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: A total of 175 patients aged 51-95 years with low-energy hip fracture who underwent hip computed tomography scans were divided into ＜80 year-old 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 genders and groups, and correlation analysis was used to determine the relationships between hip muscle fat area and age and BMI. Result:s The hip TAA, SAA and MFI of males were significantly lower than those of females (t = −2.356, −2.550, −3.090), and CSMA was significantly higher than that of females. The CSMA in the ＜80 year-old group was higher than that of the ≥80 year-old group, and the MFI was lower than that found in the ≥80 years old group. When controlling for BMI, the age of males and females was positively correlated with IMAA and MFI (r = 0.445 and 0.612 for males, r = 0.202 and 0.390 for females), and negatively correlated with CSMA (r = −0.673 for males, r = −0.428 for females). When controlling for age, the BMI of males was positively correlated with TAA, IMAA, SAA and CSMA (r = 0.430, 0.491, 0.389, 0.623), while the BMI of females was 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, but the intermuscular fat was similar to that of women. Hip muscle mass decreases and intermuscular fat increases with age. Generally, the higher the BMI, the more muscle and fat was found; however, MFI in men was not related to BMI.