CONGENITAL PSEUDO ARTHROSIS TIBIA

SAIKRISHNA .K

Definition

• Pseudarthrosis is a false joint associated with abnormal movements at the site

Introduction• Congenital pseudarthrosis of tibia refers to

nonunion of tibial fracture that develops spontaneously or after trival trauma in a dysplastic bone segment of tibia diaphysis.

• CPT is rare & Usually develops in first 2 yrs of life.

• Etiology is unclear.

• Incidence is 1: 250,000

• There is a strong association of CPT with neurofibromatosis type 1.

• 6% of the patients with Neurofibtomatosis have the deformity and up to 55% of cases with anterolateral bowing and pseudoarthrosis are associated with neurofibromatosis.

• Some authors have also found anterolateral bowing to be ultimately associated with neurofibromatosis in nearly every instance.

• The presence or absence of neurofibromatosis doesn’t affect the outcome of the tibial pseudoarthrosis.

• Fibrous dysplasia is seen upto 15% of patients with Anterolateral bowing.

Neurofibromatosis• NF-1 occurs due to mutation on the gene coding for

NEUROFIBROMIN on chromosome 17.

• Neurofibromin is expressed in a broad range of cells & tissue type.

• It negatively regulates Ras activity ( cell proliferation & function)

• It’s deficiency leads to increased Ras activity.

• Affects Ras-dependent MAPK( mitogen activated protein kinase) activity which is essential for osteoclast function & survival.

Signs of neurofibromatosis

Diagnostic criteria of neurofibromatosis

• 6 or more café-au-lait macules (>5mm before puberty & >15mm after puberty).

• Axillary or inguinal freckling.• 2 or more neurofibromas or 1 plexiform

neurofibroma.• 2 or more Lisch nodules.• Optic glioma.• A distinctive osseous lesion such as sphenoid

dysplasia or thinning of long bone cortex with or without pseudarthrosis.

• A first degree relative with NF-1.

Pathology

• Unclear

• Recent studies have shown that there is hyperplasia of fibroblast with the formation of dense fibrous tissue.

• This invasive fibromatosis is located in the periosteum & between broken bones ends causing compression, osteolysis & persistance of pseudarthrosis.

Pathology

• Paley et al theorized that pathology of pseudarthrosis is not bony but rather its periosteal in origin.

This theory was also considered by CODAVILLA a century ago.

• This theory is supported by following observation :- Thickening with hamartomatous transformation of periosteum. Appearance of strangulation of bone with atrophic changes followed by

avascular changes. Failure of remodelling of pin tracts leading to stress fractures.

Classification

• There is no universally agreed system based on both clinical features & radiographic findings.

CAMURATI - 1930 ADGLEY - 1952 BOYD - 1958 APOIL - 1970 ANDERSEN - 1973 CRAWFORD - 1986 CRAWFORD - 1999

• BOYD & ANDERSEN are commonly used.

Boyd classification

• Boyd divided CPT into 6 types :-

Type 1 :-

Pseudarthrosis occurs with anterior bowing.

A defect in tibia present at birth.

Other congenital deformities may be present which may affect the management of pseudarthrosis.

Boyd classificationType 2 :- Pseudarthrosis occur with anterior bowing & a hourglass

constriction of the tibia is present at birth. Spontaneous fractures or after minor trauma. Commonly occur before 2 yrs of age. Also known as HIGH RISK TIBIA. Tibia is tapered, rounded, sclerotic & obliteration of medullary

canal. Most common type. Associated with NF-1 Poorest prognosis.

Boyd classification

Type 3 :-Pseudarthrosis develops in a

congenital cyst usually near the junction of middle & distal third of tibia.

Anterior bowing may precede or follow the development of fracture.

Recurrance of fracture is less common after treatment.

Boyd classificationType 4 :-

Originates in a sclerotic segment of bone.

Without narrowing of tibia.Medullary canal is partially or

completely obliterated.An insufficiency or stress

fracture develops in the cortex of tibia & gradually extends through the sclerotic bone.

Prognosis is good.

Boyd classificationType 5 :-Pseudarthrosis of tibia occurs with a dysplastic

fibula.Pseudarthrosis of both bone may develop.Prognosis is good if the lesion is confined to fibula. If the lesion progress to tibia then the natural h/o

usually resembles type 2.

Type 6 :-Occurs as an intraosseous neurofibroma or

schwannoma Extremely rare.

Crawford classification• Divided broadly divided into 2 types:-1-Non-DysplasticAnterolateral bowing with increased density &

sclerosis of medullary canal.

2-Dysplastic 2aAnterolateral bowing with failure of tubularization.2bCystic changes.2cFrank pseudarthrosis.

Classification by paley

Clinical features

• Associated with anterolateral bowing of tibia.

• Bowing usually occurs at the junction of middle & distal third.

• Deformity may be associated with skin dimple, limb shortening, dysplasia of fibula & ankle valgus.

• Usually unilateral.

• If cutaneous signs of neurofibromatosis are present the diagnosis is readily apparent.

IMAGING Magnetic resonance imaging

• extent of the disease • preoperative planning in that the borders for resection can be defined

precisely. • The area of the pseudarthrosis is hyper intense on fat-suppressed and

T2-weighted images and slightly hypo intense on T1-weighted images with contrast enhancement after administration of gadolinium.

Computed tomography scan

Confirm radiographic findings.

Total bone scintigraphy

Level of the pseudarthrosis .

Problem

• Except for the resolving form, the natural history of tibial dysplasia is extremely unfavourable,and once fracture occurs there is little tendency for the lesion to heal spontaneously,particularly for fractures occuring before the walking age.

• Regardless of the treatment method used,there is general pessimism regarding the quality and longevity of the union attained.

AIMS

1. Achieve union

2. Prevent refracture

3. Correct limb length inequality

4. Correct associated growth abnormalities

5. Prevent ankle deformity and arthritis.

1. Strategies to achieve union

1. Microvascular free fibular transfer.2. the Ilizarov technique3. Bone grafting with intramedullary nailing.

• Excision of the pseudarthrosis should be an integral part of the procedure.

2. Strategies for minimizing the risk of refracture

• Splint the limb in an orthosis until skeletal maturity.

• Retain an intramedullary nail until skeletal maturity.

3. Strategies for dealing with shortening of the limb

● Minimize the extent of shortening by obtaining union of the pseudarthrosis as early as possible.

● Established shortening can be addressed by limb equalization procedures

4. Strategies for minimizing valgus deformity of the ankle

● Ensure union of the fibular pseudarthrosis.

● Retaining an intramedullary rod that crosses the ankle joint can also prevent ankle deformity although the motion is lost.

Prophylaxis

• Once the diagnosis of a non resolving anterolateral bowing of the tibia has been made the first step is to prevent fracture if possible.

• In an infant before walking age,no specific treatment is needed other than education of the caretakers.

• Once the child begins weight bearing prophylactic bracing should be attempted although there is no documentation that such a program can prevent a fracture.

• A clam shell like orthosis that provides circumferntial support is usually recommended.

• Protection of the unfractured tibia should be continued indefinitely till skeletal maturity or until patient approaches skeletal maturity.

SURGICAL OPTIONS

1. Vascularized fibular graft2. External fixation3. Intramedullary rod 4. BMP5. Electrical stimulation

Intra medullary fixation

• The procedure of choice for the first attempt to gain union entails resection of pseudoarthrosis,shortening and fixation with an intramedullary rod and autogenous bone grafting.

• The procedure can be performed at any age and rates of union of around 85% have been reported although solid long lasting union without deformity is another matter.

Williams technique

• Williams conceived the novel technique of threaded male and female components of the rod that when joined,can be placed antegrade through the pseudoarthrosis site and out the bottom of the foot.

• After retrograde insertion back in to the proximal intra medullary of the tibia the male end is unscrewed and removed from thebottom of the foot with the female threaded rod left intraosseously in the tibia or across the ankle in talus/calcaneus.

• The undesirable effect of ankle immobilisation by IM fixation is thought ot be necessary evil to adequately immobilise the small distal fragment.

• As the tibia grows the foot and ankle may eventually grow off the distal end of the IM rod and thus allow ankle to regain motion

• The possibility of ankle valgus is also almost inevitable especially if there is a fibular pseudoarthrosis despite the acheivement of a solid union.

• Limb length discrepancy is yet another untoward event with shortening at maturity averaging as much as 5 cm.

• Weak and stiff ankle and subtalar joint secondary to cross ankle fixation producing a poorly functioning foot.

• The need for fibular surgery remains controversial. Researchers concluded that it is crucial to resect a fibular pseud- arthrosis or, if the fibula is intact, to perform a fibular osteotomy in order to achieve optimal limb alignment and union.

1. Vascularized fibular graft

• The procedure entails harvesting a long segment of the opposite fibula along with its vascular pedicle.

• This is transferred into the gap created after radical excision of the pseudarthrotic segment. • The vessels of the transferred fibula are anastomosed to the local vessels. The transferred fibula

is fixed securely to the tibia.

• Intra medullary fixation of the donated fibula is contraindicated theoretically because of the possibility of disturbance of blood supply of the microvascular graft.

• Because the transfer brings tissue with its own blood supply, free fibular vascularised transfer has been recommended as procedure of choice for gaps > 3cm after resection of pseudoarthrosis.

• Success rate for free fibula transfer is 92%-95% if union alone is considered.

• Refracture has been reported in a third of the patients probably a direct result of not being able to apply a permanent intra medullary fixation and thus ignoring a major principle in treatment.

• Morbidity of the donor leg—• The distal end of fibula must be synostosed to

the tibia(Langenskiold procedure) or the fibula of the donor site must be reconstructed with bone graft to prevent ankle valgus.

• In addition weakness may ensue in the donor leg due to resection of origins of flexor muscles.

Case series

Good union

Case 2

Dec 5,2016

Bone morphogenic protein• BMP2 is useful to speed up the union rates in CPT• BMP 7 seems to be ineffective in the absence of an actively

differentiating osteoblastic cell line.

Electrical stimulation

• Electrical stimulation doesnot correct existing deformities and thus its appplication is probably limited to the earlier phases of pseudoarthrosis treatment when union is the primary goal.

Amputation

• The final function in a patient who has undergone multiple operations but must still protect the leg in an orthosis may well be worse than if an earlier amputaion and prosthetic fitting had been performed.

Paley X union

Complications1. Refracture2. Malalignment of the tibia3. Limb length discrepancy4. Ankle valgus5. Ankle stiffness

1. Refracture.

• 14% to 60%.

• Anatomic alignment of the tibia and fibula minimize the risk of re-fracture.

• Intramedullary rod and external bracing must be continued as effective protection against re-fractures.

2. Malalignment of the tibia

• Diaphyseal malalignment of the tibia (procurvatum or valgus deformity) are progressive and do not remodel

3. Limb length discrepancy

• Residual limb length discrepancy following successful union is a major problem.

• Growth abnormalities of the tibia, fibula, and the ipsilateral femur abnormalities are also noted with CPT

• which include inclination of the proximal tibial physis, posterior bowing of the proximal third of the tibial diaphysis, proximal migration of the lateral malleolus.

4. Ankle valgus

4. Ankle valgus• Compromises functional outcome.

• Progressive ankle valgus is a problematic postoperative donor-site morbidity of a vascularized fibular graft in children.

•

• Tibiofibular metaphyseal synostosis (the Langenskiöld procedure)

5. Ankle stiffness

• Progressively regresses once intramedullary rod is removed from ankle.

• Pain secondary to degenerative changes of the ankle can be treated with limitation of activity and shoe modification.

• Severe pain may require ankle arthrodesis

Follow up.

• till skeletal maturity to identify and rectify residual problems.

Take Home message.

• Rare.• The natural history of the disease is extremely unfavorable and

• Little or no tendency for the lesion to heal spontaneously. • challenging to treat effectively• Aims to obtain a long term bone union, to prevent limb length discrepancies, to avoid

mechanical axis deviation, soft tissue lesions, nearby joint stiffness, and pathological fracture.

• The key to get primary union is to excise hamartomatous tissue and pathological periosteum.

• Age at surgery, status of fibula, associated shortening, and deformities of leg and ankle play significant role in primary union and residual challenges after primary healing.

• Surgical options such as intramedullary nailing, vascularized fibula graft, and external fixator, have shown equivocal success rate in achieving primary union

• Amputation must be reserved for failed reconstruction, severe limb length discrepancy and gross deformities of leg and ankle..

THANK YOU.