A New Threshold for Appendicular Lean Mass Discriminates Muscle Weakness in Women With Hip Fracture: A Cross-Sectional Study

OBJECTIVE: The aim of the study was to investigate the relationship between measures of muscle mass and grip strength in women with subacute hip fracture. Firstly, we aimed to assess the capability of the current thresholds for appendicular lean mass, appendicular lean mass/body mass index ratio and appendicular lean mass/height to separate weak and nonweak women. Secondly, we aimed to explore alternative thresholds for the three measures of muscle mass to discriminate weakness. DESIGN: This is cross-sectional study of 160 women with hip fracture admitted to a rehabilitation hospital. We assessed appendicular lean mass by dual-energy x-ray absorptiometry and grip strength by a Jamar hand dynamometer. Weakness was defined as grip strength of less than 16 kg. RESULTS: Weakness was not significantly associated with appendicular lean mass of less than 15.02 kg, appendicular lean mass/body mass index ratio of less than 0.512 or appendicular lean mass/height of less than 5.67 kg/m. For appendicular lean mass (but not for the other 2 measures of muscle mass), an alternative threshold (11.87 kg instead of 15.02 kg) significantly discriminated weakness: χ (1, n = 160) = 10.77 (P = 0.001). The association between appendicular lean mass of less than 11.87 kg and grip strength of less than 16 kg persisted after adjustment for age and body mass index (odds ratio = 2.50, 95% confidence interval = 1.17-5.34, P = 0.018). CONCLUSIONS: Data suggest that the current thresholds for measures of muscle mass do not discriminate weakness in women with subacute hip fracture. For appendicular lean mass, an alternative cutoff point actually separated weak and nonweak women.