The bone mineral density(BMD) of women with low back pain(LBP) was suspected of low level due to the progression of osteoporosis which might affect the lumbar spine. The dual-energy X-ray absorptiometry(DXA) was the most effective method for BMD measurement but the precise projection process of anteroposterior or lateral method was controversial.

To examine the role of the osteoporosis in LBP and to compare which method of projection with DXA estimates BMD of the lumbar spine more precisely, we studied lumbar BMD of 84 healthy women and 87 women with LBP and/or spine fracture.

The mean postmenopausal period was longer as 11.8 years in women with LBP and than 9.2 years in healthy women(p<0.05). The BMD decreased with increasing age(p<0.05). The mean BMD of the total 2nd, 3rd, and 4th lumbar vertebrae of healthy women was 0.614g/cm², women with LBP was 0.567 g/cm², and women with LBP and spine fracture was 0.516 g/cm². The women with LBP with or without fracture, all had lower BMD than healthy women(p<0.05). The body weight and height decreased with age but the body mass index(BMI) did not change. The BMD of healthy women group correlated with the BMI but that of the group with low back pain did not. The BMD of all subjects decreased with age. The ratio of lateral/AP lumbar BMD of women with LBP decreased with age and lower than that of healthy women.