Postoperative Hip Function as a Predictor of the Forgotten Joint Score-12 at One Year Following Total Hip Arthroplasty.

Background

The Forgotten Joint Score-12 (FJS-12) measures joint awareness after total hip arthroplasty (THA) with minimal ceiling effects. It is unclear whether early postoperative function predicts later joint awareness. This study aimed to examine whether hip range of motion (ROM), quadriceps muscle strength, perceived leg-length discrepancy (PLLD), and pain levels at three months postoperatively predict FJS-12 scores at 12 months postoperatively.

Methods

This single-center retrospective cohort study included consecutive patients who underwent primary THA between January 2022 and December 2023 in Japan. After applying the exclusion criteria, 392 patients (mean age 68 years; 84.2% women) who had complete three- and 12-month postoperative data were analyzed. The FJS-12 was used to assess joint awareness at 12 months postoperatively. At three months postoperatively, we measured hip ROM, quadriceps muscle strength, pain using a numeric rating scale ranging from 0 to 10, and PLLD. Multiple linear regression was used to investigate the associations between these variables and the FJS-12 at 12 months postoperatively, adjusting for age, sex, body mass index, surgical approach, and contralateral hip status.

Results

The mean FJS-12 score at 12 months postoperatively was 73.4 ± 22.2. Greater hip ROM (B = 0.09, P = 0.026) and quadriceps muscle strength (B = 11.05, P = 0.002) at three months postoperatively were associated with higher FJS-12 scores at 12 months postoperatively. Higher pain scores were inversely associated with FJS-12 scores (B = -2.90, P < 0.001), whereas PLLD was not clearly associated (B = -0.53, P = 0.349).

Conclusions

Greater hip ROM, stronger quadriceps muscle, and lower pain at three months postoperatively were linked to less joint awareness at 12 months after THA, whereas PLLD was not clearly linked. Early rehabilitation focusing on hip mobility, quadriceps muscle strength, and pain control may help improve joint awareness at 12 months.