Objectives: The aim of this study is to determine whether there is a difference between right and left femur bone mineral density (BMD) in postmenopausal women. Methods: We performed a retrospective chart review of postmenopausal women who underwent bone mineral density (BMD) measurement from 2010 to 2019 at a single center using dual-energy X-ray absorptiometry (DXA). Data, including BMD and T-scores of bilateral hip and lumbar spine, was gathered for all postmenopausal women above the age of 50 years. The continuous variables were expressed as means with standard deviation for normal distribution and analyzed with a two-sample t-test. Multiple regression analysis was used to test the effect of underlying medical conditions on T-score of bilateral hips. For all analyses, a p-value of ＜0.05 was considered significant. Results: 346 patients were included in the study with a mean age at imaging of 62 + 9.7 years and body mass index (BMI) of 23.4 + 6.1 kg/m2 . There were no significant differences between right and left femoral BMDs in all patients. There were significant differences in BMD of both total femurs in women in their 60s and women with normal BMD. There was no difference in both femur BMDs between those taking hormone therapy and those not taking hormone therapy. In patients undergoing osteoporosis treatment, there was a difference in the BMD of both femur neck. Calcium and vitamin D intake were not associated with differences between both femur BMD. We found a significant correlation between the BMD measures at lumbar spine and both femur (p ＜ 0.01). Conclusion There were no significant differences between right and left femoral BMDs in postmenopausal women. Therefore, BMD may be measured at either hip. The correlation of bone density between lumbar spine and femur neck is shown to be statistically meaningful. Based on the knowledge of the correlation coefficients between lumbar spine and femur neck, it seems possible to predict the BMD result of one location through the measurement of another.

Objectives: Bone mineral density (BMD) is measured in the hip and posteroanterior spine; moreover, according to the 2019 International Society for Clinical Densitometry guidelines, unilateral hip can be used. This study aimed to determine whether there is a difference between the BMD of both the femurs in postmenopausal women. Methods: A total of 343 postmenopausal women were enrolled in this study from January 1, 2010, to December 31, 2019 at a single tertiary hospital. By using the Hologic® Horizon W DXA System, the femur and spine BMD was measured; BMD was recorded in g/cm 2 .Following regions were analyzed in both the femurs: the femur neck, the trochanter area, and total femur. Results: Mean age at imaging was 62 ± 9.7 years, and significant difference in the total BMD of both the femurs (P = 0.003) was observed. In secondary analysis, patients with osteoporosis showed significant contralateral BMD discrepancies in trochanter and total proximal femur BMD (P = 0.041 and P = 0.011, respectively). However, in women with normal BMD, no significant difference between the right and left femur BMD was observed. Furthermore, measurement of solely the unilateral hip can lead to a 16.9% of underdiagnosis in postmenopausal women. Conclusions In conclusion, it is necessary to check BMD in both hips, particularly in patients suspected of osteoporosis.