Congenital Pseudoarthrosis Tibia

By Prof Kit Song, Seattle Children’s Hospital, USA

POSICON 2012
Courtesy:
Dr Taral Nagda, India
Dr Sandeep Patwardhan, SIOR, Pune

CONGENITAL PSEUDOARTHROSIS OF TIBIA
ETIOLOGY
• Unknown
• Speculation: Many theories
• Sporadic familial associations
• Approximately 50% associated with NF-1
• Only 2-6% of NF-1 patients have CPT
• Presence of NF-1 does not impact healing rates

HISTOPATHOLOGY
-Focal isolated lesions
-Fibrous hamartoma: fibromatosis like tissue at CPT site
• Highly cellular
• Undifferentiated
• capable of several mesenchymal line differentiation
• Poor vascularity
• Thickened periosteum

• Nf1 gene implicated in rat model pseudarthrosis
• Encodes neurofibromin
• Negative regulator for Ras-GTP to inactive Ras GDP
• Impaired osteoblast differentiation
• May be increased osteoclast commitment/differentiation

CLASSIFICATION
Several descriptive classifications exist

Boyd-6 types
Anderson -5 types
Crawford -4 types
El-Rosasy Paley -3 types
Masserman -3 types

No classification provides guidance as to treatment Or predictor of outcome

Early fracture = worse prognosis

Prognosis depends on

• Presence or absence of fracture
• Age at which fracture first occurs (Early onset /= 4 years)
• Severe LLD, poor ankle function, fibular Pseudarthrosis

Treatment Goals

Once Fracture occurs, surgery is required

• Obtain bony union and Maintain union Rate
• If treated nonoperatively, ability to unite is only 25-40% by5 Years
• Maintain functional Alignment
• Minimize limb Length inequality
• Preserve joints

Non operative management less Successful

Surgical Management

Principles :
• Resect hamartomatous Tissue
• Resect periosteum
• Resect fibular Pseudarthrosis if Present

Methods :
• Bone to bone contact using IM rodding
• Bone grafting
• Vascularized fibula graft
• Synostosis – bypass graft
• RhBMP-2

IM Stabilization (80-90%)

• Williams rods
• Rush rods
• Telescoping rods
• Flexible rods
• K-wire/Steinman pins
Stabilize fibula and ankle (avoid crossing ankle whenever possible as long term function could be affected)

External fixation

• Stability + lengthening via
• Proximal corticotomy
• Risk of proximal nonunion
• High union rates (60- 100%)
• Late refracture (15-40%)
Combine with IM fixation
Combine with vascularized Fibular graft

Vascularized fibular graft

• Union rates 95% (recent studies: 60%
• Technically demanding
• Contralateral / Ipsilateral Graft
• Average rate of surgeries to obtain Union: 2. 5 Surgeries per patient, as they need secondary bone graft
• Can lead to LLD, Angular deformities, Valgus deformity

Amputation

• Traditionally viewed as “when all else fails”
• Limited access to child prosthetics
• Sensate limb superior to Prosthesis
• Prognosis at first visit
  • Higher initial union rates
  • Better stabilization
  • ?Better biology RhBMP-2

Reality in Limb Preservation:

• High refracture rates
• Limited function
  • LLD
  • Residual deformity
  • Joint function
• Loss of life to save the Limb
• Excellent prostheses for Children are available nowadays

Indications/risk factors for Amputation

• Anticipated LLD > 5 cm
• Presence of NF
• Failure to achieve union by age 6 years
• >32 months to achieve Union

 

AMPUTATION

• Syme’s amputation-  retain the tibial stump (even there is nonunion at pseudoarthrosis site)
• Goal is wearable Prosthesis
• Nonunions rarely painful

SUMMARY
• CPT is rare/difficult problem
• Little understanding of pathology
• No consensus of management
• Initial reconstructive efforts better
• Unclear if longer term function improved
• Advise families of possibility and consider Amputation early