Correlations of Hip Muscle Composition with Age and Body Mass Index in Middle-aged and Elderly Patients with Hip Fracture

Objective: To investigate the correlations of hip muscle composition with age and body mass index (BMI) in middle-aged and elderly patients with hip fracture. Methods: In total of 175 patients aged 51~95 years with low-energy hip fracture who underwent hip computed tomography scans were divided into ＜80 and ≥80 year-old groups. Quantitative computed tomography (QCT) was performed to obtain the cross-sectional muscle area (CSMA), total adipose area (TAA), intra-muscular adipose area (IMAA), subcutaneous adipose area (SAA) and muscle fat infiltration (MFI) of the hip. An independent t-test was used to compare the differences between gender and groups, and correlation analysis was used to determine the relationships between hip muscle fat area and age and BMI. Results: The hip TAA, SAA and MFI of men were significantly lower than those of women (t=−2.356, −2.550, −3.090), and CSMA was significantly higher than that of women. The CSMA in the ＜80 year-old age group was higher than that of the ≥80 year-old age group, and the MFI was lower than that found in the ≥80 years age old group. After adjusting for BMI, the age of men and women positively correlated with IMAA and MFI (r=0.445 and 0.612 for men, r=0.202 and 0.390 for women), and negatively correlated with CSMA (r=−0.673 for men, r=−0.428 for women). After adjusting for age, the BMI of men positively correlated with TAA, IMAA, SAA, and CSMA (r=0.430, 0.491, 0.389, 0.623), whereas the BMI of women positively correlated with TAA, IMAA, SAA, CSMA, and MFI (r=0.510, 0.389, 0.478, 0.295, 0.296). Conclusion: In middle-aged and elderly patients with hip fragility fractures, men had more muscle and less total fat than those in women, but similar intermuscular fat to that of women. Hip muscle mass decreased and intermuscular fat increased with age. Generally, higher BMI, correlated with more muscle and fat. However, MFI in men was not associated with BMI.