Congenital pseudoarthrosis of the tibia

Last revised by Khalid Alhusseiny on 20 Feb 2023

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, up to 80% 4,5 of cases are associated with neurofibromatosis type 1 (NF1); in which there is a loss of activity of the protein neurofibromin causing defective differentiation of osteoblasts 5. 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)

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