Definition
Anterolateral bowing
True bone dysplasia
- hamartomatous area in the tibia
- non union or potential non union through pathological fracture in this region
The defect in the bone is filled with mature, fibrous connective tissue
- not really a pseudoarthrosis
- by definition, a pseudarthrosis has a cleft lined by fibrocartilage containing fluid and bounded by a capsule
- the name is so firmly embedded in the literature that it is retained
Epidemiology
Rare
- 1:200 000
M = F
50% have NF type 1
- 1-3% of NF have CPT
Aetiology
Cause unknown
Theories include
- intrauterine fracture
- localised vascular abnormality
Pathology
Hamartomatous cuff present at site of lesion site
Even with NF, no clear histological evidence that fibrous tissue is NF
Crawford Classification
Type I: Non-dysplastic
- anterolateral bowing
- thickened sclerotic cortex
Type II: Dysplastic
IIA Anterolateral bowing
- wide medullary canal
- failure of tubularisation
IIB Cyst +/- Fracture
IIC Frank pseudarthrosis
- atrophied ends
Boyd
Type 1: Congenital anterior bowing
- defect present in tibia on x-ray
- rare
Type II: Congenital anterior bowing with hourglass constriction of tibia
- tapered, rounded & sclerotic
- medullary cavity non continuous on xray
- spontaneous fracture or 2° minor trauma usually < 2 years
- most common & worst prognosis
Type III: Fracture develops at site of bone cyst
Type IV: Sclerotic bony segment
- segment may produce complete or partial obliteration of medullary canal
- no narrowing of tibia
- fracture develops like stress fracture
Type V: Congenitally dysplastic tibia
- mild bowing ± pseudarthrosis
Type VI: Intraosseous NF or Schwannoma
- ± Pseudarthrosis
- Very rare
NHx
Neurofibromatosis
- virtually all will fracture by 2 years
- therefore reasonable to prophylactically treat involved segment if has NF
Management Algorithm
No Fracture / Type I or IIA
Corrective osteotomy contra-indicated
- wll not heal
- must excise hamartoma
Brace all
- KAFO in walking child
- PTB in older child until skeletal maturity
Prophylactic surgery
- NF
- discuss excision + graft + stabilisation
Fracture / Type II B&C
Principle
- won't heal non operatively
- treatment is surgical
- excise segment, graft & rod / frame
- try to avoid until > 2
Surgery timing
- controversial
- delay: shorter underdeveloped leg
- older patient: increased union rate
- brace till large enough or not controlled by AFO
Difficult surgery
- union difficult to achieve
- high refracture and recurrence rate
- increased with residual malalignment / provides an ongoing stress riser
- failure of OT with graft resorption associated with amputation in 50%
Prognosis
- varies by type
- worse with tapering and sclerosis
Ankle
Valgus deformity common
- sloping tibial epiphysis or fibular pseudoarthrosis
- can treat with guided growth
Surgical Options
1. IM Rod
Several options
- Sheffield / Fassier-Duval growing rod / Rush pin / Steinman pins
- use Steinmann pin, Rush nail or IM nail depending on size of patient & medullary canal
Technique
- anterior incision
- excise hamartoma and sclerotic bone
- balance between bony resection & minimising LLD
- iliac bone graft
- stabilise with intra-medullary rod extending from calcaneum across STJ / AKJ into proximal tibial metaphysis
- with growth, rod migrates proximally & releases AKJ
- must graft & rod any co-existing fibular pseudarthrosis
Post operatively
- prolonged immobilisation
- spica cast for 6/12
- once united PTB till skeletal maturity
- rods left until skeletal maturity to avoid fracture
Results
Vascularised Free Fibular Graft
Technique
- pseudarthrosis segment resected
- contralateral fibula as graft
- can use ipsilateral fibula if no pseudoarthrosis
- stability with external fixation
Complication
- valgus deformity of normal AKJ 2° overgrowth of distal tibial epiphysis
- distal fibula acts as tether
- treat with tibia / fibula synostosis
- avoid by using ipsilateral fibula
- only possible if fibula not involved
Ilizarov Technique
Technique
- pseudarthrosis resected
Bone transport
- 3-level ring fixator applied
- corticotomy of proximal metaphysis performed
- middle tibial segment moved distally
- metaphyseal lengthening
- pseudarthrosis compression / docking
Indication
- child > 5
Disadvantage
- high rate of refracture after removal of frame
Electrical & US Stimulation
Independent use has unknown benefit
- combine with graft / rod
Amputation
"Should not be the operation of first resort or last resort"
- severe lesions with poor prognosis
- make early decision