Treatment of subchondral cystic lesions of the medial femoral condyle of mature horses with growth factor enhanced chondrocyte grafts: a retrospective study of 49 cases

Reasons for performing study: To evaluate the long‐term clinical outcome after allogeneic chondrocyte and insulin‐like growth factor‐I (IGF‐I) grafting of subchondral cystic lesions (SCLs) of the femoral condyle in horses. Objective: To test the hypothesis that chondrocyte and IGF‐I grafts will improve the long‐term clinical outcome in arthroscopically debrided SCLs. Methods: Medical records of 49 horses with SCLs of the femoral condyle treated by debridement and implantation of chondrocytes and IGF‐I were reviewed. Preoperative radiographs were obtained, and caudocranial radiographic projections were used to establish a ratio between cyst and femoral condyle size. Arthroscopic cyst debridement followed by filling of the bone void with autologous cancellous bone (45 horses) or tricalcium phosphate granules (4 horses) was performed. A paired syringe containing a fibrinogen and chondrocyte mixture in one syringe and calcium‐activated bovine thrombin with IGF‐I in the other was used to cover the surface. A successful outcome was defined as a horse that performed to its intended use without lameness. Results: A successful outcome was achieved in 36 of 49 horses (74%). Preoperative radiography was performed in all horses, with 33 horses having unilateral SCLs of the medial femoral condyle, 15 horses having bilateral SCLs of the medial femoral condyle, and one horse having bilateral SCLs of the lateral femoral condyle. Median age of the horses was 3.3 years. Fifteen horses had preoperative radiographic and arthroscopic evidence of osteoarthritis (OA). A successful outcome was not influenced by age of horse, presence of pre‐existing osteoarthritis or preoperative size of the subchondral cyst. Grafting resulted in success for 80% of horses >3 years old, and in 80% of horses with OA. Conclusions: Implantation of allogeneic chondrocytes supplemented with IGF‐I is an effective treatment for horses with SCLs of the femoral condyle, and particularly for older horses and horses with pre‐existing osteoarthritis. Potential relevance: Chondrocyte implantation may offer a greater chance of long‐term success in older horses and horses with osteoarthritis than has been previously reported with cyst debridement alone.