Abstract
Introduction and Aims: A growing number of studies suggest worse pre-operative functional status is associated with worse outcome in terms of both function and pain after total hip (THA) and knee (TKA) arthroplasty. A gap in these studies, however, is the lack of physical performance measures to validate the self-reported findings.
Method: Using a repeated measures design, 152 subjects with endstage osteoarthritis were assessed at multiple points over the first four post-operative months. Outcome measures included the six-minute walk test (6MWT), timed up and go test (TUG), and the pain and physical function subscales of the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC). Average growth curves and individual variations in the pattern were characterised using hierarchical linear modelling. Following validation of the basic developmental models, predictors of recovery were sequentially modelled. Gender, baseline pre-operative function, site of replacement, age, additional outpatient rehabilitation, and number of co-morbidities were investigated as predictors.
Results: In the models explored, a second-degree polynomial growth term provided a reasonable fit for the data over the study interval. Baseline pre-operative score was a significant predictor (p< .001) in all of the models. A significant interaction (p< .0005) was observed between the growth parameter (weeks post-surgery) and baseline pre-operative score for the 6MWT. Patients with better pre-operative scores are predicted to improve their 6MWT distances faster. Although gender was a significant predictor (p< .0005) of TUG and 6MWT performance at one week post-operatively (women slower), it was not a predictor in the WOMAC models. No significant interaction was observed between the growth parameter and gender in either of the 6MWT or TUG models. Site of replacement (hip or knee) was a significant predictor (p< .001) of one-week scores in all of the models except for the WOMAC physical function subscale. In both performance measure models, the average growth curves demonstrate that patients post-THA are predicted to start with worse function, however, their growth rates are faster over the studied interval. Co-morbidities, age and additional outpatient rehabilitation were not explanatory variables for any of the models.
Conclusions: Performance measurement demonstrated that women started with worse function than men one week after surgery, but thereafter had similar rates of improvement. The importance of pre-operative function as a predictor of post-operative recovery cannot be overlooked. Patient and surgeon’s expectations of outcome need to take pre-operative function into account.
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.
