical candidates who receivedvide a benefit.15 Although much of the published clinical TKA in a Canadian health care region, Capital Health. Awork has focused on recovery, little evidence exists on health care region is a geographical area administereddeterminants of recovery from TKA. One group of by a regional health authority. Patients in this study wereresearchers3 concluded that baseline pain and function selected based on time of placement on the regional(ie, pain and function on date of decision to proceed joint arthroplasty waiting list rather than on the time ofwith surgery) were the single best predictors of func- surgery. Waiting time for a TKA ranged from 7 to 487tional recovery at 6 months. Fortin and colleagues3 days, with a median wait of 78 days. All patients hadsurmised that patients who reported greater pain and surgery between February 1996 and February 1998.dysfunction prior to surgery were more likely to have Patients were eligible for this study if they: (1) weremore pain and dysfunction after surgery than patients scheduled for elective primary TKA, (2) were placed onwho had less pain and dysfunction. In a prospective the joint arthroplasty waiting list at least 7 days beforecohort study,16 psychosocial factors such as motivation surgery (which would help to ensure that emergencyand social function were more influential than medical surgeries were excluded), (3) resided in the healthfactors or initial function in predicting 3-month function region, (4) were 40 years of age or older, and (5) spoke698 . Jones et al Physical Therapy . Volume 83 . Number 8 . August 2003
  4. 4. English. Exclusion criteria included hemiarthroplasties 3 health care professionals (a physical therapist and 2and revision and emergency arthroplasties. nurses) who were trained using a standardized study protocol and were not involved in the care of anyPatients who resided in long-term care institutions participants. We did not examine the reliability of theirbefore being placed in the joint replacement waiting list goniometric measurements.also were excluded. Rarely is any elective joint arthro-plasty performed in patients from long-term care facili- All patients received a primary TKA and were managedties. We felt that patients from long-term facilities rep- using a clinical pathway for TKA in an effort to ensureresent a small unique group of this patient population standardized treatment of medical, pharmaceutical, andand are atypical of patients who receive elective knee rehabilitation care over the 5- to 7-day hospital stay. Anarthroplasty. After meeting the selection criteria and important part of the clinical pathway was early mobili-agreeing to participate, each patient signed a consent zation. The protocol for physical therapy interventionform before participating in the study. consisted of commencing basic activities of daily living with assistance on postoperative day 1. Active-assistedOf the 377 patients eligible to participate in the study, 53 range-of-motion exercises were started on postoperative(14%) refused to participate, and 18 (5%) were lost to day 2, after removal of the hemovac. Ambulation,follow-up. Another 30 patients (8%) had completed assisted by a physical therapist, was started after post-their preoperative assessments but had their surgeries operative day 1, with weight bearing as tolerated unlesscancelled for either medical reasons or personal choice. otherwise stated. The discharge goal related to mobilityOf those patients who had their surgeries, the participa- was independent and safe ambulation with assistivetion rate was 79.5%. There were no differences between walking devices on a level surface between postoperativeparticipants and nonparticipants with respect to age or days 5 and 7. Patients were discharged home with ansex. exercise program and referral for community therapy as required. Only 10 patients (4%) were not seen by aPatient characteristics are shown in Table 1. Of the 276 physical therapist during their hospital stay, and 257patients in our study, the majority of patients tended to patients (93%) were seen by postoperative day 2. Nobe elderly women with osteoarthritis. Sixty-seven percent participants had simultaneous bilateral knee arthroplasties.of patients (n 186) reported unilateral joint involve-ment. Hypertension (39%) and back pain (26%) were Standardized medical chart reviews were completed by 2the 2 most commonly reported comorbid conditions. health care professionals. The following surgical and perioperative data were extracted from the medicalProcedure charts: implant fixation (cemented, hybrid, or cement-When the orthopedic surgeon and patient agreed that a less), number and type of in-hospital complicationsTKA was necessary, the patient’s name was placed on the (wound infection, dislocation, manipulation underhealth care region’s joint arthroplasty waiting list. Names anesthesia, cardiovascular/pulmonary complications,were retrieved from the joint arthroplasty waiting list on peripheral/central nervous system involvement, urinarya weekly basis, and patients were contacted to request infection, acute confusion, blood loss requiring transfu-participation in the study. When the patient agreed to sion after surgery), medical information (diagnosis,participate, in-person interviews were completed within height, weight), and preoperative ambulatory status31 days before surgery and 6 months after surgery. The (walking distance and use of assistive walking devices).initial interview consisted of questions regarding demo- Rehabilitation received within the community wasgraphic information, joint pain, function and stiffness, retrieved from administrative databases and treated as aHRQL, comorbid conditions, medical status, and ambu- dichotomous variable.latory status. During the interview, passive range ofmotion for the operated knee was measured with a large Measuresstandard universal goniometer with the patient in a The interview included a disease-specific questionnaire,supine position. The hip was placed in a comfortable the Western Ontario and McMaster Universitiesflexed position (degree of hip flexion varied among the (WOMAC) Osteoarthritis Index,20 which is a self-patients), and the maximum amount of knee movement, administered health questionnaire designed to measureas tolerated by patient, was measured. The reliability and disability of the osteoarthritic hip and knee. Thevalidity of goniometric measurements of the knee have WOMAC provides an aggregate score for each of the 3been reported by others.18,19 Rothstein and colleagues19 subscales: joint pain (5 items), physical joint functionreported the intrarater reliability (r) of knee goniomet- (17 items), and joint stiffness (2 items). The 5-pointric measurements in the clinical setting to be .91 to .99, Likert version of this measure was used in our study. Inand interrater reliability of knee flexion was slightly the calculation of each of the 3 subscale scores, thelower (r .88 –.97). Assessments were completed by 1 of range of the subscale score was transformed to a rangePhysical Therapy . Volume 83 . Number 8 . August 2003 Jones et al . 699
  5. 5. Table 2.Preoperative and 6-Month Health Statusa Preoperative Health Status 6-Month Health Status n X SD n X SD WOMAC Physical function 275 42.8 17.4 270 70.5 18.2 Pain 275 43.4 17.6 271 76.0 19.1 Joint stiffness 275 39.7 21.5 271 63.3 22.0 SF-36 Physical function 276 21.0 18.1 273 44.8 25.3 Bodily pain 276 30.8 17.6 273 53.4 22.8 Role–physical 276 12.0 24.7 271 35.2 40.0 Social function 276 54.0 27.2 273 72.1 27.7 Mental health 276 68.9 19.5 272 75.0 19.0 Role–emotion 274 55.2 44.3 271 67.3 40.4 Vitality 276 42.0 20.9 272 52.9 22.7 Health perception 276 62.1 19.4 273 64.5 19.8 Physical component summary 274 25.9 7.5 269 34.6 10.1 Mental component summary 269 50.1 11.4 269 52.5 10.8a Range of scores for both the Western Ontario and McMaster Universities (WOMAC) Osteoarthritis Index subscales and Medical Outcomes Study 36-Item Short-Form Health Survey (SF-36) dimensions was 0 to 100, with better functional status represented by higher scores.from 0 to 100 points, with a score of 100 indicating no of 23 comorbid conditions identified by the Charlsonpain or dysfunction. This type of transformation has Comorbidity Index29 was used. The weighting of severitybeen used by others to allow an easier comparison used with this index was not used in our study becausebetween the WOMAC and the Medical Outcomes Study the weights were not derived from function. The num-36-Item Short-Form Health Survey (SF-36).21 The ber of comorbid conditions was treated as a summativeWOMAC is a responsive instrument that yields reliable score.and valid measurements and that has been extensivelyused to evaluate this patient population.20,21 Data Analysis The dependent variables, the 6-month function scores ofA multidimensional generic health measure, the the WOMAC and SF-36, were examined as continuousSF-36,22–24 was used to measure HRQL. The SF-36 exam- variables given the normal distributions. Functionalines 8 health dimensions: physical function, role limita- improvement from the baseline value was defined as a gaintion (physical), bodily pain, mental health, emotional of at least 60% of the baseline standard deviation androle function, social functioning, vitality, and general was considered a moderate effect.30 This equated tohealth perception. Scoring for each dimension ranges approximately a 10-point gain (Tab. 2). This definitionfrom 0 to 100, with higher scores representing better posed a potential problem for patients with preoperativehealth. There is no global score; however, 2 component scores of 80 or greater because the WOMAC may have asummary measures—physical component summary ceiling effect. Because the improvement at 6 months was(PCS) and the mental component summary (MCS)— expected to be large, the net difference preoperativelyhave been derived from the 8 dimensions and standard- and postoperatively may be artificially low for thoseized using norm-based methods. Summary measures patients with higher preoperative scores. To compensatedescribe the overall changes in HRQL, but do not for this effect, we arbitrarily defined those patients withcapture the smaller changes within the specific dimen- preoperative scores of 80 or more who maintained asions. Reliability and validity have been extensively eval- 6-month score of at least 80 as having improved. If theuated in a variety of patient populations, including 6-month score dropped below 80 for those patients, itpeople with total hip and knee arthroplasties and was considered as no elderly people.21,25–28 Independent variables consisted of: (1) demographicThe types of comorbid conditions were recorded by the variables (age, sex), (2) baseline medical variables (diag-patient or reported on the medical chart. Comorbidities nosis, body mass index (BMI), number of comorbidwere defined as differing from complications, in that conditions, previous joint arthroplasty, preoperativecoexisting medical conditions are chronic conditions quality of life as measured by the SF-36, preoperativethat exist before surgical intervention or hospital admis- joint function and pain as measured by the WOMAC,sion. Only those medical conditions identified at the preoperative passive range of motion for the knee,time of admission to the hospital were recorded. The list preoperative ambulatory status, type of residence and700 . Jones et al Physical Therapy . Volume 83 . Number 8 . August 2003
  6. 6. living arrangements), and (3) perioperative variables Sixty-seven percent of the patients (n 183) did not have(the number of in-hospital complications, type of in-hospital complications; however, the primary types ofimplant fixation, waiting times, and length of stay). complications were urinary tract infection (n 18) andRehabilitation received during the 6 months after sur- deep venous thrombi or emboli (n 13). There were 2gery within the community may have had a potential deaths due to pulmonary embolism within a month ofconfounding effect and was examined. discharge and another death at 3 months that was unrelated to the knee arthroplasty.Univariate linear regression analyses for each of thesevariables were examined on the dependent variables. All More than half of the patients (n 156 [57%]) wereindependent variables that met an initial statistical level discharged directly home, and all patients returned toof less than .25 or were considered to be clinically the community within 6 months after surgery. Thosemeaningful were examined in the multivariate analysis. patients who were discharged directly home tended to be younger (mean age 66.2 years, SD 9.0) than thoseMultiple linear regression using stepwise entry with patients who were transferred to another facility (meanseparate models was developed to examine those signif- age 73.3 years, SD 7.9) (P .001). Patients dischargedicant variables associated with function of the knee and directly home also had better preoperative WOMACoverall function. Both joint function—as measured by function scores (X 45.3, SD 18.0) than the patientsthe WOMAC—and overall function—as measured by the who were transferred to another facility (X 39.4,SF-36 physical function dimension—were examined SD 16.4) (P .006). A higher proportion of womenbecause these measures examined slightly different (53%) than men (27%) were transferred to a rehabili-aspects of function. The SF-36 physical function exam- tation facility (P .001); however, more women (32%)ined the overall function that could be influenced by than men (13%) lived alone (P .001). Within theother problems, whereas the WOMAC physical joint community, 129 patients (47%) received communityfunction measurement specifically examined how the rehabilitation over the 6 months after their surgery.knee affected function. Forty-six percent of the patients (n 125) walked without any assistive devices 6 months after surgery. The meanStepwise forward model selection techniques were used passive knee range of motion at 6 months was 99 degreesto obtain the final models. In addition, because age and (SD 14).sex were considered to be potential confounding vari-ables, they were forced into the final models. Model Functional Statusdiagnostics, such as residual plots, were inspected toverify that the model assumptions of linearity were not WOMAC. The preoperative and 6 month scores of theviolated. Finally, multicollinearity was assessed by an WOMAC and SF-36 are shown in Table 2. The meanexamination of correlation matrixes of all independent preoperative physical joint function score reported wasvariables. 42.8 (SD 17.4); however, the 6-month score improved 28% to 70.5 (SD 18.2). Despite the improvement, 53All statistical testing was performed with 2-tailed tests (20%) patients did not report an improvement fromand at a .05 level of significance unless otherwise stated. their preoperative scores; that is, they did not report atStatistical analyses were performed using the SPSS soft- least a 10-point gain. In particular, questions that con-ware version 11.01 for Windows.* cerned domestic duties and stairs were rated difficult at 6 months. Sixty-four percent of the patients (n 165)Results reported “moderate” to “extreme” difficulty for heavyThe median length of stay in the acute care hospitals was domestic duties (eg, vacuuming), and 60% (n 160)7 days (range 3–20). All procedures for TKA used a reported moderate to extreme difficulty descendingmedial peripatellar exposure with a midline skin inci- stairs.sion. Of the TKA procedures, 157 (58%) were hybrid, 73(27%) were cemented, and 42 (15%) were cementless. SF-36 physical function. Overall function as measuredThe hybrid prosthesis routinely involved a porous coated by the SF-36 physical function subscale showed lessfemoral component and a cemented tibial component. improvement—24%. The mean preoperative score, 21.0Twenty-nine percent of the patients (n 77) received (SD 18.1), improved to 44.8 (SD 25.3) at the 6-monthpatellar components. Thirty percent of the patellae follow-up; however, 77 patients (28%) did not report at(n 79) were resurfaced. All patellar components were least a 10-point improvement from their preoperativecemented, all-polyethylene (non–metal-backed) scores. When matched for age and sex to the general UScomponents. population, the 6-month score was significantly less than the mean score reported for the general population— 67.6 (SD 7.5) (P .002).31 The overall physical compo-* SPSS Inc, 233 S Wacker Dr, Chicago, IL 60606-6307.Physical Therapy . Volume 83 . Number 8 . August 2003 Jones et al . 701
  7. 7. Table 3.Unadjusted Regression Coefficients Relating Preoperative Variables to 6-Month Physical Function for Both the Western Ontario and McMasterUniversities (WOMAC) Osteoarthritis Index and Medical Outcomes Study 36-Item Short-Form Health Survey (SF-36) Physical Function Scores WOMAC Physical Function SF-36 Physical Function Unstandardized Unstandardized Baseline Variables Coefficient P Coefficient P Diagnosis (osteoarthritis) 12.4 .008 17.66 .007 Body mass index 0.65 .001 0.87 .001 Previous joint arthroplasty 2.78 .280 3.95 .269 SF-36 physical function 0.22 .001 Not evaluated Bodily pain 0.30 .001 0.47 .001 Role–physical 0.16 .001 0.24 .001 Social function 0.21 .001 0.32 .001 Mental health 0.22 .001 0.27 .001 Role–emotion 0.03 .213 0.01 .828 Vitality 0.28 .001 0.43 .001 Health perception 0.27 .001 0.36 .001 WOMAC pain 0.29 .001 0.40 .001 Knee range of motion 0.07 .328 0.14 .174 Walking distance 4.29 .001 See Tab. 5 Living alone 2.38 .361 4.85 .176 No. of in-hospital complications 0.32 .861 0.03 .989 Implant fixation (cemented) 5.30 .075 2.74 .252 Waiting times 0.01 .531 0.01 .527 Length of stay in acute care setting 1.71 .004 1.26 .125nent is derived from the physical function, bodily pain, To control for confounding effects, age and sex wererole–physical, and health perception dimensions and is force entered into both final models of joint functionstandardized using norm-based methods. The physical and overall function. The amount of postoperative reha-component score improved almost one standard devia- bilitation may have had potential confounding effects,tion (9 points) from 25.9 (SD 7.5) to 34.6 (SD 10.1). but this was not significant either in the preliminary univariate analyses or in the multiple linear regressionMultivariate Regression Models model. Therefore, rehabilitation after surgery was notThe unadjusted regression coefficients of preoperative included in the final model.variables that were not included in the final multivariatemodels are seen in Table 3. While many domains of the Preoperative joint function was a predictor of jointSF-36, BMI, and a diagnosis were significant in the function (WOMAC) and overall function (SF-36 physicalunivariate analysis, they were not significant when function). This finding can be interpreted by theadjusted in the final model. A higher preoperative score unstandardized coefficient; a 10-point increase in pre-of the SF-36 (bodily pain, role–physical, social function, operative WOMAC physical joint function scores wasmental health, vitality, and health perception), a lower associated with a 3.0-point increase in WOMAC physicalBMI, and a diagnosis of osteoarthritis rather than a joint function scores at 6 months (Tab. 4) and with asystemic arthritis had an association of higher function 3.9-point increase in SF-36 physical function scoresscores (WOMAC and SF-36 physical function). (Tab. 5). The standardized beta coefficient indicated that preoperative joint function was the most influentialThe results of the multiple linear modeling for predic- variable in predicting both joint function (as deter-tors of 6-month function are presented in Tables 4 and mined by WOMAC joint function scores) and overall5. No strong correlations (r .50) were noted between function (as determined by SF-36 physical functionindependent variables; therefore, multicollearity did not scores) at 6 months.affect the regression analyses. Of the variables that metthe level of significance in the univariate analyses, 3 The type of walking devices used before surgery was alsovariables met the level of significance and were included associated with 6-month function. For instance, a patientin the final multivariate models (Tabs. 4 and 5). who ambulates independently will have a WOMAC702 . Jones et al Physical Therapy . Volume 83 . Number 8 . August 2003
  8. 8. Table 4. Multiple Linear Regression: Western Ontario and McMaster Universities (WOMAC) Osteoarthritis Index Function at 6 Months Unadjusted Adjusted (R2 .20) Unstandardized Standardized Unstandardized Standardized Partial Variable Coefficient Coefficient CIa P Coefficient Coefficient r CI P Intercept 41.59 (24.14, 59.05) .001b Age 0.21 0.11 ( 0.03, 0.45) .08 0.35 0.18 .18 (0.10, 0.60) .005 Female 4.73 0.13 ( 9.15, 0.31) .04 0.26 0.01 .01 ( 4.85, 4.32) .91 Preoperative joint function (WOMAC) 0.39 0.36 (0.27, 0.51) .001b 0.30 0.28 .28 (0.16, 0.43) .001b Comorbid conditions 1.89 0.21 ( 2.98, 0.80) .001b 1.62 0.18 .19 ( 2.75, 0.49) .005b Preoperative walking devices 4.98 0.21 ( 7.94, 2.02) .001b 4.15 0.17 .17 ( 7.23, 1.06) .009b a CI 95% confidence interval. bPhysical Therapy . Volume 83 . Number 8 . August 2003 Statistically significant at P .05. Table 5. Multiple Linear Regression: Medical Outcomes Study 36-Item Short-Form Health Survey (SF-36) Physical Function at 6 Months Unadjusted Adjusted (R2 .27) Unstandardized Standardized Unstandardized Standardized Partial Variable Coefficient Coefficient CIa P Coefficient Coefficient r CI P Intercept 5.51 ( 31.67, 20.65) .68 Age 0.07 0.03 ( 0.26, 0.40) .67 0.26 0.09 0.01 ( 0.06, 0.58) .12 b Female 10.31 0.20 ( 16.34, 4.28) .001 2.63 0.05 0.19 ( 8.65, 3.40) .39 Preoperative joint function (WOMAC)c 0.59 0.40 (0.43, 0.76) .001b 0.39 0.27 0.41 (0.21, 0.58) .001b Preoperative walking distance 9.28 0.36 (6.28, 12.27) .001b 5.29 0.21 0.38 (2.02, 8.57) .002b Preoperative walking devices 10.68 0.32 ( 14.64, 6.72) .001b 6.78 0.20 0.33 ( 10.99, 2.57) .002b a CI 95% confidence interval. b Statistically significant at P .05. c WOMAC Western Ontario and McMaster Universities Osteoarthritis Index.Jones et al . 703
  9. 9. 6-month score approximately 12 points higher than that reported that exercise programs can produce pain reliefof a patient who ambulates with a walker before surgery. in patients with knee osteoarthritis. Further investigation may be warranted given the implications of preoperativePreoperative walking distance was predictive of overall functional status on functional outcome, particularly forfunction as determined by SF-36 physical function scores those patients with poor preoperative function.(ie, patients who were able to walk longer distancesbefore surgery were more likely to have better overall The relationship between initial function and functionalfunction at 6 months after surgery). Patients who report outcome following TKA also has implications for identi-that they are able to walk more than 10 blocks before fying those patients who might require further inpatientsurgery are likely to have a score, that is, 26 points higher rehabilitation. With the current trend toward early dis-than patients who are unable to ambulate. charge, not all patients are suitable candidates for early discharge directly home. Munin and colleagues15Twenty percent of the variance in the 6-month WOMAC reported that older age, living alone, a greater numberjoint function scores was explained by age, sex, preop- of comorbid conditions, and function were predictive oferative joint function (WOMAC), comorbid conditions, inpatient rehabilitation after a total joint arthroplasty.and preoperative walking devices. Age, sex, preoperative Patients who have lower levels of preoperative functionwalking devices, walking distance, and joint function will likely need further rehabilitation in addition to the(WOMAC) explained 27% of the variance in the SF-36 therapy received in the acute care setting. Althoughphysical function scores. limited research has compared different models of deliv- ery for rehabilitation of joint arthroplasty,40 furtherDiscussion evidence is needed regarding the specific treatmentOur results indicate that preoperative joint function is a protocols and the most appropriate settings to achievepredictor of function at 6 months after TKA. Those these treatment goals for patients with high-riskpatients who had lower preoperative functional status characteristics.related to knee arthritis functioned at a lower level at 6months than patients with a higher preoperative func- Although we did not specifically address effectiveness oftional status. These findings concur with those of Fortin rehabilitation for people with TKAs, we believe a moreand colleagues,3 who reported not only that worse proactive treatment plan for patients with poor preop-preoperative function resulted in a worse postoperative erative function should be planned before surgery. Afunctional status, but that these differences were more treatment plan may include more intensive physicalpronounced in patients with TKAs than in patients with therapy interventions during the 6 months after surgerytotal hip arthroplasties. regardless of whether it is in a rehabilitation setting or a community setting.The variables in the final models accounted for 20% and27% of the variance seen in the 6-month WOMAC and Preoperative knee flexion was not a strong predictor forSF-36 physical function scores, respectively. These vari- 6-month function as may have been expected. Ourances are comparable to those seen in other studies of findings, however, suggest that preoperative joint func-TKA3,16 as well as other studies that have examined risk tion, comorbid conditions, preoperative walking dis-factors of total hip arthroplasties.32 We believe that the tance, and walking devices were more predictive ofvariances seen in this study’s models are not unreason- function at 6 months than preoperative knee given the dependent and independent variables. Thirteen percent of the patients (n 33) in our cohort had less than 90 degrees of knee flexion prior to surgery.We believe the relationship between baseline function A minimum of 90 degrees of knee flexion is typicallyand functional outcome has implications related to the required for activities of daily living.41 We believe thatissue of waiting times for TKA. Very few studies have our cohort was representative of patients with TKA andexamined the effect of waiting time on function,33–35 yet reflected the preoperative knee range of motion seen init is of interest in the present context. Earlier findings of this patient population because it was a community-this cohort reported minimal functional deterioration based cohort, not restricted to one surgeon or center.with longer waiting times.33 In light of the effect of Although these results did not show a significant rela-preoperative function, one goal of rehabilitation would tionship between preoperative knee flexion andbe to maximize function while patients wait for surgery. 6-month functional status, we believe the measurementA preoperative exercise program may help so that dete- of knee flexion may be more informative to the therapistrioration of function might be minimized while waiting postoperatively than preoperatively.for surgery. Little quantitative evidence exists regardingthe effect of preoperative exercise programs for knee The 6-month follow-up used in this study could be seenarthroplasties36 –38; however, other researchers39 have as a limitation. We feel that the 6-month follow-up was704 . Jones et al Physical Therapy . Volume 83 . Number 8 . August 2003
  10. 10. appropriate, given the objective of our study and sup- 6 Kirwan JR, Currey HL, Freeman MA, et al. Overall long-term impactporting evidence from previous literature of pain and of total hip and knee joint replacement surgery on patients with osteoarthritis and rheumatoid arthritis. Br J Rheumatol. 1994;33:functional recovery after total joint arthroplasty. The 357–360.greatest change with pain and function occurs duringthe first 3 to 6 months after surgery,9,42,43 with more 7 van Essen GJ, Chipchase LS, O’Connor D, Krishnan J. Primary total knee replacement: short-term outcomes in an Australian population.gradual improvement occurring over 2 years.9,43 A J Qual Clin Pract. 1998;18:135–142.longer follow-up would provide information about the 8 Aarons H, Hall G, Hughes S, Salmon P. Short-term recovery from hipsuccess of the prosthesis, but we believe it most likely and knee arthroplasty. J Bone Joint Surg Br. 1996;78:555–558.would not change the functional outcomes we observedin our study. From a clinical perspective, evaluation over 9 Rissanen P, Aro S, Sintonen H, et al. Quality of life and functional ability in hip and knee replacements: a prospective study. Qual Life Res.the 6 months after surgery provides valuable practical 1996;5:56 – 64.information to assist the therapists with management of 10 Ritter MA, Albohm MJ, Keating EM, et al. Comparative outcomes ofthe patient during the recovery phase. total joint arthroplasty. J Arthroplasty. 1995;10:737–741.Another limitation of our study concerns the accuracy of 11 Salmon P, Hall GM, Peerbhoy D, et al. Recovery from hip and knee arthroplasty: patients’ perspective on pain, function, quality of life, andself-report measurement of function. Both joint function well-being up to 6 months postoperatively. Arch Phys Med Rehabil.and overall function were evaluated with self-report 2001;82:360 –366.assessments. No performance-based functional measures 12 Rorabeck CH. Mechanisms of knee implant failure. Orthopedics.were used. Some authors44 have reported discrepancies 1995;18:915–918.between self-report and performance-based measures of 13 Mancuso CA, Salvati EA, Johanson NA, et al. Patients’ expectationsactivities of daily living during hospitalizations when and satisfaction with total hip arthroplasty. J Arthroplasty. 1997;12:functional status was changing. We feel that information 387–396.gained from self-report assessment of function for our 14 Dickstein R, Heffes Y, Shabtai EI, Markowitz E. Total knee arthro-study was valid because function was assessed during plasty in the elderly: patients’ self-appraisal 6 and 12 months postop-stable times (ie, within a month before surgery and 6 eratively. Gerontology. 1998;44:204 –210.months after surgery). 15 Munin MC, Kwoh CK, Glynn N, et al. Predicting discharge outcome after elective hip and knee arthroplasty [published erratum appears inConclusion Am J Phys Med Rehabil, 1995:74(6), following table of contents]. Am JDespite these limitations, findings from this study, along Phys Med Rehabil. 1995;74:294 –301.with others,3 present persuasive evidence that patients 16 Sharma L, Sinacore J, Daugherty C, et al. Prognostic factors forwith greater dysfunction prior to surgery will not attain functional outcome of total knee replacement: a prospective study.comparable functional outcomes as those patients with J Gerontol A Biol Sci Med Sci. 1996;51:M152–M157.less preoperative dysfunction. Those patients who have 17 Kelly KD, Voaklander D, Kramer G, et al. The impact of healthlow preoperative function may require supplemental status on waiting time for major joint arthroplasty. J Arthroplasty.rehabilitation while waiting for surgery and further 2000;15:877– 883.rehabilitation after discharge from the acute care 18 Gogia PP, Braatz JH, Rose SJ, Norton BJ. Reliability and validity ofsetting. goniometric measurements at the knee. Phys Ther. 1987;67:192–195. 19 Rothstein JM, Miller PJ, Roettger RF. Goniometric reliability in aReferences clinical setting: elbow and knee measurements. Phys Ther. 1983;63:1 Katz BP, Freund DA, Heck DA, et al. Demographic variation in the 1611–1615.rate of knee replacement: a multi-year analysis. Health Serv Res. 1996; 20 Bellamy N, Buchanan WW, Goldsmith CH, et al. Validation study of31:125–140. WOMAC: a health status instrument for measuring clinically important2 Hawker G, Wright J, Coyte P, et al. Health-related quality of life after patient relevant outcomes to antirheumatic drug therapy in patientsknee replacement. J Bone Joint Surg Am. 1998;80:163–173. with osteoarthritis of the hip or knee. J Rheumatol. 1988;15:1833–1840.3 Fortin PR, Clarke AE, Joseph L, et al. Outcomes of total hip and knee 21 Bombardier C, Melfi CA, Paul J, et al. Comparison of a generic andreplacement: preoperative functional status predicts outcomes at six a disease-specific measure of pain and physical function after kneemonths after surgery. Arthritis Rheum. 1999;42:1722–1728. replacement surgery. Med Care. 1995;33(suppl 4):AS131–AS144.4 Callahan CM, Drake BG, Heck DA, Dittus RS. Patient outcomes 22 Stewart AL, Hays RD, Ware JE Jr. The MOS short-form generalfollowing tricompartmental total knee replacement: a meta-analysis. health survey: reliability and validity in a patient population. Med Care.JAMA. 1994;271:1349 –1357. 1988;26:724 –735.5 Jones CA, Voaklander DC, Johnston DW, Suarez-Almazor ME. 23 Ware JE Jr, Sherbourne CD. The MOS 36-Item Short-Form HealthHealth related quality of life outcomes after total hip and knee Survey (SF-36), I: conceptual framework and item selection. Med Care.arthroplasties in a community based population. J Rheumatol. 2000;27: 1992;30:473– 483.1745–1752. 24 McHorney CA, Ware JE Jr, Lu JF, Sherbourne CD. The MOS 36-Item Short-Form Health Survey (SF-36), III: tests of data quality, scaling assumptions, and reliability across diverse patient groups. Med Care. 1994;32:40 – 66.Physical Therapy . Volume 83 . Number 8 . August 2003 Jones et al . 705
  11. 11. 25 Kantz ME, Harris WJ, Levitsky K, et al. Methods for assessing 36 Rodgers JA, Garvin KL, Walker CW, et al. Preoperative physicalcondition-specific and generic functional status outcomes after total therapy in primary total knee arthroplasty. J Arthroplasty. 1998;13:knee replacement. Med Care. 1992;30(suppl 5):MS240 –MS252. 414 – 421.26 Brazier JE, Harper R, Jones NM, et al. Validating the SF-36 health 37 D’Lima DD, Colwell CW Jr, Morris BA, et al. The effect of preop-survey questionnaire: new outcome measure for primary care. BMJ. erative exercise on total knee replacement outcomes. Clin Orthop.1992;305(6846):160 –164. 1996;(326):174 –182.27 Lyons RA, Perry HM, Littlepage BN. Evidence for the validity of the 38 Weidenhielm L, Mattsson E, Brostrom LA, Wersall-Robertsson E.Short-Form 36 Questionnaire (SF-36) in an elderly population. Age Effect of preoperative physiotherapy in unicompartmental prostheticAgeing. 1994;23:182–184. knee replacement. Scand J Rehabil Med. 1993;25:33–39.28 Stucki G, Liang MH, Phillips C, Katz JN. The Short Form-36 is 39 Thomas KS, Muir KR, Doherty M, et al. Home based exercisepreferable to the SIP as a generic health status measure in patients programme for knee pain and knee osteoarthritis: randomised con-undergoing elective total hip arthroplasty. Arthritis Care Res. 1995;8: trolled trial. BMJ. 2002;325(7367):752–757.174 –181. 40 Mahomed NN, Koo Seen Lin MJ, Levesque J, et al. Determinants29 Charlson ME, Pompei P, Ales KL, MacKenzie CR. A new method of and outcomes of inpatient versus home based rehabilitation followingclassifying prognostic comorbidity in longitudinal studies: develop- elective hip and knee replacement. J Rheumatol. 2000;27:1753–1758.ment and validation. J Chronic Dis. 1987;40:373–383. 41 Papagelopoulos PJ, Sim FH. Limited range of motion after total30 Cohen J. Statistical Power Analysis for the Behavioral Sciences. Hillsdale, knee arthroplasty: etiology, treatment, and prognosis. Orthopedics.NJ: Lawrence Erlbaum Associates, Publishers; 1988. 1997;20:1061–1065; quiz 1066 –1067.31 Ware JE Jr. SF-36 Health Survey: Manual and Interpretation Guide. 42 MacWilliam CH, Yood MU, Verner JJ, et al. Patient-related riskBoston, Mass: The Health Institute; 1993. factors that predict poor outcome after total hip replacement. Health Serv Res. 1996;31:623– 638.32 Braeken AM, Lochhaas-Gerlach JA, Gollish JD, et al. Determinantsof 6 –12 month postoperative functional status and pain after elective 43 Laupacis A, Bourne R, Rorabeck C, et al. The effect of elective totaltotal hip replacement. Int J Qual Health Care. 1997;9:413– 418. hip replacement on health-related quality of life. J Bone Joint Surg Am. 1993;75:1619 –1626.33 Kelly KD, Voaklander DC, Johnston DW, et al. Change in pain andfunction while waiting for major joint arthroplasty. J Arthroplasty. 44 Sager MA, Dunham NC, Schwantes A, et al. Measurement of2001;16:351–359. activities of daily living in hospitalized elderly: a comparison of self-report and performance-based methods. J Am Geriatr Soc. 1992;40:34 Williams JI, Llewellyn-Thomas H, Arshinoff R, et al. The burden of 457– 462.waiting for hip and knee replacements in Ontario. J Eval Clin Pract.1997;3:59 – 68.35 Llewellyn-Thomas HA, Arshinoff R, Bell M, et al. In the queue fortotal joint replacement: patients’ perspectives on waiting times. J EvalClin Pract. 1998;4:63–74.706 . Jones et al Physical Therapy . Volume 83 . Number 8 . August 2003