[An animal model foundation of articular full-thickness cartilage defect by saving calcified cartilage zone on femoral trochlea in porcine].

OBJECTIVE: To establish a porcine model of articular full-thickness cartilage defect characterized by remaining cartilage calcified zone on femoral trochlea, so as to provide a considerable and comparative control group for investigating repair effects of tissue engineered scaffolds in articular cartilage defects with cartilage calcified zone remaining. METHODS: The full-thickness cartilage column defects (6 mm in diameter, 0.2-0.5 mm in depth) without damage on calcified cartilage zone were made on the femoral trochlea in 9 clean-grade 6-month-old Guizhou minipigs by standard cartilage-defect-making suites. Microscopical observation was performed after modeling. Scanning were made by 3.0T MRI at 4 weeks. Then general observation, stereomicroscope, and histological staining were used to observe cartilage repair. RESULTS: All animals were alive. No infection of incisions or patellar dislocations occurred; they were able to walk with partial weight-bearing immediately after surgery and could move freely without limp at 1 week. Obvious signal discontinuity in trochlea and subchondral bone could be observed in MRI, without deep signal change in defects surrounding. Microscopical observation showed a few repair tissue and petechia at base of the defect with clear boundary. Nearly intact calcified zone of cartilage and zonal collapse of subchondral bone in defects could be observed with stereomicroscope. Under common microscope, no chondrocytes was found in defects, as well as negative staining of fast green-safranin O and alcian blue. Under polarized microscope, the bottom of defects were filled with a little of fibrous tissue presenting continuous and strong light-refraction by sirius red staining. CONCLUSION: The animal model of articular full-thickness cartilage defect on femoral trochlea by standard cartilage-defect-making suites can be applied for the research of cartilage disease in early human osteoarthritis and function of calcified cartilage zone in pig.