Predictors of quality of life outcomes after revision total hip replacement

Transcription

1 Predictors of quality of life outcomes after revision total hip replacement G. S. Biring, B. A. Masri, N. V. Greidanus, C. P. Duncan, D. S. Garbuz From University of British Columbia, Vancouver, Canada G. S. Biring, MSc(Ortho)Eng, FRCS(Trauma & Orth), Consultant Orthopaedic Surgeon Buckinghamshire Hospitals NHS Trust, Mandeville Road, Aylesbury, Buckinghamshire HP21 8AL, UK. B. A. Masri, MD, FRCSC, Professor & Chairman N. V. Greidanus, MD, FRCSC, Assistant Professor C. P. Duncan, MB, FRCSC, Professor D. S. Garbuz, MD, FRCSC, Assistant Professor Department of Orthopaedics, Division of Adult Lower Limb Reconstruction & Oncology University of British Columbia, Room 3114, 910 West 10th Avenue, Vancouver, British Columbia V5Z 4E3, Canada. Correspondence should be sent to Mr G. S. Biring; British Editorial Society of Bone and Joint Surgery doi: / x.89b $2.00 J Bone Joint Surg [Br] 2007;89-B: Received 30 April 2007; Accepted after revision 5 July 2007 A prospective cohort of 222 patients who underwent revision hip replacement between April 2001 and March 2004 was evaluated to determine predictors of function, pain and activity level between one and two years post-operatively, and to define quality of life outcomes using validated patient reported outcome tools. Predictive models were developed and proportional odds regression analyses were performed to identify factors that predict quality of life outcomes at one and two years post-operatively. The dependent outcome variables were the Western Ontario and McMaster Osteoarthritis Index (WOMAC) function and pain scores, and University of California Los Angeles activity scores. The independent variables included patient demographics, operative factors, and objective quality of life parameters, including pre-operative WOMAC, and the Short Form-12 mental component score. There was a significant improvement (t-test, p < 0.001) in all patient quality of life scores. In the predictive model, factors predictive of improved function (original regression analyses, p < 0.05) included a higher pre-operative WOMAC function score (p < 0.001), age between 60 and 70 years (p < 0.037), male gender (p = 0.017), lower Charnley class (p < 0.001) and aseptic loosening being the indication for revision (p < 0.003). Using the WOMAC pain score as an outcome variable, factors predictive of improvement included the pre-operative WOMAC function score (p = 0.001), age between 60 and 70 years (p = 0.004), male gender (p = 0.005), lower Charnley class (p = 0.001) and no previous revision procedure (p = 0.023). The pre-operative WOMAC function score (p = 0.001), the indication for the operation (p = 0.007), and the operating surgeon (p = 0.008) were significant predictors of the activity assessment at follow-up. Predictors of quality of life outcomes after revision hip replacement were established. Although some patient-specific and surgery-specific variables were important, age, gender, Charnley class and pre-operative WOMAC function score had the most robust associations with outcome. In an ageing population it is expected that the requirement for joint replacement and subsequent revision will continue to increase. In the USA, an estimated one-quarter of the projected total adult population of 67 million will have medically-diagnosed arthritis by the year 2030 compared with the 42.7 million in In the last decade in the USA, the number of primary and revision hip procedures increased by 50% and 60%, respectively. 2 Those patients requiring revision surgery place a greater financial burden on health-care expenditure, as they require longer hospital stays and generally have higher rates of morbidity, 3 and derive less improvement in quality of life compared with patients receiving primary total hip replacement (THR). 4,5 There have been many long-term follow-up studies of clinical and technological features of revision THR defining outcome in terms of survival, with most efforts concentrating on the technical aspects of this intervention to improve the success rate further. 6-8 However, there are only a few short-term studies addressing quality of life outcomes following revision THR using validated measures. 5,9-11 One meta-analysis has attempted to assess the impact of patient-, surgical- and implantrelated factors on the outcomes of revision THR, but there were insufficient data to identify factors associated with improved functional rather than technical outcomes. 12 Recently, Davis et al 11 showed that preoperative pain and comborbidity were significant predictors of pain two years after revision 1446 THE JOURNAL OF BONE AND JOINT SURGERY

2 PREDICTORS OF QUALITY OF LIFE OUTCOMES AFTER REVISION TOTAL HIP REPLACEMENT 1447 hip arthroplasty. They identified a trend which did not reach statistical significance towards pre-operative function predicting function at two years. The aims of our prospective study were to describe quality of life outcomes following revision THR at one and two years using the Western Ontario and McMaster Osteoarthritis Index (WOMAC) scale, 13 the Short Form 12 (SF-12) 14 and the University of California Los Angeles (UCLA) activity score, 15 and, more importantly, to identify factors that predict physical function, pain and activity at follow-up. Patients and Methods A total of 235 patients undergoing revision THR were prospectively recruited to the study, for which Institutional Review Board approval had been obtained. The revision THRs were performed by four participating surgeons (BAM, NVG, CPD, DSG) at our institution between April 2001 and March Patients were considered eligible for inclusion if either the acetabular or the femoral components, or both, were revised for any reason including aseptic loosening, periprosthetic fracture, infection or instability. Patients undergoing an isolated replacement of the polyethylene liner or femoral head, or those for whom a tumour prosthesis was required, were excluded. Patients who were not fluent in English or unable to understand and complete the questionnaires were also excluded. Pre-operative data were recorded on admission to hospital and at one- and two-year follow-up in a longitudinal database. All patients completed a WOMAC and an SF-12 questionnaire at the time of admission. At follow-up, WOMAC, SF-12 and UCLA activity rating questionnaires were collected. The WOMAC is a self-administered multidimensional index containing dimensions for pain (five items), stiffness (two items), and function (17 items). Each item is represented by a Likert scale 16 response between 0 (best health state) and 4 (worst state). We normalised each raw score into the 0 to 100 scale, with 0 being the worst quality of life and 100 the best. 13 The SF-12 mental component score is a subscale of the Short Form 36 and is calculated on a 0 to 100 worst to best scale. 14 The UCLA activity rating has ten descriptive activity levels, ranging from wholly inactive and dependent on others (level 1), to moderate activities such as unlimited housework and shopping (level 6), to regular participation in impact sports such as jogging or tennis (level 10). 15 The one- to two-year questionnaires were returned by 222 patients, giving a response rate of 94%. Of these patients, there were 99 men and 123 women with a mean age of 65 years (23 to 96). The mean follow-up for these patients was 1.8 years (1 to 3). Surgical details, comorbidities and complications were obtained from the patient records and the hospital complications database by an independent orthopaedic clinical fellow (GSB). The Charnley classification 17 was used for the assessment of comorbidity; class A patients have an ipsilateral joint replacement; class B1, an ipsilateral joint replacement with degenerative change in the contralateral hip; class B2 have both hips replaced, and class C have multiple joint disease or other disabilities leading to difficulties in walking. Ordinal regression models were used to assess predictors of pain, function and activity level. 18 The dependent variables were WOMAC function, WOMAC pain and UCLA activity. The outcome values for these were divided into three-part categorical responses (poor (0 to 63), good (64 to 85), and excellent (86 to 100)), and the proportional odds model used for analysis of outcome variables with calculation of odds ratio (OR) for selected covariates. This model calculated a single OR and 95% confidence intervals (CI) for each covariate, independent of the rank of the response category. The assumptions of proportionality across thresholds was tested. 19 Summary proportional ORs and CIs were then calculated for selected independent variables which included various demographic and surgical parameters. The covariates tested in all analyses included patient characteristics such as age, gender, body mass index (BMI) and Charnley class 17 (A, B1, B2 or C); pre-operative quality of life, such as preoperative WOMAC function score (continuous), preoperative WOMAC pain score (continuous) and preoperative SF-12 mental component score (continuous); surgical parameters such as duration of operation in minutes, the surgeon (one of four participating fellowshiptrained surgeons, (BAM, NVG, CPD, DSG)), prior revisions (yes, no), acetabular or femoral component revision or both, indication for revision (aseptic loosening, and other causes including instability, infection, fracture), surgical approach (posterolateral, anterolateral, extended trochanteric osteotomy), femoral head size (< 28 mm, 28 mm, > 28 mm), use of bone graft (morsellised or structural), and the presence or absence of peri- and post-operative complications. Statistical analysis was performed using the SAS version 9.1 (SAS Institute, Cary, North California) software package. The difference between pre-operative and follow-up scores was used to show improvements in WOMAC function and pain, and SF-12 (mental component) scores. This was analysed using a t-test. In the proportional odds model for each covariate outputs included an estimate of the regression coefficient, its standard error, Wald chi-squared statistic, p-value and the corresponding OR and confidence limits. Statisitical significance was set at a p-value of < Results The demographic details of the study cohort are summarised in Table I. Complications occurred in 32 patients (14%), the most common being an intra-operative fracture of the femur, which occurred in 22 (9.9%) (Table II). There were no deaths. There was a significant improvement (t-test, p < 0.05) in all patients post-operative quality of life scores from the VOL. 89-B, No. 11, NOVEMBER 2007

3 1448 G. S. BIRING, B. A. MASRI, N. V. GREIDANUS, C. P. DUNCAN, D. S. GARBUZ Table I. Patient characteristics (n = 222) Age (yrs) < to > Mean age (range) 65 (23 to 96) Male:female 99:123 BMI* (kg/m 2 ) < > Indication for revision Aseptic loosening 187 Other Infection 14 Instability 11 Fracture 10 Previous revision None 49 Yes 173 Components revised Acetabular 85 Femoral 30 Both 107 Approach Posterolateral 116 Anterolateral 64 Extended trochanteric osteotomy 42 Femoral head size (mm) < > Bone graft (morsellised or structural) Yes 123 No 99 Charnley class A 61 B1 18 B2 56 C 87 Complications Yes 32 No 190 Mean duration of surgery in minutes (range) 168 (106 to 230) Mean length of stay in days (range) 7.1(3.5 to 10.7) * BMI, body mass index Table II. Total number of complications documented for revision hip arthroplasty out of 222 patients Complication type Number Percentage Intra-operative peri-prosthetic fracture Cardiovascular Dislocation Wound infection Neurovascular injury Pulmonary embolism Table III. Quality of life scores pre-operatively and at one- and two-year follow-up Mean score (SD; range) WOMAC * function Pre-operative 46.2 (22.0; 0.0 to 100.0) One-year 72.5 (20.8; 16.2 to 100.0) Two-year 73.3 (21.4; 8.3 to WOMAC pain Pre-operative 46.2 (22.1; 0.0 to 100.0) One- year 80.5 (20.6; 5.0 to 100.0) Two-year 80.3 (20.5; 15.0 to 100.0) SF-12 (mental component) Pre-operative 45.7 (12.4; 17.3 to 69.0) One- year 52.3 (10.7; 18.6 to 68.4) Two-year 52.1 (11.2; 14.7 to 69.3) UCLA activity One-year 4.9 (1.8; 2.0 to 10.0) Two-year 5.0 (1.9; 2.0 to 10.0) * WOMAC, Western Ontario and McMasters Osteoarthritis Index 13 SF-12, Short Form UCLA, University of California, Los Angeles 15 pre-operative scores (Table III). The change in scores for WOMAC function were 25.6 (t-test, p < power = 1), WOMAC pain 28.8 (t-test, p < power = 1) and SF-12 mental component 6.0 (t-test, p < power = 1). The UCLA activity was not recorded preoperatively, but the follow-up scores remained static between one and two years. The assessment of independent predictors of quality of life outcomes (WOMAC function and pain, and UCLA activity) are shown in Tables IV to VI. Table IV indicates that the pre-operative WOMAC function score was predictive of the post-operative WOMAC function score. With an increasing pre-operative score, the OR for improving post-operative function was 1.03 (95% CI 1.01 to 1.04). Other predictive factors of increased functional outcome are patient age between 60 and 70 years, male gender, lower Charnley class and the indication for revision being aseptic loosening rather than other causes. Table V demonstrates that for WOMAC pain as an outcome variable, factors predictive of improving category outcome included a higher pre-operative WOMAC function score (OR 1.03; 95% CI, 1.01 to 1.04). The pre-operative WOMAC pain score did not predict final outcome for pain. The surgical parameter predictive of the final WOMAC pain THE JOURNAL OF BONE AND JOINT SURGERY

4 PREDICTORS OF QUALITY OF LIFE OUTCOMES AFTER REVISION TOTAL HIP REPLACEMENT 1449 Table IV. Predictor of WOMAC * function after revision hip replacement Odds ratio 95% confidence interval Probability (chi-squared test) WOMAC function score (0 to 100) to 1.04 < Age in yrs (> 70, < 60, 60 to 70) to Gender (female, male) to Charnley class 17 (C, B2, B, A) to 2.13 < Indication for revision (other, aseptic loosening) to Duration of surgery (mins) to BMI (kg/m 2 ) to * WOMAC, Western Ontario and McMasters Osteoarthritis Index 13 BMI, body mass index Table V. Predictors of WOMAC * pain after revision hip replacement Odds ratio 95% confidence interval Probability (chi-squared test) Pre-operative WOMAC pain score (0 to 100) to Baseline SF-12 mental component score (0 to 100) to Age in yrs (< 60, > 70, 60 to 70) to Gender (female, male) to Charnley class 17 (C, B2, B, A) to Prior revision (yes/no) to Length of stay (days) to * WOMAC, Western Ontario and McMasters Osteoarthritis index 13 SF-12, Short-Form Table VI. Predictors of UCLA* activity after revision hip replacement Adjusted cumulative odds ratio Odds ratio 95% confidence interval Probability (chi-squared test) Pre-operative WOMAC function score (0 to 100) to Age in yrs (< 60, > 60, 60 to 70) to Surgeon (1, 2, 4, 3) to Prior revision (yes/no) to Indication (other, aseptic loosening, loosening) to Charnley class 17 (C, B2, B, A) to Approach (posterolateral, anterolateral, slide) to * UCLA, University of California Los Angeles 15 WOMAC, Western Ontario and McMasters Osteoarthritis Index 13 score is the absence of previous revisions. Predictive patient characteristics included age between 60 and 70 years, male genderand a lower Charnley class. Considering UCLA activity (Table VI), factors predictive of improvement included a higher pre-operative WOMAC function score, aseptic loosening as the indication for the operation, and the operating surgeon. There was a trend for lower Charnley class to be associated with an improved outcome, but this just failed to reach statistical significance (OR 1.29; 95% CI, 1.00 to 1.67, ordinal regression analysis, p = 0.053). The following covariates did not have a statistically significant predictive value for any of the three quality of life outcomes: if the patient had an isolated acetabular com- VOL. 89-B, No. 11, NOVEMBER 2007

5 1450 G. S. BIRING, B. A. MASRI, N. V. GREIDANUS, C. P. DUNCAN, D. S. GARBUZ Table VII. Predictors of Western Ontario and McMasters Osteoarthritis Index (WOMAC) 13 function, pain, and University of California Los Angeles (UCLA) 15 activity WOMAC UCLA Function Pain activity 1. Pre-operative WOMAC function score (0 to 100) 1. Pre-operative WOMAC function score (0 to 100) 2. Age in yrs (> 70, < 60, 60 to 70) 2. Age in yrs (< 60, > 70, 60 to 70) 2. Surgeon 1. Pre-operative WOMAC function score (0 to 100) 3. Gender (female, male) 3. Gender (female, male) 3. Indication for revision (other, aseptic loosening) 4. Charnley class (C, B2, B, A) 4. Charnley class (C, B2, B, A) 5. Indication for revision (other, aseptic loosening) 5. Prior revision (yes/no) * the probability of improving thresholds increases as covariates go from left to right ponent or femoral component revision or revision of both components (ordinal regression analysis; function: p = 0.79,pain: p = 0.90, UCLA: p = 0.49), surgical approach (ordinal regression analysis, p = 0.85; pain: p = 0.38, UCLA: p = 0.12), femoral head size (ordinal regression analysis; function: p = 0.77, pain: p = 0.72; UCLA: p = 0.77), the use of morsellised or structural bone graft (ordinal regression analysis; function: p = 0.96, pain: p = 0.96; UCLA: p = 0.24), or peri-operative complications (ordinal regression analysis; function: p = 0.79; pain: p = 0.87; UCLA: p = 0.11) Discussion The majority of studies on revision THR report on rerevision rates, complication rates and function using a variety of hip rating scales on short- to mid-term results. 20,21 Several authors have investigated health-related outcomes with respect to economic benefits, 22 changes in pain, mobility, and the activities of daily life. 23,24 A few have reported results based on validated disease-specific patient-centred outcome measures, 5,25 but only one recent study has reported on the predictors of quality of life outcomes following revision THR. 11 Although revision THR is a technically demanding operation, our results show that patients obtain favourable outcomes. Most patients achieved significant improvements in WOMAC subscales and SF-12 scores. Our results show that in all quality of life scores the preoperative functional score predicts outcome in relation to function, pain and activity. This concurs with evidence available for primary THR that patient s with poorer preoperative function have poor post-operative scores. 26,27 In the study by Davis et al 11 the pre-operative function of their revision THR patients did not predict the function at 24 months post-operatively, although a trend was observed. With a larger sample size we have shown that pre-operative function is an important predictor of post-operative function. When considering predictors of pain, a low pre-operative WOMAC function, age less than 60 years, female gender, a high Charnley class and previous revision were associated with a worse outcome. Psychosocial variables can influence the pain response, 28 but the SF-12 (mental component) was poorly correlated with the follow-up WOMAC pain score and was shown not to be a predictor in our cohort, although this questionnaire may not have been sufficiently sensitive to identify a difference. Predictors of poor WOMAC function included age over 70 years. Previous reports have highlighted that older patients with self-reported conditions restricting mobility as well as arthritic pain in the hip are at a higher risk of physical dysfunction and psychological distress. 29 The effect of age on outcome has been variably reported in the literature. 30 Field, Cronin and Singh 31 reported that patients under the age of 60 undergoing revision hip replacement had better outcomes than those over the age of 80. In our cohort, a younger age appears to be more important for improvement in physical function than for improvement in pain scores, as reported by others. 30 The influence of gender on outcome has been documented previously, with males having greater improvement after primary THR or total knee replacement with respect to social function, mental health, energy and pain scores. 32 Holtzman, Saleh and Kane 33 observed similar differences between the genders. In their study, males had a significantly higher activity of daily living score at one year postoperatively. However, other authors have found no difference between pre- and post-operative WOMAC or SF-36 scores. 30 The impact of Charnley class was profound and affected all parameters assessed. The extent of the change in function with time was markedly dependent on the Charnley class, with a higher class being associated with worse function and pain score. It has been suggested that comorbidities in older patients may explain why health-related quality of life is further reduced in this subgroup after surgery. 34 Predictors of improvement of UCLA activity category include a higher pre-operative WOMAC function score, the surgeon performing the operation, and aseptic loosening as THE JOURNAL OF BONE AND JOINT SURGERY

6 PREDICTORS OF QUALITY OF LIFE OUTCOMES AFTER REVISION TOTAL HIP REPLACEMENT 1451 the indication for revision. The surgeon factor might be related to different post-operative protocols but this was not specifically examined in this study. A strength of this study was the examination of outcome of the work of four surgeons in a single institution who followed similar treatment algorithms with the same instrumentation, and implants, with 94% of possible participating patients returning questionnaires, which can probably be considered representative of the group as a whole. This is only the second study to look at predictors of outcome after revision THR. We have examined numerous variables that have not previously been addressed. Additionally, this study outlines factors predictive not only of pain and function but of activity level. The study by Davis et al 11 found that preoperative pain and comorbidity were the only factors predictive of outcome. In our study, other factors were also found to be predictive of outcome, including indication for revision, age, gender, and number of previous revisions. Another strength is the use of the proportional odds model, which is simple to use and produces an interpretable parameter that summarises the effect between groups over all levels of outcome. The important predictors for function, pain and activity outcome are shown in Table VII. The variables that were not statistically significant in our regression model may have been a result of small sample size. Future studies with more patients should be undertaken to explore these variables further. One limitation of the study was the short-term follow-up. Continued follow-up of this cohort will be essential to determine trends for long-term outcome. In addition, when examining outcome against the indication for revision, causes such as infection, instability and fracture had to be grouped into one category as the numbers were small. If larger numbers had been assessed, then further categorisation might have been possible within these subgroups. In conclusion, this prospective study has shown that most patients had improvement in quality of life outcomes after revision THR. We have identified predictors of function, pain and activity which can assist the orthopaedic surgeon in advising patients and setting realistic goals and expectations for patients. No benefits in any form have been received or will be received from a commercial party related directly or indirectly to the subject of this article. References 1. Hootman JM, Helmick CG. Projections of US prevalence of arthritis and associated activity limitations. Arthritis Rheum 2006;54: Kurtz S, Mowat F, Ong K, et al. Prevalence of primary and revision total hip and knee arthroplasty in the United States from 1990 through J Bone Joint Surg [Am] 2005;87- A: Barrack RL. Economics of revision total hip arthroplasty. 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