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Responsiveness and clinically important differences for the WOMAC and SF-36 after hip joint replacement
J M Quintana1, A Escobar, A Bilbao
1Hospital de Galdakao, Unidad de Investigacion, Barrio labeaga s/n, 48960 Galdakao, Vizcaya, Spain. jmquinta@hgda.osakidetza.net
Osteoarthritis and Cartilage
|September 13, 2005
Summary
Total hip replacement (THR) significantly improves health-related quality of life, as measured by the SF-36 and WOMAC. Minimal clinically important difference (MCID) and minimal detectable change (MDC) values provide benchmarks for expected gains post-THR.
Area of Science:
- Orthopedics
- Rheumatology
- Health Outcomes Research
Background:
- Hip osteoarthritis (OA) significantly impacts patients' quality of life.
- Total hip replacement (THR) is a common surgical intervention for end-stage hip OA.
- Assessing patient-reported outcomes is crucial for evaluating THR effectiveness.
Purpose of the Study:
- To evaluate the responsiveness of the SF-36 and WOMAC in patients undergoing THR.
- To establish the minimal clinically important difference (MCID) for these instruments post-THR.
- To determine the minimal detectable change (MDC) for assessing meaningful improvements after THR.
Main Methods:
- Prospective observational study in three public hospitals.
- Consecutive patients with hip OA awaiting THR completed SF-36 and WOMAC at baseline, 6 months, and 2 years.
- Transitional questions assessed joint changes at 6 months postoperatively.
Main Results:
- Significant improvements observed in SF-36 and WOMAC domains at 6 months post-THR, with smaller gains between 6 months and 2 years.
- MCID values ranged from 10.78 to 29.26 across different domains and instruments.
- MDC values ranged from 18.99 to 42.05, indicating the threshold for detecting true change.
Conclusions:
- The established MCID and MDC values reflect expected improvements following THR.
- These values should be interpreted cautiously due to estimator uncertainty.
- MCID and MDC should not be treated as definitive absolute thresholds for clinical significance.