A single center prospective study: Influences of different hip flexion angles on the measurement of lumbar spine bone mineral density by dual energy X-ray absorptiometry

To investigate whether there is an influence on the results of lumbar spine bone mineral density (BMD) measured by dual-energy X-ray absorptiometry (DXA) under three different hip flexion angles (90°, 45°, 0° of hip flexion). We collected a total of 60 outpatients, including 44 females (56.4 ± 5.7 years) and 16 males (50.2 ± 13.7 years). The DXA results of the lumbar spine were scanned and analyzed in three different positions with hip flexion of 90°, 45°, and 0°. We found that there was no significant difference in the area of interest, bone mineral content, BMD, and vertebral body height of the lumbar vertebral body measured by DXA in three hip flexion positions of 90°, 45°, and 0°; Pearson’s correlation analysis showed that lumbar BMD in hip flexion 90° was correlated with it in hip flexion 45° (r = 0.998, P＜0.01) and in hip flexion 0° (r = 0.996, P＜0.01) respectively. There was no statistically significant difference in the diagnosis of BMD between 90° and 45° hip flexion (P = 0.903), which was the same as 90° and 0° hip flexion (P = 0.822). Therefore, we conclude that different hip flexion angles can be used in lumbar BMD detection by DXA, which is beneficial to patients who have difficulty in hip flexion, especially for elderly patients with osteoporosis.