Congenital Pseudarthrosis of the Tibia

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types of deformity (1) anterolateral bowing associated with

the limb-threatening condition pseudarthrosis, or dysplasia, of the tibia, although a benign form also exists;

(2) posteromedial bowing, usually benign (3) anterior or anteromedial bowing with

congenital deficiency of the fibula.

Tibial bowing

CPT is actually a rare disease entity

Incidence 1 : 140.000-190.000 births

Subject to a wide range of scientific discussion

Remains one of the most challenging cases a pediatric orthopedic surgeon treats

Congenital Pseudarthrosis of the Tibia

CPT dysplasia of the bone with failure of normal bone

formation

Segmental weakening

Anterolateral angulation

Pathologic fracture

Etiology as of yet still unclear Considered a specific type of non union or

potential non union that occurs through a hamartomatous area of fibrous tissue at the tibia.

The dysplasia is present at birth and associated with anterolateral bowing of tibia, usually at the junction of middle and distal thirds

epidemiology study : 340 patients from 13 countries

Symptoms of NF-1 were present in 54.7%, the rest has no clinical signs of NF-1 (occult?)

Correlation? Only 6% of NF-1 patients has CPT

Neurofibromatosis 1:◦ A single copy of the NF1 gene is defective◦ The other copy is functional◦ CPT : “Second hit theory” local somatic

mutation

Model of doubly-inactivated NF gene (NF-1null)

NF-1null mice has poor healing and non-union of fracture site

Abundant un-differentiated fibrotic tissue at callus site

dysplasia present since birth leading to progressive anterolateral bowing of the tibia eventually within 2 to 5 years a pathologic fracture occurs resultant pseudoarthrosis develops because of the non union.

Methods of Treatment?◦ Difficult to achieve union◦ Generally poor prognosis regarding the quality

and longevity of achieved union◦ Function of limb in the future?◦ No consensus

Boyd: “the success in treating CPT can be known only by following the patient to maturity”

Goals of Treatment :1. To obtain and maintain union while

optimizing the function of the involved extremity

2. To minimize the angular deformity (ankle valgus) and LLD

Treatment of CPT

Problems of management of established pseudarthrosis : Obtaining union Preventing shortening of the limb Tendency of refracture after union

Non surgical treatment : brace before weight bearing : AFO After weight bearing : KAFO

Surgical treatmentBasic principles of treatment Resect pseudarthrosis Correct angular deformity Stable fixation Autologous bone grafting

Tadjihan : (1)alignment of the leg must be maintained, (2)permanent intramedullary fixation to maintain such alignment or to provide internal bracing for a united tibia is desirable

Currently only three modalities have achieved union rates above 70% :

Current treatment Options

Intramedullary Rod/Nail

23 pts with CPT treated by intramed rodding f/u at 4-14 years

11 achieved unequivocal union with full weightbearing function and maintenance of alignment requiring no additional surgical treatment

9 achieved equivocal union with useful function, with the limb protected by a brace, and/or deformity

3 had persistent nonunion or refracture, requiring full-time external support

Dr. Benjamin Joseph’s method using an intramedullary rod fixation augmented by onlay grafting Good results were obtained

Long term follow up at 10 years published in a subsequent article also showed good long term results

Illizarov Technique

Illizarov technique offers advantage of :◦bone lengthening◦correction of deformity◦excellent union rates

data of 340 patients who underwent 1287 procedures

The Ilizarov technique emerged as being the optimal method, having the highest rate of fusion (75.5%) of pseudarthrosis and high rate of success in correction of the additional deformities

tibial defect greater than 3 cm after resection of the pseudarthrosisfibula

Pseudarthrotic segment is resected and replaced by living contralateral

Free vascularized fibular graft

Advantages: Primary bone lengthening Correction of deformity Union occurs in relatively short period of

time

Disadvantages : Technically demanding procedure Requires microsurgical experience Involves operation on normal leg Major problem is development of valgus

deformity of normal ankle

Used to augment healing effort of the techniques above ◦ Rh-BMP2 : studies support faster repair but not

higher union rate and no data yet on maintenance of union

◦ Rh-BMP7 : still under investigation, some case reports no significant results

Rh-BMP2 soaked sponges applied around excised pseudoarthrosis site after immobilization by intramedullary rod

Bone Morphogenetic Protein

Primary surgical intervention augmented with rhBMP-2 resulted in radiographic union of the pseudarthrosis in five of the seven patients at an average of 6.4 months

The primary functional outcome was classified as grade 1 for five patients, grade 2 for one, and grade 3 for one

20 patients in series treated with a combination of periosteal grafting and fixation with intramedullary rod and Illizarov ring fixator all achieved union, with some (8 patients) experiencing subsequent refracture

Good results achieved, no long term morbidities found

Comparable results with Ilizarov technique in achieving union

Considered easier to achieve multiplanar correction by gradual correction of deformities

Taylor Spatial Frames

Case report of 16 yo pt with CPT and histroy of 14 prior surgeries which has failed to achieve union

success of TSF in obtaining easy correction of a severe deformity with improvement of contact area, which in return promotes healing, in addition to permitting excellent stability and ability to an early weight bear

A group of pediatric orthopedic surgeons employed the Masquelet technique in CPT

Masquelet technique originally was developed as a method of treatment for long bone defects

Result at two years was excellent

Very seldom a consideration in the early management of the child with CPT but consider in :◦ anticipated shortening limbs of more than 2 or 3 inches (5 to 7.5

cm),◦ a history of multiple failed surgical procedures◦ stiffness and decreased function of a limb that would be more

useful after an amputation and fitting with a prosthesis◦ functional loss resulting from prolonged medical care and

hospitalization. Ankle disarticulation (Syme or Boyd type) rather than

amputation through the pseudarthrosis or tibial bone◦ prevents spike formation at the transected bone end and

subsequent stump revisions and covers the stump with end-bearing heel pad skin.

◦ Persistent motion at the pseudarthrosis site is managed by the prosthetic socket.

Amputation

Electrical Stimulation. early research : increased calcification of

fibrocartilage, increased angiogenesis, & decreased osteoclastic resorption

application of pulsed electromagnetic fields. adjunct to conventional bone grafting and

internal fixation confounded by an inability to separate the

effect of the stimulation from the effect of other treatment modalities

Other methods

Stifness of ankle & hindfoot◦ Even if stiffness persists, it rarely hampers

functional results. Refracture

◦ removal of the rod after union is not recommended until skeletal maturity

Valgus ankle deformity◦ prognostic : presence of fibular insufficiency.

Tibial shortening ◦ well-timed contralateral epiphysiodesis◦ limb lengthening of the proximal tibia.

Complications

CPT is a rare but challenging case to treat Large body of evidence, but no clear

definition of etiology No single method of treatment agreed upon

◦ Three established methods : intramed rod, Ilizarov frames, FVFG

◦ BMP may have a role in promoting union◦ Taylor spatial frames and Masquelet techniques

show promising results long term results? Remains a difficult case to treat

(amputation?)

Conclusion

BENIGN FORM OF ANTEROLATERAL BOWING OF THE TIBIA never suffered a fracture, and the anterolateral bowing

gradually resolved with growth Eventually the bowing in these patients remodeled and

they required only management of a residual limb length discrepancy

< 6 years : a one and one-half spica cast (minimal rotational stress) replaced with a long-leg cast after 6 to 8 weeks, discontinued after approximately 4 months.

Older children are treated with long-leg casts : 4 months. Once cast protection is discontinued a custom-

fabricated KAFO with a locked ankle joint and free

Additional

Congenital Posteromedial Bowing of the Tibia natural history of the bowing is spontaneous

resolution, especially during the first 6 months nondysplastic condition with no increased risk for

fracture or pseudarthrosis. Shortening, however, commonly exceeds 2.5 cm

and averages 13% of total limb lengthInitial treatment of a newborn gentle stretching of the dorsiflexion contracture, stretching of the lateral ankle structures into a

supinated or inverted position. severe case, serial casting into plantar flexion

and the use of splints or bracing to maintain position until weight bearing have been prescribed