Equis ISSN 2398-2977

Carpus: hygroma

Synonym(s): Capped knee

Contributor(s): Steve Adair, Chris Whitton, Graham Munroe

Introduction

  • A hygroma is a fluid-filled cavity or bursa underneath the skin. 
  • Carpal hygroma occur on the dorsal aspect of the carpus.
  • Cause: repetitive trauma to dorsal aspect of carpus, secondary to subcutaneous hematoma.
  • Signs: usually painless, uniform fluctuant swelling overlying the dorsal aspect of the carpus Carpus: hygroma; not usually lame unless infected.

Pathogenesis

Etiology

  • Usually chronic, repetitive, direct, blunt trauma to the dorsal aspect of the carpus. Very occasionally acute trauma may be a factor or it may occur as a rare complication of arthroscopic surgery Joint: arthroscopy - overview or carpal arthrotomy.
  • Usually unilateral.

Predisposing factors

General

  • Horses that bang door in stable with front legs.
  • Subcutaneous hematoma formation may precede hygroma.
  • May follow rupture of an extensor tendon sheath.

Pathophysiology

  • Typically formed by the accumulation of transudate following tearing of subcutaneous tissues.
  • Subcutaneous acquired bursa forms in chronic cases lined by secretory cells.
  • If sufficiently large can mechanically restrict the range of movement of the carpus.
  • Adhesions and fibrosis may ensue and restrict normal movement.
  • May become secondarily infected → discharge, abscessation, fistulae, granulation tissue formation.
  • Very rarely may occur following previous arthroscopic surgery Joint: arthroscopy - overview where a portal is inadvertently made through the extensor tendon sheath/s.

Timecourse

  • Usually chronic.

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

Other sources of information

  • Kirker-Head C A (1999) Carpal Hygroma. In: Equine Medicine & Surgery. 5th edn. Eds: Colahan P T, Merritt A M, Moore J N & Mayhew I G. Mosby, USA. pp 1636-1638.
  • Ruggles A J (1999) The Carpus. In: Equine Surgery. Eds: Auer J A & Stick J A. W B Saunders, USA. pp 827-828.


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