DOES SELF-REPORTED PHYSICAL FUNCTION PREDICT PHYSICAL ACTIVITY BEHAVIOR AFTER TOTAL HIP ARTHROPLASTY? THE PREDICTIVE VALUE OF THE WOMAC

Abstract

Introduction: Despite growing awareness of the beneficial effects of physical activity on health, little is known about the amount of physical activity after THA. Although the WOMAC does not give direct information about the amount of physical activity it can be hypothesized that when patients experience limitations this will have an adverse effect on the amount of physical activity they are involved in. In this way the WOMAC can be predictive for the amount of physical activity. The aim of this study is to determine the correlation between the WOMAC and the amount of physical activity and to determine the predictive value of the WOMAC on meeting the (inter-) national guidelines of health -enhancing physical activity.

Materials and Methods: 364 patients with a THA (minimal one year postoperative) were included. Self-reported physical functioning was assessed by means of the WOMAC and the amount of physical activity by means of the SQUASH. Correlations between the WOMAC and SQUASH-scores were assessed using Pearson’s correlation coefficient. Binary logistic regression modelling was used to determine to which extent the score on the WOMAC was predictive in meeting the (inter-)national guidelines.

Results: A significant, low correlation between the WOMAC and SQUASH-scores (range 0.14 – 0.24) was found. Although the WOMAC was a significant predictor to meet the (inter-) national guidelines of physical activity (p< 0.001), the odds-ratio was low (1.022, 95%CI 1.0121.033). The Nagelkerke R2 was 0.069, implicating that 6.9% of the variance could be explained.

Conclusion: The WOMAC is not suitable to predict the amount of physical activity after THA, necessitating the use of additional quantitative outcome measures.