Terminal plate fracture in vertebrae of the aged.
The terminal plate fracture of human vertebrae was studied morphologically on midsagittal specimens from 92 autopsy cases which included 82 patients over 60 years. 1. Histologically, the terminal plate fracture was classified into three types by its representative histology. (a) Fracture with intervertebral disk (ID) prolapse: a healed fracture characterized by the presence of the prolapsed ID at the fractured site. ID prolapse in the marrow cavity may or may not be present. The group includes the typical case of the Schmorl's nodule. (b) Fracture with the granulation tissue: The fracture site was embedded by the granulation tissue. Callus and ID prolapse, if any, were insignificant. (c) Diffuse replacement of the hyaline cartilage layer by osteoid tissue: The alteration is seen often at a concaved surface of the terminal plate of significantly deformed vertebrae. 2. The fracture may be classified by the depth of the ID prolapse. (a) Grade 1: ID prolapse may be seen within the fracture aperture, but, not in the marrow cavity. (b) Grade 2: ID prolapse is confined to a labyrinth of subcortical trabeculae. (c) Grade 3: ID prolapse extends to a deep marrow space. The typical Schmorl's nodule belongs to this group. 3. In the present study, the terminal plate fracture was noted in 78% of the patients over 60 years. The female group was affected more often (68% in male, 86% in female). Grade 2 was more often seen in atrophic vertebrae than Grade 1. However, in Grade 3, the fracture appeared unrelated to the atrophy of the vertebrae. 4. The terminal plate fracture was more often seen in the lower deck than the upper deck at the site of two-thirds dorsal from the ventral edge of the vertebral body. The site corresponds roughly to the nucleus pulposus. 5. Histologic variations of the terminal plate fracture and of ID prolapse may relate to senescence of both vertebrae and ID.