Tibial bowing Flashcards
Neurofibromatosis Fibular hemimelia Posteriomedial bowing Tibial Deficiency/ Hemimelia
1
Q
Define neurofibromatosis?
A
- An autosomal Dominant disorder of Neural crest origin
- characterised by
-
Extremity deformities
- congential anterolateral bowing & pseudoarthrosis of tibia/fibula/ forearm
- hemihypertrophy
-
Spine invovlement
- scolosis & kyphosis
- Atantoaxial instability
-
Extremity deformities
2
Q
What is the epidemiology of neurofibromatosis?
A
- 1: 3,000 births for NF1
- Genetics
- Autosomal dominant
- Mutation in NF1 gene on chromosome 17q21
- Codes for neurofibromin protein
- negatively regulates Ras signalling pathway
- Neurofibromin def-> increaed Ras activity
- affects RAS dependent MAPK activity which is essential for Osteoclast function and survival
3
Q
Name associated conditions of neurofibromatosis ?
A
- Scoliosis
- anterolateral bowing of tibia
- forearm bowing - less common than tibia
- neoplasiaa
4
Q
What is the prognosis of NF?
A
- Normal life expectancy
- high incidence of malignancy & hypertension
5
Q
What is the diagnostic criteria of Neurofibromatosis?
A
- 2 or more of the following
- 6 or more cafe au lait macules >5mm diameter in pretubertal individuals and >15mm in postpubertal individuals
- 2 or more Neurofibrommas of any type or one plexiform neurofibroma
- freckling in axillary or inguinal region
- optic glioma
- 2 or more Lisch modules- iris haemartomas
- a distincitve osseous lesion- eg sphenoid dysplasia/ thinning of cortex with or wout pseudarthrosis
- a first degree relative w NF1
6
Q
What is the classification of NF?
A
- NF1
- Von recklinghaussen disease
- Most common
- NF2
- assoc with bilateral vestibular schwannomas
- Segmental NF2
- Features of NF1 but involving a single body segment
7
Q
What is the presentaton of NF?
A
- Anterolateral bowing of tibia
- Radial bowing
8
Q
What is seen on examination of a pt with NF?
A
- Veroccous hyperplasia
- hemihypertrophy- see pic
- cafe au lait spots
- axillary freckling
- scoliosis
- anterolateral bowing or pseudoarthrosis of tibia
- dermal plxiform neurofibroma
- Lish nodules - benign pigmented haemartomas of iris
9
Q
Name the neoplasias of NF?
A
-
Neurofibromas plexiform- type
- pathogonomic for NF1
- Present in 4% of NF1
- maybe dermal or deep tissue
- often assoc with limb overgrowth
- can undergo malignant change-> Neurofibrosarcoma
- Wilms Tumour
10
Q
Describe the scoliosis in NF?
A
- Most common site for invovlement of NF1
- Not seen in NF2
- 2 forms
-
Idopathic
- __long curves
- tx resembles that for idiopathic scoliosis
-
Dystrophic
- curve is typically thoracic kyphoscoliosis
- short segmented and steep curve ( invovled 4-6 vertebra)
- disorted ribs and vertebra
-
Idopathic
11
Q
What is seen in maging the spine in NF scoliosis?
A
- xrays
- Vertebral scalloping
- penciling of ribs- >3 assoc with rapid curve progression
- enlarged foramina
- MRI
- always obtained preop to identify any dural ectasia /dumbell lesions- neurofibroma of the nerve root
12
Q
Describe the tx of NF scoliosis?
A
Non operative
-
observation vs bracing
- not efective in dystrophic scoliosis
- NF idiopathic scoliosis tx like adolescent idopathic scoliosis
- cobb angle <25o observe
- Cobb angle 25-45o bracing
- cobb angle >450 = operation
Operative
-
Decompression ASF, PSF + instrumentation
- for dystrophic scoliosis in young children <7 yrs
- complx
- high rate of pseudoarthrosis w PSF alone 40%
- pseudoarthrosis high w ASF& PSF 10%
13
Q
Describe the epidemiology of anterolateral bowing in NF?
A
- assoc with NF-1
- 50% with anterolateral bowing have NF1
- only 10% of NF1 have anterolateral bowing
- thinning cortices-> pathological fx
- Repeated fx ->may progress to pseudoarthrosis
14
Q
What are the DDX of anteromedial bowing
A
- Fibular hemimelia and congenital loss of lateral rays of foot
15
Q
What are the ddx of this bowing?
A
- Postermedial bowing
- usually congential due to …
- abnormal uterine position
- dorsiflexed foot pressed against anterior tibia
- wlll develop-> LLD
- assoc with Calcaneovalgus foot deformity
16
Q
What is the tx of anterolat bowing in NF?
A
Non operative
-
Bracing in total contactorthosis
- bowing without pseudoarthrosis/ fx
- goal is to prevent furthur bowing
- spontaneous remodelling is not expected
- osteotomy for bowing is CI
Operative
-
Bone grafting with surgical fixation
- for bowing with pseudoarthrosis/ fx
-
Amputation with prothesis fitting
- for 3 failed surgical attempts
- Syme superior to BKA due to atrophic and scarred calf muscle
17
Q
What sugical techniques are available for correction of pseudoarthrosis/ tibia fx bowing?
A
-
Intramedullary nailing with bone graft
- resecr pseudoarthrosis
- insert charnley- williams rod antegrade thru resection site and retrograde thru heel
- at <4yr fix to calcaneus
- 5-10 fix to talus
- at 2 yrs post 2 nd surgery to push rod proximally to free ankle joint
-
Free fibular graft
- often need to take from contralateral side because ipisalteral fibular is not normal
- ilizarov ex fix
18
Q
What is fibular hemimelia?
A
- Fibular deficiency
- most common congential long bone deficiency
- consists of shortening or entire absence of fibula
19
Q
What is the genetics of fibular hemimelia?
A
- No known inheritance pattern
- linked to Sonic hedge-hog gene
20
Q
What are the associated conditions of fibular hemimelia?
A
-
Anteromedial tibial Bowing
- most common cause is fibular hemimelia
- Ankle instability
- secondary to ball and socket joint
- Tarsal Coalition- 50%
- equinovalgus foot deformity
- Absent lateral rays
- femoral abnormalities- Proximal femoral focal deficiency, coxa vara
- Cruciate ligament deficiency
- Genu valgum
- secondary to lateral femoral condyle hyperplasia
- Significant leg length discrepancy
- shortening of femur/tibia
21
Q
Name a classification system of fibular hemimelia?
A
- Birch
- based on limb length and foot function
- directs tx
22
Q
What are the classical findings on examination of fibular hemimelia pt?
A
- Short limb
- skin dimpling over midanterior tibia
- equinovalgus foot
- often missing lateral toes
- genu valgum
23
Q
What is seen on xrays of fibular hemimelia?
A
- Fibula is either absent or shortened
- tibial spines are underdeveloped
- intercondylar notch is shallow
-
ball and socket ankle joint
- secondary tarsal coalition
24
Q
What is the tx of fibular hemimelia?
A
- Goal is by stability and level of foot and ankle function as well as degree of limb shortening
Non operative
- Observation
- shoe lift
- bracing
OPerative
-
Contralateral Epiphysiodesis
- mild LLD <5cm
- stable , plantigrade foot
-
Limb Length procedure
- Plantigrade, functional foot with stable ankle
- LLD <30%
- involves resection of fibular analge to avoid future foot problems
-
Syme or Boyd amputaton
- non functional, unstable foot
- LLD >30%
- usually done at 1 yr of age
25
What is this and the cause ?
* **posteromedial bowing of tibia-**
* physiological bowing result of..
* **intrauterine positioning**
* usually involves medial and distal third of tibia
* no genetic involvement
26
What are the associated conditions of posteromedial tibial bowing?
* **Calcaneovalgus foot**
* PM bowing is often confused with calcaneovalgus foot
* may occur together or independent of each other
27
What is the most common sequlae of posteromedial bowing?
* **Leg length discrepancy of 3-4cm**
28
What are the symptoms and signs of postmedial tibial bowing?
* Present at birth :)
Signs
* **Posteromedial bowing**
* apex deformity is in the distal tibia- see pic
* **Calcaneovalgus foot deformity**
* apex of deformity is at the ankle
29
What is seen on imaging a posteriomedial tibial bowing?
* Ap and lateral radiographs
* **Posteriomedial bowing**
*
30
What is the tx of posteriomedial tibial bowing?
* _Non operative_
* **observation**
* for bowing deformity that usually corrects over 5-7 years
* tx with parental strectchiing if assoc with calcaneovalgus foot
* Operative
* **Age- appropriate epiphysiodesis of long limb**
* for projected leg length discrepancy
31
What are the complciations of posteromedial tibial bowing?
* Leg length discrepancy
* pt may have residual 2-5cm length leg discepancy at maturity
* may require age-appropriate epiphysiodesis of long limb
32
What is tibia deficiency?
* **A longitudinal deficiency of the tibia with varying degrees of tibial absence**
* previously known as tibia hemimelia
* Genetics
* **Autosomal Dominance inheritance pattern**
* genetic counselling
33
What are the associated conditions of tibia deficiency?
* Musculoskeletal conditions present in **75% of pts**
* **Lobster claw hand**
* **preaxial polydactyly**
* **ulnar aplasia**
34
What is the classification of tibia deficiency?
* **Jones**
* **Complete absence of tibia**
* **Partial absence of tibia into **
* proximal
* distal
* ankle diastasis
35
What is seen on physical exam of a child with tibial deficiency?
* **Shortening** of affected extremity
* **anteriorlateral bowing of tibia**
* **prominent fibular head**
ROM and stability
* **Knee usually flexed** w assoc flexion contracture
* important to evaluate for **active knee extension- intact quads and any FFD of knee**
* tx based on stability of knee
Foot deformity
* Often rigid equinovarus & supination deformity
* Sole of foot faces perineum
36
What is seen with imaging in a case of tibial deficiency?
* AP and lateral tibia/fibula
* **shows deficiency of tibia**
* early radiographs show small & minimally ossified distal femoral epiphysis
37
What is the tx of tibial deficiency?
* Operation
* **_Knee disarticulation + prothesis fitting_**
* for **complete absence of tibia**
* **no active knee extension-** most cases
* **_Tibiofibular synostosis with modified Syme ampitation_**
* prox tibia present with **intact extensor mechanism** & minimal flexion contraction
* **_Syme/Boyd amputation_**
* for ankle diastasis
* Brown Procedure
* centralisation of fibula under femur
* high failure rate no longer recommended
