Introduction: Bone tendon junction (BTJ) healing has been found to be both histologically and biomechanically sub-optimal. Tendons heal to bone by fibrous scar formation without restoration of the normal transitional fibrocartilage zone. We postulated that chondrocytes might stimulate the healing process and restoration of a transitional fibrocartilage zone.

Aim: To study chondrocyte pellets cultured in vitro which were then used as interposition material in an animal BTJ healing model.

Method: Eighteen weeks old, New Zealand rabbits, each with a partial patellectomy followed by repair was used as the animal model for BTJ healing. Chondrocyte pellets cultured from cartilaginous ribs of a six weeks old rabbit were used as interposition material. No interposition material was used in control group. Samples were harvested at two, four, six, eight, 12 and 16 weeks for histological studies.

Results: Twenty-two samples were harvested. Each group had two and three samples for early and late time-points respectively. The samples taken at two weeks showed persistence of the chondrocyte pellets. Structural continuity was established at four weeks. Histological sections showed gradual cell migration. New bone formation was seen at the original BTJ at the 12th and 16th weeks, with disappearance of the chondrocyte pellet, and formation of a new BTJ. No BTJ formation was seen in the control group.

Conclusion: Our study indicated that cultured chondrocyte pellets had a stimulatory effect on BTJ healing. The mechanism of action requires further elucidation. This finding has a potential clinical application in improving BTJ healing.