Reasons for performing study
Osteochondritis dissecans (OCD) of the distal sagittal ridge of the third metacarpal bone (McIII) has not previously been described in the literature.
To describe the clinical, radiological and arthroscopic features of OCD of the distal sagittal ridge of the McIII and to report outcome in a series of cases.
Retrospective case series.
Case records and images of horses with OCD of the distal sagittal ridge of the McIII admitted to a single referral centre between February 2006 and February 2013 were reviewed. Follow-up information was obtained by telephone questionnaire and/or racing performance.
Osteochondritis dissecans of the distal sagittal ridge of the McIII was found in 16 lame horses; 9 unilaterally and 7 bilaterally. Lesions were consistently identified with flexed lateromedial radiographs and in 21 joints in dorsopalmar projections also. These were arthroscopically accessible from the dorsal compartment with metacarpophalangeal joints maximally flexed. This permitted fragment removal and lesion debridement. Thirteen of 14 horses with follow-up of ≥12 months post surgery performed athletically including 11 of 12 Thoroughbreds that raced.
Unlike more proximal lesions, OCD of the distal sagittal ridge appears to affect the McIII preferentially. Lesions were identified on dorsopalmar and flexed lateromedial radiographs only and are amenable to arthroscopic surgery. Clinicians should be aware of the potential for OCD to affect the distal sagittal ridge of the McIII together with the radiographic projections needed to identify its presence. A modified arthroscopic approach to the dorsal metacarpophalangeal joint is necessary in order to access lesions.