Congenital Pseudarthrosis of Tibia
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Direct answer
Congenital pseudarthrosis of the tibia is a non-union of the tibia, usually in the distal third, preceded by anterior bowing that often presents in early childhood. It is closely linked with neurofibromatosis type 1 in many cases, and union is difficult because the fracture site is fibrous and cystic. Treatment usually combines excision of the pseudarthrosis, intramedullary fixation and bone grafting, sometimes with a vascularised fibula.
What you must remember
- Precursor: anterior bowing of the distal tibia, often noticed in infancy, comes before the fracture and pseudarthrosis.
- Association: neurofibromatosis type 1 is found in a considerable share of cases, so cafe-au-lait macules and axillary freckling must be sought.
- Crawford classification: grades the disease from bowing without fracture through to established pseudarthrosis, guiding the choice of treatment.
- Why union fails: the fibrous or cystic pseudarthrosis, with dysplastic bone and a poor periosteal response, does not form callus.
- Bracing: used for the bowing before fracture, although it does not reliably prevent a fracture.
- Surgery: excision of the pseudarthrosis, intramedullary rodding and bone grafting, with vascularised fibular transfer in selected cases.
- Recurrence: refracture and recurrence remain common, so follow-up continues through growth.
- Amputation: considered only after repeated failed attempts at union, with the child and family involved in the decision.
From anterior bowing to a healed tibia
A 2-year-old with anterior bowing of the right distal tibia and a cafe-au-lait patch on the trunk breaks the leg after a minor fall. The management plan depends on staging the disease and checking for neurofibromatosis.
- Examine for NF1: count cafe-au-lait macules, look for axillary freckling and neurofibromas, since the presence of these features changes the expected course.
- Image the whole leg: full-length radiographs show the bowing, cortical thinning and cystic change at the fracture site.
- Brace the bowing: a brace protects the bowed segment from fracture, although it does not reliably prevent one.
- Operate for established non-union: the fibrous pseudarthrosis is excised, and an intramedullary rod is placed with bone grafting to bridge the gap.
- Add vascularised grafting where needed: a vascularised fibular transfer is considered for large defects or when simple grafting has failed.
- Plan for recurrence: the child is followed through growth, since refracture is common, and amputation is discussed only after repeated failure.
Where the exam tries to catch you
Examiners test the biology of non-union and the link with neurofibromatosis.
- Trap: assuming a tibial non-union in a child will heal with casting alone. Correct: congenital pseudarthrosis rarely unites with casting, so surgical excision and fixation are usually required.
- Trap: attributing the non-union to the minor fall. Correct: the lesion is developmental, and the fall is only the trigger, so neurofibromatosis should be sought.
- Trap: using a fibular graft without fixation. Correct: a graft without stable fixation fails, so intramedullary rodding is combined with the bone graft.
Frequently asked questions
Why is union so difficult in congenital pseudarthrosis of the tibia?
The pseudarthrosis is fibrous or cystic, with dysplastic bone and a poor periosteal response that fails to form callus. Bone grafts and stable fixation are therefore needed to overcome this biological failure.
Which syndrome is most closely associated with congenital pseudarthrosis of the tibia?
Neurofibromatosis type 1 is the syndrome most closely linked with congenital pseudarthrosis of the tibia. Examination of a child with this condition looks for cafe-au-lait spots, axillary freckling and neurofibromas, which support the diagnosis.
What does the Crawford classification describe?
The Crawford classification grades congenital pseudarthrosis of the tibia by the stage of disease, from anterior bowing without fracture to established pseudarthrosis. It helps guide the choice of treatment for each child.
When is amputation considered for congenital pseudarthrosis of the tibia?
Amputation is considered when repeated surgical attempts at union have failed and the limb remains functionally poor. The decision is individualised, with the child and family consulted and the prosthetic outcome weighed.