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Congenital pseudoarthrosis

Congenital tibial pseudoarthrosis describes abnormal bowing of the tibia that can progress to a segment of bone loss simulating the appearance of a joint.  The condition is usually apparent shortly after birth and is rarely diagnosed after the age of two.

The eitiology is unclear however around 50% of cases are associated with neurofibromatosis type 1 (NF1). Overall, 10% of patients with NF1 are diagnosed with tibial pseudoarthrosis.

Congenital ulnar psuedoarthrosis and radial pseudoarthrosis can also occur, but much less frequently, and usually only in patients with NF1.   

Radiographic features

  • progressive bowing (usually anterolateral in the tibia)
  • resorption of short segment of bone
    • usually at site of maximal bowing
    • usually between mid and distal one third of shaft
  • angulation at site of absent bone segment
  • often mimics appearance of a joint
    • cupping of the bone proximal to the absent section
    • sharpened narrow appearance of the distal bone
  • often fracture or bowing of accompanying bone (fibular with tibia, radius with ulnar)

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