Updated: 6/14/2021

Developmental Coxa Vara

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  • summary
    • Developmental Coxa Vara is a rare condition that causes a decreased neck-shaft angle that is associated with an ossification defect in inferior femoral neck.
    • Diagnosis can be confirmed with plain radiographs of the hip. 
    • Treatment can be nonoperative or surgical corrective valgus derotation osteotomy depending on patient symptoms, the severity of varus deformity, and degree of angle progression. 
  • 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
    • Anatomic location
      • bilateral in 1 in 3 cases
    • Risk factors
      • congenital defects
      • differential diagnosis
        • trauma
        • SCFE
        • Legg-Calve-Perthes
  • Etiology
    • 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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