OBJECTIVE: To describe the diagnosis, treatment, and prognosis of fetlock breakdown due to interosseus medius muscle rupture in cattle.
STUDY DESIGN: Retrospective clinical study.
ANIMALS: Dairy heifers with unilateral or bilateral interosseus medius muscle rupture (n = 11).
METHODS: Breakdown injury due to rupture of the interosseus medius muscle was documented clinically, radiographically, and ultrasonographically. Breakdown was bilateral in 4 heifers (3 in forelimbs, 1 in hind limbs) and unilateral in 7 (all hind limbs). One heifer with severe bilateral hind limb breakdown was slaughtered and the remaining 10 were treated by transfixation pin cast (1 heifer), box rest (n = 2), and/or a cast and splint (7).
RESULTS: Hyperextension of the fetlock and hyperflexion of the proximal interphalangeal joints during weight bearing were characteristic for interosseus muscle breakdown. Ultrasonographically, the origin and body of the interosseus muscle and the branches to the sesamoid bones were primarily affected by the rupture. Conservative treatment was successful (used for their intended purpose) in 8 of 9 heifers with a median lifespan of 32 months after discharge from the clinic (range 6-83).
CONCLUSION: Rupture of the interosseus medius muscle in young cattle may be more common than previously suggested in the literature. Imaging with ultrasound allowed more detailed localization of lesions of the musculo-tendinous structure. Interosseus medius muscle rupture had a favorable prognosis when treated conservatively in these heifers.