*Pseudoarthrosis is a false joint, that may develop after a fracture that has not united properly.
*It may be idiopathic.
*Causes of Pseudoarthrosis (in decreasing order of frequency are) :
1. Non union of a fracture - including pathological fracture.
2. Congenital - in the middle to lower third of the tibia with or without fibula. 50% present in the first year. Later there may be cupping of the proximal bone and pointing of the distal bone end.
3. Neurofibromatosis - seen in 50% of patients with pseudoarthrosis.
4. Osteogenesis imperfecta
5. Cleidocranial dysplasia - congenitally in the femur
6. Fibrous dysplasia
7. Ankylosing spondylitis - in the fused bamboo spine .