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.
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.
- 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)