equis - Articles
MCP/MTP joint: luxation
Introduction
- Uncommon, lateral or medial luxation of metacarpophalangeal or metatarsophalangeal joint - occurs with rupture of medial or lateral collateral ligaments or an avulsion fracture.
- Cause: usually associated with trapping distal limb in hole or cattlegrid, trailer/transport injury, or at high speed exercise.
- Signs: lameness, angular deformity of distal limb, injury/trauma, excessive movement in fetlock joint.
- Diagnosis: confirmed on radiography Forelimb: radiography - identifies any complicating bony injury. Ultrasound to assess collateral ligaments.
- Treatment: reduction + cast immobilization Musculoskeletal: external fixation - casts usually achieves pasture soundness; open/compound luxations require more complex surgical techniques and more aggressive treatment. Occasionally the collateral ligament is repaired.
- Prognosis: good for return to pasture/breeding soundness; open/compound luxations - guarded to poor.
Presenting signs
- Sudden onset non-weight bearing lameness.
- Angular deformity of distal limb; may be obvious without medial or lateral stress or may require applied stress.
- History of trauma or of trailer/transport injury in which the distal limb falls through the floor.
- Excessive movement in fetlock joint.
- Variable soft tissue trauma - often little swelling initially.
Cost considerations
- Euthanasia Euthanasia /loss of horse.
- Open luxations - surgical intervention, treatment of joint infection and post-operative care.
- Ongoing treatment for osteoarthritis Musculoskeletal: osteoarthritis (joint disease) or chronic desmitis.
- Closed reduction - general anesthesia and casting.
- Cost of further cast changes.
Pathogenesis
Etiology
- Trauma - distal limb trapped, eg hole or cattle grid, and animal attempting to remove its hoof.
- Occasionally occurs during high speed activity involving increased rotational forces.
Pathophysiology
- Luxation may be closed or open and occurs in association with rupture of the medial/lateral collateral ligament or an avulsion fracture.
- Open luxations have the additional complication of probable joint sepsis and possible bone loss in trailer injuries from contact with the road.
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.
- Smith M R W (2010) Management of joint instability. Equine Vet Educ 22 (3), 112-114 Wiley Online Library.
- Jalim S L, McKinnon A O & Russell T M (2009) Case report: Repair of a type IV Monteggia fracture in a foal. Aust Vet J 87(11), 463-466 PubMed.
- Tenney W A & Whitcomb M B (2008) Rupture of collateral ligaments in metacarpophalangeal and metatarsophalangeal joints in horses: 17 cases (1999-2005). JAVMA 233 (3), 456-462 PubMed.
- Balaam T M & Miller S (2007) Severe open metacarpophalangeal joint luxation in a mule foal. Equine Vet Educ 19 (10), 528-531 VetMedResource.
- Yovich J V, Turner A S, Stashak T S and McIlwraith C W (1987) Luxation of metacarpophalangeal and metatarsophalangeal joints in horses. Equine Vet J 19, 295-298 PubMed.