Equis ISSN 2398-2977

Proximal sesamoid: fracture

Contributor(s): Stephen Adams, Patrick Colahan, Jessica A Kidd-Millar, Vetstream Ltd, Chris Whitton

Introduction

Pathogenesis

Etiology

  • Hyperextension of the fetlock during maximal loading   →   internal strength of the sesamoid is exceeded   →   fracture.
  • Sagittal fractures can occur in combination with other fractures, ie condylar fractures.

Pathophysiology

  • Tensile forces of the suspensory apparatus supporting fetlock (suspensory ligament, sesamoid bones and distal sesamoidean ligaments) in extension.
  • Maximal loading, eg during strenuous exercise   →   tensile forces on sesamoid bones and cyclical loading   →   fatigue failure. Exacerbated by fatigue at end of exercise/race.
Apical fractures
  • Distraction of suspensory fibers determines the degree of displacement - usually <¼ of the suspensory branch insertion involved.
  • Tension across fracture line delays healing may get   →   fibrous union   →    rationale for recommending surgery.

Midbody fractures

  • Middle third of bone - subdivided into proximal, middle and distal areas of the middle 1/3.

Abaxial fractures

  • Includes site of suspensory ligament attachment along abaxial ridge of palmar/plantar bone - usually non-articular.

Basilar fractures

  • Distal 1/3 and usually articular - non-articular fractures involve only a portion of the base, usually axially.

Comminuted or biaxial fractures

  • Fetlock breakdown   Proximal sesamoid: fracture 17 comminuted - LM radiograph    Proximal sesamoid: fracture 18 comminuted - oblique radiograph    Proximal sesamoid: fracture 19 comminuted - DP radiograph    Proximal sesamoid: fracture 20 comminuted - LM radiograph  :
    • Disrupted collateral ligaments, fascial attachments, suspensory ligament   →   distractive forces.
    • Hyperextension   →   fetlock strikes ground   →   direct trauma to sesamoid   →   fracture, may be open with neurovascular compromise.
  • Biaxial fractures (both lateral and medial sesamoids): weightbearing   →   hyperextension and severe fragment distraction.

Sagittal fractures

  • Axial margin, often with other fetlock fractures such as condylar fractures.

Foals

  • Sesamoid fractures are often seen in foals out running with the mare:
    • Usually occurs at <2 months of age.
    • Carry a good prognosis.
    • Treated with box rest +/- bandage.

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.
  • Brokken M T, Schneider R K & Tucker R L (2008)Surgical approach for removal of nonarticular base sesamoid fragments of the proximal sesamoid bones in horses.Vet Surg37(7), 619-624 PubMed.
  • Busschers E et al(2008)Surgical repair of mid-body proximal sesamoid bone fractures in 25 horses.Vet Surg37(8), 771-780 PubMed.
  • Anthenill L Aet al(2007)Risk factors for proximal sesamoid bone fractures associated with exercise history and horseshoe characteristics in Thoroughbred racehorses.Am J Vet Res68(7), 760-771 PubMed.
  • Anthenill L Aet al(2006)Association between findings on palmarodorsal radiographic images and detection of a fracture in the proximal sesamoid bones of forelimbs obtained from cadavers of racing Thoroughbreds. Am J Vet Res67(5), 858-868 PubMed.
  • Schnabel L Vet al(2006)Racing performance after arthroscopic removal of apical sesamoid fracture fragments in Thoroughbred horses age <2 years: 151 cases (1989-2002).Equine Vet J39(1), 64-68 PubMed.
  • Schnabel L Vet al(2006)Racing performance after arthroscopic removal of apical sesamoid fracture fragments in Thoroughbred horses age > or = 2 years: 84 cases (1989-2002).Equine Vet J38(5), 446-451 PubMed.
  • Rothaug P G, Boston R C, Richardson D W & Nunamaker D M (2002)A comparison of ultra-high-molecular weight polyethylene cable and stainless steel wire using two fixation techniques for repair of equine midbody sesamoid fractures: an in vitro biomechanical study.Vet Surg31(5), 445-454 PubMed.
  • Woodie J B, Ruggles A J & Litsky A S (2000)In vitro biomechanical properties of 2 compression fixation methods for midbody proximal sesamoid bone fractures in horses.Vet Surg29(4), 358-363 PubMed.
  • Bour√© L, Marcoux M, Laverty S & Lepage O M (1999)Use of electrocautery probes in arthroscopic removal of apical sesamoid fracture fragments in 18 Standardbred horses.Vet Surg28(4), 226-232 PubMed.

Other sources of information

  • Bertone A L (1996)Fractures of the proximal sesamoid bones.In:Equine Fracture Repair.Ed: Nixon A J. W B Saunders, Philadelphia.


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