Equis ISSN 2398-2977

Distal phalanx: fractures

Contributor(s): Steve Adair, Patrick Colahan, Graham Munroe, Vetstream Ltd, Jarred Williams

Introduction

Pathogenesis

Etiology

  • Trauma.
  • Varies according to particular type of fracture:
    • Types I, II, III, VI - usually traumatic in origin, eg high speed impact on racetracks, particularly on the turn, kicking a hard object or stepping with high velocity on a non-yielding object such as a rock or stone.
    • Some Type VI - secondary to P3 changes due to laminitis Foot: laminitis or pedal osteitis Sole: collapsed 02 - pedal osteitis .
    • Type IV - more controversial in etiology: ? hyperextension injuries of the coffin joint, or ? fracture of a separate center of ossification of the extensor process of P3. Subchondral bone cysts of P3 have been associated with Type IV fractures.
    • Type V - secondary to osteomyelitis or sequestra.

Predisposing factors

General

  • Breed and use determines type of fracture seen, eg in left-handed racing in the USA, Type I are most common in lateral aspect left forelimb and medial aspect right forelimb.
  • Forelimb fractures are most common (up to 80%).

Pathophysiology

  • Seven different types of fracture occur with different etiology and incidence in breed and type of horse.
  • Trauma is the predominant cause of these fractures.
  • Other types of fracture may be secondary to pedal bone pathology or hyperextension of the coffin joint.
  • The forelimb is more commonly affected.

Type I

  • Non-articular fracture of palmar or plantar process extending obliquely from the solar margin toward the articular surface of the process but not entering the DIP joint. Sometimes referred to as wing fractures.
  • Second or fourth most common in USA; first or second most common in UK.
  • Less common than Types II, IV and VI.
  • Direct trauma.
  • Responds to digital nerve block.

Type II

  • Oblique or parasagittal articular fractures of the palmar or plantar process.
  • Some of these cases may have small comminuted fragments within the main fracture line which can be difficult to see on radiographs. MRI Magnetic resonance imaging or CT Computed tomography may be useful in detecting these cases, some of which present as poorly healing fractures in the convalescent period.
  • Most common in USA, especially in Standardbreds; Types I and II most common in UK.

Type III

  • Articular midline fracture that bisects P3 into equal halves.
  • Rare.
  • Less common type of fracture (some reports only 3-4%).

Type IV

  • Articular fractures of the extensor process.
  • May be displaced.
  • Not always clinically significant.
  • Several proposed etiologies.
  • May be due to hyperextension of the distal interphalangeal joint.
  • A separate center of ossification for the extensor process.
  • A manifestation of osteochondrosis Bone: osteochondrosis.
  • Avulsion injury of the digital extensor tendon.
  • Larger fractures of extensor process (often traumatic) usually seen in older horses → lameness - common in the Friesian Friesian.

Type V

  • Comminuted fractures; this comminution is not always clear on initial radiographs and further views may be necessary to correctly diagnose the fracture type.
  • Sequelae of osteomyelitis or sequestra; occasionally other fractures can progress to this type with further trauma.
  • Any articular component will have an effusion of the DIP joint. 

Type VI

  • Non-articular solar margin fractures Distal phalanx: fracture 09 - type VI - DPr60DPO radiograph .
  • Traumatic etiology; may be incidental finding in clinically sound horse radiographs.
  • Mainly in forelimbs and occur between the quarter and toe. 
  • Approximately two-thirds are associated with radiographic lesions of P3, eg laminitis Foot: laminitis, pedal osteitis Distal phalanx: pedal osteitis - non-septic.
  • Common in USA Distal phalanx: fracture 09 - type VI - DPr60DPO radiograph, particularly in areas where there are hard dry ground conditions (California).

Type VII

  • Foals - non-articular fractures of the palmar or plantar process involving the solar margins.
  • Proposed etiology is excessive force on the DDFT or solar cortical bone during weightbearing, possibly exacerbated by excessive trimming of the heels of the frog.
  • Low-grade short-lived lameness which may have resolved by the time radiographs are taken.

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.
  • Reesink H L (2017) Foal Fractures: Osteochondral Fragmentation, Proximal Sesamoid Bone Fractures/Sesamoiditis, and Distal Phalanx Fractures. Vet Clin North Am Equine Pract 33 (2), 397-416 PubMed.
  • Faramarzi B, McMicking H, Halland S et al (2015) Incidence of palmar process fractures of the distal phalanx and association with front hoof conformation in foals. Equine Vet J 47 (6), 675-9 PubMed.
  • Gasiorowski J C & Richardson D W (2015) Clinical use of computed tomography and surface markers to assist internal fixation within the equine hoof. Vet Surg 44 (2), 214-22 PubMed.
  • Kidd J (2011) Pedal bone fractures. Equine Vet Educ 23 (6), 314-323 VetMedResource.
  • Crowe O M, Hepburn R J, Kold S E & Smith R K (2010) Long-term outcome after arthroscopic debridement of distal phalanx extensor process fragmentation in 13 horses. Vet Surg 39 (1), 107-114 PubMed.
  • Booth T (2008) Clinical aspects of the equine foot. Part 1: pedal bone fractures. UK Vet 13 (2), 11-15 VetMedResource.
  • Robson K E, Kristoffersen M & Dyson S J (2008) Palmar or plantar process fractures of the distal phalanx in riding horses: 22 cases (1994-2003). Equine Vet Educ 20 (1), 40-46 VetMedResource.
  • Ter Braake F (2005) Arthroscopic removal of large fragments of the extensor process of the distal phalanx in 4 horses. Equine Vet Educ 17 (2), 101-105 VetMedResource.
  • Greet T R C (2005) Fragments associated with the process of the distal phalanx. Equine Vet Educ 17 (2), 105 VetMedResource.
  • Moyer W, Sigafoos R (1989) Treatment of distal phalanx fractures in racehorses using a continuous rim-type shoe. Proc Ann Conv AAEP 34, 325-328 VetMedResource.

Other sources of information

  • Richardson D (2004) Fractures of the Distal Phalanx: US Perspective. In: Proc 43rd BEVA Congress. Equine Vet J Ltd, UK. pp 116.
  • Pilsworth R (2004) Fractures of the Distal Phalanx: UK Perspective. In: Proc 43rd BEVA Congress. Equine Vet J Ltd, UK. pp 118.


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