Coxa Vara

Definition
Coxa Vara is defined as a neck-shaft angle of less than 120 degrees.

Epidemiology

Factor Details
Incidence 1 in 25,000 live births
Gender Boys = Girls
Laterality Left = Right
Racial Predilection None
Bilateral Cases 30%

Aetiology

The primary cause is an ossification defect in the infero-medial proximal femoral physis, specifically within Fairbank’s triangle. It is associated with autosomal dominant inheritance and incomplete penetrance.

Types of Coxa Vara

Type Characteristics
Developmental Due to primary ossification defect; physis becomes more vertical over time, increasing shear force and leading to physeal separation.
Congenital Associated with conditions like Congenital Short Femur (CSF), Proximal Femoral Focal Deficiency (PFFD), fibular hemimelia, etc.
Acquired Occurs secondary to conditions like Slipped Upper Femoral Epiphysis (SUFE), Perthes Disease, or Skeletal Dysplasia.

Clinical Presentation

  • Typical Onset: Once a child starts walking, usually before the age of 5.
  • Symptoms:
    • Trendelenburg gait
    • Waddling gait or limp (if bilateral)
    • Usually painless
    • Prominent trochanter

Imaging Features

  • Inverted Y Sign: A pathognomonic feature caused by fragmentation of the infero-medial physis.
  • Other Imaging Observations:
    • Delayed ossification (may resemble Developmental Dysplasia of the Hip (DDH)).
    • Infero-medial quadrant placement of metaphysis.
    • Physeal arrest.
    • Trochanteric overgrowth.

Management

The treatment approach for coxa vara depends on Hilgenreiner’s Epiphyseal Angle (HEA), which is the angle between the physis and Hilgenreiner’s line.

HEA Angle Management Strategy
< 45 degrees Non-operative; often corrects spontaneously
45-60 degrees Close observation with serial X-rays
> 60 degrees Surgical intervention with osteotomy

Surgical Approach: Pawels Y-Shaped Osteotomy

  • Purpose: Corrects HEA to approximately 16 degrees to reduce shear force on the physis.
  • Procedure:
    • Calculate osteotomy closing wedge angle as HEA minus 16 degrees.
    • Use K-wires to align cuts and saw to perform osteotomy.
    • Fixation is achieved with a Tension Band Wire (TBW), blade plate, or locking plate.
  • Trochanteric Advancement: Considered if Trendelenburg gait is present.

Complications

  • Avascular Necrosis (AVN): Especially common in intracapsular osteotomy.
  • Physeal Arrest: Occurs in about 80% of cases.
  • Trochanteric Overgrowth: May lead to hip issues.
  • Recurrence of Coxa Vara: Noted in approximately 50% of cases after treatment.

Reference

  • Lieberman, J. (2009). AAOS Comprehensive Review. American Academy of Orthopaedic Surgeons
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