Biochemical and biomechanical characterisation of equine cervical facet joint cartilage.

Abstract

The equine cervical facet joint is a site of significant pathology. Located bilaterally on the dorsal spine, these diarthrodial joints work in conjunction with the intervertebral disc to facilitate appropriate spinal motion. Despite the high prevalence of pathology in this joint, the facet joint is understudied and thus lacking in viable treatment options. The goal of this study was to characterise equine facet joint cartilage and provide a comprehensive database describing the morphological, histological, biochemical and biomechanical properties of this tissue. Descriptive cadaver studies. A total of 132 facet joint surfaces were harvested from the cervical spines of six skeletally mature horses (11 surfaces per animal) for compiling biomechanical and biochemical properties of hyaline cartilage of the equine cervical facet joints. Gross morphometric measurements and histological staining were performed on facet joint cartilage. Creep indentation and uniaxial strain-to-failure testing were used to determine the biomechanical compressive and tensile properties. Biochemical assays included quantification of total collagen, sulfated glycosaminoglycan and DNA content. The facet joint surfaces were ovoid in shape with a flat articular surface. Histological analyses highlighted structures akin to articular cartilage of other synovial joints. In general, biomechanical and biochemical properties did not differ significantly between the inferior and superior joint surfaces as well as among spinal levels. Interestingly, compressive and tensile properties of cervical facet articular cartilage were lower than those of articular cartilage from other previously characterised equine joints. Removal of the superficial zone reduced the tissue's tensile strength, suggesting that this zone is important for the tensile integrity of the tissue. Facet surfaces were sampled at a single, central location and do not capture the potential topographic variation in cartilage properties. This is the first study to report the properties of equine cervical facet joint cartilage and may serve as the foundation for the development of future tissue-engineered replacements as well as other treatment strategies.