Reconstruction of Large Osteochondral Defects Using a Hemicondylar Aragonite -Based Implant in a Caprine Model

Purpose: To investigate the safety and regenerative potential of a hemicondylar aragonite-based scaffold in the reconstruction of large osteochondral lesions occupying an extensive portion of the medial femoral condyle in a goat model. Methods: Eight Saanen goats were treated by the implantation of an aragonite-based scaffold (size: 19 x 8 x 8 mm) on a previously prepared hemicondylar osteochondral defect located in the right medial femoral condyle of the knee. Goats were euthanized after 12 months and the specimens underwent X-ray imaging, macroscopic, micro- computed tomography, histology, and immunohistochemistry evaluations to assess subchondral bone and cartilage regeneration. Results: In all 8 goats, no adverse event or persistent in flammation was observed. The evaluations per- formed showed integration of the scaffold, which almost completely resorbed at 12 months. In all animals, no signs of osteoarthritis progression were seen. Concurrent regeneration of the osteochondral unit was observed, with trabecular bone tissue replacing the implant and restoring the subchondral layer, and the formation of an overlying hyaline cartilage surface, well integrated within the surrounding native tissue, also was observed. Conclusions: The use of the hemi- condylar biphasic aragonite-based implant in the treatment of osteochondral defects in the goat model proved to be technically feasible and safe. The scaffold degraded and was replaced by regenerated tissue within the 12-month study period, restoring the osteochondral unit both at the level of the cartilaginous layer and the subchondral bone. Clinical Relevance: The present animal study describes a scaffold-based procedure for the treatment of large condylar defects, which often require massive allograft or unicompartmental replacement. The aragonite-based implant promoted a regeneration of both cartilage and subchondral bone, and its use as a biologic unicondylar prosthesis might be feasible also in the clinical setting.