Merck Manual

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Professional Version

Failure of Ossification of the Distal Tarsal Bones in Horses


Jane C. Boswell

, MA, VetMB, CertVA, CertES (Orth), DECVS, MRCVS

Last full review/revision Sep 2015 | Content last modified Jun 2016

Incomplete ossification of the central and third tarsal bones is most common in premature or twin foals and is characterized by a “sickle-hock” appearance. It may occur unilaterally or bilaterally. Radiologically, the partially ossified cuboidal bones appear smaller and more rounded than normal. Early recognition and treatment are important to prevent crushing of the bones and resultant progressive osteoarthritis. Cylinder tube casts can be used with good results to protect the immature bones until they have ossified.

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