Identification and treatment of osteochondritis dissecans of the distal sagittal ridge of the third metacarpal bone.
Authors: Wright I M, Minshall G J
Journal: Equine veterinary journal
Summary
Osteochondritis dissecans (OCD) affecting the distal sagittal ridge of the third metacarpal bone represents a previously undocumented lesion location that Wright and Minshall identified in 16 lame horses (9 unilateral, 7 bilateral cases) between 2006 and 2013. Unlike OCD at more proximal sites on the metacarpus, this distal ridge pathology requires specific radiographic projections—flexed lateromedial views consistently demonstrated lesions, whilst dorsopalmar projections identified them in 21 of the affected joints—making recognition dependent on appropriate imaging technique rather than chance findings. Arthroscopic access proved reliable via the dorsal compartment of the metacarpophalangeal joint with maximal flexion, permitting effective fragment removal and debridement; of the 14 horses with 12-month post-operative follow-up, 13 returned to athletic work, including 11 of 12 Thoroughbreds that resumed racing. This work fundamentally alters how practitioners should approach persistent metacarpal lameness, particularly in younger performance horses where standard dorsodistal metacarpal radiographs may falsely reassure, and highlights the importance of utilising both flexed lateromedial and dorsopalmar projections as part of a thorough diagnostic protocol. For those managing recurrent fore-limb lameness without obvious pathology on routine imaging, awareness of this lesion location and modified arthroscopic techniques offers a viable surgical solution with demonstrably favourable outcomes.
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Practical Takeaways
- •When investigating lameness in horses with suspected metacarpophalangeal joint disease, use both flexed lateromedial and dorsopalmar radiographic projections specifically to identify OCD of the distal sagittal ridge of McIII
- •This previously undescribed OCD location is surgically accessible and treatable via arthroscopy with good prognosis for return to athletic function, including racing
- •Awareness of this condition and appropriate imaging protocols may improve early diagnosis and treatment outcomes in lame horses with metacarpophalangeal joint involvement
Key Findings
- •OCD of the distal sagittal ridge of McIII was identified in 16 lame horses (9 unilateral, 7 bilateral), a previously undescribed location for this lesion
- •Lesions were consistently identified on flexed lateromedial radiographs and in 21 of 23 joints on dorsopalmar projections
- •Arthroscopic fragment removal and debridement via modified dorsal approach to the metacarpophalangeal joint achieved athletic performance in 13 of 14 horses with ≥12 months follow-up, including 11 of 12 racehorses
- •Unlike more proximal OCD lesions, this distal sagittal ridge location appears to preferentially affect the McIII