Biomechanics in the equine thoracolumbar spine with and without surgical intervention at the level of the dorsal spinous processes

Abstract

This study includes a literature review, detailing the different treatment options for horses with clinically relevant overriding dorsal spinous processes. The experimental part of the research further investigates the influence of pathological spinal conditions and spinal surgery on the biomechanics of the equine thoracolumbar spine. It was shown that the available evidence for different conservative and surgical treatment options is currently limited. Results indicate that a combination of treatment options including a targeted exercise program appears most promising for the individual patient. Surgical approaches for the management of equine overriding dorsal spinous processes include the desmotomy of the interspinous ligament and the dorsal spinous process ostectomy. In an experimental setup using computed tomography, equine thoracolumbar spinal biomechanics were first evaluated in equine spinal specimens without severe spinal pathology as well as specimens with spondylosis or overriding dorsal spinous processes. Both pathological conditions were associated with limited spinal mobility. Additionally, the influence of spinal surgery on the biomechanics of the equine thoracolumbar spine was investigated. Both the interspinous ligament desmotomy and the subtotal dorsal spinous process ostectomy resulted in an increased range of motion during axial rotation but had no impact on thoracolumbar flexion, extension, or lateral bending. Evidence for trauma to the epaxial Musculi Multifidi following spinal surgery was identified in all cases and supports the implementation of a postoperative rehabilitation program to strengthen the epaxial musculature. As the current study was carried out on spinal specimens without severe spinal pathology, future research should focus on the investigation of the impact of surgery on the equine spine affected by severe overriding dorsal spinous processes. The study was limited by the ex vivo character and a small sample size. Therefore, long-term clinical studies with a larger sample size investigating the consequences of spinal surgery for the equine patient would be of great interest.