Navicular bone: fracture in Horses (Equis) | Vetlexicon
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Navicular bone: fracture

ISSN 2398-2977

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Introduction

Presenting signs

  • Acute onset forelimb lameness or deterioration in a horse with navicular disease.

Pathogenesis

Etiology

Predisposing factors

General
  • Navicular disease.

Pathophysiology

  • Primary trauma.
  • Secondary to navicular disease where the bone is demineralized; abnormal soft tissue attachments disrupt function   →   stress risers in the bone.
  • Fracture leads to inflammation, pain, swelling and heat in the area.
  • As a sesamoid bone, the navicular is subject to constant movement by the deep digital flexor tendon   →   lack of stability   →   no spontaneous healing.

Timecourse

  • Chronic lameness is to be expected following fracture.

Diagnosis

Presenting problems

  • Lameness.

Client history

  • A known traumatic event with resulting lameness.
  • Deterioration in a horse with previously diagnosed navicular disease.
  • Sudden onset or deterioration in a horse that has already had a neurectomy procedure for navicular disease.

Clinical signs

Given the rarity of this fracture one would not immediately suspect it on clinical grounds alone.

  • 'Pointy' stance of navicular disease   Forelimb: pointy stance - navicular disease  .

Diagnostic investigation

Radiography

Caution in interpreting radiographs that one does not misdiagnose normal shadows from the lateral sulci of the frog as fracture lines.

Congenital bipartate or tripartate navicular bones can be confused with fracture.

Confirmation of diagnosis

Discriminatory diagnostic features

  • Clinical signs.
  • History.

Definitive diagnostic features

  • Radiography.

Differential diagnosis

  • Any cause of foot lameness. Remember fracture of the navicular bone is rare and thus one must exclude the more common foot problems first.

Treatment

Standard treatment

Non-surgical
  • Shoeing with bar shoes, quarter clips and 12° wedge pad will stabilize fracture and decrease pressure on navicular bone.
  • Surgery to stabilize the fragments - prompt referral is likelier to give better results than treatment of fractures many months old.
  • Palmar digital neurectomy   Palmar digital nerve: neurectomy  - provides pain relief but function may remain poor with the animal only being suitable for limited use.

Monitoring

  • Resolution of lameness.
  • Radiography to confirm bone union.

Prevention

Outcomes

Prognosis

  • Always guarded and euthanasia   Euthanasia  may in many cases be the only viable option.

Reasons for treatment failure

  • Probably no specific reasons, it is simply a serious injury that predominantly because of the resulting instability and continual motion at the site is not conducive to bone healing.

Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Claerhoudt S (2013) Distal navicular border fragments: Clinically significant or not, that is the question. Equine Vet Educ 25 (7), 352 VetMedResource.
  • Colles C M (2011) Navicular bone fractures in the horse. Equine Vet Educ 23 (5), 255-261 VetMedResource.
  • Lillich J D et al (1995) Fracture of the distal sesamoid bone in horses - 17 cases (1982-1992). JAVMA 207, 924-927 PubMed.

Other sources of information

  • Honnas C M (1999) The Foot. In: Equine Surgery.Eds: J A Auer & J A Stick. W B Saunders Co, USA. pp 789-790.