Equis ISSN 2398-2977

Carpus: fracture - chip

Synonym(s): Carpal osteochondral fragmentation

Contributor(s): Stephen Adams, Patrick Colahan, Chris Whitton, Graham Munroe

Introduction

Pathogenesis

Predisposing factors

Pathophysiology

  • The end result of stress-related subchondral bone injury caused by repetitive loading:
    • Initially this is adaptive but with continued loading it becomes non-adaptive bone remodeling and pathological.
    • This is seen in radiographs of the carpal bones Forelimb: radiography as bone sclerosis and remodeling of the subchondral bone, which is evident at the time of fracture.
  • Once the bone is damaged it is predisposed to fracture, as an apparent one-off event, during training or racing.
  • Osteochondral fragments, by definition, involve only one joint surface within the midcarpal or antebrachiocarpal joints. There can be single or multiple fragments in one joint, multiple joints or multiple legs.
  • There are differences between racing breeds as to the site of osteochondral chip fractures, which are explained by gait and sites predisposed to stress-related subchondral bone injury.
  • Acute overload injury, particularly in fatigued horses, does occur in the absence of pre-existing bone pathology in occasional cases, and usually involving the antebrachiocarpal joint.
  • Dorsal sites in the carpus are more prone to fragmentation because of the biomechanics of the carpal joints. Individual sites within the midcarpal and antebrachiocarpal joint are affected by the breed of the animal, its racing requirements, training regimens, surfaces it trains and races on, and carpal conformation.
  • Palmar osteochondral fragmentation is much less common.:
    • Those involving the proximal articular margin of the accessory carpal bone or other bones of the antebrachiocarpal joint may occur as one-off events such as falls, carpal hyperflexion, or recovery from a general anesthetic.
    • The most commonly affected bone is the proximal palmar articular margin of the radiocarpal bone either alone or in combination with comminuted palmar radiocarpal fractures and/or concurrent intermediate, ulnar or palmar distal radial fractures.
    • Midcarpal joint palmar carpal fragments are more often seen in combination with dorsal joint fragmentation and may be migrants from dorsally.

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.
  • Lang H M & Nixon A J (2015) Arthroscopic removal of discrete palmar carpal osteochondral fragments in horses: 25 cases (1999-2013). J Am Vet Med Assoc 246 (9), 998-1004 PubMed.
  • Wright I M & Smith M R W (2011) The use of small (2.7 mm) screws for arthroscopically guided repair of carpal chip fractures. Equine Vet J 43 (3), 270-279 PubMed
  • Steel C M et al (2006) Clinical findings, diagnosis, prevalence and predisposing factors for lameness localised to the middle carpal joint in young Standardbred racehorses. Equine Vet J 38 (2), 152-157 PubMed.
  • Shimozawa K, Ueno Y, Ushiya S & Kusunose R (2001) Survey of arthroscopic surgery for carpal chip fractures in thoroughbred racehorses in Japan. J Vet Med Sci 63 (3), 329-331 PubMed.
  • Lucas J M, Ross M W & Richardson D W (1999) Post operative performance of racing Standardbreds treated arthroscopically for carpal chip fractures, 176 cases (1986-1993). Equine Vet J 31 (1), 48-52 PubMed.
  • Kannegieter N J & Burbidge H M (1990) Correlation between radiographic and arthroscopic findings in the equine carpus. Aust Vet J 67 (4), 132-133 PubMed.


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