Low muscle mass affect hip fracture treatment outcomes in older individuals: a single-institution case-control study

Background Although sarcopenia has been known as a risk factor for hip fracture, only a few reports have described the impact of muscle mass on hip fracture treatment outcomes. The current study aimed to investigate the impact of muscle mass on hip fracture treatment outcomes. Methods This case–control study involved 337 patients (67 males and 270 females) with hip fracture aged ≥65 years (mean age: 84.1 ± 7.1 years) who underwent orthopedic surgery from January 2013 to June 2019. The mean follow-up period was 17.1 (1–60) months. Upon admission, all patients were assessed for low muscle mass according to the Asian Working Group for Sarcopenia criteria (male, SMI < 7.00 kg/m 2 ; female, SMI < 5.40 kg/m 2 ) using dual-energy X-ray absorptiometry. Treatment outcomes (stays at acute care institutions, hospital mortality, the Barthel index at discharge, and home discharge rates, and one-year mortality) were compared between patients with and without low muscle mass by Student’s t-test, Mann-Whitney U test and the Pearson Chi-Square test. A multivariate logistic regression model was used to calculate adjusted odds ratios (ORs) with 95% confidence intervals (CIs) for factors related to low muscle mass. Kaplan–Meier survival curves on one-year mortality of hip fracture patients for those with and without low muscle mass were prepared, and log-rank tests were performed. Furthermore, we determined whether low muscle mass was a risk factor for one-year mortality in hip fracture patients using a Cox proportional hazards model. Results The prevalence of low muscle mass in patients with hip fracture was 231(68.5%). Those with low muscle mass had a lower Barthel index ( P < 0.0001), hospital discharge rate ( P = 0.035) and higher one-year mortality ( P = 0.010). Cox proportional hazards regression analysis adjusted for age and sex found that low muscle mass was a risk factor for one-year mortality (hazard ratio, 3.182, 95% confidence interval, 1.097–9.226, P = 0.033). Conclusions Patients with hip fracture who had low muscle mass had a lower Barthel index, lower home discharge rate, and higher one-year mortality. Moreover, low muscle mass was identified as a risk factor for one-year mortality among those with hip fracture. The aforementioned findings may help clinicians better manage those with hip fracture.