Musculoskeletal: angular deformity

Valgus • varus

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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    .
  • 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    or valgus    conformational deformity  [Musculoskeletal: conformation]  , may be lameness  [Musculoskeletal: gait evaluation]  , abnormal posture. (Figs. 1-2)
  • Diagnosis : physical examination    , 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.

Print off the Owner factsheet on  Flexural limb deformities     to give you your client.

Diagnosis

Clinical signs

  • Conformational deformity:
    • MCP / MTP joint: angular deformity 04 - varusFig.3 MCP / MTP joint: angular deformity 04 - varus
      Varus - medial deviation of distal limb, eg fetlock varus is medial deviation of the phalanges with lateral deviation of the distal end of the third metacarpal bone   (Fig. 3)  .
    • Valgus - lateral deviation of distal limb, eg carpal valgus is lateral deviation of the metacarpus with medial deviation of the distal radius; tarsal valgus is lateral deviation of the metatarsus with medial deviation of the distal tibia       . (Figs. 4-5)
    • Tarsus: angular deformity - valgus and varusFig.6 Tarsus: angular deformity - valgus and varus
      Combined varus/valgus   (Fig. 6)  .
    • Carpus valgus and fetlock varus are the most common deformities.
    • May be inward (toe-in) or outward rotation (toe-out).
    • Sagittal deviation rare; see flexural limb deformities.
  • Lameness  [Musculoskeletal: gait evaluation]  .
  • Local heat and swelling.
  • Manual reduction:
    • Apply pressure to medial side of carpus/tarsus.
    • Apply counter pressure to lateral aspect of distal limb simultaneously.
    • Temporary correction   →   (suggests periarticular laxity, and amenity to conservative management).

Outcomes

Prognosis

  • Good; for reducible and deformities <20° up to 6 months of age.
  • Fair; for severe deformities >20° and <12 months old.
  • Guarded; for some severe deformites in older foals and those >12 months old.
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