Is bone mineral density measurements correlated with facet joint orientation? A dual energy X-ray absorptiometry study.

We aimed to study correlation between bone mineral density (BMD) and facet joint orientation in normal, osteopenic and osteoporotic patients. The correlation between more sagittally oriented facet joint and facet joint osteoarthritis and spondylolisthesis was described previously. However, the correlation between facet joint orientation and its possible correlation with BMD measurements has not been evaluated. Our study is a primary effort to describe the correlation of BMD with facet joint orientation, which is important in terms of spinal biomechanics. Thirty-seven patients who had undergone both lumbar spinal Magnetic Resonance Imaging and Dual-energy X-ray absorptiometry were included in the study. Facet joint osteoarthritis and orientation were evaluated in five levels between L1-S1. For facet joint orientation, axial images were used. For grading of facet joint osteoarthritis the classification of Weishaupt and co-workers were used. Lumbar BMD was correlated with BMD of the hip. Facet orientation was similar among the 3 groups namely patients with normal BMD values, osteopenia and osteoporosis. Facet orientation was not correlated with lumbar BMD measurements. Facet joint orientation is not correlated with BMD measurements in our patient group without spondylolisthesis. Since spondylolisthesis has been demonstrated to alter BMD measurements, we suggest that spinal degenerative disease secondary to spondylolisthesis is the main entity leading to measurement errors.