BONE-MINERAL DENSITY IN PATIENTS WITH OSSIFICATION OF THE POSTERIOR LONGITUDINAL LIGAMENT - MINIMAL DECREASE OF BONE-MINERAL DENSITY WITH AGING

Study Design. Bone mineral density of individuals with ossification of the posterior longitudinal ligament and that of normal people was det ermined by dual-energy x-ray absorptiometry. Objectives. To determine whether bone mineral density in the people with ossification of the po sterior longitudinal ligament is higher than that in normal individual s even in body parts other than the spine, and to evaluate the relatio n between bone mineral density and age in patients with ossification o f the posterior longitudinal ligament. Summary of Background Data. It is unknown whether the bone mineral density of patients with ossificat ion of the posterior longitudinal ligament is greater in body parts ot her than the spine. If so, it provides a basis for the theory that cer tain systemic factors are involved in the pathogenesis of ossification of the posterior longitudinal ligament. Because bone mineral density decreases physiologically after middle age, the influence of age must be considered in evaluating bone mineral density. Methods. In the rib area and upper and lower limb areas, which are not affected by ossific ation of the spinal ligament, bone mineral density of 45 men with ossi fication of the posterior longitudinal ligament of the cervical spine was-compared with that of 25 men without ossification of the posterior longitudinal ligament (normal group). Results. Bone mineral density w as higher in the group with ossification of the posterior longitudinal ligament in each part and significantly higher in the rib and lower l imb areas (rib: P < 0.01, lower limb: P < 0.05). The age-related decre ase was significantly less in the group with ossification of the poste rior longitudinal ligament (rib: P < 0.01, upper limb: P < 0.05, lower limb: P < 0.01). Conclusions. Systemic factors that increase bone min eral density appear to be involved in the pathogenesis of ossification of the posterior longitudinal ligament, and these factors may be acti vated after middle age.