Equis ISSN 2398-2977

Musculoskeletal: angular deformity

Synonym(s): Valgus, varus

Contributor(s): Helen Herinckx, Chris Whitton

Introduction

  • Congenital or acquired conformational abnormality in foals a few weeks to several months old.
  • Carpal valgus, fetlock varus most common.
  • Limb deviates in a frontal (medial-lateral) plane distal to a joint where there is some abnormality of growth.
  • All breeds, no sex prediliction - although high incidence reported in Quarterhorses   Quarterhorse  .
  • May be single or multiple joints affected.
  • Carpal valgus accounts for approximately half all cases; fetlock varus for 45%, followed by carpal varus and other types, eg tarsal valgus.
  • Cause: multifactorial etiology resulting in asymmetric joint pressures and growth imbalance at physis, eg dysplasia, fetal malposition, premature birth, ligament laxity, incomplete ossification of carpal/tarsal bones, trauma, sepsis, favoring of limb.
  • Signs: varus   MCP / MTP joint: angular deformity 04 - varus  or valgus   Carpus: angular deformity 01 - valgus  conformational deformity   Musculoskeletal: conformation  , may be lameness   Musculoskeletal: gait evaluation  , abnormal posture.
  • Diagnosis: physical examination   Musculoskeletal: physical examination - adult  , radiology   Forelimb: radiography    Hindlimb: radiography  .
  • Treatment: tailor to individual; medical - manual reduction, confinement, cast   Musculoskeletal: external fixation - casts  , diet management   Nutrition: growth  , or surgical - transphyseal bridging   Carpus: growth retardation - angular deformity  , hemicircumferential periosteal transection   Carpus: growth acceleration - angular deformity  , corrective osteotomy.
  • Prognosis: good - depends on cause, severity and age at treatment.

Pathogenesis

Etiology

  • Exact cause and pathophysiology not clear.
  • Many possible factors.

General factors

  • Prenatal:
    • Malposition of fetus.
    • Exogenous chemicals.
    • Hormones.
    • Nutritional imbalances.
    • Musculoskeletal immaturity.
  • Developmental:
    • Poor conformation   Musculoskeletal: conformation  .
    • Diet - excess nutrition   →   overweight relative to slight limbs; role of Ca:P?
    • Level of exercise - overactivity   →   excessive/asymmetric pressure on joints.
    • Trauma.

Specific factors

  • Immaturity of periarticular tissues, eg collateral ligament laxity.
  • Metaphyseal growth plate dysplasia.
  • Delayed or abnormal epiphyseal ossification.
  • Delayed or absent ossification of cuboidal bones of carpus   Carpus: incomplete ossification 02 - radiograph  and tarsus.
  • Diaphyseal deformities.
  • Physeal sepsis.
  • Preferential limb use, eg lameness on opposite leg.

Pathophysiology

Physeal growth imbalance
  • Excess pressure on part of metaphyseal growth plate or physis   →   decreased blood supply   →   delayed production of chondrocytes on epiphyseal side   →   retardation of new bone production on metaphyseal side   MCP / MTP joint: angular deformity 03 - DPa radiograph  .

Delayed or abnormal ossification

  • Cuboidal bone ossification occurs late in gestation.
  • Premature birth or dysmaturity   →   abnormal forces on incompletely ossified cartilage   →   deformity of carpal and/or tarsal bones:
    • Two or more carpal bones (commonly radial, intermediate, ulnar, third and fourth carpal bones).
    • Tarsal collapse.
    • ?Role in juvenile bone spavin   Tarsus: osteoarthritis (bone spavin)  .

Trauma

  • Luxation, fractures, crushing injuries to growth plate (Salter type V)   →   delayed growth (possibly complete cessation if Salter type V injury) in affected area.

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.
  • Carlson E R et al (2012) Complications after two transphyseal bridging techniques for treatment of angular limb deformities of the distal radius in 568 Thoroughbred yearlings. Equine Vet J 44 (4), 416-419 PubMed.
  • Getman L M (2011) Surgical treatment of severe, complex limb deformities in horses. Equine Vet Educ 23 (8), 386-390 VetMedResource.
  • Smith L (2010) Treatment of angular limb deformities in foals. In Pract 32 (4), 156-162 VetMedResource.
  • Kay A T & Hunt R J (2009) Single screw transphyseal bridging of the distal metacarpus and metatarsus for correction of angular limb deformity in the foal. Equine Vet Educ 21 (12), 671-672 Wiley Online Library.
  • Roberts B L, Railton D & Adkins A R (2009) A single screw technique compared to a two screw and wire technique as a temporary transphyseal bridge for correction of fetlock varus deformities. Equine Vet Educ 21 (12), 666-670 VetMedResource.
  • Bramlage L R (1999) The science and art of angular limb deformity correction. Equine Vet Educ 31 (3), 182-182 (editorial comment) PubMed
  • Brauer T S, Booth T S & Riedsel E (1999) Physeal growth retardation leads to correction of intracarpal angular deviations as well as physeal valgus deformity. Equine Vet Educ 31 (3), 193-196 PubMed.
  • Caron J P (1988) Angular limb deformities in foals. Equine Vet J 20, 225-228 PubMed.
  • Gaughan E M (1998) Angular limb deformities in horses. Comp Cont Educ 20, 944-946 VetMedResource.


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