OBJECTIVE:To investigate the effects of age, body mass index (BMI), bone mineral density (BMD), and levels of serum 25-hydroxyvitamin D (25OHD) on hip fracture on the condition of the bone density of femoral neck having reached the threshold of osteoporosis. METHODS:A total of 252 postmenopausal women patients, whose bone density had reached the threshold of osteoporosis and age ≥50 years (50-98 years), collected from the Second Affiliated Hospital of Fujian Medical University from January 2015 to December 2018, were performed by retrospective analysis. According to whether or not they had a hip fracture, including femoral neck fracture or intertrochanteric fracture, the patients were divided into two groups, including 117 cases (50-84 years old) in the non-hip fracture group and 135 cases (57-98 years old) in the hip fracture group. BMD was measured by Hologic Discovery A DXA bone mineral densitometer. Levels of serum 25OHD were detected by ROCHE detection instrument. Comparisons of age, BMI, bone density of femoral neck, and levels of serum 25OHD between the two groups were performed by using the Student's t-test. Furthermore, the statistically significant factors were analyzed by multiple regression analysis to investigate the independent risk factors of hip fracture. RESULTS:The group without hip fracture: 117 cases; average age: 67.4 ± 8.5 years; BMI: 22.3 ± 3.2 kg/m2 ; bone density of femoral neck: (0.504 ± 0.067) g/cm2 ; T-value of femoral neck: -3.1 ± 0.6; levels of serum 25OHD: (24.9 ± 8.5) ng/mL. The group with brittle hip fracture: 135 cases; average age: 80.7 ± 7.6 years; BMI: 20.3 ± 3.5 kg/m2 ; bone density of femoral neck: (0.426 ± 0.077) g/cm2 ; T-value of femoral neck: -3.8 ± 0.7; levels of serum 25OHD: (15.9 ± 8.9) ng/mL. Age, BMI, bone density of femoral neck, and 25OHD level of the group without hip fracture were markedly lower than hip fracture group (P < 0.05). The results of logistic regression analysis suggested that age, bone density of femoral neck, and levels of serum 25OHD were independent risk factors for fragile hip fracture on the condition of the bone density of femoral neck having reached the threshold of osteoporosis. CONCLUSION:Higher age, lower levels of bone density and 25OHD are the main risk factors of hip fracture on the condition of the bone density of femoral neck having reached the threshold of osteoporosis.