Development of a Clinical Prediction Rule to Identify Physical Activity After Total Hip Arthroplasty

Abstract

Objective: To develop clinical prediction rule (CPR) of physical activity 1 year after total hip arthroplasty (THA).

Design: Retrospective cohort study.

Setting: University hospital with orthopedic surgery.

Participants: The study group included 321 patients (56 men) who underwent primary THA (N=321).

Intervention: Not applicable.

Main outcomes measures: The data collected included age, body mass index, clinical score from the questionnaires, hip pain, range of motion, muscle strength, and Physical functions (10-meter walk test [10MWT], timed Up and Go test, sit-to-stand test). Patients were classified into sufficient and insufficient activity groups based on their University of California, Los Angeles (UCLA) activity score 1 year after THA. Variables measured preoperatively and 3 weeks postoperatively were analyzed using univariate and multivariate methods to derive CPR for physical activity.

Results: A CPR was developed using the following 5 factors and cutoffs: age 70.5 years or younger, preoperative UCLA activity score ≥3.5, preoperative hip abduction strength ≥0.54 Nm/kg, preoperative knee extension strength ≥1.04 Nm/kg, and 10MWT ≤8.49 seconds 3 weeks after surgery. The presence of 4 of the 5 factors predicted a sufficient physical activity level at 1 year, with a positive likelihood ratio of 5.94 and probability of 85.4%. The presence of 5 predictor variables increased the probability of sufficient physical activity after THA to 94.7%.

Conclusions: This study developed a CPR for physical activity 1 year after THA. Having 4 or more of the 5 measurements were useful indicators for predicting of physical activity 1 year postoperatively.

Keywords: Clinical prediction rule; Physical activity; Rehabilitation; Total hip arthroplasty.