Case reveal

Findings

  • Arising from the solar margin of the lateral quarter of the distal phalanx, and reaching the articular surface of the distal interphalangeal joint, a well-defined fractures line is identified (blue arrowheads). Just lateral, another fracture line is seen extending transversely from the lateral quarter of the distal phalanx (white arrowheads).
  • Multiple punctate, well-defined, metal opaque structures are present within the nail tracts.

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Diagnosis

  • Left distal phalangeal articular fracture (type II) with concurrent fissure line.

A little bit more…

  • Fractures of distal phalanx are more common in racing Thoroughbreds, Standardbreds and Quarter horses.
  • Causes include racing on hard surfaces, falling, kicking hard, foreign body puncture, and immovable objects. They can be predisposed by osteomyelitis, nutritional deficiencies, upright conformation, unbalancing shoe, and laminitis.
  • Clinical findings include the presenceĀ of lameness at a walk or trot, digital pulses and heat at the coronary band with an acute fracture; and resentment to compression of the sole and wall with hoof testers.
  • The differential diagnoses of distal phalanx fractures include sole abscess, bruised sole, pedal osteitis, navicular bone fracture, navicular disease, foreign body penetration, and laminitis.

Radiographic classification if distal phalanx fractures

  • Type I: Nonarticular fractures of the palmar/plantar process of the bone
  • Type II: Articular fractures that are not midsagittal and extend from the distal interphalangeal joint to the solar margin of the bone.
  • Type III: Midsagittal articular fractures that divide the distal phalanx into two approximately equal parts.
  • Type IV: Fractures of the extensor process
  • Type V: Comminuted fractures involving the body and solar margin of the distal phalanx
  • Type VI: Fractures on the solar margin of the distal phalanx

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  • The most common fracture is the type VI, followed by the type II
  • They are more frequent in the forelimb, probably because they bear more weight than hind limb
  • The fracture line for all types become wider in the first week until a maximum width seen at 4 to 6 weeks after injury.
  • In Racehorses, distal phalanx fractures occur more frequent in the medial aspect of the right front, and the lateral aspect of the left front.
  • CT studies allow a better approach for fractures recognition.
  • Discrete fractures are not visualized in radiographs but can be achieved with CT.

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References

  • Honnas, C. et al. Distal phalanx fractures in horses. A survey of 274 horses with radiographic assessment of healing in 36 horses. Veterinary Radiology, vol 29, No. 3, 1988. pp.99-107
  • Crijins, C.P., et al. Equine Veterinary Journal 46, 2014. pp.92-96.