Abstract
Introduction and Aims: With the current trend to minimally invasive techniques for total hip (THA) and knee arthroplasty (TKA), an understanding of early functional recovery for traditional surgical approaches is required for outcome comparison. Patterns of recovery for self-report and physical performance measures were therefore explored during the early post-operative period.
Method: One hundred and fifty-two patients were assessed pre-operatively and several times over the first four post-operative months. The pain and physical function subscales of the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), the six-minute walk (6MWT) and timed up and go test (TUG) were used as outcome measures. Hierarchical linear modelling was used to characterise the average pattern of recovery for each measure. Model development began with a parameter that estimated the patients’ self-reported or actual measured function at one week postoperatively and a parameter that estimated the patients’ rate of change for every week thereafter.
Results: Sixty-nine subjects underwent THA and 83 underwent TKA with a mean age of 63.8 + 10.2 years. Different patterns of recovery and predictors of change were observed for the WOMAC subscales and physical performance measures. The growth models for the performance measures were more complex, including more predictors and interaction terms. The model for the physical function subscale was the simplest. In addition to the growth parameters and the intercept, baseline function was the only other model parameter influencing the estimated score at one week. A striking difference between the WOMAC and performance measure growth curves concerned the point at which pre-operative scores are predicted to be met. The predicted scores for the WOMAC subscales either reach or exceed the pre-operative scores at one to two weeks post-surgery in comparison to the 6MWT and TUG, which do not reach these levels until six to eight weeks post-surgery. It would appear that the physical function subscale of the WOMAC does not reflect the early deterioration that occurs in physical function. The predicted growth curves for the TUG confirm its usefulness as a physical function measure only in the early recovery period, as a ceiling effect occurred around 10 weeks.
Conclusion: The physical function subscale of the WOMAC may not always accurately reflect physical function. Using only self-report measures to compare traditional surgical approaches to minimally invasive techniques might miss significant differences in recovery of physical function. Using both physical performance and self-report measures to monitor early recovery is recommended.
These abstracts were prepared by Editorial Secretary, George Sikorski. Correspondence should be addressed to Australian Orthopaedic Association, Ground Floor, The William Bland Centre, 229 Macquarie Street, Sydney, NSW 2000, Australia.
At least one of the authors is receiving or has received material benefits or support from a commercial source.
