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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
      • differential diagnosis
        • 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 
    • developmental 
    • congenital (e.g. congenital short femur, PFFD)
    • acquired (e.g. SCFE, infection, Perthes)
    • dysplasia (e.g OI, Jansen, Schmid, SED)
    • 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
      • varus neck shaft angle <120 degrees 
      • short femoral neck, vertical physis
      • 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
      • surgical planning
      • 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-ephyseal angle (normal <25 degrees)
          • <45 degrees – unlikely to progress
          • 45-60 – may progress
            • will require close follow-up if non-symptomatic
  • Operative
    • corrective valgus derotation osteotomy (VDRO
      • indications
        • Hilgenreiner's physeal angle > 60°
        • Hilgenreiner's physeal angle between 45-60° if symptomatic (e.g. limp & progression of varus)
        • progressive decrease in neck shaft angle < 110 °
      • aftercare
        • hip-spica or abduction pillow x 4-6 weeks depending on fixation and healing
Technique
  • Corrective valgus derotation osteotomy (VDRO) 
    • goals
      • over-correct neck shaft angle (literature suggests to reduce Hilgenreiner's physeal angle < 38°)
      • correct leg length discrepancy
      • correct hip anteversion/retroversion
      • re-establish abductor muscle tensioning
    • approach
      • typically a hip direct lateral approach is used 
    • procedure(s)
      • valgus trochanteric osteotomy – may fix with blade plate
        • supine with bump
        • perform adductor tenotomy
        • direct lateral approach
        • valgus osteotomy as template
        • overcorrect to place physis in horizontal position (to decrease shear stress)
        • derotation to antevert neck as neck
        • hip cast post-op for 6 weeks
      • greater trochanter epiphyseodesis
        • to prevent GT overgrowth in vascular coxa vara
        • lateral approach
        • fluoro to determine position of physis
        • curette or drill physis
      • greater trochanter transfer
        • lateral approach
        • free GT fragment of soft tissues 
        • transfer distal and lateral
        • freshen lateral femoral recipient bed cortex with osteotomy
        • place GT fragment so that tip is at level of femoral head
Complications
  • Loss of correction
  • Premature closure of the proximal femoral physis
  • Overgrowth of proximal femur
  • Dysplasia of acetabulum
 

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