Elbow: congenital luxation in Cats (Felis) | Vetlexicon
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Elbow: congenital luxation

ISSN 2398-2950

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Introduction

  • Very rare in cats.
  • Cause: congenital developmental abnormality.
  • 2 types:
    • Lateral luxation of ulna.
    • Caudolateral luxation of radial head.
  • Treatment: closed reduction if possible, early surgical intervention if not.
  • Prognosis: worse when surgery required or in neglected cases.

Presenting signs

  • Neonate/young animal.
  • Forelimb lameness uni- or bilateral.
  • Characteristic carriage of limb.
  • Deviation of limb - dependent on luxation type.
  • Disability dependent on luxation type - moderate to severe.

Age predisposition

Severe disability

  • 0-3 months.

Less severe disability

  • 4-5 months.

Pathogenesis

Etiology

  • Congenital developmental anomaly.

Pathophysiology

Two forms

  • Lateral luxation of ulna:
    • 90° outward rotation proximally   →  SEVERE DISABILITY.
    • Trochlear notch and articular process disarticulated from humerus and displacement of biceps (?triceps) tendon.
  • Caudolateral luxation of radial head  →  
    • Disability not as severe because of normal relationship between humerus and ulna.
    • Proximal medial epiphysis often deformed (either primarily or secondarily to absence of normal weight bearing forces).
  • Unknown - ?failure of development of medial collateral and annular ligaments and hypertrophy of lateral collateral ligament allowing outward rotation of ulna to occur.
  • Limb angulation changes seen may be secondary due to abnormal distribution of weight bearing surfaces.
  • Long-standing cases - articular surface of proximal radius deformed due to lack of contact with humerus.

Diagnosis

Presenting problems

  • Forelimb lameness.

Client history

Severe disability

  • Animal 0-3 months old.
  • Severe disability - forelimb lameness (uni- or bilateral).

Less severe disability

  • Young animal 4-5 months old.
  • Less severe disability.

Clinical signs

Severe disability

  • Characteristic limb carriage: marked rotation and lateral deviation of antebrachium, lateral rotation of paw, marked reduction in elbow extension.
  • Palpate olecranon laterally.

Less severe disability

  • Characteristic limb carriage: radius displaced caudally and laterally.

Less severe disability

  • Deformed radial epiphysis.
  • No limb deviation except may be slight outward bowing of elbow.
  • Reduced elbow extension.
  • Elbow thickened with marked lateral swelling.
  • Caudal bowing of proximal ulna.

Diagnostic investigation

Radiography

  • Normal - craniocaudal and lateral radiographs  Forelimb: normal elbow - lateral radiograph .

Severe disability

  • Craniocaudal view:
    • Normal frontal view of humerus and lateral view of proximal ulna, ie 90° rotation of proximal ulna relative to distal humerus).
  • Lateral view:
    • Normal view of proximal ulna and medial view of radius.
    • Hypoplasia or aplasia of anconeal process, trochlear notch, humeral condyles and/or coronoid processes; distortion of olecranon.

Less severe disability

  • Normal relationship between humerus and ulna, proximal radius displaced caudally and laterally.

Confirmation of diagnosis

Discriminatory diagnostic features

  • History and clinical signs.

Definitive diagnostic features

  • Radiographic findings.

Differential diagnosis

  • Developmental luxation - secondary to premature closure of distal radial or ulnar growth plates (only pertinent to older age group >4 months).
  • Fracture.
  • Acquired luxation.

Treatment

Standard treatment

Conservative management

  • Severe disability (lateral ulnar luxation):
    • Reduce luxation as soon as possible.
  • If unstable:
    • Maintain reduction using transarticular K-wires or hypodermic needles through olecranon, across humeroulnar joint and up distal humeral diaphysis (may be removed later or often fall out) Fracture fixation: wire  Fracture fixation: plate.
    • Closed reduction: transcutaneous transverse placement of 2 small Steinmann pins (1 through condyles of humerus and the other through olecranon); reduction maintained with tensioned elastic band from medial aspect of proximal pin to lateral aspect of distal pin.
    • Can also use transarticular external skeletal fixator.
      Place padded splint over olecranon to prevent pressure necrosis.
    • Severe case may require arthrodesis.
  • Less severe disability (caudolateral radial head luxation):
    • Early cases: manipulate radial head back into position (and possibly maintain by tightening surrounding soft tissues).

Chronic cases or if closed reduction fails/impossible

  • Severe disability:
    • Open reduction, eg medial capsulorrhaphy, lateral desmotomy, rotational osteotomy of ulna, transposition of olecranon, fixation of proximal ulna to radius, reconstruction of trochlear notch, partial anconeal process resection.
    • Approach joint via osteotomy of olecranon .
    • +/- transarticular K-wires.
    • +/- pins and tension band.
    • +/- external fixator.
    • Severe case ay require arthrodesis.
  • Less severe disability:
    Either Osteotomy of radius and ulna to effect reduction +/- bone plate.
    Or Resection of radial head.

Subsequent management

Treatment

  • Support limb in padded splint 10-14 days post reduction.
  • Remove pins after 10-14 days.
  • External support for further 3 weeks.

Prevention

Control

  • Do not breed from affected animals - ? heritable.

Outcomes

Prognosis

Severe disability

  • Good prognosis after closed reduction - some osteoarthritis should be expected long-term.
  • Often poor with surgical cases (surgery may be contra-indicated if animal able to bear weight on limb and walk).

Less severe disability

  • Good following closed reduction.
  • Often animals tolerate condition well; no treatment should be offered in such cases.

Further Reading

Publications

Refereed papers