Arthroscopic injection of corticosteroids into the fibrous tissue of subchondral cystic lesions of the medial femoral condyle in horses: A retrospective study of 52 cases (2001–2006)

Summary Reasons for performing study: There are no published results of subchondral cystic lesions (SCLs) in the medial femoral condyle (MFC) treated with arthroscopic injection of corticosteroids into the lining of the cyst. Objectives: 1) To determine the success rate for treatment of SCLs in the MFC with arthroscopic injection of the fibrous tissue of the cyst with corticosteroids. 2) To identify any factors that may predict outcome. Hypotheses: Injection of the fibrous tissue of SCLs of the MFC with corticosteroids utilising arthroscopic guidance yields a similar or higher chance for intended performance than does arthroscopic debridement as previously reported; this technique will be effective for treating SCLs in older horses. Methods: Horses with clinical and radiographic evidence of a SCL in the MFC were injected with corticosteroids under arthroscopic guidance, and case records and radiographs were reviewed retrospectively. A telephone survey of referring veterinarians, owners and trainers was conducted. Results: Thirty-five of 52 (67%) cases were classified as successful involving 73 SCLs of which 56 (77%) were classified as successful. There was no significant association between age group (age ≤3 years vs. >3 years) and outcome, or cyst configuration and outcome. Significantly more unilateral SCLs (28/31 [90%] SCLs) were classified as successful than bilateral (28/42: 67%). There were significant differences in outcome based on the surgeon operating the case and an association between pre-existing radiographic findings of osteophytes and negative outcome. Conclusions: Injection of SCLs utilising arthroscopic guidance is an effective alternative method of surgical treatment of SCL. Potential relevance: This technique offers a similar chance of success as has been reported with debridement and may allow for a shorter period of convalescence. If unsuccessful, the option remains to debride the cyst in a second surgery.