Abstract
Introduction Vertebral fractures in the elderly frequently involve the anterior and superior regions of the vertebral body. We hypothesise that vertebral fracture patterns reflect regional variations in bone mineral density (BMD).
Methods Nineteen motion segments (aged 48–90 yrs) were obtained from thoracic and lumbar regions of cadaver spines. Specimens were compressed to failure while positioned in moderate flexion (to simulate someone lifting in a stooped posture). Superior and inferior vertebrae were dissected and the site of fracture identified by visual inspection. The volume of each vertebral body was measured by water immersion, and BMD was measured using dual X-ray absorptiometry (DXA). BMD was also calculated for the following regions: superior and inferior end-plates; upper, middle and lower thirds of the vertebral body between the end-plates; anterior, middle and posterior thirds of the vertebral body.
Results In 16 of the 19 specimens, an obvious fracture was located in the anterior or central region of the superior end-plate of the inferior vertebral body, accompanied by collapse of supporting trabeculae. BMD of the superior end-plate was significantly lower than that of the inferior end-plate. Similarly, BMD of the upper third of the vertebral body was less than that of the lower third, and BMD increased significantly from anterior to posterior regions in the vertebral body.
Discussion Low BMD in the superior and anterior regions of old vertebral bodies predisposes them to fracture. Altered load-sharing in old spines secondary to disc degeneration may explain these regions of low BMD.
Correspondence should be addressed to SBPR c/o Royal college of Surgeons, 35 - 43 Lincoln’s Inn Fields, London WC2A 3PN
