PIP joint: luxation and subluxation in Horses (Equis) | Vetlexicon
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PIP joint: luxation and subluxation

ISSN 2398-2977

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Introduction

Presenting signs

  • Acute, non-weight-bearing lameness in traumatic cases in fore or hindlimb.
  • Malalignment of the pastern region mediolaterally or dorsopalmar/plantar.
  • Swelling either locally or generally in the pastern region.

Acute presentation

  • Lameness.

Age predisposition

  • Some of the causes are more common in foals and weanlings.

Breed/Species predisposition

Cost considerations

  • Cost of diagnosis and treatment.
  • Loss of use of horse.

Special risks

  • Normal risks for general anesthesia.
  • Recovery after arthrodesis of the pastern.

Pathogenesis

Etiology

  • Trauma.

Predisposing factors

Specific

  • Previous injury to support structures of distal limb.

Pathophysiology

Complete luxation

  • Often associated with external severe trauma:
    • Trapped foot → twisted pulling on limb → tearing of lateral or medial collateral ligament → lateral or medial luxation.
    • Uniaxial fractures of distal P1; fracture of P2 Middle phalanx: fracture.
    • Lacerations damaging collateral ligaments, joint capsule and other supporting structures.
  • More likely to be medial or lateral.
  • The proximal interphalangeal joint may be open or closed at presentation, with the former decreasing the prognosis.
  • Forelimbs may be more likely to be involved.
  • Almost always a unilateral problem.

Subluxation

  • More likely to be dorsal, palmar or plantar; relates to the position of P1 relative to P2.
  • Can involve one or both limbs, fore- or hindlimb.
  • Dorsal subluxation:
    • Injury to the soft tissue support structures of the fetlock joint in Thoroughbred racehorses may secondarily develop dorsal subluxation, sometimes called ‘Thoroughbred ringbone’.
    • In association with transection of a branch of the SDFT, severe injury of the oblique sesamoidean ligament, or rupture of the straight sesamoidean ligament.
    • Secondary to flexural deformity of distal interphalangeal joint Musculoskeletal: flexural deformity and possibly after true contracture of the DDFT.
    • Secondary to collateral ligament injury.
    • Suspensory ligament desmotomy +/- deep digital flexor tenotomy in treating severe flexural deformities of the fetlock joint.
    • Secondary to progressive and severe injury of the suspensory ligament and its branches.
    • May occur without any identifiable damage to the bones or soft tissue structures in the pastern or metatarsal region. This is mainly seen in the hindlimbs of young horses and lameness is either mild or absent. The dorsal subluxation is dynamic and resolves during full weight-bearing. If there are any changes within the PIP joint of osteoarthritis Musculoskeletal: osteoarthritis (joint disease) this has a negative effect on prognosis.
  • Palmar/plantar subluxation:
    • Overextension of the PIP joint with tearing of palmar/plantar soft tissue support structures, eg jump from height → landing on forelimbs. Possible injuries include complete tearing of the distal sesamoidean ligaments, SDFT branch injury or a combination of soft tissue injuries and fractures.
    • Biaxial palmar/plantar eminence and comminuted fractures of the middle phalanx.
    • Most common in forelimbs and in foals/weanlings.

Timecourse

  • Acute.

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.
  • Garvican E & Clegg P (2007) Clinical aspects of the equine proximal interphalangeal (pastern) joint. UK Vet 12 (6), 11-16 VetMedResource.
  • Harrison I J & May S A (1992) Bilateral subluxation of the pastern joint in the forelimbs of a foal. Vet Rec 131 (4), 68-70 PubMed.
  • Shiroma J T et al (1989) Dorsal subluxation of the pelvic limb of three horses. J Am Vet Med Assoc 195 (6), 777-780 PubMed.

Other sources of information

  • Watkins J P (2020) Arthrodesis of the Proximal Interphalangeal Joint. In: Equine Fracture Repair. Ed: Nixon A J. 2nd edn. Wiley Blackwell, USA.
  • Watkins J P (2020) Fractures of the Middle Phalanx. In: Equine Fracture Repair. Ed: Nixon A J. 2nd edn. Wiley Blackwell, USA.