Equis ISSN 2398-2977

Annular ligament: constriction

Synonym(s): Palmar / plantar annular ligament constriction

Contributor(s): Steve Adair, Patrick Colahan, Rachel Murray, Vetstream Ltd

Introduction

  • Cause: enlargement of structures in the flexor tendon sheath or thickening of the annular ligament   →   relative constriction by annular ligament.
  • Signs: lameness, pain on flexion, 'bulging' of tissues proximal and distal to annular ligament.
  • Diagnosis: history, signs, ultrasonography.
  • Treatment: as for primary cause, symptomatic, surgical transection.
  • Prognosis: good in acute cases.

Pathogenesis

Etiology

Predisposing factors

General
  • Local trauma.
  • Fetlock hyperextension.

Specific

Pathophysiology

  • The palmar/plantar ligament is an inelastic band that forms a canal for the digital flexor tendons and tendon sheath.
  • The proximal sesamoid bones form the lateral and medial walls to the canal, and the annular ligament surrounds all these structures.
  • Smooth movement of the flexor tendons within the tendon sheath is required for comfortable movement of the distal limb.
  • Enlargement of the tendons, effusion of the tendon sheath or thickening of the annular ligament   →   restriction of movement of the tendons   →   with pain and lameness. Movement   →   forces are applied to the annular ligament   →   traumatize the ligament and   →   secondary thickening and adhesions may form between the tendons or between the tendons and tendon sheath.

Timecourse

  • Acute tendinitis or tenosynovitis   →   rapid restriction of movement within the canal.
  • Primary or secondary thickening of the annular ligament may form over a period of weeks or months.

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.
  • Nixon A J, Sams A E & Ducharme N G (1993)Endoscopically assisted annular ligament release in horses.Vet Surg22(6), 501-507 PubMed.
  • Dik K Jet al(1991)Ultrasonographic evaluation of fetlock annular ligament constriction in the horse.Equine Vet J23(4), 285-288 PubMed.
  • Honnas C M, Watkins J P, Jackman B R, Schumacher J & Taylor T S (1991)Diagnosis and treatment of septic tenosynovitis in horses.Comp Contin Ed13(2), 301 VetMedResource.

Other sources of information

  • Turner A S, McIlwraith C W (1991) techniques in Large Animal Surgery.Lea & Febiger, Philadelphia.
  • Nixon A J (1990)Annular Ligament Constriction.In: Current Practice of Equine Surgery. Eds: White N A & Moore J N. J B Lippincott, Philadelphia. pp 435-441.


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