Subchondral nacre implant in the articular zone of the sheep's knee: a pilot study

The present study was designed to analyze the intra-articular behaviour of nacre, when implanted in the subchondral bone area in the sheep knee. We implanted nacre blocks in sheep's trochlea by replacing the half of the femoral trochlea (nacre group). For comparison we used complete cartilage resection (resection group) down to the subchondral bone. In the "nacre group", implants were well tolerated without any synovial inflammation. In addition, we observed centripetal regrowth of new cartilage after 3 months. In the "resection group", no chondral regrowth was observed, but, in contrast, a thin layer of fibrous tissue was formed. After 6 months, a new tissue covered the nacre implant formed by an osteochondral regrowth. Nacre, as a subchondral implant, exerts benefic potential for osteochondral repair.