ARTHROSCOPIC SURGERY FOR SUBCHONDRAL CYSTIC LESIONS OF THE MEDIAL FEMORAL CONDYLE IN HORSES - 41 CASES (1988-1991)

Clinical signs, radiographic and arthroscopic findings, and outcome fo r 41 horses with subchondral cystic lesions of the medial femoral cond yle created by arthroscopic surgery were reviewed. There were 17 Quart er Horses, 15 Arabians, 8 Thoroughbreds, and 1 Holsteiner, with 28 (68 %) of the horses being 1 to 3 years old. For all houses, the owners' c om plaint was mild to moderate hind limb lameness or an altered gait. Bilateral radiographic abnormalities of the medial femoral condyle wer e detected in 27 horses. Nineteen of the 27 horses had lesions identif ied bilaterally at arthroscopic surgery. In addition to the subchondra l cystic lesion, 13 joints in 11 houses had an osteochondritis disseca ns lesion on the articular surface of the medial femoral condyle that extended from the opening of the subchondral cystic lesion. Surgical d ebridement performed via arthroscopy was the only treatment for 37 les ions of 23 horses. Debridement followed by drilling of the defect bed was performed in 23 lesions of 18 horses. Complete follow-up informati on was obtained for 39 horses; 22 (56%) had a successful result and 17 (44%) had an unsuccessful result. In a separate analysis excluding ho rses with unsuccessful results because of factors not directly attribu table to the subchondral cystic lesion of the medial femoral condyle, 23 of 31 (74%) houses had a successful result and 8 of 31 (26%) horses had an unsuccessful result. Within this group of horses, the prognosi s for a successful result after arthroscopic surgery was not associate d with age, sex, size of lesion, unilateral vs bilateral lesions, whet her the lesion was drilled, the presence of osteochondritis associated with the subchondral cystic lesion, or whether the lesion enlarged af ter surgery. Compared with Thoroughbreds and Arabians, Quarter Houses had a poorer prognosis for success. Follow-up radiographs were availab le for 14 horses. In 9 of these 14 horses, the subchondral cystic lesi on had enlarged after surgery. Postoperative cystic enlargement was as sociated significantly with drilling of the lesion bed at the time of surgery.