Background Variance in functional recovery after total hip arthroplasty (THA) is likely explained by patient-related factors. The Risk Assessment and Predictor Tool (RAPT)  is an existing model for predicting recovery for patients after THA. Interestingly, the RAPT only contains self-reported information about the preoperative functional status while recently the Osteoarthritis Research Society International (OARSI) recommended to use performance based test, such as mobility or walking tests, to complement self-reported function . We hypothesize that augmenting the RAPT score with performance-based tests would result in more accurate predictions regarding the inpatient functional recovery of patients after THA.
Objectives The aim of this study is to evaluate the RAPT as a prediction tool for adequate or inadequate inpatient functional recovery and to study the predictive value of the model after adding performance-based functional data to this model.
Methods We used a prospective cohort study design. Preoperative screening of patients attending for primary or revision THA (Feb - Dec 2012) entailed six independent factors: the RAPT score, four performance-based tests (the timed up and go (TUG) test, the two minutes walk (2MW) test, hand grip strength (HGS) and habitual gait speed measured by ten meters walking test (10mW)), and the Charnley score for comorbidities. The dependent outcome parameter inpatient functional recovery was dichotomized: adequate functional recovery (walking independent with walking aid within 3 days after surgery) and inadequate functional recovery (4 or more days to reach independence in walking). By use of logistic modeling we determined the predictive value of a prediction model based on the RAPT. Consequently we added the performance-based measures to the model. Predictive value was tested using the Area under the curve (AUC).
Results A total of 315 consecutive patients were included in the study. Mean age was 69 years (SD 11), 68% were women,mean BMI was 26,8 (SD 4.0) and mean length of stay was 4.1 days (SD 1.6). Delayed functional recovery was apparent in 47 people (15%). All functional tests were statistically related to delayed functional recovery (p<0.05). AUC for RAPT was 0.75 (95% CI 0.68-0.82) while by adding 10mW to RAPT the accuracy (AUC 0.80, 95%CI 0.75-0.86) in predicting functional recovery increased.
Conclusions Adding a performance-based tests to the RAPT score resulted in more accurate predictions regarding the inpatient functional recovery of patients after THA. Prediction models including self-reported factors (RAPT) and performance based tests should be optimized to detect low and high risk patients in order to establish (cost)effective and efficient rehabilitation in clinical pathways for THA.
Dobson F, Hinman RS, Roos EM, Abbott JH, Stratford P, Davis AM, Buchbinder R, Snyder-Mackler L, Henrotin Y, Thumboo J, Hansen P, Bennell KL. OARSI recommended performance-based tests to assess physical function in people diagnosed with hip or knee osteoarthritis. Osteoarthritis Cartilage. 2013 Aug;21(8):1042-52.
Oldmeadow LB, McBurney H, Robertson VJ. Predicting risk of extended inpatient rehabilitation after hip or knee arthroplasty. J Arthroplasty. 2003 Sep;18(6):775-9.
Disclosure of Interest None declared