Bone mineral density in patients with spinal cord injuries

The bone mineral density (BMD) of 157 patients with a spinal cord injury (SCI) was measured using dual-photon absorptiometry (Lunar DP-4). The BMD of the second to fourth lumbar vertebrae (L2-L4) and the right femoral neck was measured and the mean density registered in grams per square centimetre. The likelihood of a fracture was based on the percentage of BMD in young normals and the degree of risk of fracture. The following criteria were used to separate the patients: (1) complete or incomplete immobility due to the SCI; (2) the time between the SCI and measurement of BMD was short ( 3 years); (3) the level at which the SCI occurred was considered to be high (i.e. from the first cervical vertebra to the tenth thoracic vertebra) or low (i.e. from the eleventh thoracic vertebra to the first lumbar vertebra). The rate of abnormal BMD (i.e. a greater risk of fracture) in each of the groups and at each site was measured and differences evaluated using the chi-square test. Fifty-four of the 157 (34%) scans revealed an abnormal BMD at the level of L2-L4 and 126 (80%) in the right femoral neck. The difference between these two incidences was significant (P < 0.001). However, there were no significant differences in abnormal BMD with regard to severity of the SCI, time elapsing since the SCI and level at which the SCI occurred. We conclude that hip demineralization is a common complication in SCI, but that lumbar BMD is better preserved.