Handgrip Strength and Dual-Energy X-Ray Absorptiometry (DXA)-Defined Skeletal Muscle Index in Relation to Early Postoperative Physical Performance After Hip Fracture Surgery in Older Adults: A Retrospective Cohort Study

Background and Objectives: To evaluate whether skeletal muscle mass and handgrip strength are associated with early postoperative physical performance, assessed using the Short Physical Performance Battery (SPPB) approximately 6 weeks after surgery, in older adults after hip fracture surgery. Materials and Methods: This single-center retrospective cohort study included 33 of 88 patients aged ≥ 65 years; 55 were excluded, mainly because perioperative dual-energy X-ray absorptiometry (DXA) data or postoperative functional assessment were unavailable. Skeletal muscle mass was assessed by DXA as the skeletal muscle index (SMI) using the Asian Working Group for Sarcopenia 2019 criteria, and handgrip strength was measured, both preoperatively or within 3 days postoperatively. The SPPB was the primary outcome; the Berg Balance Scale (BBS), Functional Ambulation Category (FAC), and Modified Barthel Index (MBI) were secondary outcomes. Results: Excluded patients were older and had lower body mass index, indicating a selected cohort. In a multivariable model including both exposures (standardized; coefficients per 1-SD increase) with age and sex, handgrip strength was associated with the SPPB score (β = 1.82, 95% CI 0.29 to 3.35, p = 0.022), whereas SMI was not (β = −0.20, 95% CI −1.47 to 1.07, p = 0.746). The coefficient difference did not reach conventional significance (Wald p = 0.070). In sensitivity analyses, the handgrip strength coefficient ranged from 1.56 to 2.21 per SD. In unadjusted analyses, handgrip strength was correlated with the BBS and MBI, whereas SMI correlated with neither; neither exposure was correlated with FAC. Conclusions: Among older adults able to attend early outpatient assessment after hip fracture surgery, handgrip strength showed a consistent adjusted association with early postoperative SPPB across model specifications, whereas the SMI estimate was near zero, with a confidence interval spanning zero. Because the difference between estimates was not statistically established, these findings are exploratory and hypothesis-generating.