Integrated rehabilitation and ambulatory recovery in older adults with hip fracture according to muscle strength and sarcopenia status: a secondary analysis of a randomized controlled trial

PURPOSE: Sarcopenia and impaired muscle strength are common in older adults with hip fractures and are strongly associated with poor functional recovery. Although integrated multidisciplinary rehabilitation improves outcomes after hip fracture, whether its benefits differ according to baseline muscle strength or sarcopenia severity remains unclear. This study aimed to examine whether the functional benefits of Fragility Fracture Integrated Rehabilitation Management (FIRM) vary according to sarcopenia status and handgrip strength (HGS) in older adults after hip fracture surgery. METHODS: This was a secondary analysis of a multicenter randomized controlled trial comparing FIRM with conventional rehabilitation in adults aged ≥ 65 years undergoing hip fracture surgery. The primary outcome was independent ambulation at 12 months. Sarcopenia was classified using three approaches: sarcopenia versus non-sarcopenia, a three-level classification (non-sarcopenia, possible sarcopenia, and sarcopenia), and low versus normal HGS. Logistic regression models, including treatment, sarcopenia status, and their interactions, were fitted with sequential adjustments for relevant covariates. RESULTS: Of the 203 randomized participants, 119 (58.6%) completed the 12-month follow-up. Treatment-by-sarcopenia interactions were not statistically significant. Stratum-specific analyses suggested a pattern of greater functional improvement with FIRM than with conventional rehabilitation, particularly among participants with low HGS and, to a lesser extent, those with sarcopenia. In the fully adjusted models, FIRM was associated with greater improvement in independent ambulation among participants with low HGS (odds ratio, 4.25; risk difference, + 34.7%; P = 0.014). CONCLUSIONS: Integrated rehabilitation may provide greater functional benefits than conventional rehabilitation in older adults with hip fractures, particularly among those with low muscle strength. However, given the lack of statistically significant interaction effects and the attenuation of the observed associations in the fully adjusted models, these findings should be interpreted as exploratory.