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Fracture of the Third Metacarpal (Cannon) Bone in Horses


A transverse fracture in the midmetacarpal region can result from direct trauma, usually from a kick. The stress of racing on a hard surface may result in a longitudinally oblique (ie, condylar) fracture that progresses up the metacarpal shaft from the fetlock and sometimes also involves the proximal sesamoids. Incomplete fractures of the dorsal cortex of the midmetacarpal region can occur as stress-type fractures. Diagnosis is confirmed by radiography; the fissure fractures can be difficult to demonstrate, and a range of oblique views may be necessary.

Midmetacarpal fractures may heal with just a cast, although prolonged immobilization may be necessary because union is often delayed. Malunion and the encroachment of callus on surrounding tendons and ligaments cause further problems. Internal fixation with dynamic compression plates and screws is the treatment of choice. Lateral condylar fractures can be treated conservatively by casting, but such articular injuries are best managed by screw fixation using interfragmentary compression if osteoarthritis is to be minimized or avoided. Medial condylar fractures often do not exit and spiral up the bone. In these cases, in addition to lag screw fixation distally, a plate is placed up the remaining metacarpus or metatarsus. Fissure fractures also may show delayed union unless a cortical bone screw is applied. (See alsobucked shins, p 1018.)

Last full review/revision March 2012 by Stephen B. Adams, DVM, MS, DACVS; Joerg A. Auer, DrMedVet, Dr h c, MS, DACVS, DECVS; James K. Belknap, DVM, PhD, DACVS; Jane C. Boswell, MA, VetMB, CertVA, CertES (Orth), DECVS, MRCVS; Peter Clegg, MA, Vet MB, PhD, CertEO, DECVS, MRCVS; Andrew L. Crawford, BVetMed, CertES (Orth), MRCVS; Jean-Marie Denoix, DVM, PhD, Agregé; Marcus J. Head, BVetMed, MRCVS; C. Wayne McIlwraith, BVSc, PhD, DSc, FRCVS, DACVS, DACVSMR; James Schumacher, DVM, MS, DACVS, MRCVS; John Schumacher, DVM, MS, DACVIM; Roger K. W. Smith, MA, VetMB, PhD, DEO, DECVS, MRCVS; Chris Whitton, BVSc, FACVSc, PhD

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