Comparison of bony healing and cartilage degeneration following strut grafting and trapdoor procedures in an ovine model.

: This experimental study compared bony healing and cartilage degeneration following strut grafting and trapdoor procedures for osteonecrosis of the femoral head in an ovine model. Osteonecrosis and a bony defect were created surgically in 16 hips of 8 Merino sheep, and the index grafting procedures were performed in a second session. Three months after surgery, the hips treated by strut grafting yielded better articular cartilage protection and bony healing compared to the osteonecrosis groups. The trapdoor group yielded better bony healing compared to the rest of the groups, but the grafts and the osteochondral flaps failed to unite with the host bone. These findings indicate elevating the osteochondral flap during the trapdoor procedure injures the cartilage and may cause degeneration.