Effect of age at presentation on outcome following arthroscopic debridement of subchondral cystic lesions of the medial femoral condyle: 85 horses (1993-2003)

Summary Reasons for performing study: Subchondral cystic lesions of the medial femoral condyle (SCMFC) are well documented in horses 3 years; arthroscopic debridement or enucleation of the cyst is currently the surgical treatment of choice. However, studies of occurence and outcome following surgery in older horses are lacking. Objective: To identify factors important in outcome for horses with SCMFC treated by arthroscopic debridement. Hypothesis: Age of horse at presentation has a significant influence on return to work following arthroscopic treatment for SCMFC. Clinical and diagnostic findings are also significant with respect to prognosis. Methods: A retrospective review of medical records from 6 equine referral centres identified 85 horses that underwent arthroscopic debridement of SCMFC. Clinical examination, radiographic and arthroscopic findings were analysed together with follow‐up data. Univariable analysis and multivariable logistic regression models were used to determine factors affecting return to soundness. Event‐time analysis was performed to evaluate return to work. Results: Older horses (>3 years) were less likely to return to soundness (P = 0.02) or to work (P = 0.04) than younger horses (> 3 years). Of 39 horses age 0‐3 years, 25 (64%, 95% CI 49‐79%) returned to soundness. Of 46 horses age >3 years, 16 (35%, 95% CI 21‐49%) returned to soundness. In addition, cartilage damage at sites other than the SCMFC negatively affected prognosis (P = 0.05). The hospital where treatment was performed had no influence on return to soundness. Conclusions: Older horses carry a worse prognosis for both return to soundness and return to work. Potential relevance: It is important for clients to be made aware of the difference in outcome between age groups.