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

REASONS FOR PERFORMING STUDY: Subchondral cystic lesions of the medial femoral condyle (SCMFC) are well documented in horses < or =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 (< or = 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.