Surgical treatment of subchondral cystic lesions of the third metacarpal bone: results in 15 horses (1986-1994).

Subchondral cystic lesions (SCLs) in the condyle of the third metacarpal bone (MCIII) were surgically treated in 15 horses. The median age at presentation was 18 months (range 10 months-12 years) with 10 of 15 horses less than age 2 years. The SCLs were confined to the front limbs in all cases with 2 horses having bilateral lesions. Lesions were isolated to the medial condyle(s) of MCIII in 13 of 15 horses; a cystic lesion occurred in the lateral condyle in one horse and in the sagittal ridge in one horse. One horse with bilateral lesions had an additional cystic lesion located in the right medial femoral condyle. Fourteen of 15 horses had a history of moderate lameness attributable to the metacarpophalangeal joint; the lesion was an incidental finding in one horse. Duration of lameness ranged from 4 weeks to 8 months and was either acute in onset, or occurred intermittently and was associated with exercise. Fetlock flexion significantly exacerbated the lameness in all cases. Synovial effusion was absent in 8 (53%) cases. Cystic lesions were curetted arthroscopically in 12 horses, and through a dorsal pouch arthrotomy in 3 horses. Concurrent osteostixis of the cystic cavity was performed in 7 horses. Two horses were treated arthroscopically for osteochondral fragmentation of the proximodorsal aspect of the proximal phalanx one year following surgical curettage of the SCL. Twelve of 15 horses (80%) were sound for intended use following surgical treatment. Two horses did not regain soundness and follow-up information was unavailable for one horse. Total period of follow-up was 1-6 years. Follow-up radiographic examinations were available for 9 horses. Mild periarticular osteophyte formation and enthesiophyte formation at the dorsal joint capsular attachments was present in 5 of the 9 horses. Bony ingrowth of the cystic lesion was detectable in 8 horses and enlargement of the cystic cavity was observed in one horse. Based on the information gained from this study, it would appear that surgical treatment of SCLs in the distal metacarpus can result in a favourable outcome for athletic use.