Healing of articular cartilage defects. An experimental study of vascular and minimal vascular microenvironment.

The repair potential in a chondral defect with (treatment A) or without access to bone marrow elements (treatment B) at the basis of the defect sealed by a rim-sutured periosteal flap was studied using adult New Zealand rabbits (22 weeks) as an experimental model. At sacrifice, macroscopical changes, synovial fluid contents, degree of filling, thickness of the cartilage rim, and the subchondral bone were evaluated. Histomorphometric measurements of extent of filling (mainly fibrous tissue) of the defect at 36 weeks postoperatively, showed 50% filling in treatment A compared with 33% in treatment B (p = 0.011). A difference in height of the cartilage rim between the experimental groups and sham-control was measured ( p = 0.005). Cartilage degeneration was observed at the cartilage rim of the original defect, and included loss of chondrocytes and disruption of surface continuity in both experimental groups. In addition, treatment A resulted in a significantly increased thickness of the subchondral bone in the defect in comparison to treatment B at 2 weeks and at 36 weeks (p = 0.021). The increased thickness of the subchondral bone may be of concern for the bone marrow stimulation techniques regarding the long-term outcome.