Structural features and thickness of the vertebral cortex in the thoracolumbar spine

Study Design. The thickness and structure of the vertebral body cortex were examined from sections of human cadaveric vertebrae. Objectives. The objectives were to identify the principal structural featur es of the cortex, to directly measure the minimum and maximum thicknesses o f the cortex in the thoracolumbar spine, and to compare regional variations in the structure of the cortex. Summary of Background Data. The thickness of the vertebral cortical shell c ontributes to the compressive strength of the vertebral body. There is litt le consensus concerning the thickness and morphology of vertebral shell and endplate along the spine in existing data. Methods. Human T1, T5, T9, L1, and L5 vertebral bodies (mean age 70.4 years ) from 20 cadaveric spines were sectioned and photographed. The minimum and maximum cortical thickness of the shells and endplates in the midsagittal plane were measured from magnified images. Results. The anterior shell thickness was significantly greater than the po sterior shell and both endplates. Endplate thickness was greatest in the lo wer lumbar vertebrae. There was a significant decrease in cortex thickness over the central portion of endplates and shells, with a mean minimum thick ness of 0.40 mm and a mean maximum thickness of 0.86 mm, with an overall me an of 0.64 +/- 0.41 mm. Increased porosity was also observed along the cent ral regions of the cortical shells. In the lower thoracic and lumbar spine, a double-layered endplate structure was observed. Conclusions. Invasive techniques provide the only means to directly resolve the thickness and distribution of bone in the vertebral cortex. The cortex thickness and structure varies along the endplates and the anterior and po sterior surfaces of the vertebral body. The implications of the so called d ouble-layered endplate structure are unknown, but indicate the need for fur ther study.