Impact of Preoperative Skeletal Muscle Quality on Functional Outcome in Total Hip Arthroplasty.

Objectives: To investigate the effect of preoperative muscle quality on functional outcomes after total hip arthroplasty (THA).

Design: Retrospective cohort study.

Setting and participants: We included 426 patients who underwent primary THA between 2015 and 2022 to evaluate the relationship between preoperative muscle quality and 1-year functional outcomes following THA.

Methods: The muscle cross-sectional area (CSA) and density at baseline were measured using preoperative computed tomography. The CSA was further divided based on muscle quality into intramuscular adipose tissue (IMAT), normal-density muscle (NDM), and low-density muscle (LDM) based on muscle density thresholds. According to their functional recovery, patients were classified into sufficient functional recovery [Harris hip score (HHS) ≥89] and insufficient functional recovery (HHS <89) groups based on their HHS at 1-year post THA. Propensity score matching was performed to balance the baseline characteristics of the patient groups, including age, sex, body mass index, HHS, University of California, Los Angeles activity scores, and gait speed. The preoperative muscle density, CSA, IMAT, NDM, and LDM of the gluteus maximus, gluteus medius, gluteus minimus, iliopsoas, and rectus femoris muscles were compared between the groups.

Results: Ninety matched pairs were analyzed following covariate adjustment using propensity scores. The insufficient group had significantly more IMAT in all muscles preoperatively than did the sufficient group (P < .05). In addition, the muscle density and NDM of the gluteus maximus, gluteus medius, and iliopsoas in the insufficient group were significantly worse than those in the sufficient group (P < .05). Conversely, the 2 groups showed no significant differences in LDM.

Conclusions and implications: Our results revealed that patients with a significantly higher IMAT prevalence and reduced NDM preoperatively were less likely to experience significant improvement after THA. Therefore, we propose that undergoing THA with good muscle quality represents the optimal timing for achieving higher functional recovery.