[Mechanisms of spinal block formation in Paget disease of bone. Radiographic study based on 14 cases]

Vertebral bridging occurs in approximately 10% of patients with spinal pagetic lesions. Diffuse idiopathic skeletal hyperostosis has been reported in patients with pagetic block vertebras and may facilitate vertebral fusion and extension of pagetic lesions. High prevalences of diffuse idiopathic skeletal hyperostosis have been found in patients with Paget's disease. To determine how pagetic block vertebras develop and to investigate relationships between Paget's disease and diffuse idiopathic skeletal hyperostosis, 244 patients with Paget's disease were studied retrospectively. Diagnostic criteria for diffuse idiopathic skeletal hyperostosis were the presence of flowing ossification along the anterolateral aspect of at least three contiguous vertebral bodies or presence of at least two anterolateral intervertebral bony bridges in the same spinal segment. Eight (33%) of the 244 patients had diffuse idiopathic skeletal hyperostosis. Two-thirds of patients with both conditions were male. There was no statistically significant association between presence of diffuse idiopathic skeletal hyperostosis and spinal involvement by Paget's disease. Fourteen pagetic block vertebras were identified in 11 male patients. Eight of these 11 patients had involvement of the fused vertebras or adjacent vertebras with diffuse idiopathic skeletal hyperostosis. Our findings confirm that diffuse idiopathic skeletal hyperostosis is common in patients with Paget's disease. The statistically significant association between diffuse idiopathic skeletal hyperostosis and pagetic vertebral fusion in the same site suggests that the former condition may be a risk factor for pagetic vertebral bridging.