Equis ISSN 2398-2977

Carpus: intercarpal ligament (MPICL) - trauma

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

Introduction

  • Cause: unknown; normal degeneration in the dorsal aspect of the medial palmar intercarpal ligament + some tearing occurs in most horses. Clinically significant damage occurs in a small percentage of performance horses.
  • Signs: forelimb lameness; unilateral may be bilateral.
  • Diagnosis: intrasynovial anesthesia (midcarpal joint); arthroscopy.
  • Treatment: rest 6-12 months; joint medication.
  • Prognosis: good-guarded depending on degree of tearing and associated joint pathology.

Pathogenesis

Etiology

  • There are two main intercarpal ligaments:
    • The medial palmar intercarpal ligament (MPIL):
      • Originates on the distal palmarolateral surface of the radial carpal bone and the body of the ligament is often split into two arms.
      • The lateral part inserts in the palmar fossa of the third carpal bone and the medial arm on the palmarolateral surface of the second carpal bone. There is considerable variation in the appearance arthroscopically of this ligament, including variation in the relative sizes of the medial and lateral branches, a lack of the lateral branch, and poor distinction of the two branches.
    • The lateral palmar intercarpal ligament (LPIL):
      • ‚ÄčOriginates primarily on the distal palmaromedial surface of the ulnar carpal bone with a smaller attachment to the lateral margin of the intermediate carpal bone.
      • It inserts primarily on the palmaromedial fourth carpal bone with a smaller insertion on the palmarolateral surface of the third carpal bone.
  • The medial and lateral ligaments help hold together the carpal bones, resisting displacement especially in extension, and helping dissipate forces acting axially in the forelimb abaxially through the carpal bones.
  • In the majority of clinical cases damage to the MPIL, and to a lesser extent LPIL, is associated with other intra-articular pathology such as osteochondral fragments or osteoarthritis Musculoskeletal: osteoarthritis (joint disease). In these cases it is often impossible to know whether the ligament injury is a cause of the other pathology or a result of it.
  • It is therefore not possible to ascribe any particular etiology to injury of either the MPIL or the LPIL.

Predisposing factors

General

Specific

  • Occasional cases occur where midcarpal joint lameness is present and the only finding at arthroscopy is damage to the intercarpal ligaments.
  • The specific factors leading to these findings are presently unknown.

Pathophysiology

  • Ligament degeneration → weakening → biomechanical stresses → tearing → joint instability → pain and subchondral bone remodeling.
  • Degeneration in the dorsal part of the medial palmar intercarpal ligament is recognized in foals from the age of 1 month.
  • Complete tearing of the dorsal bundles of the ligament occasionally occurs in horses in training probably due to overloading of a weakened ligament.

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.
  • Gray S N, Puchalski S M & Galuppo L D (2013) Computed tomographic arthrography of the intercarpal ligaments of the equine carpus. Vet Radiol Ultrasound 54 (3), 245-252 PubMed.
  • Nagy A & Dyson S (2011) Magnetic resonance anatomy of the carpus of the horse described from images acquired from low-field and high-field magnets. Vet Radiol Ultrasound 52 (3), 273-283 PubMed.
  • Beinlich C P & Nixon A J (2005) Prevalence and response to surgical treatment of the lateral palmar intercarpal ligament avulsion in horses: 37 cases (1990-2001). J Am Vet Med Assoc 226 (5), 760-766 PubMed.
  • Beinlich C P & Nixon A J (2004) Radiographic and pathologic characterization of lateral palmar intercarpal ligament avulsion fractures in the horse. Vet Radiol Ultrasound 45 (6), 532-537 PubMed.
  • Driver A J et al (2004) Ultrasonography of the medial palmar intercarpal ligament in the Thoroughbred: technique and normal appearance. Equine Vet J 36 (5), 402-408 PubMed.
  • Whitton R C, Kannegeiter N J & Rose R J (1999) Postoperative performance of racing horses with tearing of the medial palmar intercarpal ligament. Aust Vet J 77 (11), 713-717 PubMed.
  • Whitton R C, Kannegeiter N J & Rose R J (1997) The intercarpal ligaments of the equine midcarpal joint, Part 3. Clinical observations in 32 racing horses with midcarpal joint disease. Vet Surg 26 (5), 374-381 PubMed.
  • Whitton R C, McCarthy P H & Rose R J (1997) The intercarpal ligaments of the equine midcarpal joint, Part 1. The anatomy of the palmar and dorsomedial intercarpal ligaments of the midcarpal joint. Vet Surg 26 (5), 359-366 PubMed.
  • Whitton R C & Rose R J (1997) The intercarpal ligaments of the equine midcarpal joint, Part 2. The role of the palmar intercarpal ligaments in the restraint of dorsal displacement of the proximal row of carpal bones. Vet Surg 26 (5), 367-373 PubMed.
  • Whitton R C & Rose R J (1997) Postmortem lesions in the intercarpal ligaments of the equine midcarpal joint. Aust Vet J 75 (10), 19-23 PubMed.
  • Phillips T & Wright I (1994) Observations on the anatomy and pathology of the palmar intercarpal ligaments in the middle carpal joints of Thoroughbred racehorses. Equine Vet J 26 (6), 486-491 PubMed.
  • Kannegeiter N J & Colgan S (1993) The incidence and severity of intercarpal ligament damage in the equine carpus. Aust Vet J 70 (3), 89-91 PubMed.
  • McIlwraith C W (1992) Tearing of the medial intercarpal ligament in the equine midcarpal joint. Equine Vet J 24 (5), 367-371 PubMed.

Other sources of information

  • McIlwraith C W, Nixon A J & Wright I M (2015) Diagnostic and surgical arthroscopy in the horse. 4th edn. Elsevier. pp 90-92.


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