Unilateral Osteotomy of Lumbar Facet Joint Induces a Mouse Model of Lumbar Facet Joint Osteoarthritis

Study Design. The lumbar facet joint (LFJ) osteoarthritis (OA) model that highly mimics the clinical conditions was established and evaluated. Objective. Here, we innovatively constructed and evaluated the aberrant mechanical loading-related LFJ OA model. Summary of Background Data. LFJ is the only true synovial joint in a functional spinal unit in mammals. The LFJ osteoarthritis is considered to contribute 15% to 45% of low back pain. The establish of animal models highly mimicking the clinical conditions is a useful tool for the investigation of LFJ OA. However, the previously established animal models damaged the LFJ structure directly, which did not demonstrate the effect of aberrant mechanical loading on the development of LFJ osteoarthritis. Methods. In the present study, an animal model for LFJ degeneration was established by the unilateral osteotomy of LFJ (OLFJ) in L4/5 unit to induce the spine instability. Then, the change of contralateral LFJ was evaluated by morphological and molecular biological techniques. Results. We showed that the OLFJ induced instability accelerated the cartilage degeneration of the contralateral LFJ. Importantly, the SRμCT elucidated that the three-dimensional structure of the subchondral bone changed in contralateral LFJ, indicated as the abnormity of bone volume/total volume ratio (BV/TV), trabecular pattern factor (Tb. Pf), and the trabecular thickness (Tb. Th). Immunostaining further demonstrated the uncoupled osteoclastic bone resorption, and bone formation in the subchondral bone of contralateral LFJ, indicated as increased activity of osteoclast, osteoblast, and Type H vessels. Conclusion. We develop a novel LFJ OA model demonstrating the effect of abnormal mechanical instability on the degeneration of LFJ. This LFJ degeneration model that highly mimics the clinical conditions is a valuable tool to investigate the LFJ osteoarthritis. Level of Evidence: N/A

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