Spina Bifida

By admin On Jun 17, 2024

Ovid: Pediatrics

Editors: Tornetta, Paul; Einhorn, Thomas A.; Cramer, Kathryn E.; Scherl, Susan A.

Title: Pediatrics, 1st Edition

> Table of Contents > Section III: – Specialty Clinics > 19 – Spina Bifida

Spina Bifida

Laura Lemke

Luciano Dias

Spina bifida is a
nonspecific term used to describe a broad spectrum of defects that
occur during the formation of the neural tube. Spina bifida occulta is
an asymptomatic localized defect in the formation of the vertebral arch
that is present in 10% of normal adults. It is not associated with any
defect of the spinal cord or meninges. Spina bifida cystica describes
four types of defects that occur in the meninges and spinal cord.
Myelocele is a protrusion of the spinal cord. Meningocele is a
protrusion of the meninges of the spinal cord through a defect in the
spinal column. Myelomeningocele is a protrusion of the meninges and
spinal cord through a defect in the spinal column. Rachischisis is a
congenital fissure of the spine at the level of a vertebral arch. The
term spina bifida also includes anencephaly, absence of the brain, and
encephalocele, a congenital gap in the skull with herniation of brain
substance. Ninety percent of children described as having spina bifida
will have myelomeningocele, so that will be the primary focus of this
discussion.

PATHOGENESIS

Etiology

Defects causing spina bifida are a result of failure of
closure of the neural tube, as opposed to reopening after closure.
Closure of the neural tube occurs at various sites with each site
controlled by a different gene. Environmental factors also play a role
in closure of the neural tube. Maternal insulin-dependent diabetes,
maternal hyperthermia, use of valproic acid, and folate deficiency have
all been linked to myelodysplasia.

Prevention

Avoidance of hyperthermia (hot baths and saunas) and
discontinuation of valproic acid can reduce the risk of myelodysplasia.
Daily ingestion of 4 mg of folic acid supplement before and early in
pregnancy reduces the risk of neural tube defect by 60% to 72%. High
dietary intake of folic acid can also reduce risk. Screening programs
such as maternal α-fetoprotein, ultrasound, and amniotic α-fetoprotein
and cholinesterase can detect virtually all open spina bifida by 18
weeks of gestation.

Epidemiology

The most recent estimate of the incidence of neural tube
defects is 0.6 to 0.9 per 1,000 live births. The incidence, however,
has been decreasing over the last few decades, particularly with the
discovery of the correlation with folic acid deficiency.

Classification

The best classification for myelomeningocele is based on
the neurologic level of the lesion. Neurologic level can be correlated
with function and predict likelihood of ambulation. See Table 19-1 for the classification of myelomeningocele.

ASSOCIATED NEUROLOGIC CONDITIONS

Hydrocephalus

Hydrocephalus is an excessive accumulation of fluid in
the cerebral ventricles that causes thinning of the cerebral tissue and
can cause separation of the cranial bones. In infants accumulation of
fluid can also occur in the subarachnoid or subdural space.
Cerebrospinal fluid shunting is required in 80% to 90% of children with
myelomeningocele because of hydrocephalus. The incidence of
hydrocephalus is related to the level of the lesion: 83% in thoracic
and upper lumbar lesions, 60% in low lumbar and sacral lesions.
Children who do not require shunting have a better prognosis than those
who do require shunting. Those who do not require shunting have better
upper extremity function and trunk balance as well as a lower incidence
of hydromyelia and tethered cord. Infection and obstruction of the
shunt are the two most common complications and have been negatively
correlated with the child’s motor and intellectual development.

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TABLE 19-1 CLASSIFICATION OF MYELOMENINGOCELE

Group	Lesion Level	Function	Ambulation^a
1	Thoracic and high lumbar	No quadriceps function	Minimal to age 13 with HKAFO or RGO 95%-99% wheelchair-bound as adults
2	Low lumbar	Quadriceps and medial hamstring function	Require AFO and crutches. Many (79%) community ambulators as adults. L4 level better chance for ambulation with proper musculoskeletal care
3	Sacral	Quadriceps and medial hamstring function	94% ambulatory as adults
	High sacral	No gastrocsoleus strength	Use AFO but no crutches. Gluteus lurch and excessive pelvic obliquity
	Low sacral	Good gastrocsoleus strength. Normal gluteus medius and maximus function	Walk without AFO or crutches. Gait close to normal
^aBraces are described in Chapter 2.
AFO, ankle-foot orthosis; HKAFO, hip-knee-ankle-foot orthosis; RGO, reciprocating gait orthosis.

Arnold-Chiari Malformation

Arnold-Chiari malformation is a common clinical and
anatomic finding in children with myelomeningocele. This is a
displacement of the hindbrain into the foramen magnum. This occurs in
three types. In type I, the cerebellum is displaced but the brainstem
is not. This type often presents in adolescence with headaches, lower
extremity spasticity, and upper extremity pain. Type II, which occurs
in 90% of children with myelomeningocele, involves displacement of the
brainstem commonly in association with hydrocephalus. This caudal
displacement leads to dysfunction of the lower cranial nerves, causing
weakness and paralysis of the vocal cords and difficulty feeding. These
symptoms become apparent in infancy. Patients may also display ocular
disturbance, apneic episodes, and progressive respiratory difficulty.
Type III Arnold-Chiari malformation, is an encephalocele at the
craniocervical junction.

Tethered Spinal Cord

During normal fetal development, the spinal cord ascends
until it is at level L3 at birth. By the second month of life it has
reached the adult level at approximately L1. In children with neural
tube defects there is communication with the overlying ectoderm at
birth. All children with myelomeningocele have a tethered cord at birth
but with closure of the defect the spinal cord falls back within the
canal. Scarring of the overlying tissues results in most children with
myelomeningocele showing signs of tethering on magnetic resonance
imaging (MRI) but only 15% to 30% of these children show clinical
manifestations of tethered cord. Clinical signs can be variable but
commonly involve:

Loss of motor function
Lower extremity spasticity, particularly in the medial hamstrings, ankle dorsiflexors, and ankle evertors
Scoliosis before age 6 in the absence of congenital vertebral anomaly
Back pain and increased lumbar lordosis in ambulatory children
Changes in urologic function

When there is suspicion of tethered cord syndrome, MRI
or computed tomography (CT)/myelogram can be used to evaluate the
spinal cord. Shunt malfunction should also be ruled out.

Hydromyelia

Hydromyelia or syringomyelia of the spinal cord is a
fluidfilled cavity within the spinal cord itself. This occurs in up to
54% of children with myelomeningocele. The presumed mechanism is that
fluid in a hydrocephalic fourth ventricle enters the central canal.
Pressure causes gradual expansion of the canal. This problem manifests
as increasing spasticity, upper extremity weakness, back pain, and
classically, as worsening spinal deformity. Evaluation should include
CT or MRI. Treatment is controversial and includes shunt placement or
revision, posterior fossa decompression, or direct shunting of the
cavity itself. Treatment can lead to some scoliosis regression.

Cognition

Children who do not require shunting have normal
intelligence. Of those who do require shunting, 70% to 80% will have
IQs above 80; the remainder will have IQs below 80. Verbal skills are
good but perceptual scores are low resulting in a social, verbal child
with limited ability for rehabilitation.

RELATED CONCERNS

Urologic Considerations

Urologic dysfunction is common in children with myelomeningocele. Incomplete emptying is common due to bladder

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spasticity or flaccidity and predisposes these children to recurrent
urinary tract infections. Vesicoureteral reflux is also common. Urinary
diversion, intermittent catheterization, and suppressive antibiotics
have decreased the percent of patients with renal dysfunction from 75%
to 30%.

Latex Allergy

Latex allergy is a topic of great concern in patients
with myelomeningocele. Reactions range from urticaria and bronchospasms
to anaphylaxis and death. The reaction is immunoglobulin E-mediated.
Patient screening with skin testing and radioallergosorbent (RAST)
testing has shown that the incidence is 1% in adults in the general
population, 7.5% in operating room personnel, and 18% to 89%, with both
types of screening in various studies, in children with
myelomeningocele. Multiple exposures early in life have been postulated
to be a major risk factor in latex allergy. For children with
myelomeningocele, a latex-free surgical environment is safest.
Premedication with histamine-blocking agents and steroids is
controversial and has not been proven to be beneficial.

Anesthesia Considerations

Malignant hyperthermia has been reported in patients
with myelomeningocele. There is at best a weak association between the
two conditions. Treatment is the same for all patients with malignant
hyperthermia.

Infection Risks

Recurrent urinary tract infections can lead to a higher
post-surgical infection rate for patients with myelomeningocele.
Blood-borne bacteria are presumed to seed wounds but no correlation has
been found between urine, blood, and wound infections. Infection rates
have been found to decrease if preoperative antibiotics were based on
preoperative urine cultures. Other important factors include poor skin
in the area of sac closure, insensate skin, and nutrition.

ORTHOPAEDIC EVALUATION

Serial Muscle Test

This test is used to determine the neurologic level of
function. It should be done at birth before closure, 10 to 14 days
after closure, and then annually. If possible, the same therapist
should always do this. The child may be 3 or 4 years old before the
neurologic level is absolutely defined because gluteus medius and
maximus strength can be accurately determined only around this age. The
level should stay the same throughout the child’s life. Any change can
be a sign of neurologic dysfunction such as tethered cord.

Sitting Balance

The ability to sit without support is a good indicator
of nearly normal central nervous system function. If support is
required for sitting, walking ability with an orthosis or external
support is limited.

Upper Extremity Function

Abnormalities in upper extremity function have been
documented in 60% to 82% of patients with myelomeningocele. Gait
training involves the use of crutches and walkers, making upper
extremity function important for ambulation. Loss of grip strength and
thenar atrophy are reliable signs of hydromyelia. Other risk factors
for upper extremity dysfunction include thoracic or high lumbar
involvement, upper extremity spasticity, and greater than three shunt
revisions.

Spine Examination

Annual spine radiographs are recommended for patients
with high-level lesions. The incidence of scoliosis is quite low in
patients with low lumbar of sacral scoliosis. Any spinal curvature in
patients with lesions at these levels suggests tethering of the spinal
cord.

Hip Range of Motion

Hip contractures are very common, particularly in
patients with high lumbar or thoracic-level lesions. Abduction or
adduction contractures can cause infrapelvic obliquity that interferes
with bracing and ambulation. Flexion contractures are also common.
These can be measured with the Thomas test. Internal and external
rotation deformities can interfere with gait. Internal and external
rotation should always be accurately recorded. Internal rotation
deformity during gait combined with external tibial torsion is a common
cause of increased valgus stress at the knee.

Knee Alignment and Range of Motion

Knee flexion contracture is common. Contracture of
greater than 20 degrees can interfere with bracing and lead to a
crouched gait. Knee extension contractures are usually congenital.
External tibial torsion with a thigh-foot angle of more than 20 degrees
can lead to increased valgus stress at the knee. Internal tibial
torsion is often associated with congenital clubfoot deformity.

Foot and Ankle Deformities

Ankle valgus is common and may cause pressure sores at
the medial malleolus with orthotic wear. Alignment of the forefoot and
hindfoot, and ankle range of motion are very important to record in
patients with myelomeningocele. Approximately 90% of patients with
myelomeningocele have some type of foot deformity. Subtle changes that
occur with tethered cord should be recognized early.

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Gait Analysis

Clinical Application

Gait analysis is commonly used in the treatment of
patients with cerebral palsy. For patients with myelomeningocele, gait
analysis is useful for two groups:

Patients with low lumbar lesions who walk with belowknee orthosis and external supports
Patients with sacral-level lesions who walk with ankle-foot orthoses and no support

The average walking velocity for low lumbar-level
patients is 54% of normal. The average velocity for a patient with a
sacral-level lesion is 70% of normal.

Kinetic Pattern

All patients with myelomeningocele show some form of
compensatory movement with gait based on their level of muscle
weakness. Weakness of the gluteus medius and maximus necessitate pelvic
rotation and obliquity to facilitate forward progression and maintain
independent ambulation. Increased stance-phase hip abduction, increased
knee flexion, and increased ankle dorsiflexion also help to facilitate
gait. The magnitude of compensatory movement at the pelvis is related
to the level of motor deficit.

Gait analysis has been particularly helpful in
understanding the gait patterns of those with hip pathology and those
with valgus knee stress. The quality of crutch walking in children with
hip subluxation and dislocation has been found to be much more
effective than any attempts to correct these problems and have the
children walk without supports. External tibial torsion can lead to
significant valgus knee stress. When understood, correction of this
problem is very beneficial to these patients.

PRINCIPLES OF ORTHOPAEDIC MANAGEMENT

Orthotic Management

Approximately 95% of patients with myelomeningocele
require orthotic support to achieve ambulation. The goal of orthotic
treatment is to achieve effective mobility with minimal restriction.

A hip-knee-ankle-foot orthosis (HKAFO) is
used for patients with high lumbar level lesions who can perform swing
through ambulation with crutches.
A knee-ankle-foot orthosis (KAFO) is used
for patients with low lumbar-level paralysis to reduce valgus stress at
the knee when the patient is too young for osteotomies.
An ankle-foot orthosis (AFO) is used for
patients with low lumbar- and high sacral-level lesions. They are
usually made with a solid ankle and hold the ankle in neutral
dorsiflexion (90 degrees) to minimize knee crouch.
- □ Twister cables can be added to the AFOs
  when a child has rotational malalignment (in-toeing and out-toeing),
  which is frequently seen in patients with low lumbar- and high
  sacral-level lesions.
- □ Surgical treatment is usually
  recommended for patients with rotational malalignment but is best done
  after 6 years of age. Therefore, twister cables can be used from 2
  years of age until surgical correction is achieved.

Most high lumbar- and thoracic-level patients will not be ambulatory.

The A-frame is a prefabricated brace that
includes the trunk and lower extremities and allows the child to stand
without hand support.
- □ It can be used up to 3 hours per day in 20- to 30-minute intervals.
- □ It can be started at age 12 to 18 months.
The parapodium and reciprocating gait orthosis (RGO) are custom braces that also include the trunk and lower extremities.
- □ These allow ambulation but are only
  indicated in high lumbar- and thoracic-level patients with good
  sitting/ trunk balance and good upper extremity function.
- □ These can be introduced around the age of 2 years.
A wheelchair may allow independent mobility for the nonambulatory patient.
- □ Seating is very important to prevent
  ulcers, the backrest should have trunk support when necessary, and the
  armrest should facilitate easy transfer in and out of the chair.
- □ The chair should be fitted carefully to the specific need of the child.

Night splinting is used primarily as a preventive measure in both ambulatory and nonambulatory patients.

A patient with a high-level lesion and
complete lower extremity paralysis can benefit from a total body splint
at night to prevent flexion contractures at the hips and knees and
equinus deformity at the ankle.
Careful fitting of splints is very important to prevent skin breakdown.

Physical Therapy

Development is dependent on a child’s ability to move,
explore, and experience the environment. These abilities are
compromised in a patient with lower extremity paralysis and an abnormal
central nervous system. Physical therapy plays a role in maintaining
range of motion, preventing contractures, and gait training with the
necessary aides. Strengthening and physical fitness are also important.
Therapy is also used to monitor the child to assure that neurologic
deterioration does not occur. Intensive, multifaceted therapy should
lessen a child’s disability.

Fractures and Physeal Injuries

Pathologic fractures of the long bones are common in
patients with myelomeningocele. The incidence is higher in children
with high-level lesions. Patients are particularly susceptible after
the paralyzed limb has been further immobilized by casting. Fractures
can occur with no history of trauma and are most common in the
supracondylar

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femur
and proximal tibial metaphysis. Symptoms usually include erythema,
warmth, and swelling. Increased temperature, white blood cell count,
and erythrocyte sedimentation rate can also be present. Because of this
clinical presentation, fractures in patients with spina bifida can be
mistaken for infection. These fractures generally heal rapidly and
therefore rarely require surgery. Short periods of immobilization are
recommended to prevent further osteopenia. Functional alignment and
proper rotation in a well-padded cast are often enough to allow
ambulation with an orthosis.

Physeal injuries are far less common and usually occur
in the distal femur, proximal tibia, or distal tibia. These are usually
caused by repetitive trauma similar to Charcot neuropathy.
Immobilization and non-weightbearing are recommended until there is
radiographic healing. When this is hard to determine clinically, loss
of swelling and a normal anatomic contour compared to the other side
are useful clinical determinates.

Spine Deformities

Spinal deformity is common in children with
myelomeningocele. Congenital scoliosis occurs in 1% to 15% of patients.
Kyphotic deformity occurs in 5% to 20% of patients, primarily those
with thoracic-level lesions. A scoliotic curve of greater than 10
degrees occurs in 69% of patients with myelomeningocele. The prevalence
of spinal deformity increases with higher levels of involvement.

Scoliosis

Paralytic scoliosis occurs in up to 100% of children
with high-level lesions, 40% to 60% of children with low lumbar-level
lesions, and 5% to 10% of children with sacral-level lesions. Curve
development is gradual before the age of 10 and increases rapidly with
the adolescent growth spurt. Factors that lead to progression are not
well documented. Curve magnitude, Risser sign, menarchal status, and
bone age are not closely linked to the likelihood of curve progression
as they are in idiopathic scoliosis. Tethered cord, hydromyelia, and
worsening hydrocephalus have been implicated as factors in worsening
deformity. Correction of these problems may stop curve progression but
a true cause-and-effect relationship has not been proven.

The frequency of spinal deformity necessitates yearly
spinal radiographs beginning at about 5 years of age. If scoliosis is
found, MRI is often necessary to rule out the possibility of
hydromyelia or tethered cord. Any abnormalities of the spinal cord
should be surgically corrected. Observation is the treatment of choice
for curves less than 25 degrees. When curves are greater than 25
degrees, bracing is recommended. This is primarily a temporary measure
that will delay, but not stop, curve progression. The Milwaukee brace
or thoracolumbosacral orthosis (TLSO) is used. These are recommended
for either daytime or 23-hour use. Pressure sores and worsening
pulmonary status can occur and should be prevented. Surgical treatment
is recommended for progressive curves greater than 40 degrees. For the
most severe curves anterior and posterior fusion is recommended.
Pseudoarthrosis rates of 40% to 75% and infection rates of 20% to 40%
have been reported. Pseudoarthrosis has decreased to less than 20% with
the use of anterior and posterior fusion. Infection occurs in 0% to 8%
when prophylactic antibiotics are used. Fusion to the pelvis is often
necessary, and up to 57% of patients will lose some ambulatory capacity
after spinal fusion.

Kyphosis

Most myelomeningocele patients with kyphosis have high
lumbar- and thoracic-level lesions. Kyphosis usually occurs at the
thoracolumbar junction or in the lumbar spine. This deformity is
usually present at birth and can progress to greater than 90 degrees by
age 2 or 3 years. Congenital kyphosis is completely unresponsive to
bracing and requires surgical treatment. Many techniques have been
described for the kyphectomy. Each carries significant risk of
complication including spinal fluid/pressure imbalance,
pseudoarthrosis, and infection. Careful preoperative and postoperative
care is imperative.

Hip Deformities

Contracture

Hip contractures commonly occur as a result of muscle
imbalance (particularly in low lumbar-level patients); spasticity of
hip musculature is commonly seen in patients with tethered cord, or the
habitual posture of wheelchair patients with high-level lesions.
Abduction and adduction contractures can lead to pelvic obliquity,
asymmetric gait, and compensatory scoliosis. Adduction contracture is
treated with an adductor myotomy if mild and with a subtrochanteric
valgus osteotomy if necessary to correct pelvic obliquity. Abduction
contracture is usually mild and will correct with the Ober-Yount
procedure with its release of the tensor fascia latae. Postoperatively,
a hip splint and early mobilization are used.

Flexion contracture can cause anterior pelvic tilt that
is associated with decreased walking velocity and increased demand on
the upper extremities. Treatment of flexion contracture varies with the
child’s neurologic level. For a patient with a high-level lesion,
contracture up to 30 to 40 degrees can be tolerated if it does not
interfere with bracing or walking. Surgical treatment consists of a
radical release often including the anterior hip capsule. For a low
lumbar-level patient contracture up to 20 degrees can significantly
affect walking and bracing. Surgical treatment must retain hip flexor
power and therefore some muscles that are released must be reattached
more distally. Splinting and early mobilization are used
postoperatively to maintain results.

Dislocation

The incidence of hip dislocation varies with the level
of involvement. Nearly half of children with myelomeningocele
experience hip instability in the first 10 years of life (Table 19-2).

Muscle imbalance between the hip flexors and extensors
and between the abductors and adductors accounts for hip instability.
Many studies have found that the presence of hip dislocation does not
affect ambulation, bracing requirements, seating, or progression of
scoliosis, or

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lead
to hip pain. Given the high incidence of complications with hip
relocation procedures in myelomeningocele patients, including
redislocation, stiffness, seating difficulty, cost, infection, and
decreased ambulatory function, some recommend against such procedures.
Treatment can be recommended based on the functional classification
shown in Table 19-1.

TABLE 19-2 INCIDENCE OF HIP DISLOCATION BY LEVEL

Level	Incidence of Hip Dislocation
Thoracic	28%
L1-L2	30%
L3	36%
L4	22%
L5	7%
Sacral	1%

For patients in group 1, hip stability has little clinical effect.
- □ Treatment is limited to release of
  contractures and realignment osteotomies to facilitate proper sitting,
  perineal care, and brace fitting.
- □ There is little evidence to support hip relocation in this group.
Group 2 patients have a high incidence of unstable hip.
- □ Maintaining a level pelvis and flexible hips is more important than reduction.
Group 3 patients place a high demand on their hips and therefore concentric reduction is very important.
- □ Hip dislocation is uncommon in this group.
- □ Some recommend aggressive treatment to achieve and maintain reduction including hip and pelvic osteotomies.

For excessively stiff hips, proximal femoral resection
with interposition arthroplasty is recommended but rarely necessary.
Femoral head resection alone is not effective.

Knee Deformities

Flexion Contracture

One study found that all babies with myelomeningocele
had a 10-degree knee flexion contracture at birth. In many children
this corrects with growth. Factors that lead to knee flexion
contracture include the following:

The typical position when supine of hip abduction, flexion, and external rotation, knee flexion, and ankle equinus
Gradual contracture of the hamstrings, biceps, and posterior knee capsule
Spasticity of the hamstrings due to tethered cord
Paralysis of the gastrocsoleus, gluteus medius, and gluteus maximus

In children with high-level lesions knee flexion contracture can be prevented with early splinting.

A crouched gait has a high-energy cost. Knee flexion
greater than 40 degrees increases energy costs. External tibial torsion
can also lead to a crouched gait and higher energy costs. This is
addressed in the section on rotational deformities. One study suggests
that knee flexion on the examination table is doubled with
weightbearing. Therefore, knee flexion contracture of greater than 20
degrees requires surgical correction. This can be achieved in a variety
of ways. For children with high-level lesions a radical flexor release
can be performed. A knee flexor lengthening is recommended for children
with low lumbar- and sacral-level lesions. Supracondylar extension
osteotomy of the femur is rarely indicated but is used in patients who
have not had success with a radical release. Anterior stapling of the
physis can be done in a growing child to achieve gradual correction of
the flexion deformity.

Extension Contracture

Extension contracture is much less common than flexion
contracture. This usually occurs bilaterally and is associated with hip
dislocation, external rotation hip deformities, valgus knees, and
equinovarus feet. Treatment options include serial casting to achieve
90 degrees flexion or surgical treatment to lengthen the quadriceps
mechanism.

Rotational Deformities

External Tibial Torsion

External tibial torsion, internal hip rotation, and
excessive pelvic rotation and contribute to gait problems, particularly
increased valgus knee stress. External tibial torsion of greater than
20 degrees has been shown to contribute to crouch gait and an increased
valgus stress at the knee. Rotational correction of the tibia can
decrease valgus stress and improve crouch gait. Because of the high
rate of complications, osteotomy is recommended just above the distal
tibial physis with a separate incision for the fibular osteotomy.
Internal hip rotation can be corrected with an intertrochanteric
external rotation osteotomy when necessary. Excessive pelvic rotation
can be decreased only by the use of crutches.

Internal Tibial Torsion

Internal tibial torsion is usually present from birth
and is often associated with talipes equinovarus, or clubfeet. Before
age 5, correction can be attempted with AFOs and twister cables. After
age 5, external rotation tibial osteotomies are usually necessary. Gait
studies have revealed that internal tibial torsion does not
significantly increase stress at the knee. Any dynamic deformities,
such as a spastic anterior tibial tendon, must be recognized at the
time of surgery.

Hip Rotation

Excessive internal and external hip rotation can occur
with spina bifida. Initial treatment is with twister cables, but
proximal femoral osteotomies may become necessary when the child gets
older.

Foot and Ankle Deformities

Some 80% to 90% of children with myelomeningocele have deformities of the foot. Some of these are present at birth,

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such as talipes equinovarus or vertical talus, and others are
developmental due to muscle imbalance, such as calcaneal and
calcaneal-valgus deformity.

The final treatment goal for children with spina bifida
is a plantigrade, supple, braceable foot. Surgical treatment is often
necessary and two main principles should be followed:

Muscle balance should be achieved through tendon excisions, which are more reliable than tendon transfer or lengthening.
Arthrodesis should be avoided whenever possible.

Correction should be achieved through osteotomies to
preserve joint motion. A mobile, flat foot is easier to brace than a
rigid foot. Joint fusion can lead to arthritic changes in neighboring
joints and to soft tissue ulceration. Untreated muscle imbalance can
lead to bony changes and should be addressed in a timely manner.

Clubfoot

Approximately 30% of children with myelomeningocele have
clubfoot. In spina bifida, the clubfoot deformity is far more rigid
than the idiopathic clubfoot. The foot often has a supination deformity
caused by the unopposed action of the anterior tibialis, rotational
malalignment of the calcaneus, talus and calcanealcuboid joints,
talonavicular subluxation, a cavus component, and severe internal
tibial torsion. Casting is rarely completely successful but should be
attempted because improvement in the soft tissue can be seen. Surgical
correction is recommended around age 10 to 12 months.

Surgical treatment involves a radical posterior medial-lateral release:

All tendons are excised rather than lengthened.
The anterior tibialis is excised to correct the supination deformity.
The subtalar joint, including the interosseous ligament, is completely released.
The calcaneocuboid joint is released circumferentially and a plantar release is performed.
Kirchner wires are used to correct and hold the correction of the talonavicular and subtalar joints.
Correction of the rotational malalignment of the talus and calcaneus is very important.
Postoperatively, a long leg splint is used with the foot in mild equinus to decrease tension at the suture line.
A long leg cast is worn for an additional 6 weeks.
Kirchner wires are removed at the time of final cast removal and an AFO is recommended for day and nighttime use.

Results are better in children with low lumbar- and
sacral-level lesions; poor results have only been reported in 11%. On
the contrary, poor results have been reported in 50% of children with
thoracic- and high lumbar-level lesions. The most common residual
deformity is adduction of the forefoot, which is secondary to growth
imbalance between the medial and lateral columns. When bracing is
unsuccessful, osteotomies can be done around the midfoot to correct
this problem. This should be delayed until there is ossification of the
medial cuneiform, which occurs at age 4 or 5 years. The best treatment
for failed clubfoot surgery is a talectomy. Extensive scar tissue
surrounding the neurovascular bundle makes revision very difficult.

Equinus Deformity

Equinus deformity occurs more frequently in children with high lumbar- and thoracic-level myelomeningocele.

Bracing is recommended to prevent progression of deformity.
When surgery becomes necessary, Achilles tendon excision may be all that is needed.
For more severe deformity, release of the
posterior tibiotalar and talocalcaneal joints, including the
calcaneofibular ligament, is needed.
Postoperatively, a child is treated in a short leg cast for 6 weeks followed by AFOs for day and nighttime use.

Vertical Talus

At birth, approximately 10% of children with
myelomeningocele will have vertical talus deformity. The talus is
positioned vertically, the calcaneus is in equinus and valgus, the
navicular is dislocated dorsally and laterally on the talus, and the
cuboid is often dorsally subluxated in relation to the calcaneus. These
deformities are typically congenital but muscle imbalance can
contribute to the deformity. Serial casting can help stretch soft
tissues, but complete posteromedial-lateral release is almost always
required at age 10 to 12 months.

Calcaneus and Calcaneovalgus Deformities

Calcaneus deformity occurs in 30% of children with
myelomeningocele and is due to imbalance of the active dorsiflexors and
weak plantarflexors of the ankle. The deformity is typical in a child
with an L5-S1 level. Calcaneovalgus is caused by an imbalance between
the invertors and the evertors. When the deformity is present at birth,
it is most often flexible, but if rigid, it can be corrected with
serial casting. More often this is a developmental deformity. Tendon
excision of the ankle dorsiflexors, peroneus brevis, and peroneus
longus can often achieve a braceable, supple, plantigrade foot. In one
study, 18% of patients had recurrent deformity with this treatment and
required either repeat tendon excision or correction of equinus
deformity. In older children, bony correction of the calcaneus, along
with soft tissue releases, is required to allow bracing and prevent
pressure sores.

Ankle Valgus and Hindfoot Valgus

Valgus deformity of the ankle is commonly seen in
children with L4-L5 level spina bifida. This can lead to problems with
pressure sores and difficulty with brace fitting. Additionally, these
children often have a calcaneus foot, due to absence of
gastrocnemius-soleus strength, and external tibial torsion. The
calcaneovalgus position of the foot can also be associated with an
abnormally short fibula that promotes further valgus tilt of the talus
in the ankle mortise.

Surgical treatment of ankle valgus is indicated when
there are problems with orthotic fitting. Achilles tenodesis to the
fibula has been described but is no longer recommended.

P.210

Hemiepiphysiodesis of the medial malleolus is done for mild deformities with a single screw in the malleolus.
- □ The screw is removed within 2 years after its insertion in order to cause only temporary growth arrest.
For more severe deformities a supramalleolar varus internal rotation osteotomy is indicated.
If valgus of the hindfoot is also present, a medial sliding osteotomy of the calcaneus may also be required.

Supination and Forefoot Adduction Deformities

Supination deformity, which is often associated with
adduction deformity of the forefoot, is caused by the unopposed action
of the tibialis anterior when the peroneus brevis and longus are
paralyzed. This occurs in children with an L5-S1 level.

For supple deformity, tenotomy of the anterior tibial tendon is recommended.
For patients who are able to walk without
an orthosis, the anterior tibial tendon can be transferred to the
lateral cuneiform but split transfer is not recommended.
When the deformity is fixed, tendon
transfer or tenotomy, along with a plantar closing wedge of the medial
cuneiform is performed to plantarflex the first ray and realign the
forefoot.
If the supination deformity is more severe, a midtarsal osteotomy is done.

The most common residual deformity is forefoot
adduction. This is often secondary to growth imbalance between the
medial and lateral columns.

Surgical correction is achieved with
medial opening and lateral closing wedge osteotomies with an abductor
hallicus and plantar fascia release.

Varus and Cavovarus Deformities

A cavovarus deformity is seen primarily in patients with
sacral-level lesions. Cavus is the primary deformity, and the varus is
caused by the cavus.

The Coleman block test is used to determine the rigidity of the deformity.
For a supple deformity, a plantar release can be performed without hindfoot surgery.
For a rigid deformity, plantar release, midtarsal or first metatarsal osteotomy, and calcaneal osteotomy are often required.
Postoperatively, a short leg cast is worn for 6 weeks followed by day and nighttime bracing.