Elizabeth A. Lingard

Validity and Responsiveness of the Knee Society Clinical Rating System in Comparison with the Sf-36 and Womac

Background: The aim of this study was to validate the Knee Society Clinical Rating System (knee and function scores) and to compare its responsiveness with that of the Western Ontario and McMaster University Osteoarthritis Index (WOMAC) and the Medical Outcomes Study Short Form-36 (SF-36). Methods: Patients were recruited as part of a prospective observational study of the outcomes of primary total knee arthroplasty for the treatment of osteoarthritis in four centers in the United States, six centers in the United Kingdom, and two centers in Australia. Independent research assistants at each site collected the Knee Society clinical data. The WOMAC, SF-36, patient satisfaction, and demographic data were obtained with self-administered questionnaires. Results: A total of 862 eligible patients were recruited, and complete preoperative and twelve-month data were available for 697 (80.9%) of them. The mean age was seventy years (range, thirty-eight to ninety years), and the majority of the patients (58.9%) were women. Low correlations were found among the items of both the knee and the function score at both assessment times. The Knee Society pain and function scores had moderate-to-strong correlations with the corresponding pain and function domains of the WOMAC and SF-36 (r = 0.31 to 0.72). Measurement of the standardized response mean showed the Knee Society knee score to be more responsive (standardized response mean, 2.2) than the WOMAC (standardized response means, 2.0 for pain and 1.4 for function) and the SF-36 (standardized response means, 1.0 for bodily pain and 1.1 for physical functioning). The Knee Society function score was the least responsive measure (standardized response mean, 0.8). Correlation of changes in scores at twelve months with patient reports of satisfaction and improvement in health status showed the WOMAC and SF-36 to be more responsive than the Knee Society scores. Conclusions: There is a poor correlation among the items of the Knee Society Clinical Rating System, but the rating system has adequate convergent construct validity. The WOMAC and SF-36 are more responsive measures of outcome of total knee arthroplasty. As they are less labor-intensive for researchers to use and as use of these instruments removes observer bias from the study design, they are preferable for knee arthroplasty outcome studies.

Patient expectations regarding total knee arthroplasty: differences among the United States, United Kingdom and Australia

BACKGROUND Total knee arthroplasty is an effective treatment for severe osteoarthritis of the knee. Our aim was to determine whether patients from the United Kingdom, United States, and Australia have different preoperative expectations regarding total knee arthroplasty and whether these expectations have an impact on outcomes and patient satisfaction. METHODS Patients from the United Kingdom, the United States, and Australia were recruited into a prospective observational study of primary total knee arthroplasty for the treatment of osteoarthritis. Preoperative expectations, Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) and Short Form-36 (SF-36) scores, and demographic, socioeconomic, and follow-up data, including satisfaction with outcome, were obtained from self-administered patient questionnaires. RESULTS A total of 598 patients with a mean age of sixty-nine years at the time of the index arthroplasty were recruited; 58% were women. The majority of patients expected to have no pain at twelve months after the surgery, and with the numbers available there was no significant difference among the countries with regard to pain expectations. Australian patients were more likely than patients in the United Kingdom or the United States to expect better function at twelve months after the surgery. With the numbers available, satisfaction scores at twelve months did not differ significantly among the countries and were not influenced by preoperative expectations. Australian patients were more likely than patients in the United Kingdom or the United States to be unwilling to undergo total knee arthroplasty again at twelve months under similar circumstances. CONCLUSIONS Patients from different countries have different expectations regarding total knee arthroplasty, which are not fully explained by differences in sociodemographic factors, clinical characteristics, and pain and functional status. Australian patients had the highest expectations but, despite reporting similar outcomes and satisfaction following total knee arthroplasty, they were more likely not to want to have the surgery again under similar circumstances.

Impact of psychological distress on pain and function following knee arthroplasty

BACKGROUND Preoperative psychological distress has been reported to be an important risk factor for poor outcome following lower-extremity arthroplasty. We determined the independent impact of preoperative psychological distress on three, twelve, and twenty-four-month WOMAC (Western Ontario and McMaster Universities Osteoarthritis Index) pain and function scores and on change scores over those time periods. METHODS Data were obtained from an international group of 952 patients in thirteen centers participating in the Kinemax Outcomes Study. Patients completed the WOMAC and Short Form-36 (SF-36) questionnaires. The mental health (MH) scale of the SF-36 was used to quantify the impact of psychological distress on WOMAC pain and function scores. We also dichotomized patients into groups with and without psychological distress on the basis of evidence-based cut-points. Repeated-measures models were used to derive mean preoperative and three, twelve, and twenty-four-month WOMAC pain and function scores and general linear models were used to derive change scores for patients with and without psychological distress after adjustment for covariates. RESULTS Psychological distress, when examined on a continuous scale, was found to predict pain and function at all time-points. WOMAC pain scores for psychologically distressed patients were 3 to 5 points lower, depending on the time-frame, than the scores for the non-distressed patients, after adjustment for covariates. WOMAC function scores did not differ significantly between the two groups following surgery. The changes in the WOMAC pain and function scores for the psychologically distressed patients were not significantly different from those for the non-distressed patients. CONCLUSIONS Many patients with psychological distress demonstrate a substantial decrease in that distress following surgery. Patients who are distressed have slightly worse pain preoperatively and for up to two years following knee arthroplasty as compared with patients with no psychological distress. With the exception of preoperative scores, these differences are not likely to be measurable at the individual patient level. WOMAC pain and function change scores do not differ between patients with and without distress after adjustment for covariates. LEVEL OF EVIDENCE Prognostic Level I.

Development and testing of a reduced WOMAC function scale

We used prospective data from 862 total knee and 716 total hip replacements three years after surgery in order to derive and validate a reduced Western Ontario and McMasters University Osteoarthritis Index (WOMAC) function scale. The reduced scale was derived using the advice of clinical experts as well as analysis of data. The scale was tested for validity, reliability and responsiveness. Items which were retained included: ascending stairs, rising from sitting, walking on the flat, getting in or out of a car, putting on socks, rising from bed, and sitting. The reduced and full scales had comparable, moderate correlations with other measures of function, confirming convergent validity. Cronbachs alpha was high (alpha > 0.85) with the reduced scale confirming reliability. Responsiveness was greater for the reduced scale (full = 1.4, reduced = 1.6). This reduced version of the WOMAC function scale provides a practical, valid, reliable and responsive alternative to the full function scale for use after total joint replacement. Further work is needed to demonstrate its wider applicability.

Patient-Reported Outcome and Survivorship After Kinemax Total Knee Arthroplasty

BACKGROUND We examined the long-term survivorship and patient-reported outcomes at a minimum of ten years following primary total knee arthroplasty. We hypothesized (1) that the survival rate would be at least 90% at ten years; (2) that age, gender, body-mass index, and primary diagnosis would not affect the survival rate; and (3) that the functional status of patients would be comparable with that of an age and gender-matched normal population. METHODS A total of 407 patients (523 knees) who had had primary total knee arthroplasty between January 1988 and April 1991 were identified. The mean age of the patients at the time of surgery was sixty-nine years, and 68% of the patients were women. At ten years, 165 patients (211 knees) had died; seven of these 211 knees had been revised before the time of death. Of the remaining 242 patients, 208 (86%) completed a questionnaire, which included the Western Ontario and McMaster University Osteoarthritis Index (WOMAC), the Short Form-36 (SF-36), and questions regarding patient satisfaction and revision surgery. In the group of patients who participated in the study, ten patients (eleven knees) had had a revision before the review. RESULTS A total of eighteen knees were revised. Twelve knees were revised because of aseptic failure and, of these, nine were revised because of polyethylene wear. The probability of survival at ten years was 96.1% with revision for any reason as the end point (and 97.2% when only aseptic failures were considered). Because of the small number of failures, we were unable to draw conclusions about associations between failure and age, gender, diagnosis, and body-mass index. The mean WOMAC scores (and standard deviation) at the time of the evaluation were 88 +/- 17 for pain and 79 +/- 20 for function. The SF-36 scores were similar to those for an age and gender-matched normal population, with only the physical functioning score being significantly lower (p < 0.001) and with the general health score being significantly higher (p < 0.001). Patients generally were very satisfied with all aspects of the outcome. CONCLUSIONS At ten years, the survival of the prosthesis was excellent and the majority of patients were functionally independent, had very little knee pain, and were very satisfied with the result. The health benefits of this total knee arthroplasty were maintained after a minimum duration of follow-up of ten years.

Patient-reported outcomes after fixed- versus mobile-bearing total knee replacement: A MULTI-CENTRE RANDOMISED CONTROLLED TRIAL USING THE KINEMAX TOTAL KNEE REPLACEMENT

We compared patient-reported outcomes of the Kinemax fixed- and mobile-bearing total knee replacement in a multi-centre randomised controlled trial. Patients were randomised to the fixed- or the mobile-bearing prosthesis via a sealed envelope method after the bone cuts had been made in the operating theatre. Randomisation was stratified by centre and diagnosis. Patients were assessed pre-operatively and at eight to 12 weeks, one year and two years post-operatively. Validated questionnaires were used which included the Western Ontario MacMasters University, Short-Form 12, Mental Health Index-5, Knee Injury and Osteoarthritis Outcome Score for Knee-Related Quality of Life and Function in Sport and Recreation scales and a validated scale of satisfaction post-operatively. In total, 242 patients (250 knees) with a mean age of 68 years (40 to 80) were recruited from four NHS orthopaedic centres. Of these, 132 patients (54.5%) were women. No statistically significant differences could be identified in any of the patient-reported outcome scores between patients who received the fixed-bearing or the mobile-bearing knee up to two-years post-operatively.

Pitfalls of Using Patient Recall to Derive Preoperative Status in Outcome Studies of Total Knee Arthroplasty

Background: It is essential to adjust for the level of preoperative pain and functional status when measuring the outcome of total knee arthroplasty. Some study designs rely on postoperative patient recall to derive preoperative status. In this study, we compared prospectively collected preoperative data with data derived from patient recall of preoperative status three months after total knee arthroplasty. Methods: Patients were recruited as part of a prospective observational study of the outcome of primary total knee arthroplasty for osteoarthritis at four centers in the United States, six centers in the United Kingdom, and two centers in Australia. Independent research assistants recruited patients and collected data with use of a uniform documentation system preoperatively and three months postoperatively. Preoperative data included the findings of a clinical history and physical examination, demographic information, socioeconomic status, and scores from two health-status instruments: the Western Ontario and McMaster University Osteoarthritis Index (WOMAC) and the Medical Outcomes Study Short Form‐36 Health Survey (SF‐36). Postoperative data included the WOMAC and SF‐36 scores and patient recall of preoperative status on selected items from these health-status measures. Results: A total of 862 patients were recruited, and recall data were available for 770 patients (89%). The mean age was seventy years (range, thirty‐eight to ninety years), and 59% of the patients were women. Comparisons of prospective and recall data on individual pain and function items showed poor-to-fair agreement (weighted kappa, 0.20 to 0.41). Patients recalled significantly more pain than they had reported preoperatively (p < 0.001), but there were random recollection errors for the function items. There was only moderate correlation between the prospective and recalled summary scores for pain (Spearman r = 0.53) and function (Spearman r = 0.48). In addition, 61% of the recalled pain scores and 50% of the recalled function scores differed from the prospective scores by more than 10 points (10% of the total range). Conclusions: Patients’ recall of preoperative pain and functional status three months after total knee arthroplasty demonstrated only moderate agreement with what the patients had reported prospectively. Researchers who use recall data to derive preoperative status must recognize these limitations when drawing conclusions about the effectiveness of total knee arthroplasty.

Metal-on-metal total hip arthroplasty.

The effects of elevated levels of metal ions in patients who have undergone metal-on-metal total hip arthroplasty are not fully understood. The effects of femoral head size on serum metal-ion levels have been the subject of conflicting reports, and further investigation is needed to evaluate the impact of acetabular and femoral component alignment. The conduct of clinical trials of metal-on-metal total hip arthroplasties has been inadequate as few investigators have used a randomized controlled design to compare metal-on-metal bearings with other bearing surfaces. Additional clinical research needs to include appropriate validated patient-reported outcome measures, activity monitoring, and health economics.

The prevalence of osteoporosis in patients with severe hip and knee osteoarthritis awaiting joint arthroplasty

BACKGROUND the presence of osteoporosis in patients with hip and knee osteoarthritis (OA) has important implications for understanding disease progression and providing optimal surgical and medical management. OBJECTIVE to determine the prevalence of osteoporosis among patients with osteoarthritis awaiting total knee arthroplasty or total hip arthroplasty aged between 65 and 80 years. DESIGN cross-sectional observational study. SETTING tertiary referral centre in Newcastle upon Tyne, UK. SUBJECTS patients with osteoarthritis awaiting total knee hip arthroplasty aged between 65 and 80 years. METHODS lumbar spine, bilateral femoral and forearm bone mineral density (BMD) measurements were obtained using dual-energy X-ray absorptiometry. RESULTS the cohort consisted of 199 patients with a mean age of 72 years (SD 4), and 113 (57%) were women. The overall rate of osteoporosis at any site was 23% (46/199) and a further 43% (85/199) of patients would have been classified as osteopaenic according to World Health Organization criteria. Osteoporosis was more commonly detected in the forearm (14%) than the lumbar spine (8.5%) and proximal femur of the index side (8.2%). CONCLUSIONS in summary, a significant proportion of patients with end-stage OA have osteoporosis but this diagnosis may be missed unless BMD measurements are performed at sites distant from joints affected by OA.

All-polyethylene compared with metal-backed tibial components in total knee arthroplasty at ten years. A prospective, randomized controlled trial.

BACKGROUND Several studies have described equivalent performance on radiostereometric analysis at two years for metal-backed compared with all-polyethylene stemmed tibial implants. The purpose of this study was to determine the ten-year survivorship results of these two designs from a large randomized controlled trial. METHODS Patients who were fifty years old or more, with no history of infection, and were undergoing primary total knee arthroplasty were randomized at the time of surgery to receive either an all-polyethylene or a metal-backed tibial component. Patients were assessed preoperatively and at one, three, five, eight, and ten years postoperatively. All assessments included a clinical history, a physical examination, and a radiographic evaluation. A total of 510 consecutive patients (566 knees) were recruited from August 1993 to January 1997. The mean age of the patients at the time of the index arthroplasty was 69.3 years, and 299 (59%) were women. The primary diagnosis was osteoarthritis for 458 knees (80.9%) and rheumatoid arthritis for 108 knees (19.1%). RESULTS Two hundred and ninety-three patients returned for the ten-year follow-up evaluation. A total of twenty-eight knees had been revised. Ten-year survivorship, with revision for any reason (or the time at which patients were documented as requiring revision but were unfit for surgery) as the end point, was 94.5% (95% confidence interval, 90.4% to 96.8%) for the all-polyethylene design and 96% (95% confidence interval, 92.6% to 97.8%) for the metal-backed design. Ten-year survivorship, with aseptic failure as the end point, was 97% (95% confidence interval, 93.3% to 98.7%) for the all-polyethylene design and 96.8% (95% confidence interval, 93.6% to 98.4%) for the metal-backed design. On the basis of the numbers available at ten years, there was no significant difference in survivorship between the two designs (p > 0.05). CONCLUSIONS The long-term results demonstrate excellent survivorship, with revision as the end point, for both the metal-backed and the all-polyethylene tibial component designs with no differences noted between the two.