Bioengineered osteochondral precursor for treatment of osteochondritis dissecans in a Thoroughbred filly

Case report A 13‐month‐old Thoroughbred filly was diagnosed with osteochondritis dissecans (OCD) of the medial tibial malleolus. A sponge impregnated with platelet‐rich plasma, bone morphogenetic protein‐2, mesenchymal stem cells and gelatin β‐tricalcium phosphate was applied to the OCD site following arthroscopy and debridement. Postoperative radiography (every week for 16 weeks), computed tomography (CT) (16 weeks postoperatively), arthroscopy (16 weeks postoperatively) and biopsy of the regenerated tissue (16 weeks postoperatively) were performed to evaluate the outcome. Radiographically, the defect began to diminish 3 weeks postoperatively and had disappeared by 12 weeks. CT images showed that the debrided site was filled with ossified tissue and arthroscopy showed that the regenerated tissue was covered with smooth tissue, which a biopsy showed was fibrocartilage. Conclusions Placing the impregnated sponge in the OCD lesion facilitated satisfactory regeneration of tissue in the debrided area, but the regenerated cartilage was fibrocartilage. This method may be a viable option for the treatment of cases of equine OCD, but further work to determine how to induce hyaline cartilage regeneration is required.