Conditions

, Ratna Maheshwari² and Shalin Maheshwari²

(2)

Pediatric Orthopedics, Childrens’ Orthopedic Centre, Mumbai, India

Take-Home Message

Supplementation with folic acid decreases the risk of myelodysplasia, but only if taken in the first weeks following conception.
Serial neurologic examinations are critical. Changes in strength and/or spasticity are early signs of a tethered cord.
Prior to kyphectomy surgery, ventriculoperitoneal (VP) shunt function must be checked. It must be patent and functioning or the patient must be shunt independent.
Hip dislocations in children with myelodysplasia rarely require treatment.
Fusions should be avoided during foot surgery to decrease the risk of pressure sores.
Prenatal diagnosis via maternal serum α-fetoprotein is 60–95 % accurate.
L4 level or lower (active quadriceps) is considered necessary for community ambulation.

Definition

Myelodysplasia is part of a spectrum of deformities resulting from failure of closure of the neural tube late in the first month following conception.

Etiology

Multifactorial pattern of inheritance.
Environmental factors include genetic, geography, and drugs (valproic acid and carbamazepine).
History of previously affected pregnancy, low folic acid intake, pregestational maternal diabetes, high maternal alcohol intake.

Pathoanatomy

Lesions can occur at any level along the spinal column but predominate in the lumbosacral area. The next most common site is the cervical spine.
The basic deformity of myelomeningocele is an open neural placode, which represents the embryologic form of the caudal end of the spinal cord. A narrow groove passes down the placode in the midline. This represents the primitive neural groove and is directly continuous with the central canal of the closed spinal cord above (and occasionally below) the neural placode.

Classification

Spina bifida may be subdivided into:

Spina bifida cystica, where there is a visible cyst present
Spina bifida occulta, where the defect is hidden but may be suspected because of the presence of a dimple, a patch of hair, pigmentation, or a lipoma

Types of spina bifida cystic
Myeloschisis – The vertebral arches are deficient with neural plate material spread out in the surface, commonly over a cystic swelling of the meninges.
Myelomeningocele – This is a cystic swelling lined by dura and arachnoid, protruding through a defect in the vertebral arches. The spinal cord and nerve roots are carried into the fundus of the sac.
Meningocele – It is a cystic swelling of dura and arachnoid, protruding through a defect in the vertebral arches under the skin. The cord is confined within the vertebral arches.

Evaluation

Antenatal diagnosis:

Maternal serum alpha-fetoprotein is usually tested routinely as a screening test between the 16th and 20th week of pregnancy.
Ultrasound at 16–18 weeks identifies virtually all anencephalics and over 80 % of spina bifidas.

Assessment of neurosegmental levels: (Table 1)

Table 1

Motor level and functional status for myelomeningocele

Lesion level	Muscle involvement	Function
Thoracic	No active movement of limbs	Sitter
L1	Iliopsoas grade 2 or better	Wheelchair dependant
L2	Iliopsoas, sartorius, and adductors grade 3 or better	Possible household ambulators with RGO
L3	Quadriceps grade 3 or better	Household/community ambulator with KAFO or AFO
L4	Medial hamstring or tibialis anterior grade 3 or better	Significant difference between L3 and L4 level, medial hamstring needed for community ambulation
L5	Lateral hamstrings grade 3 or better + criteria for L4	Community ambulators as adults, wheelchair for long distances
	Gluteus medius grade 2 or better
	Peroneus tertius grade 4 or better
	Tibialis posterior grade 3 or better
Sacral	Quadriceps and gluteus medius function	Community ambulator with AFO, UCBL, or none
High sacral	No gastrosoleus strength	Community ambulator with AFO, UCBL, or none. May have gluteus lurch and excessive pelvic obliquity and rotation during gait
Low sacral	Good gastrocnemius-soleus strength, normal gluteus medius, maximus	Walk without AFO, gait close to normal

RGO reciprocating gait orthosis, UCBL University of California/Berkeley Lab (orthosis), KAFO knee-ankle-foot orthosis, AFO ankle-foot orthosis, HKAFO hip-knee-ankle-foot orthosis

Treatment

Walking ability is related to level of paralysis, knee flexion deformity, mental status, family compliance, and gait training. It is not related to hip reduction status.
The long-term medical and skeletal issues associated with myelodysplasia are often best addressed by multidisciplinary teams.
- Nonsurgical treatment
  
  Frequent skin checks for pressure sores.
  
  Well-fitting braces and wheelchairs are important because these patients often have significant sensory deficits.
  
  Rehabilitation efforts should include early mobilisation, PT, bracing, and functional wheelchair fitting.
  
  Bracing – Hip-knee-ankle-foot orthoses (HKAFOs), knee-ankle-foot orthoses (KAFOs), or AFOs are frequently used to support stance and/or to prevent contracture.
- Surgical
  
  Spine – Neurosurgeons perform closure of myelomeningocele within 48 h with a shunt for hydrocephalus. Later issues can develop with the shunt, a tethered cord, or syrinx, so diligent neurologic examinations need to be repeated and documented.
  
  Tethered cord can cause progressive scoliosis, change functional levels, or cause spasticity.
  
  Syrinx, shunt problems, or new hydrocephalus can cause new upper extremity symptoms such as weakness or increasing spasticity.
  
  Arnold-Chiari malformation is often addressed with shunting in infancy but may require later decompression.
  
  Scoliosis and kyphosis may be progressive. Ninety per cent of patients with thoracic myelodysplasia may require kyphectomy and posterior fusion. Prior to kyphectomy, it is important to check shunt function, because shunt failure can result in acute hydrocephalus and death when the spinal cord is tied off during the kyphectomy.
  
  Scoliosis may cause suprapelvic obliquity increasing the risk of decubitus ulcer formation, sitting problems, and impaired hand function. Severe or progressive deformity must be corrected and the pelvis must be levelled to distribute skin loading evenly under the pelvis.
  
  Poor soft-tissue coverage, contractures, impaired sensation, fragile bone, and deficient posterior elements complicate treatment. Pseudoarthrosis rates are decreased with combined anterior-posterior fusions and rigid segmental instrumentation.
- Hip
  
  Flexion contractures are common but are often not severe. If the contracture is >40° in patients with lower lumbar level involvement, they may require flexor release.
  
  Hip dysplasia and/or dislocation – Currently, the trend in treatment is not to reduce a dislocated hip in any child with myelodysplasia, as the recurrence rate is high.
  
  Operative indications include painful dysplasia in the ambulatory patient and fixed pelvic obliquity, which makes sitting difficult or skin care unmanageable.
- Knee
  
  Flexion contracture >20° should be treated with hamstring lengthening, capsular release, and/or distal femoral extension osteotomy. There is, however, a significant rate of recurrence after extension osteotomy in growing children.
  
  Extension contracture can be treated with serial casting or V-Y quadriceps lengthening.
  
  Knee valgus, often with associated external tibial torsion and femoral anteversion, is common in patients with midlumbar level involvement because they lack functional hip abductors and have a significant trunk shift when walking with AFOs. This can be addressed by the use of KAFOs or crutches with AFOs.
  
  External tibial torsion can be addressed with a distal tibial derotational osteotomy.
- Foot
  
  About 30 % of children with myelodysplasia have a rigid clubfoot. This deformity in myelomeningocele patients is truly teratologic, in that the deformity is nearly always rigid, with less propensity to respond to conservative treatment; requires extensive surgery to correct; and is likely to recur. It can be initially managed with serial casting. It may need extensive posteromedial release, in addition to bony procedures or salvage procedures like talectomy.
  
  With surgical treatment, a portion of the tendons (e.g. Achilles, posterior tibialis, FHL, flexor digitorum communis [FDC]) may be resected rather than lengthened to decrease the risk of recurrence.
  
  Calcaneus foot position can occur with unopposed tibialis anterior (L3–L4 level). Manage with an orthotic, anterior tibialis and ankle release, tenodesis of the tendoachilles, or transfer of the anterior tibialis to the Achilles tendon.
  
  Equinovarus, equinus, and calcaneal foot deformities often are best treated with simple tenotomy rather than tendon transfer, achieving a flail but braceable foot.
  
  Valgus foot deformities are common in L4–L5 level patients. If surgery is necessary to achieve a plantigrade foot, fusion should be avoided to maintain foot flexibility and to decrease the risk of pressure sores.
  
  Planovalgus foot is best managed by calcaneal lengthening, which provides correction and maintains foot mobility.
  
  Vertical talus deformities require operative correction during the first year. Correct with a single-stage procedure.
  
  Cavus deformity often causes skin breakdown and significant disability. Manage in two stages. First perform a plantar medial release. Follow with osteotomies and tendon transfers to maintain correction.
  
  Toe deformities include dorsal bunion, clawing, or simple flexion deformities. Manage by releases and osteotomies to preserve function. Avoid fusions when possible.
  
  Ankle valgus is secondary to a triangular distal tibial epiphysis. Manage by placing a medial malleolar screw that restricts medial physeal growth to correct the valgus. A valgus deformity at the end of growth may require a distal tibial osteotomy for correction.

Complications

Pathologic fractures may follow minimal trauma, manipulative treatments, or operative procedures. Pathologic fractures may be confused with osteomyelitis.
Cord tethering is suggested by loss of function, increasing deformity, or pain.
Skin breakdown includes sacral decubitus and foot ulcers. Reduce risk by correcting rigid foot deformities and severe pelvic obliquity.
Latex allergy occurs in about 5 % of patients.