Preoperative Activity Levels in Patients Who Undergo Total Hip Arthroplasty Distinctively Affect the Postoperative Recovery Process and Forgotten Joint Score-12: A Prospective Cohort Study Using a Triaxial Accelerometer.

Abstract

This study aimed to evaluate changes in objective physical activity (OPA) after total hip arthroplasty (THA) and their impact on patient-reported outcomes. This prospective cohort study involved 212 patients who underwent THA for unilateral hip osteoarthritis and were followed up for 12 months. Step count, exercise, and wearing time were measured using a compact triaxial accelerometer before surgery and at one, two, three, six, and 12 months postoperatively. This study investigated the recovery process of OPA in patient groups classified by age and preoperative activity levels and examined its impact on patient-reported outcomes, including the Forgotten Joint Score-12 (FJS-12). Multiple regression analyses revealed a significant association between preoperative activity levels and FJS-12 at 12 months postoperatively (P = 0.004). The median value of total exercise increased from 2.23 (interquartile range [IQR], 1.32 to 3.35) preoperatively to 3.45 (IQR, 2.01 to 4.78) at 12 months postoperatively (P < 0.001), while FJS-12 improved from 60.2 (IQR, 39.6 to 75) at one month to 75 (IQR, 62.5 to 89.6) at 12 months postoperatively (P < 0.001). In patients who had higher preoperative activity, the 12-month FJS-12 significantly increased from six months postoperatively in both younger (P = 0.008) and older groups (P = 0.002). The mixed-design analyses of variance revealed time-related changes and group differences in OPA levels and trajectories (P < 0.001). Post hoc analysis showed that OPA at 12 months exceeded preoperative levels (P < 0.001) in patients who had lower preoperative activity; however, it remained lower than in those who had higher activity. Conversely, patients who had higher preoperative activity experienced a significant decline postoperatively (P < 0.001), followed by recovery to preoperative baseline levels. The relationship between the subjective experience of "forgetting" the joint and actual physical activity levels was clarified, providing a new perspective on postoperative functional assessment. Preoperative OPA may predict FJS-12 at one year postoperatively.