Study design: A biomechanical investigation using indentation tests in human cadaveric lumbar vertebrae.
Objectives: To determine the effect of endplate removal on the structural properties across the lower lumbar vertebral bodies (L3-L5).
Summary of background data: The structural properties of the vertebral endplates exhibit substantial regional variation. In addition, several recent studies of the endplate-implant interface have suggested that the endplate is not a significant structural element.
Methods: The bony endplates on the left or right side of seven intact human vertebrae (L3-L5) were removed with a high-speed burr. Indentation tests were performed at standardized test sites on both sides of the endplate using a 3-mm diameter, hemispherical indenter with a test rate of 0.2 mm/s to a depth of 3 mm. The failure load and stiffness at each site were determined from the load-displacement curves. Three-way repeated measures analyses of variance were used to analyze the resulting data for variation in the anterior-posterior and lateral directions, as well as to determine the effect of endplate removal.
Results: For the intact endplates, both the failure load and stiffness varied significantly across the endplate surfaces (P < 0.0001), with the posterolateral regions being stronger and stiffer than the central regions. With endplate removal, the mean failure load decreased to about 33% of the intact failure load, a significant drop (P = 0.04), and there was a trend toward greater decreases posteriorly (P = 0.05). With endplate removal, the mean stiffness also decreased significantly (P = 0.01), with the greater decreases occurring laterally (P = 0.04).
Conclusions: There was a significant effect of endplate removal on the local structural characteristics of the vertebral endplate.