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Developmental Coxa Vara

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Topic updated on 02/14/16 1:50pm
Introduction
  • A decreased neck-shaft angle that is associated with an ossification defect in inferior femoral neck
  • Epidemiology
    • incidence:
      • 1 in 25,000 live births in the US
    • demographics
      • males and females affected equally
      • presents between age of ambulation and 6 years of age
    • location
      • bilateral in 1 in 3 cases
    • risk factors
      • congenital defects
      • acquired conditions 
        • trauma
        • SCFE
        • Legg-Calve-Perthes
  • Pathophysiology
    • proximal femoral cartilaginous physis or ossification center defects lead to
      • decreased proximal femoral neck-shaft angle
      • vertical position of the proximal femoral physis and varus
    • pathomechanics
      • coxa vara and vertical physis increases
        • physeal sheering forces
        • inferior medial neck compressive forces
  • Genetics
    • no clear inheritance pattern
  • Associated conditions
    • femoral neck stress fractures
    • decreased limb length
    • early hip osteoarthritis
Classification
  • Etiologies of Coxa Vara
    • congenital 
    • acquired 
    • dysplasia
    • developmental
    • cretinism 
Presentation
  • History
    • previous hip trauma or infection
    • associated skeletal abnormalities
    • prenatal and developmental history
    • family history of similar deformity
  • Symptoms
    • usually painless
    • gait abnormality
      • waddling or limp (trendelenburg gait)
        • caused by abductor weakness from tension abnormality
  • Physical exam
    • inspection
      • leg length discrepancy 
      • high riding greater trochanter
      • limb shortening
      • excessive lumbar lordosis 
    • motion
      • restricted hip range of motion in all planes that is usually non-tender
Imaging
  • Radiographs
    • recommended views:
      • AP hip with limb internally rotated + lateral hip
    • findings
      • neck shaft angle <125 degrees 
      • increased Hilgenreiner's epiphyseal angle (normal <25 degrees)
        • determined on AP as angle between Hilgenreiner's line and a line through the proximal femoral physis  
      • triangular metaphyseal fragment in inferior femoral neck (looks like inverted-Y radiolucency) 
      • decreased femoral anteversion
  • CT
    • indications
      • delineate proximal femur defects
      • orientation of deformity
    • views
      • consider all views including 3D reconstructions
    • findings
      • deformity configuration
      • bone stock
      • physeal widening
Treatment
  • Nonoperative
    • observation alone
      • indications
        • Hilgenreiner's physeal angle < 45
        • most will correct spontaneously without surgery
  • Operative
    • corrective valgus derotation osteotomy (VDRO
      • indications
        • Hilgenreiner's physeal angle > 60, or 45-60° with limp & progression of varus
        • (neck shaft angle < 110 °)
      • technique (see below)
      • aftercare
        • hip-spica for approximately 6 weeks
Technique
  • Corrective valgus derotation osteotomy (VDRO) 
    • goals of treatment
      • correct neck shaft angle
      • correct leg length discrepancy
      • correct hip anteversion/retroversion
      • re-establish abductor muscle tensioning
    • approach
      • typically a hip direct lateral approach is used 
    • procedure
      • protect periosteum and physis
      • perform valgus producing osteotomy in sub-trochanteric
      • may need to transfer greater trochanter to properly tension abductor muscles
Complications
  • Loss of correction
  • Premature closure of the proximal femoral physis
  • Overgrowth of proximal femur
  • Dysplasia of acetabulum

 

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