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

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