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Quantifying self-report measures' overestimation of mobility scores postarthroplasty
Paul W Stratford1, Deborah M Kennedy, Monica R Maly
1School of Rehabilitation Science, McMaster University, Hamilton, Ontario, Canada. stratfor@mcmaster.ca
Physical Therapy
|July 2, 2010
Summary
Patient self-reports of function after joint replacement, using the Lower Extremity Functional Scale (LEFS) and Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), systematically overestimate mobility. These differences are significant and exceed minimal clinical importance.
Area of Science:
- Orthopedic surgery
- Rehabilitation medicine
- Biomedical engineering
Background:
- Patient self-reported functional outcomes may not accurately reflect actual mobility post-arthroplasty.
- Overestimation of functional ability can impact treatment efficacy and patient expectations.
Purpose of the Study:
- To quantify the systematic differences between self-reported function (LEFS, WOMAC-PF) and objective performance measures (6MWT, TUG) before and after total knee arthroplasty (TKA) or total hip arthroplasty (THA).
- To assess the consistency of these differences across different time points and surgical procedures.
Main Methods:
- Secondary analysis of a prospective cohort study involving 85 patients undergoing primary TKA or THA.
- Regression analysis comparing LEFS and WOMAC-PF scores with Six-Minute Walk Test (6MWT) distances and Timed "Up & Go" Test (TUG) times at 9-13 weeks post-surgery.
- Examined the relationship between self-report and performance measures across pre-arthroplasty and post-arthroplasty periods.
Main Results:
- A consistent, yet differing, relationship was found between self-report and performance measures pre- and post-arthroplasty.
- Systematic overestimation of function by self-report measures was observed, varying by arthroplasty type.
- LEFS scores overestimated function by ~11 points (TKA) and ~13 points (THA); WOMAC-PF scores overestimated by ~12 points (TKA) and ~19 points (THA).
Conclusions:
- Self-reported functional scores alone, without considering the magnitude of systematic differences, lead to an overestimation of patient mobility post-arthroplasty.
- Findings are specific to the 9-13 week post-arthroplasty period.
- These identified discrepancies exceed the minimal clinically important difference, highlighting the need for careful interpretation of patient-reported outcomes.
