Our pilot study demonstrated that a comprehensive outpatient rehabilitation program is well-tolerated by patients less than 65 years of age who undergo THA. All subjects completed the intervention and no adverse reports were reported. Our findings also emphasize the need to carefully evaluate and select appropriate outcome measures. Although our pilot sample was small and did not achieve statistical significance, we measured CID between groups in strength measures only. Outcomes that have proven useful in other studies of THA did not detect any CID between our study groups, which were a young cohort of patients undergoing THA.
Using a hand held dynamometer, we were able to measure CID in all strength measures between groups at the initial post-intervention assessments . Although both groups made substantial gains in strength over time, the mean changes measured in strength were much greater in the Intervention group, particularly at the four month evaluation.
Interestingly, this strength difference did not impact performance on the six-minute walk test, which has been shown to be a useful measure to assess outcomes following TJA . No CID was measured between groups over time. The six minute walk test was selected because it measures both speed and endurance. However, in this younger group, more challenging performance-based functional tests may be required . Use of a formal gait laboratory assessment also did not detect any CID between groups. This was a particularly disappointing finding as formal gait re-training was a component of the intensive rehabilitation program.
Similar to others [3, 4], marked improvement occurred in self-reported HRQL over the first year following THA in our pilot study. Ceiling effects were reported in more than 40% of WOMAC Pain scores, but only 5% of WOMAC Function scores. However, with all subjects reporting substantial improvements in pain and function, the WOMAC was unable to discriminate between groups with group differences being well under the established CID .
Our study followed the recommendations of the Medical Research Council’s Guidelines on developing complex interventions . Rehabilitation falls into the category of complex interventions because rehabilitation programs typically involve multiple components and may be delivered and evaluated in different formats [6, 15, 16]. Rehabilitation practitioners often do not adequately describe their intervention content or do not consider the impact of selected outcome measures and timing of the evaluation. Our goal with this pilot study was to determine the feasibility of our comprehensive program as well as to explore appropriate outcomes and outcome measures, and the timing of the evaluations prior to undertaking a definitive RCT.
Evaluation of the impact of the intervention both immediately after the intervention and again eight months later demonstrated that Intervention subjects maintained their earlier strength gains, but also demonstrated that Control subjects regained their strength more slowly over the first post-operative year in most hip musculature. Further evaluation is needed to determine if there is any long-term impact to the intensive rehabilitation program or if it allows earlier return to activity and work in this younger cohort.
This pilot study was a useful preliminary step in determining the feasibility of the intervention as well as determining appropriate outcome measures and assessment time points. Using a randomized design with blinded assessment of outcomes at multiple time points increases the likelihood that our findings were measuring the impact of the intervention. Although we found that the program was feasible and well-tolerated by our subjects, we also determined that commonly used self-report and performance-based outcome measures for subjects undergoing THA do not appear to be appropriate to detect differences in postoperative rehabilitation in this younger cohort. Thus, this initial pilot study circumvented a large and expensive randomized trial being undertaken with inappropriate outcome measures.
However, the sample was small and there were some baseline imbalances between groups in HRQL that might have affected our results. Although the Intervention group reported more overall preoperative health limitations, they surpassed the Control group in these same health dimensions at the one-year assessment. We were able to detect CID in strength measures, but cannot be assured that these findings will be re-produced in a large well-powered RCT. Further, we did not record the specific care provided to the Control group. In the future RCT, ‘usual care’ should be as standardized as possible and recorded to fully measure the differences between the usual care and intervention programs.