Evaluation of a Permanent Synthetic Osteochondral Implant in the Equine Medial Femoral Condyle.

ABSTRACT

OBJECTIVE: To evaluate bone ingrowth, integration, and tolerance of a synthetic osteochondral implant in the medial femoral condyle (MFC) of normal horses. STUDY DESIGN: Experimental study. ANIMALS Adult horses (n = 6). METHODS: Horses were anesthetized and bilateral femorotibial arthrotomies were performed for placement of 1 implant consisting of polycarbonate urethane with a titanium base in 1 MFC. The contralateral MFC served as a sham-operated control without reaming of cartilage or subchondral bone. Lameness evaluations and radiographs were performed pre-operatively with subsequent monthly lameness exams and radiographs at 6 months. Synovial fluid was collected for analysis from the adjacent femoropatellar joints pre-operatively and at several intervals post-operatively. Horses were euthanatized 6 months post-operatively. Stifles were harvested for gross and histologic evaluations. RESULTS: Two horses were never lame, 2 were mildly lame, and 1 exhibited moderate lameness. Synovial fluid inflammatory parameters of the adjacent femoropatellar joints were not significantly different. No significant changes occurred radiographically over time in either stifle. Histologic assessment of synovium from the medial femorotibial joint revealed no differences in inflammatory changes between implant and sham stifles. Integration and osteoconductivity of the implant were graded as good in 4 and 3 of 5 specimens, respectively. Complications included joint sepsis resulting in euthanasia (1 horse), persistent lameness (1 horse), incisional seromas (4 horses), and incisional dehiscence (2 horses). CONCLUSION: Results of this pilot study indicate that the implant was compatible with placement in the MFC of normal horses. Implant design allowed bone ingrowth within the titanium base and provision of a synthetic articular surface.