Lateral scanning of the lumbar spine: Bone mineral density determination with dual energy X-ray absorptiometry

Abstract

In order to exclude the metabolically less-active cortical bone in the posterior portion of the lumbar spine, and to exclude the calcification of abdominal aorta which frepuently occurs in elderly persons, both of which are included in the conventional anteroposterior (AP) bone mineral determinations, clinical interest has been directed toward lateral scanning. In this paper, the performance and clinical application of lateral scanning with dual energy X-ray absorptiometry (DEXA) have been reviewed.

The precision, estimated as the reproducibility of measurements, of lateral bone mineral density (BMD), is inferior to that of AP-BMD (N=5, C.V. 5.57% vs 1.80%). With lateral scanning, the distributions of bone mineral within the vertebral body was different. The highest BMD was observed in the posterior inferior portion (100%), followed by the posterior superior (89%), anterior inferior (77%), and anterior superior portions (65%). In lateral scans, BMD within the region of interest (ROI) containing the shell, composed of cortical bone, is higher than BMD within the ROI without the shell (N=28, 87.8±5.9% for shell (+) vs 81.5±10.3% for shell (−), p<0.01, when AP-BMD in L₃ is defined as 100%). Age-related bone loss in males was recognized from lateral BMD measurements (r=−0.342, p<0.01), while no significant correlation was recognized between age and AP-BMD.

In conclusion, although lateral scanning needs further improvement in precision, lateral scanning of the lumbar spine with DEXA will provide more informations in evaluating age-related bone loss.