Congenital Pseudarthrosis of Tibia

• Incidence: 1 in 140,000 to 250,000 live births
• Male to female ratio: 1.5:1
• Bilateral involvement: 10-15% of cases
• Left side slightly more common
• Strong association with NF1 (50-90% of cases)

CPT results from abnormal bone formation and healing. The exact mechanism is unknown but involves:

• Hamartomatous tissue at pseudarthrosis site (fibrous, non-ossifying)
• Abnormal periosteum (thickened, constrictive)
• Poor vascularity at pseudarthrosis site
• Abnormal bone biology (osteoclasts, osteoblasts dysfunction)
• NF1 gene mutation (when associated)

The tibia is the primary weight-bearing bone of the lower leg. It has a triangular cross-section with anterior, medial, and lateral surfaces. The medullary canal contains bone marrow and provides a pathway for intramedullary fixation.

In CPT, there is:

• Anterior bowing: Characteristic deformity (anterolateral)
• Hamartomatous tissue: Fibrous, non-ossifying tissue at pseudarthrosis site
• Abnormal periosteum: Thickened, constrictive, prevents healing
• Narrowed medullary canal: In Type II, canal becomes sclerotic and narrowed
• Cystic lesions: In Type III, cystic changes precede fracture
• Established nonunion: In Type IV, complete pseudarthrosis with no healing potential

The hamartomatous tissue at the pseudarthrosis site prevents normal bone healing. The tissue is:

• Fibrous and avascular
• Contains abnormal cells (not true bone-forming cells)
• Creates a barrier to healing
• May be related to NF1 gene mutation (when associated)

When CPT is associated with NF1:

• NF1 gene mutation affects bone biology
• Abnormal periosteal function
• Poor vascularity
• Worse prognosis than isolated CPT

• Anterior bowing noted at birth or early infancy
• May have history of minor trauma leading to fracture
• Family history of NF1 (if associated)
• Difficulty with weight-bearing or walking
• Previous treatment attempts (if established pseudarthrosis)

• Assess anterior bowing (characteristic)
• Evaluate medullary canal (intact, narrowed, cystic, or nonunion)
• Measure bowing angle
• Assess for pseudarthrosis (Type IV)
• Evaluate fibula (may also be affected)

• Measure limb length discrepancy
• Assess alignment
• Evaluate ankle deformity

• May help assess medullary canal status
• Evaluate cystic lesions (Type III)
• Plan surgical approach

• Assess soft tissue (hamartomatous tissue)
• Evaluate vascularity
• Plan vascularized fibula transfer

• Genetic testing (NF1 gene mutation)
• Ophthalmology examination (Lisch nodules)
• Family history assessment
• Dermatology assessment (café-au-lait spots, neurofibromas)

• May assess vascularity at pseudarthrosis site
• Less commonly used now

After radical excision of the pseudarthrosis and the surrounding dysplastic hamartomatous periosteum, the freshened tibial ends are apposed and the adjacent fibula is united to the tibia both proximal and distal to the defect. Choi and colleagues termed this "4-in-1 osteosynthesis" because the four bone ends - proximal and distal tibia, proximal and distal fibula - are grafted into one continuous mass. The result is a wide, large-cross-sectional-area load-sharing block rather than a narrow single-bone union that is prone to refracture.

• Radical resection of pseudarthrosis, sclerotic bone and the constrictive periosteal sleeve back to healthy bleeding bone.
• Autograft (iliac crest) packed into the tibiofibular interval, frequently augmented with rhBMP-2.
• Intramedullary fixation (Williams or Fassier-Duval telescoping rod) to hold alignment and share load.
• Circular/Ilizarov external fixation for compression and simultaneous correction of length and deformity.

uniting the fibula to the tibia widens the fusion mass, removes the unsupported dysplastic fibula as a source of ongoing deformity and ankle valgus, and mechanically buttresses the reconstruction. The trade-offs are loss of independent tibiofibular motion and reliance on small series with short follow-up - it is the current direction of travel, not a proven, durable gold standard.

• A dysplastic or ununited, shortened fibula fails to buttress the lateral ankle.
• The lateral malleolus migrates proximally, the talus tilts into valgus, and progressive ankle valgus and instability follow (El-Gammal series: mean ankle valgus around 12 degrees despite union).
• Ankle valgus compounds any limb-length discrepancy and accelerates degenerative change at the ankle.

• Achieve fibular union - restoring the lateral column (a major rationale for the cross-union/synostosis strategy) prevents progression.
• Guided growth in the skeletally immature ankle: medial distal tibial hemiepiphysiodesis (for example a medial malleolar screw) gradually corrects the valgus while growth remains.
• Distal tibiofibular synostosis (Langenskiold procedure) can stabilise the mortise and prevent proximal fibular migration.
• Supramalleolar osteotomy for fixed deformity near or after skeletal maturity.
• Long-term surveillance to skeletal maturity, since valgus and instability can recur even after tibial union.

• Infection (5-10%)
• Wound healing problems
• Neurovascular injury (microsurgery)
• Graft failure (vascularized fibula)
• Hardware problems

• Persistent pseudarthrosis (30-50% failure rate)
• May require multiple surgeries
• Amputation after 3-4 failures

• Recurrent anterior bowing
• Ankle deformity (valgus, equinus)
• Limb length discrepancy

• Shortening of affected limb
• May require lengthening procedures

• Stiffness (IM rod through ankle)
• Deformity (valgus, equinus)
• May require ankle fusion

• Fibular nonunion (rare)
• Ankle instability (if too much fibula removed)
• Peroneal nerve injury

• Careful patient selection
• Meticulous surgical technique
• Adequate excision of hamartomatous tissue
• Stable fixation
• Long-term bracing
• Realistic expectations

• PTB orthosis long-term
• May need until skeletal maturity
• Prevents refracture
• Activity modification

• Vascularized fibula transfer: 50-70%
• Autogenous iliac crest: 30-50%
• Ilizarov: 40-60%
• Overall: 50-70% with best treatment

• Early treatment (before multiple fractures)
• Adequate excision of hamartomatous tissue
• Vascularized bone graft
• Stable fixation
• NF1-negative (better than NF1-positive)

• NF1 association (worse prognosis)
• Multiple previous surgeries
• Large defect
• Poor vascularity
• Inadequate excision

• Most patients function well after union
• May have activity limitations
• Ankle problems common
• Limb length discrepancy may require lengthening
• Psychosocial support important

• Refracture risk: 20-30% even after union
• Long-term bracing often needed
• Ankle problems may require fusion
• Limb length discrepancy may worsen
• Regular follow-up essential

• No dedicated CPT implant registry exists given rarity. Evidence is driven by pooled systematic reviews (e.g. Rastogi 2022, 1227 patients) and multicentre paediatric collaboratives rather than arthroplasty-style national registries.
• NF1 disease registries and rare-disease networks increasingly capture orthopaedic outcomes.

• High-resource settings: microsurgical VFG, BMP adjuncts, modern telescoping rods, cross-union, and combined IMR plus Ilizarov are feasible; early referral to specialist limb-reconstruction centres.
• Limited-resource settings: vascularized transfer and BMP may be unavailable; emphasis falls on non-vascularized autograft with IM rodding or Ilizarov, longer bracing, and earlier consideration of amputation with prosthetic fitting where multiple reconstructions are not feasible.

Paediatric orthopaedic surgeon, microsurgeon/plastic surgeon, clinical geneticist, physiotherapist, orthotist/prosthetist, and psychological support for child and family.

• High failure rate and likelihood of multiple operations
• Realistic union expectations and 30-50% refracture risk even after union
• Amputation framed as a functional treatment option, not a failure
• Long-term follow-up to skeletal maturity for refracture, LLD and ankle deformity