Equis ISSN 2398-2977

Humerus: fracture

Contributor(s): Jeffrey Watkins, Graham Munroe

Introduction

  • Uncommon fractures in most types of horse and pony because of short thick configuration and extensive muscular covering.
  • Cause: foals/weanlings usually secondary to falls or direct trauma; adults as a result of accumulated stress (microfracture(s)) or catastrophic race falls.
  • Signs: severe lameness. Crepitation and instability at fracture site in complete fractures, marked soft tissue swelling.
  • Diagnosis: radiography (complete fractures) Forelimb: radiography; scintigraphy (incomplete/stress fractures) Bone: scintigraphy.
  • Types: proximal humerus and greater tubercle; deltoid tuberosity; middle and distal diaphyseal; distal condylar and epicondylar; stress fracture.
  • Treatment: varies with fracture type and position.
  • Prognosis: varies with position, type and age; poor for complete diaphyseal in adults; good for stress fractures in adult.

Pathogenesis

Etiology

  • The cause is often not clear in individual cases, although trauma is suspected in most.
  • Kicks, falls, concentrated training regimes.

Predisposing factors

General

  • Concentrated training regimes.

Pathophysiology

  • Fractures resulting from direct trauma or impact injuries to upper forearm and shoulder regions.
  • Spontaneous failure in race as a result of accumulated stress and microfracture. Stress fractures most commonly occur in caudal aspect of proximal metaphysis and distal aspect of cranial/caudal metaphysis.
  • Type of humeral fracture:
    • Proximal humeral head.
    • Greater and lesser tubercles.
    • Deltoid tuberosity - individual fractures rare - usually portions of greater tubercle also included.
    • Mid diaphysis - many are short to long oblique spiral fractures with ends over-riding and variable comminution in adults; many oblique fractures spiral proximocaudal to distocranial cortex → proximal fragment resting in the intercondylar region of distal humerus and limiting further over-riding.
    • Distal metaphysis.
    • Distal condyle/epicondyle.
    • Proximal physeal injuries:
      • Rare but Type 1 and 2 Slater Harris fractures have been recorded in animals <2 years of age.
      • Surgical treatment is necessary as conservative treatment leads to poor results.

Diagnosis

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Treatment

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Outcomes

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Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Glass K & Watts A E (2017) Diagnosis and treatment considerations for nonphyseal long bone fractures in the foal. Vet Clin North Am Equine Pract 33 (2), 431-438 PubMed.
  • Levine D G & Aitken M R (2017) Physeal fractures in foals. Vet Clin North Am Equine Pract 33 (2), 417-430 PubMed.
  • Dimock A N et al (2013) Humeral stress remodelling locations differ in Thoroughbred racehorses training and racing on dirt compared to synthetic racetrack surfaces. Equine Vet J 45 (2), 176-181 PubMed.
  • Madron M, Caston S & Kersh K (2013) Placement of bone screws in a standing horse for treatment of a fracture of the greater tubercule of the humerus. Equine Vet Educ 25 (8), 381-385 VetMedResource.
  • Mez J C et al (2007) Fractures of the greater tubercle of the humerus in horses: 15 cases (1986-2004). J Am Vet Med Assoc 230 (9), 1350-1355 PubMed.
  • O'Sullivan C B & Lumsden J M (2003) Stress fractures of the tibia and humerus in Thoroughbred racehorses: 99 cases (1992-2000). J Am Vet Med Assoc 222 (4), 491-498 PubMed.
  • Carter B G et al (1993) Assessment and treatment of equine humeral fractures: retrospective study of 54 cases (1972-1990). Equine Vet J 25 (3), 203-207 VetMedResource.
  • Markel M D, Nunamaker D M, Wheat J D & Sams A E (1988) In vitro comparison of three fixation methods for humeral fracture repair in adult horses. Am J Vet Res 49 (4), 586-593 PubMed.

Other sources of information

  • Nixon A J, Watkins J P (1996) Fractures of the Humerus. In: Equine Fracture Repair. Ed: A J Nixon. W B Saunders, USA.


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