The 3D anatomy of the cervical articular process joints in the horse and their topographical relationship to the spinal cord.

The research explores the 3D structure of the articular process joints (APJs) located in a horse’s neck, their relation to the spinal cord, and whether their distension might cause spinal cord compression. The findings suggest that under normal conditions, APJ effusion alone is unlikely to cause spinal cord compression, but further anatomical changes could potentially lead to compression.

Study Motivation

• Horses can exhibit severe symptoms like weakness and ataxia due to spinal cord compression, often linked with disorders in the cervical articular process joints (APJs).
• Despite this, detailed anatomical studies focusing specifically on the APJs have been sparse, prompting this particular exploration into the APJs’ 3D anatomy and its relationship with the spinal cord.

Methodology

• A total of six cadaveric necks from clinically normal horses were utilized for this study.
• To understand the impact of APJ distension, a negative contrast agent was injected to simulate maximal distension, followed by a computed tomography (CT) scan of the cervical APJs.
• The scanned images were then processed by semi-automatic segmentation using greyscale thresholding, culminating in a 3D reconstruction via polygonal surface meshing.
• These 3D images helped evaluate the anatomical position of the APJs concerning the spinal cord and to calculate the joint volume at each cervical vertebra relative to the vertebrae size.

Results

• The volume of the joint varied substantially depending on its position and showed a positive correlation with the vertebral site.
• In none of the horses, it was observed that after distension, the medial outpouch of the APJs, which extends towards the vertebral canal from a dorsolateral location, compressed the protective dura mater surrounding the spinal cord.
• Neck flexion did result in minor changes to the APJs’ shape; however, this did not cause the medial outpouch to encroach any closer to the spinal cord.

Conclusions

• The results suggest that APJ distension alone does not cause spinal cord compression unless there are other soft tissue or bony changes.
• This suggests that health practitioners should consider the presence of other anatomical changes when evaluating potential spinal cord compression cases.
• It was also observed that the APJs extended into the dorsolateral aspect of the vertebral canal in a ventromedial direction, indicating that oblique myelographic views are beneficial for diagnosing spinal cord compression when APJ pathology is suspected.