Subchondral Bone Density Distribution in Canine C6-C7 Vertebral Endplates Affected by DA-CSM: A CT-OAM Study

Disc-associated cervical spondylomyelopathy (DA-CSM) is a clinically relevant disorder of the canine cervical spine frequently requiring surgical stabilization, with implant subsidence remaining a common complication. This study aimed to evaluate subchondral bone mineral density (sBMD) distribution in the C6-C7 vertebral motion unit of DA-CSM-affected dogs and to compare these findings with a previously established cohort of clinically unaffected dogs. Computed tomography osteoabsorptiometry (CT-OAM) was applied to eight affected specimens, and sBMD was analyzed across predefined annulus fibrosus (AF) and nucleus pulposus (NP) regions, including detailed topographic subdivisions. Statistical comparisons were performed using paired and independent t-tests with correction for multiple testing, while the topographic pattern of bone density minima and maxima was compared using Chi-squared testings. DA-CSM-affected vertebral endplates demonstrated a consistent and significant reduction in overall sBMD compared to controls (p < 0.0001), affecting both AF and NP regions as well as all topographic subdivisions. Despite this global decrease, the characteristic spatial distribution pattern was not significant different between affected and unaffected vertebrae, with higher sBMD values in peripheral AF regions and lower values in central and centro-dorsal NP regions. These findings indicate that DA-CSM is associated with a generalized reduction in subchondral bone density without alteration of the intrinsic load-adapted distribution pattern. The persistence of structurally weak central regions, combined with reduced overall bone quality, may contribute to the risk of implant subsidence. Consideration of both global and regional sBMD characteristics may therefore be relevant for optimizing implant design and surgical strategies in canine cervical spinal distraction and stabilization.