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)
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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
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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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