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Myelodysplasia (myelomeningocele, spinal bifida)

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Topic updated on 02/23/16 7:34pm
Introduction
  • Group of congenital abnormalities caused by the fetal spinal cord failing to completely close
  • Epidemiology
    • demographics
      • 0.1-0.2% incidence
    • risk factors
      • folate deficiency
        • supplementation can decrease risk by 70%
      • maternal hyperthermia
      • maternal diabetes
      • valproic acid
  • Genetics
    • chromosomal abnormalities
      • up to 10% of fetuses have a chromosomal abnormality
        • trisomy 13
        • trisomy 18
        • triploidy
        • various single-gene mutations
  • Associated conditions
    • orthopaedic manifestations
      • pathologic fractures
      • spine deformities
        • scoliosis
        • kyphosis
      • hip dysplasia
        • hip dislocations
        • contractures
      • knee deformities
        • tibial torsion
        • contractures
      • foot deformities 
    • neurosurgical manifestations
      • Type II Arnold-Chiari malformation
        • most common associated congenital abnormality
      • hydrocephalus
        • 70% incidence
      • tethered cord
    • urological manifestations
      • neurologic bladder
  • Prognosis
    • survival and neurologic impairment depend on level of spinal segment involved
    • untreated infants have a mortality rate of 90-100%
    • ability to ambulate
      • L3 or above are mostly confined to a wheelchair
      • L5 level patients have a good prognosis for independent ambulation
  • Special considerations
    • IgE mediated latex allergy 
      • results in profound anaphylaxis
      • present in 20 to 70% of patients with this disorder
Classification
  • Forms of myelodysplasia
    • spinal bifida oculta 
      • defect in vertebral arch with confined cord and meninges
    • meningocele 
      • protruding sac without neural elements
    • myelomeningocele 
      • protruding sac with neural elements
    • rachischisis
      • neural elements exposed with no covering
  • Function level (described by lowest functioning level)
x
Function
Primary Motion
Primary Muscles
L2 • Nonambulatory    
L3 • Marginal Household ambulator
• High risk of hip dislocation
Hip flexion
Hip adduction
Iliopsoas (lumbar plexus, femoral n.) 
Hip adductors (obturator n.)
L4 • Household ambulator plus
• Key level because quadriceps can function
Knee extension
Ankle dorsiflexion & inversion

Quadriceps (femoral n.) 
Tibialis anterior (deep peroneal n.)
L5 • Community ambulator Toe dorsiflexion 
Hip extension
Hip abduction
EHL (deep peroneal n.) 
EDL (deep peroneal n.) 
Gluteus med.& min. (superior gluteal n.)
S1 • Normal ambulator Foot plantar flexion Gastroc-soleus (tibial n.)
S2 • Normal ambulator Toe plantar flexion FHL (tibial n.)
S3,4 • Normal ambulator Bowel & bladder function  
 
Imaging
  • Radiographs
    • useful for monitoring
      • scoliosis/kyphosis
      • hip dysplasia
      • pathologic fractures
  • MRI
    • change in neurologic exam prompts urgent MRI to rule out cord tethering
Studies
  • Labs
    • alpha-fetoprotein (AFP)
      • elevated in 75% of children with open spina bifida
      • obtain during second trimester
Pathologic Fractures
  • Introduction
    • fractures of the long bones are common due to osteopenia
    • frequency increases with the higher the level of the defect
    • common in hip and knee in children ages 3 to 7 years of age
    • fractures are often confused with
      • infection
      • osteomyelitis
      • cellulitis
  • Treatment
    • short period of immobilization in a well-padded splint
      • indications
        • fractures in satisfactory alignment
      • technique
        • well-padded cast
        • avoid long-term casting
          • may lead to
            • osteopenia
            • repeat fractures
Scoliosis
  • Introduction
    • may result from
      • muscle imbalance (neurogenic) or
      • congenital malformation (e.g., hemivertebrae)
        • defined as curve > 20°
    • higher the functional level, the greater the incidence of scoliosis
      • 100% scoliosis rate with defects in thoracic levels
    • consider cord tethering in rapidly progressing deformities
  • Treatment
    • nonoperative
      • bracing not effective
    • operative
      • ASF and PSF with pelvic fixation
        • indications
          • progressive curve
          • indicated in most situations as bracing is not effective
        • technique
          • anterior fusion required due to dysplastic posterior elements that may impair posterior fusion
        • complications
          • high psuedoarthrosis rate
          • high incidence of infection (15 to 25%)
            • due to poor soft tissue coverage of posterior spine
Congenital Kyphosis
  • Introduction
    • present in 10-15% with myelodysplasia
    • usually congenital and progressive
  • Physical exam
    • Gibbus deformity may cause recurrent skin breakdown due to pressure points when sitting
  • Treatment
    • operative
      • kyphectomy with fusion and posterior instrumentation
        • indications
          • progressive deformity
        • technique
          • check shunt function prior to kyphectomy
            • shunt failure during surgery may result in death
Hip Disorders
  • Hip dislocation
    • introduction
      • most common at L3 level due to unopposed hip flexion and adduction

        L1
        L2
        L3
        L4
        L5
        S1
        HIP FLEXION
         
         
        HIP EXTENSTION
         
        HIP ADDUCTION
        HIP ABDUCTION
         
    • treatment
      • nonoperative 
        • indications
          • all levels
        • technique
          • close observation
      • operative
        • indications
          • surgical treatment of dislocated hips is controversial
  • Hip abduction contracture
    • introduction
      • can cause pelvic obliquity and scoliosis
    • treatment
      • proximal division of fascia lata and distal iliotibial band release (Ober-Yount procedure)
        • indications
          • contractures interfere with sitting or bracing
  • Hip flexion contracture
    • introduction
      • common in high lumbar or thoracic defects
    • treatment
      • anterior hip release with tenotomy of the iliopsoas, sartorius, rectus femoris, and tensor fascia lata
        • indications
          • contractures greater than 40 degrees
Knee Disorders
  • Weak quadriceps
    • introduction
      • common condition affecting children with myelodysplasia
    • treatment
      • KAFO (knee-ankle-foot orthotic)
  • Flexion contracture
    • introduction
      • not as important to treat in wheelchair bound patients
    • treatment
      • hamstring lengthening +/- posterior capsulotomy
        • indications
          • greater than 20 degrees of knee flexion contracture
      • supracondylar extension osteotomy
        • indications
          • older patients
          • those who have failed soft tissue procedures
  • Extension contracture
    • introduction
      • less common than flexion contractures
    • treatment
      • serial casting
        • indications
          • extension contracture limiting ambulation or sitting
        • technique
          • goal is to reach 90 degrees of flexion
  • Tibial rotational deformities (torsion)
    • treatment
      • observation and orthotics
        • Indications
          • children less than 5 years old
      • distal tibial derotational osteotomy
        • indications
          • children older than 5 years
Foot and Ankle deformities
  • Introduction
    • very common
      • 60 - 90% incidence
      • due to high incidence of lower nerve root involvement 
Myelodysplasia foot deformity by level
Level
Foot Deformity
Proper orthosis
L1 & L2 Equinovarus  HKAFO
L3 Equinovarus  KAFO
L4 Cavo varus  AFO
L5 Calcaneovalgus  AFO
S1 foot deformity shoes
  • Clubfeet (talipes equinovarus)
    • introduction
      • 30% incidence with myelodysplasia
        • most common foot deformity
      • very rigid
      • insensate in the foot (different from idiopathic clubfeet)
    • treatment
      • serial casting
        • indications
          • initial treatment of choice
        • complications
          • high complication rate with serial casting
      • posteromedial lateral release
        • indications
          • failure of serial casting
        • technique
          • perform when child 12-18 months old
  • Foot dorsiflexion deformity
    • introduction
      • seen with L5 or sacral level patients
      • unopposed anterior tibialis causes dorsiflexion deformity
    • treatment
      • posterior transfer of the anterior tibial tendon 
        • indications
          • inability to achieve neutral foot with bracing
  • Vertical talus

 

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Qbank (4 Questions)

TAG
(OBQ11.90) A 4-year-old girl with an L3 myelomeningocele presents for routine follow-up. Pelvic radiographs reveal a complete dislocation of the left hip with well formed acetabulum, and a normal right hip. Her gait is symmetric with use of a walker and brace. Which of the treatment options should be offered to the patient at this time? Topic Review Topic

1. Right sided femoral shortening osteotomy
2. Continued observation and routine follow-up
3. Left greater trochanteric advancement
4. Left sided pelvic osteotomy
5. Open reduction of the left hip

PREFERRED RESPONSE ▶
TAG
(OBQ10.27) A 6-year-old boy with spina bifida presents to your clinic with a progressive foot deformity. He can walk independently and ankle dorsiflexion and toe extension demonstrate full strength. He has a bulky, hypertrophied heel pad, but no open ulceration. Foot radiographs are displayed in Figure A. What myelomeningocele level does this patient have and what surgical procedure is indicated for the foot?
Topic Review Topic
FIGURES: A          

1. L1 level requiring triple arthrodesis
2. L3 level requiring triple arthrodesis
3. L3 level requiring posterior transfer of the anterior tibial tendon
4. L5 level requiring triple arthrodesis
5. L5 level requiring posterior transfer of the anterior tibial tendon

PREFERRED RESPONSE ▶
TAG
(OBQ10.133) An 18-year-old ambulatory female with spina bifida presents with a painful planovalgus left foot. She has failed treatment with orthoses and heel-cord stretching regimens. Ankle radiographs demonstrate that the distal tibia is tilted 15° into valgus relative to the long axis. Which of the following treatment options would best correct the deformity? Topic Review Topic

1. Triple arthrodesis of the ankle
2. Supramalleolar osteotomy
3. Medial tibial epiphysiodesis
4. Calcaneal lengthening osteotomy and tendo-Achilles lengthening
5. Midfoot osteotomy combined with plantar release

PREFERRED RESPONSE ▶
TAG
(OBQ09.53) Patients with myelomeningocele have an allergic response (type 1 hypersensitivity) to latex by what cellular mechanism? Topic Review Topic

1. IgE-directed antibodies
2. IgM-directed antibodies
3. IgA-directed antibodies
4. Overactive complement system
5. Hyperactive killer-T cells

PREFERRED RESPONSE ▶



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HPI - Patient was referred to our institution 3 months ago from another state. She has...
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3/7/2012
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