Congenital pseudoarthrosis of the tibia

Congenital pseudoarthrosis of the tibia describes abnormal bowing 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.

Pathology

The etiology 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.

Fibular, ulnar, and radial pseudoarthroses 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 a short segment of bone
    • usually at the site of maximal bowing
    • usually between mid and distal one-third of the shaft
  • angulation at the site of absent bone segment
  • often mimics the 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 (fibula with tibia, radius with ulna)