The "mirror image" and "two-thirds" types of hemispherical spondylosclerosis.

Clinical and radiological examination of 167 hemispherical spondylosclerosis (HSS) patients (56 male, 111 female) revealed a total of 186 cases of HSS with multiple incidences occurring in 18 patients. Radiologically these HSS cases were characterized by erosion and new bone formation at the inferior and upper end plate of the vertebra below, periosteal bone apposition or ossification of the anterior longitudinal ligament, spondylophytes, and signs of degenerative alteration of the vertebra and disc. In addition, the size and location (anterior, middle, posterior third) of each HSS in the lateral view was investigated. The cases were also investigated for reflection phenomenon between supra- and infradiscal sclerosis and for kyphotic angulation of the two adjacent vertebrae. The results showed that in 105 cases (56.5%) the HSS filled out the entire vertebral area; 97 cases (52.2%) showed a mirror-image type HSS; while in 8 cases (4.3%), the infradiscal sclerosis was polymorphic. In 81 cases (43.5%), the sclerosis was limited to the anterior two-thirds; this is termed "two-thirds" type. All 81 of these cases of HSS showed a kyphotic angulation of at least 4 degrees. Of these, 61 (32.8% of the total) showed reflection phenomenon while 20 (10.7% of the total) had polymorphic infradiscal sclerosis. Overall, 158 cases of HSS (85%) exhibited the reflection phenomenon between supra- and infradiscal sclerosis, whereas 28 cases (15%) revealed polymorphic sclerosis of the subadjacent vertebra. Kyphotic angulation was completely absent when HSS was visible in the entire vertebra. A dorsal gap of the disc space was seen in 36 cases (19.4%).(ABSTRACT TRUNCATED AT 250 WORDS)