INTRODUCTION: Endplate disturbances are known to be related with disc degeneration. Whereas changes of vertebral cancellous bone are well described, only few reports focus on the subchondral bone of the vertebral endplate, which, however, is most important for disc nutrition. Subchondral bone permeability is reduced in experimental and human disc degeneration with a consequent reduction of disc nutrition. Disc nutrition over the endplate may also influence the cellular composition of the disc. Therefore we wanted to analyze differences between endplates from animals with and without notochordal cells in the nucleus.
MATERIALS: We analyzed lumbar endplates from skeletally mature porcine and bovine spines with micro‐computed tomography. Samples included the disc together with cranial and caudal vertebral endplates. Disc height and endplate architecture were determined. For quantitative analysis, a standardized volume of interest was designed for the subchondral bone area of the vertebral endplate, to analyze total bone volume (BV), tissue volume (TV), and bone volume fractions (BV/TV) as a measure for the relation between calcified bone and open vascular channels.
RESULTS: Bovine discs were 2‐3‐times higher than porcine discs. Endplate architecture showed equal layers: cartilage endplate, subchondral bone, cartilage growth plate. Bovine endplates were larger in total, vascular channels had greater diameters, and BV/TV was significantly different for subchondral bone caudal to the disc (70%) and cranial to the disc (92%). Porcine samples showed a mean BV/TV of 83% with no significant difference caudal to cranial.
DISCUSSION: Skeletally mature pigs and cows are quadrupeds with similar biomechanical loading of the spine caused by axial muscle forces. Though, cellular composition of their discs is different, which might be related to differences in subchondral bone channels in their endplates and disc height influencing disc nutrition by diffusion.