Osteoarthritis Surgery
The following two studies are focused on identification of predictors of total joint arthroplasty in patients with osteoarthritis. These abstracts represent an important area of research that is relevant to ever growing numbers of older Americans with disabling osteoarthritis of weight-bearing joints. In keeping with existing literature, factors associated with need for total joint arthroplasty may not be identical to those that contribute to disease development, or to disease progression. One would also anticipate that these factors may be quite different from those that predict successful functional outcomes following arthroplasty.
Abstract #916 The Risk of Contralateral Total Knee Arthroplasty After Knee Replacement for Osteoarthritis M McMahon, J Block.
McMahon and Block reported on a cohort of 117 conecutive patients who were followed for up to 14 years following total knee arthroplasty for osteoarthritis. Radiographic severity of the contralateral knee was established at the time of arthroplasty. The demographic characteristics of the sample were typical of OA patients. Kaplan Meier survival analysis was used to estimate the length of time to contralateral arthroplasty. Patients underwent the contralateral procedure 120 to 144 months following the initial arthroplasty, with a mean survival time of 132 months. Overall, time to contralateral arthroplasty was inversely related to disease severity of the knee at risk. Those with moderate severity underwent arthroplasty approximately 128 months following the initial arthroplasty, while time to replacement was approximately 80 months for those with severe OA of the knee at risk. Conventional risk factors for OA (BMI, age and female gender) were not significantly associated with survival time. The authors conclude that OA severity at the time of total knee arthroplasty is the single most important determinant of time to replacement of the contralateral knee.
Editorial Comments: This study uniquely addresses the issue of time to contralateral total knee arthroplasty, and examines the association of disease-associated risk factors with time to surgery. However, these factors should be examined concurrently with factors that might influence ones decision to proceed with this elective procedure such as level of disability, depressive symptoms, sleep and life quality. It would be interesting to know the extent to which, if any, use of medical therapies for painful symptoms delayed the time to total knee arthroplasty.
Abstract #918 The Need for Total Hip Replacement in Patients Newly Presenting with Hip Pain F Birrell, A Silman, P Croft, C Cooper, G Hosie, G Macfarlane.
Birrell and colleagues presented a study of a cohort of 195 patients who were followed for 4 years or more and who had reported hip pain to their primary care practitioner. 68% of the cohort was female, and 54-71 years of age at baseline. Joint space narrowing of more than 2.5 mm was strongly predictive of total hip arthroplasty (hazard ratio 9.1), impaired internal rotation was associated with a hazard ratio of 2- per quintile, reported difficulty walking a mile hazard ratio of 3, pain severity (5 or more of 10) with a hazard ratio of 2.5. The 3-factor model of impaired range of motion (lower 2 quartiles), pain severity (5 or more out of 10), and difficulty walking a mile was 74% sensitive and 77% specific for the outcome of total hip arthroplasty. Inclusion of radiographic severity in the 4-factor model increased sensitivity to 81% and specificity to 83%. The authors conclude that hip replacement is common in the first 4 years after initial presentation to a primary care practitioner with hip pain, and that radiographic severity adds little to the clinical 3-factor model.
Editorial Comments: This study emphasizes the importance of clinical characteristics over radiographic severity, and integrates pre-operative joint impairments and mobility function in the predictive models. This study represents an important step towards defining which of the many factors is associated with proceeding to total hip arthroplasty. However, one must also account for disease extent and severity elsewhere, and representativeness of this sample, given the unexpectedly frequency of arthroplasty.
Abstract #895 Predicting the Outcome of Total Knee Arthroplasty From Preoperative Status E Lingard, J Katz, E Wright, C Sledge.
A prospective, multi-center, observational study was conducted by Lingard and colleagues to determine which, if any, pre-operative characteristics determine functional outcomes as measured by the WOMAC 12 months following total knee replacement for OA. The analysis was restricted to 742 patients who underwent unilateral TKA for OA who also completed WOMAC questionnaires. 60% were women with a mean age of 70 years. Data were analyzed using linear regression analysis, with an average of 2 co-morbidities. Low pre-operative WOMAC function, low scores on the mental health scale of the SF 36, and higher number of co-morbidities were associated with lower post-operative WOMAC function. The authors conclude that the above pre-operative characteristics are valuable indicators of function assessed by WOMAC score 12 months following knee arthroplasty.
Editorial Comments: This important study examines the independent value of demographic, functional, and psychosocial factors as predictors of self-reported function 1 year following knee replacement. The study highlights the importance of comorbidities as independent determinants of function. Others have previously shown that the presence of specific co-morbid conditions, i.e. depression or heart disease, may be more important than the total number of co-morbidities in determining post-operative function.
