Spina Bifida

Definition

• Congenital disorder in which the 2 halves of the posterior vertebral arch (or several arches) fail to fuse
• Anencephaly = cranial end equivalent
• Multiple organ involvement due to abnormal innervation of structures supplied by affected part of nerve

Demographics

• Isolated laminar defects are seen in 5% of lumbar spine X-rays
• <1 per 1000 live births in Australia
• up to 5 per 1000 in some countries
• If one child is affected then there is a 10 fold risk for the next child

Aetiology

• Dysraphism
  • Embryonic defect associated with maldevelopment of the neural tube & the overlying skin
• Environmental implications
  • Folate deficiency
  • Selenium deficiency in soil
  • Maternal alcohol
  • Maternal diabetes
  • Fever at critical antenatal stage
• Usually occurs in the lumbar or lumbosacral region
• With neural involvement there can be motor, sensory & autonomic dysfunction

Pathology

Spina Bifida Cystica

• Severe dysraphism with absent laminae & prolapse of the theca ± its contents
• Visible Cyst Present

• Meningocoele
  • CSF filled sac through the defect
  • Cord & roots still confined within vertebral arches
• Myelomeningocoele
  • Cyst including cord/ cauda/ nerve roots prolapsing
  • Cyst lined by dura & arachnoid
  • Commonest form
• Rachischisis
  • Open Myelomeningocoele
  • If the cord is still in its primitive state (ie. unfolded)
  • neural plate forms the roof of the prolapsing sac
• Closed Myelomening
  • If the neural tube is formed the roof of the sac is formed by dural membrane

Spina Bifida Occulta

• Midline laminal defect without prolapsing neural tissue
• Hidden defect
• There can be associated intraspinal defects
  • Tethering of the conus
  • Diastematomyelia
  • Cysts or lipomata of the cauda
• There may be skin signs of this with a dimple, a pit, or a tuft of hair

Multisystem Involvement

Hydrocephalus

• ~ 72%
• Secondary to Arnold Chiari malformation ± tethering of the cord
  • brainstem may be dragged distally, herniating through the foramen magnum
  • obstructing outflow of CSF
• If untreated it will lead to cerebral atrophy & retardation

Neurological Deficit

• Myelomeningocoele is always associated with neurological changes at & below level of the lesion
• Even with occulta there can be neurology
• Many patients have upper limb neurology because of subtle neurological lesions

Visceral

• Bowel & bladder paralysis
• Tendency to trophic ulceration of sacral / buttock / feet skin

Clinical Features

• Assess early for level of lesion & annual full neuro check
• Clinical assessment of level of lesion is easier after 5 y.o.

Spina Bifida Occulta

• If there are skin signs then neurological deficit is more common
• May present at any age
• Usually partial cauda equina symptoms with bladder symptoms along with motor & sensory features

Spina Bifida Cystica

• Obvious saccular lesion at birth, that may have skin or just membrane covering
• An open myelomeningocoele will have neural elements merging with plum coloured skin around
• the periphery
• head may be enlarged with widened sutures due to hydrocephalus
• posture may suggest the neurological level
• associated abnormalities;
  • hip dislocation
  • genu recurvatum
  • CTEV
  • Claw toes
    • Such deformities may be due to muscle imbalance or foetal positioning
• Neurological deficit;
  • Is complete in a third
  • Is complete at the level but there is some distal preservation in a third
  • Is incomplete in a third
• 60% have upper limb neurological deficits (often require both hands free to perform simple tasks)
• Walking
  • Thoracic – Most will not walk into adult life
  • Lumbar – May continue walking if strong quads & no significant hip deformity
  • Sacral – Useful walkers, often without orthoses in adult life

• Children with L-1 & L-2 neurosegmental levels are rarely community ambulators as adolescents
  • but time spent walking in braces may be longer than in children with thoracic lesions
  • so surgery to improve brace fitting should be considered
• Children with L-3, L-4, & L-5 neurosegmental levels with strong quads are usually good walkers.
  • They usually require an ankle-foot orthosis to stabilise the ankle
  • need for crutches or walking aids depends on the strength of abductors at hip
• Most children with sacral lesions are effective community ambulators until adulthood,
  • when some deteriorate & cease walking. Hip deformity is uncommon
  • but surgery is often necessary for foot & toe deformities

Investigations

• Genetic counselling
  • One affected » 1 in 25 risk for subsequent babies for neural tube deficits
  • Two affected » 1 in 10 risk
  • Three affected » 1 in 4 risk
• Screening using
  • Maternal Alphafetoprotein levels in serum
    • 16th to 20th week
    • If high, then need USS ± amniocentesis for Diagnosis
  • Ultrasound
    • detects most anencephalics by 10 – 12 weeks on PV USS
    • detects most by 16 – 18 weeks on standard abdo USS
    • detects > 80% of spina bifida on standard USS at 18 weeks
  • Amniocentesis
    • Alphafetoprotein levels
    • May still miss small skin-covered defects
• XR
  • Midline bony defect
  • Associated bony anomalies
    • Unsegmented bars
    • Hemivertebrae
    • Fused rib s
  • All of these can lead to abnormal curves
• MRI
  • To visualise the cord & the lesion
  • Brainstem herniation
  • Diastematomyelia
  • Syringomyelia
  • Cysts/lipomata in the theca

Prevention

• Folate / multivitamins
• Some elect for antenatal Diagnosis » abortion
• If detected NTD » consider elective LUSCS at 36 weeks (less severe neurological defects than NVD at term)

Treatment

• Multidisciplinary in large centre
  • Coordinator, neurosurgeon, orthopaedic, urologist, paediatric surgeon, psych, social worker, physio, orthotist, stomal, school aids etc
• For the focal deformity:
  • Closure of skin over the defect within 48 hours
• For the hydrocephalus:
  • Ventriculocaval shunt
• For the urogenital abnormalities:
  • Permanent catheter or a diversionary procedure
• For the musculoskeletal problems:
  • 2 important things to remember:
    • the bones are weak – therefore forceful corrections may lead to Fracture
    • the skin is insensate – therefore splinting must avoid pressure areas, & plasters are to be avoided
  • Postoperative heterotopic calcification around hip may be problematic if high lesions

Abnormalities & Their Management by Region

Spine

• Combination curves are common & can be severe
• Braces may slow the progression but many require surgical correction
• Kyphosis
  • If present at birth » usually associated with hydrocephalus
  • Usually lumbar
  • Increase > 8o per year
  • Correct if skin integrity compromised
• Scoliosis
  • Most = paralytic (some are congenital or mixed)
  • Most common in thoracic lesions
  • Brace only for those with rapidly progressing curves & too young for surgery
  • Indications for surgery
    • Stable posture for standing & sitting
    • Aim for level pelvis & trunk vertical on this
    • Try to avoid need for hand support for sitting
    • For stable fusion & prevent recurrence
    • Skin integrity
    • Respiratory function
  • Most surgical corrections = >35o & 8 – 14 y.o

Hip

• 3 problems
  • Deformity
  • Dislocation
  • Weakness (extension & abduction)
• Aim
  • enable the child to stand straight in calipers & also to be able to sit in a chair
• Flexion
  • Commonest deformity
  • <20° & good walking potential » observe
  • >20° & good walking potential » soft tissue release anterior & lateral
• Dislocation
  • Reduction of dislocated hip does not improve walking potential
  • May reduce to correct leg length discrepancy
  • Usually associated with pelvic osteotomy to maintain reduction
• Weakness
  • Above L1
    • then all the muscles are flail
    • splintage is all that is required
  • Below L5
    • deformity is one of flexion
    • either a flexor muscle ‘slide’ on the ilium or a psoas tendon elongation can be performed
  • Usually the lesion is between these levels
    • imbalance leads to hip subluxation
    • 50% of SB kids have subluxated or dislocated hips by the age of 2!
  • In view of the dangers of splinting & plasters
    • it is important to achieve muscle balance
    • psoas tendon transfer from lesser to greater trochanter achieves this
    • by decreasing flexor strength & increasing abduction & extensor strength
    • (Sharrard advocates passing the tendon through a hole created in the ilium)
    • (Mustard prefers to pass the muscle in front of the bone)
  • As the child gets older it becomes more difficult to reduce the hip
  • If the child is functionally OK then it is better to observe

Knee

• Aim
  • knee that can be held straight in a caliper, & can also be flexed to sit in a chair
• Recurvatum can be treated with a careful quadriceps elongation
• Undeformed knee with Quads weakness = common
• Fixed Flexion
  • Common with thoracic lesion
    • < 20° can be observed
    • >20° = if walker » posterior hamstring release ± capsular release
• Recurvatum
  • Problematic > 6y.o
  • Subcutaneous tenotomy of patella tendon

Tibia

• External torsion
  • Often with ankle valgus
  • Perform supramalleolar derotation osteotomy after 8y.o
• Internal torsion
  • < 3 y.o. can perform osteoclasis of tibia & fibula
  • Later stage = supramalleolar derotation osteotomy

Foot

• The aim is a plantargrade foot
• May be worth correcting deformity in non-walkers to look normal & wear normal shoes
• Varus
  • Results in weight bearing on outer border of foot
  • Surgical correction
• Valgus
  • Need to determine if mortise or STJ origin
    • Ankle
      • Distal end of fibula more proximal than normal
      • XR = growth plate more proximal than mortise
      • Lower tibial physis is wedge-shaped
      • Correct during growth by partial epiphysiodesis of tibial growth plate
      • (Staples, Phemister, Closed drilling)
      • Correct at later age by supramalleolar osteotomy
    • STJ
      • Usually controllable with footwear & orthoses until adolescence
      • Os calcis osteotomy (medial based wedge + medial translation)
      • STJ valgus often accompanied by external torsion & valgus of ankle mortise
      • Consider Grice extra-articular subtalar fusion or triple arthrodesis
• Equinovarus
  • May be anything from mobile to stiff +++
  • Early casting with regular changes
  • Closed TAL
  • PMR may be required for CTEV at age 6 months
  • If recurrent deformity » consider later triple arthrodesis
• Equinus
  • Closed or open TAL
• Cavus
  • Minor deformity » division of tight plantar tissues
  • After 4 y.o. & heel varus » Os calcis osteotomy
  • At skeletal maturity » Consider triple arthrodesis
• Calcaneus
  • Tib anterior transfer through interosseous membrane to heel
  • If fixed deformity » anterior ankle release ± TA tenodesis
  • If late deformity & “pistol grip” heel » Osteotomy of os calcis
• Vertical talus
  • Paralytic Convex Pes Valgus
  • < 2 %
  • Should be reduced operatively at age 3 years
  • to avoid a boatshaped foot with the potential for plantar ulceration
  • Cincinnati
• For claw toes flexor to extensor transfers can be performed for the outer 4 toes
• For the great toe FHL tenodesis (to the base of the proximal phalanx) is preferable

Prognosis

• A third achieve independent walking, two thirds use a wheelchair

Reviewed by Professor Phong Tran, Head of Orthopaedic Surgery, Western Health. Last updated 10 October 2026.