Equis ISSN 2398-2977

MC/MT 2 and 4: fracture

Contributor(s): Olin Balch, Graham Munroe, Chris Whitton

Introduction

Pathogenesis

Etiology

  • External trauma - direct blow.
  • Internal forces - biomechanical stresses during fast exercise, particularly in associated with suspensory desmitis.

Specific

Pathophysiology

Distal fractures
  • Usually occur at junction between proximal two thirds and distal one third of the metacarpal bone and less commonly metatarsal bone.
  • With age   →   interosseus ligament loses flexibility and splint bone more brittle.
  • Stresses going around bends   →   hyperextension of fetlock   →   ligamentous traction (fibrous bands from distal end of bones to medial and lateral proximal sesamoid bones) on splint bones   →   fracture.
  • Suspensory desmitis   Suspensory ligament: desmitis - midbody  with marked enlargement   →   pressure on splint bone with modeling and progressive deviation of the distal part of the bone from the MC/MT 3 predisposing to fracture.
  • Direct trauma, eg kick, is uncommon.

Mid and proximal fractures

  • Direct trauma is more common in this area usually from a direct kick from another horse or kicking a stationary object   →   open fracture   →   osteomyelitis   Bone: osteitis - septic  . Fractures can also be closed and may be simple or more likely comminuted and variably displaced.
  • The proximal part of the fourth metatarsal bone is much more commonly affected than anywhere else.
  • Racing stresses   →   axial compressive loading due to articulation with carpus   →   fracture.
  • Exacerbated by conformational abnormalities   Musculoskeletal: conformation  , eg bench knees.

Diagnosis

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Treatment

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Prevention

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Outcomes

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Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Milner P (2008) Case study: Sequestrum formation and splint bone fracture in a horse. UK Vet 13 (7), 9-12 VetMedResource.
  • Lischer C J (2008) Fractures of the splint bones: The importance of soft tissue attachments. Equine Vet Educ 20 (7), 380-382 Wiley Online.
  • Jackson M, Furst A, Hassig M & Auer J (2007) Splint bone fractures in the horse: a retrospective study 1992-2001. Equine Vet Educ 19 (6), 329-335 VetMedResource.
  • Jenson P W et al (2004) Segmental ostectomy of the second and fourth metacarpal and metatarsal bones in horses: 17 cases (1993-2002). JAVMA 224 (2), 271-274 PubMed.
  • Kidd J (2003) Management of splint bone fractures in horses. In Pract 25 (7), 388-395 VetMedResource.
  • Harrison L J, May S A & Edwards G B (2001) Surgical treatment of open splint bone fractures in 26 horses. Vet Rec 128 (26), 606-610 PubMed.
  • Peterson P R, Pascoe J R & Wheat J D (1987) Surgical management of proximal splint bone fractures in the horse. Vet Surg 16 (5), 367-372 PubMed.
  • Allen D & White N A (1987) Management of fractures and exostosis of the metacarpals and metatarsals II and IV in 25 horses. Equine Vet J 19 (4), 326-330 PubMed.

Other sources of information

  • Doran R (1996) Fractures of the small metacarpal and metatarsal (splint) bones. In: Equine Fracture Repair. Ed: A J Nixon. W B Saunders, USA.


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