Abstract: BACKGROUND: Studies have shown that reduced diameter and number of muscle fibers are related to muscle atrophy, especially type II muscle fibers.
OBJECTIVE: To explore the correlation between the distribution characteristics of skeletal muscle fibers and bone mineral density in postmenopausal women with hip fractures. 
METHODS: The clinical data of 60 female postmenopausal patients undergoing surgical treatment for hip fractures were included. Bone mineral density and muscle content were measured by dual energy X-ray, and the Appendicular Skeletal Muscle Mass Index (ASMI) was calculated. According to the diagnostic criteria for osteoporosis, the included patients were divided into four groups with normal bone mass, reduced bone mass, osteoporosis, and severe osteoporosis, with 15 cases in each group. During operation, the patient’s gluteus medius muscle fibers were taken, and their diameter and distribution characteristics were observed under a microscope after slicing, fixing, and staining. Muscle content and femoral neck bone density at the healthy side were tested. Pearson correlation analysis was used to analyze the correlation between muscle fiber diameter and skeletal muscle content at the affected side and the bone mineral density of the contralateral femoral neck. 
RESULTS AND CONCLUSION: The body muscle content and trunk muscle content of the severe osteoporosis group were significantly lower than those of the other three groups (P < 0.05), but there was no significant difference between the other three groups (P > 0.05). The muscle content of the limbs in the normal bone mass group was significantly higher than that in the osteoporosis group and severe osteoporosis group (P < 0.05), and the muscle content of the limbs in the reduced bone mass group was higher than that in the severe osteoporosis group (P < 0.05). The ASMI value of the limbs in the severe osteoporosis group was significantly lower than that in the normal bone mass group and reduced bone mass group (P < 0.05). The femoral neck bone mineral density of postmenopausal women with hip fractures had a certain correlation with age, body mass, and type II muscle fiber diameter. The linear fitting R2 of femoral neck bone density with type II muscle fiber diameter and muscle content of the limbs was 0.103 and 0.243, respectively. To conclude, the bone mineral density of female patients with hip fractures is closely related to age, body mass index, muscle content of different body parts (body, limbs, trunk), and ASMI. Type II muscle fiber diameter and muscle content of the limbs have a positive correlation with femoral neck bone mineral density, suggesting that in the prevention of hip fractures in postmenopausal elderly women, we should adopt a comprehensive program of exercise, nutrition and drug treatment to increase bone mass and improve muscle quality.

Key words: bone, fracture, postmenopausal, osteoporosis, bone mineral density, muscle fiber, sarcopenia, body mass index