ISSN 2398-2977      

MC / MT 3: condylar fracture

pequis

Introduction

  • Cause: fatigue failure of bone from repetitive loading; common racing injury especially Thoroughbred forelimb, Standardbred fore and hindlimbs.
  • Signs: acute lameness after hard exercise Musculoskeletal: gait evaluation, joint effusion, pain on flexion Musculoskeletal: manipulative tests.
  • Diagnosis: physical examination, radiography.
  • Treatment: surgery.
  • Prognosis: good for incomplete fractures; guarded for more serious injuries.

Pathogenesis

Etiology

  • Stress or fatigue fractures.
  • Repetitive high loading of condyle, ie race training leads to subchondral bone remodeling and areas of weakness in the bone in the distal condyle.
  • Acute loading of the bone subsequently in training or racing can lead to fracture(s), which propagate for varying distances proximally through the bone.

Predisposing factors

General

  • Racing and training at high speed.

Specific

  • Thoroughbred racehorses.

Pathophysiology

  • Unbalanced loading of limbs during racing on circular tracks → forces concentrated on a condyle → accumulation of concussive injury → fatigue failure of bone → fracture.
  • Intense remodeling activity has been observed at the fracture site distally and in Thoroughbred racehorses in training. This is more common in the palmar lateral condyle.
  • Scanning electron microscopic studies have confirmed consistently branching microcracks in the thickened compact bone of the palmar/plantar condylar groove of the distal cannon bone in Thoroughbreds in training. Accumulation and coalescence of these microcracks produce a longer and wider dominant defect, which can then propagate into a larger fracture.
  • Subchondral bone remodeling can also lead to cartilage and subchondral defects especially in the palmar surface of the condyle, which complicate the repair and worsen the prognosis.
  • Acute failure without pre-existing bone remodeling may occur due to unusual loading of the condyles at high speed.
  • As these fractures are more common in 2 or 3-year-old horses it is considered that in these horses they may represent failure of adaptation rather than cumulation fatigue.
  • Other injuries may occur simultaneously, eg axial sesamoid fracture Proximal sesamoid: fracture, soft tissue structures supporting the metacarpophalangeal joint, eg collateral ligaments and suspensory ligaments.
  • Lateral condylar fractures are the most common in the foreleg (approximately 90%); they rarely spiral and may extend a variable distance from the joint surface towards the lateral cortex:
    • Those that extend only 1-2 cm proximally can be difficult to identify.
  • Fractures may be unicortical or bicortical, incomplete or complete, non-displaced or displaced:
    • Fractures that extend into the diaphysis of the metacarpus or metatarsal bone are described as propagating and can be either in a sagittal or parasagittal plane, or spiral into oblique or frontal planes.
    • Propagating fractures are more likely to be medial.
    • Comminution occurs only in complete fractures.
    • Fractures usually start adjacent to the sagittal ridge but occasionally they are nearer the abaxial margin. The latter are usually shorter in length.
    • Fracture classification is important for treatment selection and long-term prognostication.
  • Bilateral spontaneously occurring fractures and those involving both fore and hindlimb are occasionally recorded.
  • Sagittal ridge and medial condylar fractures tend to variably extend proximally into the diaphysis, spiraling or dividing into a Y-shape, thereby increasing the risk of a complete fracture.
  • Fractures of the third metatarsal bone are less common (half the incidence of forelimb). Many medial MT3 fractures have a tendency to spiral.
  • See Musculoskeletal: fracture.

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.
  • Boorman S et al (2020) Racing performance after surgical repair of medial condylar fracture of the third metacarpal/metatarsal bone in thoroughbred racehorses. Vet Surg 49 (4), 648-658 PubMed.
  • Peloso J G et al (2019) Association of catastrophic condylar fracture with bony changes of the third metacarpal bone identified by use of standing magnetic resonance imaging in forelimbs from cadavers of Thoroughbred racehorses in the United States. Am J Vet Res 80 (2), 178-188 PubMed.
  • Anne-Archard N et al (2019) Differences in third metacarpal trabecular microarchitecture between the parasagittal groove and condyle at birth and in adult racehorses. Equine Vet J 51 (1), 115-122 PubMed.
  • Tranquille C A, Murray R C & Parkin T D (2017) Can we use subchondral bone thickness on high-field magnetic resonance images to identify Thoroughbred racehorses at risk of catastrophic lateral condylar fracture? Equine Vet J 49 (2), 167-171 WileyOnline.
  • Ramzan P H, Palmer L & Powell S E (2015) Unicortical condylar fracture of the Thoroughbred fetlock: 45 cases (2006-2013). Equine Vet J 47 (6), 680-683 PubMed.
  • Trope G D et al (2015) Can high- resolution peripheral quantitative computed tomography imaging of subchondral and cortical bone predict condylar fracture in Thoroughbred racehorses? Equine Vet J 47 (4), 428-432 PubMed.
  • Powell S E (2012) Low-field standing magnetic resonance imaging findings of the metacarpo/metatarsophalangeal joint of racing Thoroughbreds with lameness localised to the region: a retrospective study of 131 horses. Equine Vet J 44 (2), 169-177 PubMed.
  • Payne R J & Compston P C (2012) Short- and long-term results following standing fracture repair in 34 horses. Equine Vet J 44, 721–725 PubMed.
  • Tranquille C A, Parkin T D & Murray R C (2012) Magnetic resonance imaging-detected adaptation and pathology in the distal condyles of the third metacarpus, associated with lateral condylar fracture in Thoroughbred racehorses. Equine Vet J 44 (6), 699-706 PubMed.
  • Whitton R C et al (2010) Third metacarpal condylar fatigue fractures in equine athletes occur within previously modelled subchondral bone. Bone 47 (4), 826-831 PubMed.
  • Smith L C, Greet T R & Bathe A P (2009) A lateral approach for screw repair in lag fashion of spiral third metacarpal and metatarsal medial condylar fractures in horses. Vet Surg 38 (6), 681-688 PubMed.
  • Wright I M & Smith M R W (2009) A lateral approach to the repair of propagating fractures of the medial condyle of the third metacarpal and metatarsal bone in 18 racehorses. Vet Surg 38 (6), 689-695 PubMed.

Other sources of information

  • Nixon A J (2020) Ed Equine Fracture RepairW B Saunders, USA. pp 378-424.
  • Richardson D W & Dyson S J (2011) The Metacarpophalangeal Joint. In: Lameness in the Horse. 2nd edn. Eds: Ross W R & Dyson S J. Elsevier, USA. pp 408-409. ISBN: 978-1-4160-6069-7.

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