Congenital pseudarthrosis of tibia

definition

      specific type of non union or potential non union

      occurs through a hamartomatous area in the tibia

      present at birth

      associated with anterolateral bowing

      term used to include

      all congenital fractures of the tibia

      pseudarthrosis of tibia arising after pathological fracture in tibia with congenital bowing

      bowing usually occurs at junction of middle and distal thirds

epidemiology

      rare disease (1:200 000)

      40-80% have neurofibromatosis

      1-3% of patients with neurofibromatosis have CPT

aetiology

      cause unknown

      theories include

      intrauterine trauma

      localised vascular abnormality of tibia

      constriction due to proliferating fibrous tissue

      localised lesions (eg. fibrous dysplasia)

pathology

      hamartomatous cuff present at site of lesion site

      even with associated neurofibromatosis, no clear histological evidence that the fibrous tissue is a neurofibroma

classification
Crawford

      simplest classification

      anterolateral bow plus

Type 1 - nondysplastic

      nondysplastic

      increased cortical density

      normal medullary canal

Type II - dysplastic

II-A

      increased medullary canal width

      failure of tubulation

II-B

      cystic postfracture lesion

II-C

      fracture, cysts and frank pseudarthrosis

Boyd

      most complete classification

Type 1

      congenital anterior bowing

      defect present in tibia on x-ray

      other congenital deformities may be present

      rare

Type II

      congenital anterior bowing

      hourglass constriction of tibia

      spontaneous fracture or fracture after minor trauma usually occurs before age 2

      tibia is tapered, rounded and sclerotic

      medullary cavity not continuous on x-ray

      most common and has worst prognosis

      prognosis worse when there is associated neurofibromatosis

      50% of cases

Type III

      fracture develops at site of bone cyst

      usually near junction of middle and distal thirds

      anterior bowing may precede or follow development of fracture

Type IV

      sclerotic segment of bone initially present at junction of middle and distal thirds

      segment may produce complete or partial obliteration of medullary canal

      no narrowing of tibia

      fracture develops similar to stress fracture

      fracture does not heal and develops into pseudarthrosis

Type V

      congenital dysplastic tibia

      bowing usually present but not severe

      pseudarthrosis may or may not develop

Type VI

      intraosseous neurofibroma or schwannoma

      pseudarthrosis may or may not develop

      very rare

treatment
Principles

      difficult conditions to treat

      will not heal by casting alone

      before fracture has occured, treatment is preventative (bracing)

      after fracture, treatment is surgical

      treatment depends on

      age of patient

      type of pseudarthrosis

      surgery indicated as early as feasible

      the longer grafting delayed, the shorter and more poorly developed leg will be

      likelihood of obtaining union increases with increasing age

Surgical techniques

Bone grafting

      may be performed prophylactically in concavity of bowed tibia

      grafting alone is method of choice for type III lesion

      less successful for type II lesion (30%)

Osteosynthesis

      should be first approach for type II lesion

      is most reliable technique at present

      technique described by Umber, Moss and Coleman

Operative technique

      approach tibia through anterior incision

      excise hamartomatous (fibrous) tissue

      excise enough sclerotic bone

      balance between

      sufficient resection to leave good quality bone at each end

      preservation of enough bone to minimise leg length discrepancy

      apply autogenous iliac bone graft

      move muscle over graft site

      fix tibia with intramedullary rod extending from calcaneus across ankle and into proximal tibial metaphysis

      use Steinmann pin, Rush nail or intramedullary nail depending on size of patient and medullary canal

      with progressive growth, rod migrates proximally and eventually ankle joint is free

      concurrently graft and rod any coexisting fibular pseudarthrosis

      some suggest to use fibular rod regardless to improve distal fixation

      prolonged postoperative immobilisation

      initially in spica cast for 6 months

      once union achieved, protective brace until skeletal maturity

      encourage early weight bearing

      rods left in place until skeletal maturity to pevent refracture

      60% union rate

Vascularised free fibular graft

      pseudarthrotic segment resected and replaced by living contralateral fibula

      good results reported

      has advantage that can achieve

      primary bone lengthening

      correction of deformity

      union occurs in relatively short period of time

      technically demanding procedure

      requires microsurgical experience

      involves operation on normal leg

      major problem is development of valgus deformity of normal ankle

      due to overgrowth of distal tibial epiphysis

      distal fibula acts as tether

      treated with tibiofibular synostosis

      can be overcome by using ipsilateral fibula

      only possible if fibula not involved

Ilizarov technique

      pseudarthrosis resected

      corticotomy of proximal metaphysis performed

      3-level ring fixator applied

      middle tibial segment moved distally to provide metaphyseal lengthening and pseudarthrosis compression

      allows

      bone lengthening

      correction of deformity

      excellent union rates

Amputation

      for severe lesions with poor prognosis

      decision should be made before too much invested in saving limb

      amputation may be performed through lesion or through ankle (Syme)

Electrical stimulation

      independent use of doubtful benefit

      may be combined with grafting and rodding

prognosis

      varies with type

      worse with

      congenital or early onset

      shortening

      tapering

      sclerosis

      failure of operative repair with graft resorption

      leads to amputation in 50%

      25% of patients develop CNS glioma