Instability-induced osteoarthritis in the metacarpophalangeal joint of horses.

OBJECTIVE

To establish an instability model of osteoarthritis (OA) that mimics the early changes of naturally acquired OA.

ANIMALS

6 mature radiographically normal horses. Procedure-The collateral and lateral collateral sesamoidean ligaments were transected in a metacarpophalangeal (MCP) joint in each horse. Lameness examinations were performed every 7 days after surgery for 8 weeks. Radiographs were taken immediately before and after desmotomy and 8 weeks after surgery. Eight weeks after surgery, bilateral MCP joints were grossly evaluated, specimens of articular cartilage were harvested for histologic examination and tissue culture, and synovial membrane was harvested for histologic examination.

RESULTS

Lameness scores significantly increased over time (mean score of 1.6 for the 8-week study period). Joint circumference was significantly greater and range of motion significantly less in OA joints, compared with contralateral joints. Number and size of osteophytes were significantly greater in OA joints. Amount of newly synthesized proteoglycan (PG) was significantly greater at 18 and 72 hours of cartilage explant culture for OA joints, compared with contralateral joints. Total PG content and PG degradation did not differ between OA and contralateral joints. IMPLICATIONS FOR HUMAN MEDICINE: This instability model in horses may be useful in the study of OA in humans.

CONCLUSION

Desmotomy of the lateral collateral and lateral collateral sesamoidean ligaments induced instability similar to that of naturally acquired OA in horses, as documented by lameness, clinical signs of OA, osteophyte formation, and erosions of articular cartilage surfaces and score lines in OA joints.