Chapter Outline
Myelomeningocele
Other Forms of Spinal Dysraphism
Spinal Muscular Atrophy
Myelomeningocele
Management of a child with myelomeningocele is one of the most challenging tasks faced by pediatric orthopaedic surgeons. *
* References .
Typically, patients with myelomeningocele are referred to as having what is termed spina bifida, but a more specific definition of terms is in order. Myelomeningocele is one of the more severe forms of what is termed spinal dysraphism, which also includes meningocele, lipomeningocele, and caudal regression syndrome (or lumbosacral agenesis). Neural tube defects is another collective term, encompassing the disorders of anencephaly, myelomeningocele, and encephalocele.Spina bifida occulta is the mildest form of spinal dysraphism; this condition can be a simple radiographic curiosity or an incidental finding of incomplete formation of the posterior arch of the spinal column, usually identified in the lower lumbar or sacral spine. Typically, neither the overlying skin nor the underlying neural elements are affected, and the patient is otherwise completely normal clinically and on imaging studies. In an occasional patient, spina bifida occulta may be associated with an overlying sinus, fatty deposit, or hemangioma. In these cases, there may be associated myelodysplasia that requires further investigation, typically consisting of magnetic resonance imaging (MRI) of the spinal cord.
Meningocele is a condition in which the meninges are exposed in a saclike protrusion, almost always posteriorly, but rarely anteriorly or laterally. Because of the risk of breakdown of the meninges and secondary infection of the central nervous system (CNS), surgical repair is usually required. This lesion may be present in the cervical, thoracic, lumbar, or sacral spine. When located at the base of the skull, it is usually referred to as an encephalocele. In meningocele, there is typically no involvement of the neural elements (i.e., no myelodysplasia), so there is usually no associated bowel, bladder, or lower extremity paralysis. Affected patients do have a higher than average risk for congenital vertebral anomalies, progressive noncongenital scoliosis during growth, or the development of tethered cord syndrome, presumably because of scarring in the meninges; as a result, they require monitoring during growth.
Myelomeningocele (spina bifida, or sometimes meningomyelocele) is a severe developmental anomaly characterized not only by exposure of the meninges but also by myelodysplasia of the underlying neural elements and CNS malformation. Dysplasia of the spinal cord and nerve roots results in bowel, bladder, motor, and sensory paralysis distal to the malformation in most patients. Patients with myelomeningocele often have other lesions of the spinal cord, such as diastematomyelia and hydromyelia, which may be found at sites remote from the myelodysplastic lesion itself. Structural abnormalities of the brain cause hydrocephalus in most patients, potentially compromising neurologic function at yet another level.
Myelomeningocele is a multisystem disorder that demands a coordinated approach from numerous health disciplines to maximize each patient’s potential. The orthopaedist should remember that the patient’s neurologic dysfunction is rarely limited to the level corresponding to the site of the spinal column dysraphism. Untreated hydrocephalus, Arnold-Chiari malformations, ventricular shunt revisions, CNS infections, and scarring of the residual spinal cord (tethered cord syndrome) may all compromise what would otherwise be considered a stable neurologic disorder. The orthopaedic surgeon should always document the level of neurologic function, and any loss of function should be evaluated.
Incidence
The incidence of myelomeningocele varies around the world. †
† References .
Regional and national variations may be the result of different genetic compositions among different populations, as well as environmental factors. The birth prevalence rate of myelomeningocele from 1983 to 1990 for 16 states in the United States was 4.6 cases/10,000 live births. Prevalence by individual state varied from 3.0/10,000 in Washington to 7.8/10,000 in Arkansas. The ratio of affected females to males was 1.2:1; this slight female predilection has been noted in other studies.The incidence of infants born with neural tube defects has been decreasing. ‡
‡ References .
Some of this decrease may be the result of natural or unidentified causes, but two identifiable factors also appear to play a role. The more important factor is prenatal screening using ultrasonography, measurement of the maternal serum alpha-fetoprotein (AFP) level, or both, and elective termination of affected pregnancies. AFP is a protein normally present in fetal tissues and amniotic fluid from weeks 6 to 14 of gestation. With closure of the abdominal wall anteriorly and the neural tube posteriorly, AFP is no longer released into the amniotic fluid, so amniotic AFP decreases to undetectable levels. If the neural tube or abdominal wall remains open, AFP remains detectable in amniotic fluid and maternal serum. A maternal serum AFP screening program has reportedly reduced the birth incidence of neural tube defect by 80% in Scotland. Other studies of AFP screening programs have reported a decrease in the birth incidence of anencephaly (by 96% to 100%) and myelomeningocele (by 60% to 82%).The second factor in the decrease of neural tube defects is the administration of folate to women before and during pregnancy. §
§ References .
It has been demonstrated that adequate intake of folic acid periconceptionally can reduce the incidence of neural tube defects by 50% to 70%. The incidence of neural tube defects in the United States decreased 36% after the U.S. Food and Drug Administration (FDA) mandated folate fortification in all standardized enriched cereal grain products in 1998.Embryology
In the embryo, the CNS begins as a dorsal focal thickening caused by the proliferation of ectodermal cells. These cells increase in number and in height, ultimately forming a layer of pseudostratified epithelium. As the cells proliferate, a groove forms in the sagittal plane of the cell mass. This groove deepens, bringing the lateral portions of the neural plate toward each other. Contractile proteins located within the superficial margin of these cells are thought to be responsible for the actual contraction and drawing together of the neural folds. Progressive flexion brings the peripheral edges of the neural folds into contact. On about day 21, cell adhesion occurs at the point of contact, fusing the neural folds into the neural tube. Initially, fusion occurs near the center of the embryo at a point destined to become the craniovertebral junction. Fusion then proceeds longitudinally in both directions, forming the long neural tube. The cephalic (brain) end of the embryo closes first.
As the neural folds fuse to form the neural tube, the superficial ectoderm separates from the underlying (now fused) neural ectoderm and fuses with itself across the midline to close the back. The separation of superficial and neural ectoderm creates a plane into which mesenchymal cells migrate. This mesenchyma gives rise to the neural arch of the vertebrae and to paraspinal muscles. Closure of the neural ectoderm into a tubular structure and separation of the neural tube from the superficial ectoderm are critical events in the development of the CNS, and they are completed by 4 weeks after fertilization ( Fig. 36-1 ).
Causative Factors
The embryonic origin of myelomeningocele likely stems from developmental abnormalities occurring at 26 to 28 days of gestation, during the phase of closure of the neural tube. Abnormalities that develop during this process are termed neurulation defects and include myelomeningocele and anencephaly. Abnormalities arising in the next phase (canalization), from 28 to 48 days of gestation, are termed postneurulation defects and include meningocele, lipomeningocele, and diastematomyelia. Although considerable insight into normal tube closure and the factors that can disrupt this process has been gained in recent years, the exact mechanisms whereby human myelomeningocele and anencephaly arise remain elusive.
Morgagni is often credited with developing the theory that myelomeningocele results from rupture of the distal end of the neural tube. According to his theory, when cerebrospinal fluid (CSF) cannot escape from the ventricular pathways, it flows instead into the central canal of the neural tube, distends the tube, and bursts it open at the distal end, creating the myelomeningocele. It appears unlikely that Morgagni actually developed this theory because the pathophysiology of CSF flow was not understood at that time (1769). Morgagni’s real contribution was to note an association between hydrocephalus and spina bifida. A different mechanism for the development of myelomeningocele was postulated by Gardner. He thought that intrauterine hydrocephalus caused the distal end of the neural tube to rupture, producing myelomeningocele.
It was von Recklinghausen who postulated that myelomeningocele resulted from failure of the neural tube to close. This view was supported by Patten, who showed that overgrowth of the neural tube in embryos implied lack of closure or interference with closure of the neural tube.
As has been proven over time, myelomeningocele can be produced by interference with closure of the neural tube and by rupture of the already closed neural tube. Distention and rupture of the developing spinal cord in mouse embryos can be caused by poisoning the pregnant mouse with vitamin A. Thus primary failure to close and secondary rupture of the closed neural tube are possible causes of myelomeningocele.
Folate
Although several factors contributing to the development of myelomeningocele have been proposed in the literature, the most important one identified is the association between folate deficiency in pregnant women and an increased risk of neural tube defects, including myelomeningocele, in their offspring. One study that compared mothers of children with neural tube defects, mothers of children with other abnormalities, and mothers of normal children found no difference in folate intake during pregnancy among the groups. Most studies, however, have demonstrated a 60% to 100% reduction in the risk of neural tube defects with the administration of adequate levels of folate to pregnant women. ‖
‖ References .
The U.S. Public Health Service recommends that all women of childbearing age who are capable of becoming pregnant should consume 0.4 mg of folic acid/day to reduce the risk of having a child affected by spina bifida or other neural tube defect. Total folate consumption should normally be less than 1 mg/day.Heredity
Genetic factors also appear to play an important role in myelomeningocele. Genetic studies have investigated the possible role of cell adhesion molecules in neural tube formation and closure. Variations in these molecules may influence the risk for human neural tube defects. There is a significantly greater incidence of neural tube defects, including myelomeningocele, in the siblings of children affected with anencephaly or myelomeningocele than in the general population; the familial incidence of major neural tube defects has been reported as 6% to 8%. ¶
¶ References .
For a couple with one affected infant, the risk of subsequent siblings incurring a major CNS malformation is approximately 1 in 14.The exact nature of this increased familial incidence is not understood. An overall prevalence of 21.4% compared with 4.5% in adult controls was reported in one study. The risk is higher in larger families and in specific socioeconomic and geographic groups. Thus families with a history of neural tube defects should be counseled about this potential development, and pregnancies should be screened (see earlier, “Incidence”).
Pathology
A thorough description of the pathologic findings of myelomeningocele was provided in 1886 by von Recklinghausen, who accurately dissected the spinal cord and meninges in cases of myelomeningocele and recognized every variety of spina bifida. 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 (usually as an encephalocele or meningocele only), and a smaller number of lesions are scattered along the thoracic spine. The great majority of lesions are posterior, but a rare anterior or lateral meningocele may be encountered. In this case, the anterior cyst protrudes through the vertebral body, not through the vertebral arch.
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. CSF passes down the central canal of the spinal cord and discharges from a small pit at the upper end of the placode to bathe the external surface of the neural tissue. This fluid does not indicate rupture of the myelomeningocele.
Skin
Skin is almost always absent over the myelomeningocele sac. Between the edge of the skin and neural placode is a zone of thin epithelium. At points, skin may actually reach the edge of the neural placode. In the usual type of lesion, there is a raised mass on the back covered laterally at its base by normal skin, but the apex of the mass is devoid of skin ( Fig. 36-2 ); it is covered by a paper tissue–thin membrane (arachnoid) through which nerve roots can be seen. Within 1 or 2 days, this tissue breaks down to an ulcerated granulating surface. The lesion may heal over completely by epithelial growth from the periphery. Usually, however, the mass sloughs from secondary infection, which, without intervention, usually leads to meningitis and death. Hemangiomatous or other pigmented lesions are frequently seen in the skin surrounding the sac.
Meninges
Underlying the neural placode is the arachnoid sac and subarachnoid space. Because the superficial (dorsal) surface of the neural placode represents the everted interior of the neural tube, the deep (ventral) surface represents the entire outside of what should have been a closed neural tube. Thus the ventral and dorsal nerve roots arise from the deep (ventral) surface of the neural placode and pass through the subarachnoid space to their root sleeves. Because the placode is everted, the two dorsal roots are lateral to the two ventral roots.
Within a few millimeters of the edge of the skin is the junction between the skin and dura mater. Outside the dura mater is a true epidural space that contains epidural fat. The underlying vertebral bodies are flattened and widened. The pedicles are everted and lie almost horizontal in the coronal plane. The laminae are hypoplastic and often everted. The spinous processes are absent. The paraspinal muscle masses are present but are everted with the pedicles and laminae; thus they lie anteriorly and, as a result, often act as flexors of the spine instead of extensors. The muscles may be markedly attenuated because of the lack of innervation from the CNS.
The size of the sac on the child’s back at the time of birth depends on the amount of spinal fluid that has collected ventral to the neural placode.
Spinal Cord
Dysplasia of the spinal cord is invariably present. The cord may be (1) cystic or cavitated, (2) solid but degenerated and disorganized, or (3) grossly proliferated. Frequently, all these features are found together in varying degrees.
Peripheral Nerve Roots
Peripheral nerve development is not affected in myelomeningocele. At surgery and on dissection of postmortem specimens, normal peripheral roots are found in every case. However, inside the dura mater, the roots appear to have tenuous connections with the cord itself and are occasionally hard to identify.
Vertebrae
The principal defect is the arrested development of the posterior elements (laminae and spinous process). The posterior elements may be completely absent, in which case the pedicles alone are present, or there may be partial lamina formation. In the latter case, the intraspinal canal is widened as a result of lateral displacement of the pedicles on the vertebral bodies.
Brain
There may be associated anomalies of the cerebellum and brainstem (Chiari type II deformity) in which the posterior lobe of the cerebellum, medulla, and fourth ventricle have herniated through the foramen magnum into the cervical spinal canal ( Fig. 36-3 ). Rarely is a Chiari I deformity seen in myelomeningocele. In the more severe Chiari type III malformation, the entire cerebellum and lower brainstem are inferior to the foramen magnum. Hydrocephalus develops from the obstruction of CSF flow at the roof of the fourth ventricle because of dislocation of the ventricle, occlusion of the subarachnoid space at the site of herniation, occlusion of the same space at the tentorial level by adhesive arachnoiditis, or associated aqueduct stenosis. Other causes of hydrocephalus in myelomeningocele are the Dandy-Walker malformation, which consists of marked distention of the fourth ventricle from occlusion of the foramina of Luschka and Magendie, and so-called forking of the aqueduct of Sylvius, in which the aqueduct is represented by two narrow channels situated in a sagittal plane. Radiologic studies of CSF dynamics in children with hydrocephalus have shown increased production of CSF. Secondary changes in the brain develop as a result of increased pressure caused by the hydrocephalus.
Natural History
Before the introduction of the Holter valve for the shunting of hydrocephalus and adequate closure of the myelodysplastic lesion, death frequently occurred in infancy because of hydrocephalus or sac breakdown followed by meningitis; survivors usually died from renal failure (55 of 57 in one study). Shunting of the hydrocephalus combined with sac closure led to a significant increase in survival but resulted in a large number of severely handicapped children. This led to the introduction of selection criteria to determine which infants should receive aggressive surgical care. Specific criteria against aggressive surgical treatment of patients born with myelomeningocele were proposed by Lorber after a review of 524 cases. He found that the presence of severe paralysis (upper lumbar or higher), head circumference at or above the 90th percentile, congenital kyphosis, other major congenital anomalies such as heart disease, and severe birth injury were associated with a significantly greater likelihood of death in infancy or severe handicaps in survivors. These factors became known as Lorber’s criteria, and their presence at birth was taken as a contraindication to aggressive surgical intervention.
However, other studies have noted that the level of paralysis is not an indicator of survival in patients who are not treated surgically. At present, most U.S. centers do not have specific criteria for early surgical treatment, and the parents of all affected infants are offered surgical closure of the sac, followed almost invariably by ventriculoperitoneal shunting.
Fetal surgery for myelomeningocele was first performed in 1997 in the hope that intrauterine repair of the defect would result in less hindbrain herniation and improved mental and motor function. The Management of Myelomeningocele Study (MOMS) was a randomized, multicenter, fetal surgery study started in 2003. The study was stopped after enrollment of 183 of the planned 200 patients because of the efficacy of prenatal surgery in decreasing the need for shunt placement at 1 year and improving mental and motor function at 30 months. Prenatal surgery was also associated with an increased risk of preterm delivery and uterine dehiscence. Despite this landmark study, fetal surgery for myelomeningocele remains controversial, both ethically and clinically.
Prognosis
Although most infants with myelomeningocele survive and most of these children can attend regular school, a recent study of adults with spina bifida demonstrated low rates of employment and independent living.
Gross motor function in patients with myelomeningocele has been studied extensively. Numerous studies have addressed factors affecting the short- and long-term potential for ambulation. # The single most important physical factor for maintaining ambulation in adulthood seems to be the strength of the quadriceps muscle. Most patients with a lower lumbar (L4 or L5) or sacral lesion are community ambulators (95%); those with higher levels affected (thoracic) usually are not (<24%). Additional factors in nonambulation are obesity, hip deformity, scoliosis, foot and ankle deformity, and age.
# References .
Schopler and Menelaus found that only 4 of 51 patients with normal quadriceps strength in the first 3 years of life demonstrated deterioration in strength over time. Most patients (21 of 22) initially assessed as having at least grade 4 strength improved, but none of the patients with less than grade 4 strength improved. Quadriceps strength was strongly correlated with ambulation ability—98% with grade 4 or 5 quadriceps strength were at least household ambulators, and 82% were community ambulators; in contrast, 88% with grade 0 to 2 quadriceps strength were nonambulatory. McDonald and colleagues reported that the strength of specific muscle groups predicted 86% of the mobility outcome. All patients with an iliopsoas strength of grade 3 or less relied on wheelchairs for some or all of their mobility, whereas none of those with an iliopsoas strength of grade 4 or 5 relied solely on wheelchairs. Patients with good iliopsoas and quadriceps strength and antigravity gluteal strength could be expected to ambulate without a wheelchair, and those with grade 4 or 5 gluteal and tibialis anterior strength usually walked without aids or braces.Associated Health Problems
General or Universal Problems
Inexperienced physicians may be led to believe that myelomeningocele represents a congenital lower extremity paralysis that can be characterized by the level of the lesion, with a readily definable border between functioning and nonfunctioning motor and sensory root levels and a predictable lower extremity and overall patient function to match. It must be noted that myelomeningocele is a complex congenital anomaly that is often dynamic and changing in its neuromuscular components, affecting the patient’s mobility capabilities and orthopaedic surgery requirements. In addition, patients typically have bowel and bladder paralysis, CNS anomalies (especially hydrocephalus), and congenital anomalies of the spine and lower extremity, all of which confound the clinical picture. Neurologic function can change over time as a result of unchecked or complicated hydrocephalus or scarring of the spinal cord. The most important organ systems requiring management in these patients, in addition to the musculoskeletal system, are the neurologic, gastrointestinal, and genitourinary systems.
Upper Extremity Function
Upper extremity function is often disturbed in patients with myelomeningocele (92%). * a
References .
Upper extremity dysfunction can be secondary to neurologic impairment by hydrocephalus, brainstem compression by the Arnold-Chiari malformation, hydromyelia involving the cervical spinal cord, or cerebral insult caused by the placement of ventricular shunts or infection of these shunts. Patients with higher lesions (thoracic or upper lumbar) and patients who have undergone more than three shunt operations are more likely to have abnormal hand function, although one study found no correlation with the level of the myelodysplastic lesion. Upper extremity dysfunction can take the form of spasticity, ataxia, dyspraxia, or a combination of these. The presence of spasticity may be particularly important because patients with upper extremity spasticity are less likely to be independent in activities of daily living (ADLs). Decreased grip strength also is common. Several authors have noted that hand function can improve over time in school-age children. An assessment of hand function by therapists and orthopaedists is important to establish appropriate goals for ADLs, classroom performance, and the need for mobility aids.Early Puberty
Girls in particular are at risk for the development of early or precocious puberty, thought to be related to increased intracranial pressure and a higher incidence of shunt malfunctions and revisions. Furman and Mortimer noted that girls with myelomeningocele began menstruating at an average age of 10 years, 3 months, significantly younger than their mothers, siblings, and the U.S. mean.
Cognitive Problems
Cognitive learning difficulties are regularly reported in patients with myelomeningocele, particularly those requiring shunts. Thus difficulties at school should be assessed and addressed by the health care team caring for the patient. Performance level tends to improve with increasing age, emphasizing the importance of monitoring the overall health and neurologic function of the child. Children with myelomeningocele tend to have difficulty adjusting to their nondisabled peers, and those with myelomeningocele and normal IQs have a higher rate of psychosocial maladjustment than mentally disabled children in mainstream schools. Rüdeberg and associates emphasized the importance of coordinated, aggressive rehabilitation if these children attend regular schools. One study noted poorer school performance in ambulatory patients, suggesting that the energy devoted to ambulation by children not using a wheelchair impairs their intellectual performance in school.
Psychosocial Implications
The impact of myelomeningocele on the patient, family, and community health care system is significant. †a
†a References .
Appleton and colleagues noted that children with myelomeningocele aged 9 to 18 years were at greater risk for depressive mood, low self-worth, and suicidal ideation. Girls were more effected than boys, and self-evaluation of physical appearance was associated with depressive symptoms. A study of a large Scandinavian myelomeningocele population found that families with children with myelomeningocele coped surprisingly well compared with control families. However, responsibility for care of the disabled children fell largely to the mothers, who were less likely than controls to think that they were receiving adequate support. Both parents reported more frequent absences from work than controls. Mothers of children with myelomeningocele were significantly less likely to work outside the home. These findings were not related to the severity of the children’s disabilities. A study by Holmbeck and colleagues found that families with the least physically impaired children reported the most family difficulties.Specific Problems by Spinal Level
Thoracic Level
Patients with thoracic level lesions essentially have flail lower extremities and, based solely on the limbs’ total flaccid paralysis, would not be expected to develop muscle imbalance–induced lower extremity deformities. In fact, however, a frog-leg deformity is frequently present in these patients at birth, characterized by hip flexion, abduction, and external rotation contractures. In addition, there may be knee flexion and ankle equinus contractures. These may respond to judicious passive manipulation, but the hip contractures often do not respond adequately to this treatment, and the surgeon is faced with the decision whether to release the contractures to allow the lower limbs to be placed in a position for upright mobility. Occasionally, these patients develop secondary flexion deformities from spasticity in their lower extremities, which is actually presumed to be involuntary reflex motor function below the level of the myelodysplastic cord lesion. The most frequent deformities encountered by the orthopaedic surgeon in this patient group are spinal—congenital scoliosis, developmental scoliosis, and progressive congenital kyphosis.
Many patients with thoracic level lesions can achieve exercise or household ambulation as young children. All require extensive bracing above the hip and upper extremity aids (walker or crutches), and they ambulate with a swing-through gait using their upper extremities and abdominal muscles. The family must be aware that for most of these patients, this is a temporary capability. Because of the energy expenditure required for such ambulation, most patients ultimately choose to use a wheelchair full time, except for transfers. ‡a
‡a References .
Charney and co-workers found that compliant parents, physical therapy, and the absence of mental retardation were the most important factors in predicting community ambulation in children with thoracic lesions, whereas scoliosis and hip surgery were not factors. Swank and Dias found that 24% of patients with thoracic lesions were community ambulators, 41% were household ambulators, and 35% were nonambulatory (accounting for all but one of the nonambulators in the entire population); of these, 70% had associated orthopaedic defects at birth, most commonly clubfeet, kyphosis, hip dislocation, and knee flexion deformity.Upper Lumbar Level
Patients with upper lumbar lesions have hip flexor power and some adductor power, but no motor control of the knees or feet. For the most part, their ambulation potential and needs parallel those of patients with thoracic level function; theoretically, however, they may be more efficient walkers as children because their hip flexor and adductor strength can be recruited to provide a better swing-through gait or, with the use of a reciprocating gait orthosis (RGO), a reciprocating gait (see later, “Orthotic Management”). This iliopsoas strength is usually not sufficient in adolescence and adulthood, when the natural history resembles that of patients with thoracic lesions, in that they rarely continue to ambulate as adults. §a
§a References .
Hoffer and colleagues, however, found no differences in ambulation between adult patients with upper and lower lumbar lesions. Patients in this group experience significantly more paralytic hip dysplasia and dislocation because of imbalance at the hip, with hip flexors and adductors present, but no hip extensors or abductors.Lower Lumbar Level
Patients with lower lumbar lesions have greater hip adductor strength and, more importantly, quadriceps power to provide active knee extension. Those with L5 functioning have a functioning tibialis anterior, and they may have medial hamstring function as well. Hip strength is usually adequate to allow these patients to walk with the hips unbraced—that is, with knee-ankle-foot orthoses (KAFOs). Their gait exhibits a compensatory combined maximus-medius lurch (the limb in external rotation, and a backward and lateral lean of the trunk over the hip to stabilize it in stance). Some patients may be able to walk with only ankle-foot orthoses (AFOs); however, weakness of the foot, ankle, and hip abductors and extensors leads to a lurching gait that imposes a great deal of stress on the unbraced knee. These patients are also at high risk for the development of progressive hip subluxation and dislocation. Surgical treatment of the hip is most controversial in this group of patients in terms of its influence on the preservation of long-term ambulation. ‖a
‖a References .
In the childhood population studied by Swank and Dias, 33 of 36 patients (92%) were community ambulators, and the other 3 (8%) were household ambulators. Factors that led to decreased ambulation included deterioration of the neurologic level of the lesion, spasticity, knee and hip flexion contractures, and lack of motivation. Clubfeet and hip dislocation are also frequent in this group.Sacral Level
Patients with sacral level myelomeningocele have near-normal knee function and more stable hip, foot, and ankle function. Their partial paralysis and insensate skin can lead to a number of foot problems, however, including cavovarus deformity, claw toes, and neurogenic ulcers. ¶a
¶a References .
Hip subluxation can occur but is less frequent than in those with lumbar lesions. Knee problems can be associated with torsional or angular stress during ambulation. Excessive ankle dorsiflexion or external rotation may make ankle orthoses difficult to fit or ineffective in stabilizing the ankle. In theory, most sacral level patients could ambulate without orthoses but, in practice, weak gastrocnemius and foot intrinsics result in abnormal foot and ankle function; gait studies have demonstrated that even patients with sacral level myelomeningocele ambulate most effectively with AFOs and crutches because of stresses at the knee and weakness in the foot and ankle.Long-term reviews of patients with sacral level paralysis are a sobering reminder of the multifactorial risk of losing neurologic function and mobility. Brinker and colleagues found that the ability to walk had declined in 11 of the 35 community ambulators (average age, 29 years), and a household ambulator had become nonambulatory; 15 patients had developed osteomyelitis, and 11 required amputations. In Selber and Dias’ report, 41 of 46 slightly younger patients (average age, 23 years) were still community ambulators, but 39 had undergone a total of 217 orthopaedic procedures and 12 had tethered cord release.
Complications
Latex Allergy
Patients with spina bifida are at risk for the development of a serious allergy to latex. #a
#a References .
Contact with latex in sensitized patients may produce local rashes or mucosal irritation.Cardiovascular collapse is the most serious manifestation of latex allergy. About 10% to 15% of patients studied reported a definite allergy to latex. Risk factors for the presence of latex allergy include a history of prior allergic reactions and multiple previous surgeries, particularly urologic and orthopaedic procedures. Sensitivity to latex can be ascertained by a latex skin prick test or an assay for latex-specific immunoglobulin E in serum. However, current practice is to perform surgery and other invasive procedures in a latex-free environment in all patients with myelomeningocele. This can prevent sensitization and, over time, may reduce sensitization in those who were previously sensitized. All personnel involved in the management of a myelomeningocele patient, including parents, nursing staff, anesthesiologist, and surgeon, must be cognizant of the risk of latex allergy or of inducing it in this patient population.
Infection
Patients with myelomeningocele have a higher rate of complications, including postoperative infections, for almost all orthopaedic surgical procedures compared with patients undergoing similar procedures who do not have myelomeningocele. The reason is multifactorial, including poor nutrition, bladder paralysis, absence of protective pain perception, poor tissue perfusion and, in the case of spinal deformity surgery, poor skin condition overlying the lumbar spine.
Bladder paralysis and its management usually lead to the presence of bacteria in the urinary tract. Diminished pain perception and skin insensitivity lead to more frequent wound breakdown and subsequent infection from unrecognized direct compromise of the wound under a cast or from excessive swelling in patients who move, ambulate, or otherwise challenge the operated part in ways that a patient with normal sensation would not.
Pressure Sores
Patients with myelomeningocele invariably have loss of protective sensation of the lower extremities corresponding to the level of the lesion and, even more importantly, of the buttocks and sacral area. As a consequence, these patients are prone to the development of pressure sores, which may occur on the soles of the feet from walking on bony exostoses or other prominences secondary to deformity or from walking on rough or hot surfaces without adequate foot protection. Patients who crawl may get pressure sores on the dorsum of their foot from similar trauma, especially those with paralytic, uncorrected, or recurrent equinovarus deformity, or in the prepatellar area. The medial malleolus is a common site of pressure sores in patients with valgus deformity of the distal tibia who use AFOs or KAFOs that do not or cannot adequately accommodate the medial malleolar prominence.
Patients who are primarily sitters are especially prone to pressure sores. These can develop in the sacrococcygeal area or over the ischial tuberosities or greater trochanters. Patients with urinary incontinence who cannot stay dry and clean are particularly susceptible to the development of recalcitrant pressure sores, as are patients with pelvic obliquity secondary to asymmetric hip deformity or lumbosacral spinal deformity. Patients whose pelvic obliquity is fixed, such as after spinal fusion to the pelvis, are at a relatively higher risk for the development of sores, and the surgeon must be very careful in the early postoperative period to guard against this complication. Patients with insensate skin over a kyphotic deformity may also develop sores over the apex of the deformity from internal pressure necrosis or from rubbing of the skin against the back of the wheelchair. Many children require special adaptations to their wheelchairs such as custom-molded back supports or Roho cushions (Roho Group, Belleville, Ill.) to distribute weight-bearing forces and prevent excess pressure over bony prominences.
The management of pressure sores involves education of the child and family in prevention techniques, careful postoperative management in at-risk patients, correction of deformities that cause recalcitrant lesions, appropriate brace modifications to prevent the brace from serving as a source of skin breakdown and, as much as possible, a bowel and bladder management protocol that keeps the child dry and clean. This is particularly important in those who are wheelchair-dependent. Patients and their families must be educated to guard against skin contact with rough or hot surfaces, inspect orthoses and wheelchairs for pressure points, and shift and relieve body weight regularly while sitting. Good perineal hygiene is essential. Established pressure sores need prompt and aggressive treatment with weight relief and correction of the source of excessive or constant pressure. Pressure sores that are not treated in this manner can lead not only to extensive soft tissue breakdown and scarring but also to deep recalcitrant osteomyelitis requiring repeated surgical débridement.
When placing patients in casts postoperatively, surgeons must do so with great care and expertise. Cast padding must be evenly and smoothly applied, with bony prominences protected. Similarly, the casting material must be carefully and evenly applied, without any pressure points inadvertently created by fingers indenting the cast or changing the position of the patient’s limb after the padding and casting material have been applied. Lower extremity casts should extend beyond the toes but leave them visible to protect the toes if the patient crawls or strikes them against some hard surface ( Fig. 36-4 ). Similarly, the surgeon must educate the family to watch for sores developing on the dorsum of the toes in a child permitted weight bearing in a cast. As the plantar surface of the cast softens with ambulation, the toes or dorsum of the foot will be pushed against the dorsal surface or edge of the cast. Any undue swelling, erythema, odor, or unexplained systemic reaction is an indication to remove a postoperative cast completely and inspect the surgical wound and limb for evidence of skin breakdown.
Fractures
Patients with myelomeningocele are susceptible to pathologic fractures of the lower extremities, particularly in the supracondylar femoral and supramalleolar tibial regions. Risk factors include inattention toward insensate parts by the patient or caretakers, joint contracture, postsurgical cast immobilization, and higher levels of paralysis. * b
References .
Newborns with higher levels of paralysis and joint contractures are susceptible to birth fractures. Bone mineral density has been found to be lower in patients with myelomeningocele than the normal population; patients with a history of fracture have been found to have bone densities lower than those in patients without a history of fracture. Treatment with hydrochlorothiazide, known to increase bone mineral density in patients with hypercalciuria, did not have a favorable effect on bone mineral density in patients with myelomeningocele.Several precautions should be taken to prevent fractures in this patient population. Caretakers and ultimately the patient must be educated about safe transfer techniques. Any passive manipulation of joint contractures must be gentle, and the proper technique should be taught by an experienced therapist or physician. Patients who must be immobilized postoperatively in a cast should have the affected extremity placed in a functional position to the greatest extent possible, avoiding plantar flexion or excessive knee flexion in particular. Mobilization from the postoperative cast into removable splinting should be done as soon as feasible. The physician and caretakers should be alert to the development of signs and symptoms of fracture after cast removal.
Fractures manifest with localized erythema, heat, and swelling. Crepitus and deformity occur only with displaced fractures. The warmth and swelling and frequent absence of a specific history of trauma often cause an inexperienced physician or caretaker to suspect infection rather than fracture, and this impression may be fueled by a low-grade fever. Although hematogenous osteomyelitis can occur in patients with myelomeningocele, in the absence of direct contamination of the bone by long-standing or extensive pressure sores or surgical intervention, the correct diagnosis is almost always fracture in this clinical scenario. Fractures in patients with myelomeningocele tend to heal rapidly, with abundant callus formation ( Fig. 36-5 ). Fractures do not, however, invariably heal without incident; malunion, delayed union, and physeal growth disturbance have all been reported. Therefore adequate maintenance of alignment and immobilization are required. Physeal fractures may be slow to heal and require reevaluation to detect subsequent growth disturbance.
Immobilization of the limb, whether after a fracture or postoperatively, should be to the minimal extent and shortest duration possible, in a position of function. Protective orthoses should be available when the cast is removed, and cautious range-of-motion and weight-bearing exercises should be initiated under supervision. Failure to follow these principles can lead to a prolonged and frustrating clinical sequence of mobilization after fracture or surgery, juxtaarticular fracture, immobilization, increased osteopenia and joint contracture, mobilization, and repeat fracture.
Treatment
Multidisciplinary Care
The health problems of patients with myelomeningocele encompass many organ systems; their management must be integrated to treat the whole child and provide the family with the necessary support. Thus children with myelomeningocele are best assessed and treated in multidisciplinary clinics. †b
†b References .
Ideally, the clinic should use an administrative or registered nurse coordinator to function as a patient advocate, coordinate the disciplines evaluating the patient, schedule ancillary investigations, and secure the results. This coordinator also ensures that all the patient’s needs are being met over time, including educational, vocational, and sexual counseling. Other health care workers involved with the patient or parents include the following: an orthotist to provide and repair lower extremity and spinal orthoses; a physical therapist to aid in lower extremity functional assessment, bracing needs, and instructions in range-of-motion exercises and mobility; an occupational therapist to assess upper extremity function, adaptations for ADLs, and educational modifications; a nurse to teach the parents and subsequently the child about skin care and self-catheterization; a psychologist to help parents cope with the many challenges and stressors related to their child’s disabilities, ameliorate self-destructive or hostile behavior associated with these disabilities, and address the low self-esteem and peer adjustment issues common in patients with visible disabilities and limited mobility; a urologist to monitor genitourinary function and maximize bladder control; a neurosurgeon who, after closing the myelodysplastic lesion and placing a ventriculoperitoneal shunt in infancy, must monitor for shunt dysfunction and evidence of tethered cord development; a social worker to assist the family in finding financial support and obtaining educational and vocational counseling; and, ideally, an experienced neurodevelopmental pediatrician to oversee the whole process and provide a general assessment of the child’s health.Kinsman and Doehring reviewed the costs and indications for 353 hospital admissions of 99 adults with myelomeningocele over an 11-year period and found that 47% of hospital admissions were for potentially preventable secondary conditions, such as serious urologic infections, renal calculi, pressure ulcers, and osteomyelitis. The results of this study emphasize the need for coordinated care among adults with myelomeningocele and the importance of their continuing education in self-care to prevent such problems. Kaufman and colleagues specifically assessed the impact of the disbanding of a multidisciplinary clinic on the myelomeningocele population. Despite the availability of specialty care in the same area, 66% of patients did not see a physician regularly, and the authors recorded a serious increase in morbidity in the affected patient population, including amputation and nephrectomy. After the closing of the multidisciplinary clinic, no one assumed the duties of coordinator of care.
Neurosurgical Treatment
The neurosurgeon is an important member of the health care team involved in the management of children with myelomeningocele. The initial challenge faced by the neurosurgeon is closure of the myelomeningocele sac; in 70% to 90% of patients, sac closure is closely followed by the need for ventriculoperitoneal shunting. In follow-up, the neurosurgeon is actively involved in identifying and treating shunt malfunction, shunt infection, brainstem compression by the Chiari II (or Arnold-Chiari) malformation, development of hydromyelia within the spinal cord, and tethering of the distal nervous system tissue in scar, producing the so-called tethered cord.
Closure of the Myelomeningocele Sac
Early closure of the sac (within 48 hours) is a cornerstone in the management of children with myelomeningocele. Before this became the standard protocol, death was almost universal secondary to meningitis and ventriculitis. Depending on the extent of the dermal defect and underlying bony deformity (specifically, congenital kyphosis), closure can be achieved by direct approximation of the skin over the defect, with or without undermining of the skin, local rotational flaps, or musculocutaneous latissimus dorsi or gluteus maximus flaps. Defects larger than approximately 18 cm are much more likely to dehisce after primary direct closure, and consultation with a plastic surgeon is generally indicated for the purpose of covering the skin defect with a flap. If required because of the underlying bony deformity, kyphectomy can be safely performed at the time of dural sac closure in neonates, with excellent initial correction. Eventual recurrence of the kyphotic deformity over time should be expected, however, despite the procedure. Fetal closure is discussed in the next section.
Hydrocephalus
The Chiari II malformation, characterized by herniation of the cerebellum and brainstem, is almost universally associated with myelomeningocele. This deformity, especially after closure of the myelomeningocele sac, produces an obstructive hydrocephalus, necessitating ventriculoperitoneal shunting in approximately 70% to 90% of infants. These shunts must be reevaluated periodically by the neurosurgeon to ensure continued function and absence of infection. Despite the presence of a shunt, the developmental delays, learning difficulties, and problems with executive functions are frequently seen in patients with myelomeningocele.
Although many patients have enlarged ventricles at birth, symptomatic hydrocephalus usually develops only after closure of the myelomeningocele sac. Thus many infants undergo closure of the sac within 48 hours of birth, develop hydrocephalus, and then undergo ventriculoperitoneal shunt placement. A study comparing staged and simultaneous sac closure and shunting found that patients treated by the simultaneous technique had a significantly reduced incidence of wound leakage at the closure site and no deleterious effects with respect to shunt failure, hydrocephalus, or CSF infection.
There is increasing evidence that the neurologic deficits in myelomeningocele patients are caused by the primary myelodysplasia compounded by exposure of the neural elements to amniotic fluid in utero. As noted, this led to the development of fetal surgical techniques to close the sac in utero in the hope of limiting the secondary neurologic injury. Preliminary reports in the small group of patients treated in this way have suggested that the need for ventriculoperitoneal shunting is reduced, from 90% to 60%. However, fetal surgery is associated with maternal and pregnancy complications, premature birth chief among them. Brainstem compression, presumably by the Chiari II malformation, can lead to respiratory obstruction and apnea. Sleep disturbances related to air hunger, dyspnea, and squeaky voice may all require assessment by a neurosurgeon for the possible presence of brainstem compression as the cause of these complaints.
Other Spinal Cord Abnormalities
Patients with myelomeningocele are subject to a number of other spinal cord lesions that may require assessment or treatment by a neurosurgeon, including hydromyelia, diastematomyelia, and tethered cord syndrome. ‡b
‡b References .
Hydromyelia (sometimes termed hydrosyringomyelia ) is a dilation of the central canal of the spinal cord. This lesion is often detected as an asymptomatic finding on MRI, but has been implicated in upper extremity weakness or spasticity in some patients; thus patients with these clinical findings should undergo MRI and neurosurgical evaluation. Diastematomyelia is a congenital anomaly of the spinal cord and column consisting of a central splitting of the spinal cord by a fibrous, cartilaginous, or bony spicule (diastematomyelia is also discussed in Chapter 12 ). Myelomeningocele patients with other congenital vertebral anomalies may have an associated diastematomyelia, which should be investigated by MRI if there is hypertrichosis, progressive lower extremity weakness, spasticity, or back pain or if corrective spinal surgery is planned.Tethering of the spinal cord in scar tissue at the site of repair of the initial myelodysplastic lesion may be the source of significant symptoms as the child grows. §b
§b References .
Symptoms attributed to the presence of a clinically significant tethered spinal cord include back pain, especially at the site of sac closure, progressive lower extremity weakness, lower extremity spasticity, progressive foot deformity or scoliosis, and changes in bladder habits and function. Because a low-lying conus suggesting spinal cord tethering is demonstrated on MRI in almost all patients ( Fig. 36-6 ), the diagnosis of tethered cord is usually based on the presence of one or more of the symptoms or signs noted earlier, typical MRI findings, and exclusion of hydromyelia or shunt malfunction as an alternative explanation. Evidence of deterioration in somatosensory evoked potentials or urodynamic testing has been used by some to document symptomatic tethering of the spinal cord.
Sarwark and associates found that back pain resolved after surgical untethering, and curves stabilized or improved in 60% of patients with scoliosis and in 78% of patients with lower extremity weakness. Spasticity was least affected by surgical untethering, improving in only 43% of patients but stabilizing in the remainder. Pierz and colleagues reported that patients with curves less than 40 degrees experienced some improvement after an untethering procedure, but those with curves more than 40 degrees or thoracic neurologic levels had no improvement in scoliosis. McLaughlin and co-workers found that intraspinal rhizotomy and distal cordectomy were effective in ameliorating symptoms and lower extremity deformities caused by spasticity in patients with thoracic lesions. However, this treatment is indicated only for patients with no voluntary lower extremity function and in whom symptoms of spasticity cannot be controlled with lower extremity bracing or surgery.
Urologic Treatment
Bladder paralysis and its attendant medical and social problems are significant issues for affected children and their families. ‖b
‖b References .
Bladder paralysis is almost universal in the myelomeningocele patient population. At birth, this paralysis is usually flaccid, manifesting as uncontrolled constant dribbling of urine. Uncontrolled, spasmodic bladder contractions and bladder neck obstruction commonly develop and can produce overflow dribbling, a smaller, less compliant bladder, and vesicoureteral reflux. Hydronephrosis results, with risk of injury to the renal parenchymal tissue from urinary obstruction or an exacerbating upper urinary tract infection. Lower urinary tract infections are also frequent. In the past, chronic renal failure or fulminant infections of the urinary tract were the most common causes of delayed mortality in patients with myelomeningocele.The goals of urologic management are to make these patients continent, keep them free of lower and upper urinary tract infection, and preserve renal function. The mainstay of management is to teach caretakers—and ultimately the patients themselves—the technique of clean intermittent catheterization. ¶b
¶b References .
Such a program can help prevent the development of hydronephrosis and maintain bladder compliance and capacity. Instituting a clean intermittent catheterization program before 1 year of age may result in fewer patients requiring bladder augmentation to correct loss of bladder compliance. Total continence has not been achieved in most adult studies, but a reduced need for pads and preservation of upper urinary tract function may result from clean intermittent catheterization. Patients also need routine evaluation of the lower urinary tract for evidence of infection, reduced bladder compliance and capacity, and hydronephrosis. Screening examinations, consisting of voiding cystometrography and renal ultrasonography performed every 6 to 12 months, suffice for most patients. Abnormalities may require more thorough urodynamic investigation.The surgical treatment of spinal deformities may influence urinary tract management or function. In one study, eight of nine patients who underwent cordectomy with kyphectomy had improved bladder compliance and capacity postoperatively, but the ninth patient had poorer function secondary to the development of bladder spasticity, requiring surgery. In another study, 6 of 16 patients who underwent spinal surgery had urologic problems postoperatively, including one female patient who could no longer self-catheterize because of a change in body posture. Thus patients undergoing major spinal procedures should have a baseline urologic evaluation, with postoperative reevaluation as necessary.
Orthopaedic Treatment
Goals of Orthopaedic Management
Orthopaedists participating in the care of children with myelomeningocele are members of the health care team seeking to maximize function and minimize disability and illness. Over time, the specific goals change, based on the child’s needs and abilities and changes in neurologic status. One of the major goals of the orthopaedist is to correct deformities to help patients meet their maximal functional capability. Almost all patients need orthoses to replace muscle strength and joint stability so that they can stand and walk. Regardless of the extent of the deformity and paralysis, it is possible for most children to walk at a young age with a combination of deformity correction, bracing, upper extremity aids, and instruction. Thus one of the primary functions of the orthopaedist is to correct lower extremity deformities that prevent the patient from using orthoses to ambulate during childhood. Many patients, especially those with thoracic or upper lumbar paralysis, will be unable or unwilling to maintain the same level of independent ambulation as adolescents or adults because the extent of bracing and energy consumption required for ambulation will be too great. Patients with myelomeningocele should be prepared for independent, self-sufficient living, which means that they should not be devoting a substantial portion of their energy solely to walking for its own sake. Excessive emphasis on ambulation over the use of a wheelchair may even adversely affect academic achievement.
The orthopaedic surgeon must monitor spinal balance and deformity in the myelomeningocele patient. There is a high incidence of congenital and neurologically related scoliosis and kyphosis, conditions that can jeopardize posture or sitting comfort or increase the likelihood of the development of pressure sores.
Finally, the orthopaedic surgeon must assist in monitoring the neurologic status of the growing patient because hydrocephalus, hydromyelia, or tethered cord syndrome secondary to diastematomyelia or another anomaly or to scarring at the original level of myelodysplasia can occur. Any of these conditions can result in a subtle deterioration in the patient’s intellectual function and upper or lower extremity function.
In an effort to help orthopaedic surgeons understand what is required to achieve treatment goals for this complex disorder, experts from around the world convened in a symposium in 2000. The discussions from that meeting were published in a comprehensive report from the American Academy of Orthopaedic Surgeons describing the many facets of the orthopaedic care of children with spina bifida.
Physical and Radiographic Examination of the Newborn
When examining a newborn with myelomeningocele for the first time, the goal of the orthopaedic surgeon is to identify the level of paralysis for each extremity and screen for associated deformities. Sphincter control, the presence of hydrocephalus, and the condition of the myelomeningocele sac are also important to note. Commonly, the orthopaedist is consulted after closure of the sac and shunting for hydrocephalus. The infant should be examined in a quiet warm environment to allow the best assessment of joint range of motion, sensory preservation, and evidence of spinal deformity. A stimulated or crying infant, however, allows the examiner to appreciate the child’s voluntary lower extremity muscular function better. Sharrard described the neurosegmental function of the lower extremity, and this root by root assessment has become the standard for describing lower extremity function and the basis for establishing a prognosis for long-term ambulation and the nature of secondary deformities likely to develop during childhood. The level of spinal cord lesion as visualized on prenatal ultrasonography has been positively correlated with the level of postnatal paralysis noted on physical examination, so if this information is available, it may be helpful. Caution is advised, however, because determining the precise level of function can be difficult, and the level may change over time, may be asymmetric, or may not correspond exactly to Sharrard’s neurosegmental scheme. In a longitudinal serial evaluation of 308 patients older than 5 years, McDonald and colleagues found that quadriceps strength correlated with iliopsoas strength, medial hamstring function could be present without tibialis anterior function, gluteus medius and maximus strength correlated strongly with each other and with tibialis anterior strength, and muscle weakness was most frequently noted in the gastrocnemius-soleus group.
During the examination, the orthopaedist should first develop a sense of the child’s overall vigor because lack of vigor may suggest CNS depression caused by untreated hydrocephalus. Whenever expedient, the examiner should turn the infant prone on the mother’s lap, an examining surface, or the palm of the examiner’s hand to determine at what level the myelodysplastic deformity is located, its extent, and the state of the skin overlying it, especially if the examination is being conducted after neurosurgical closure of the myelodysplastic lesion. The infant should also be assessed for obvious spinal deformities or congenital scoliosis or kyphosis associated with the myelodysplastic lesion. The examiner then looks for more subtle evidence of spinal dysraphism at other levels—specifically, for discoloration or hemangiomas, hairy patches, or dimpling along the spinal column remote from the obvious myelodysplastic lesion. The entire spinal column is palpated, with the examiner looking for curvature or defect.
With the child supine, neck mobility and upper extremity formation and function are assessed; these are generally normal in the myelomeningocele patient. Next, the examiner visually inspects the posture of the lower extremities, which provides a clue to the extent of the paralysis. For example, a child with a thoracic level lesion most often lies supine with the legs in a flopped open, frog-leg position, with no spontaneous movement. Patients with lower levels of paralysis exhibit spontaneous movement of the lower extremities; if necessary, the examiner can stimulate the child to observe such movement. Specifically, the examiner should look for hip flexion and adduction, knee extension and flexion, and ankle dorsiflexion and plantar flexion. A note of caution is in order, however, because observed toe movements should not be taken as indicative of volitional control of the digits, and movement of the toes usually results from root sparing below the myelodysplastic lesion and is not under volitional control. The examiner should try to assess the level of preservation of sensation by gently stroking the skin, beginning distally, and observing the infant’s facial and lower extremity muscular response. The examiner checks for the usually obvious foot deformities, such as clubfoot and vertical talus. Range of motion of the hips is assessed, with specific noting of abduction, adduction, external rotation, and/or flexion contractures. The hips are also assessed for concentricity and stability. Knee flexion contractures and their extent should be documented. The examiner strokes the patient’s legs on both sides individually, from distal to proximal, by dermatome, to identify the level of sensory preservation. Finally, the examiner checks for the almost invariably present patulous anus and urinary dribbling, suggesting bowel and bladder paralysis.
The physical examination should be supplemented with good anteroposterior and lateral radiographs of the entire spine. These radiographs should be carefully inspected for the level of the last closed posterior element, any congenital spinal deformity (particularly one remote from the myelodysplastic level), and pedicular widening, especially with associated congenital vertebral anomalies, which may suggest underlying diastematomyelia. In general, the level of paralysis noted on physical examination should correspond to the first open level of the spine; however, there may be a substantial discrepancy between these two findings, which suggests that other deformities of the spinal cord or proximal CNS are contributing to the paralysis. Ultrasonography or MRI of the spinal cord may be indicated in these cases. In general, radiographs of the lower extremities merely confirm what has been determined from the physical examination. Ultrasonography can clarify the relationship of the femoral head and acetabulum if the clinical examination of the hip is not definitive.
This examination provides the orthopaedic surgeon with a good understanding of the lower extremity anomalies, extent of lower extremity paralysis, and presence of vertebral anomalies that need to be monitored with growth. The sum of these findings allows the surgeon to provide the patient’s parents with a reasonable outline of what will be required to correct the deformities and what they should expect in the future in terms of bracing needs and mobility expectations.
Periodic Assessment
Patients with myelomeningocele require periodic reassessment throughout growth, usually on a semiannual or annual basis. These assessments are typically carried out in a multidisciplinary clinic; this reduces the number of physician visits for the patient and family and allows the health care team to provide a comprehensive evaluation and coordinated treatment plan when interventions are required. Within this complex screening and treatment program, at each routine visit, the orthopaedist assesses whether the following are present:
- 1.
The child’s motor and sensory function have remained stable.
- 2.
The child’s mobility and bracing needs have remained stable.
- 3.
Orthoses and upper extremity aids are appropriate to the patient’s requirements, provide the desired effect of maximizing mobility, are in good repair, and are not causing any undue pressure points on the patient’s lower extremities.
- 4.
The range of motion of the patient’s lower extremity joints is stable and sufficient to allow the patient maximum mobility based on preserved motor strength.
- 5.
The patient’s upper extremity function is stable.
- 6.
Spinal deformity is stable or absent.
- 7.
The patient’s skin is in good condition over the spinal deformity, in the perineal and ischial areas, at pressure points under orthoses, and over the knees and around the feet, where abuse of the skin may occur with crawling, walking, or swimming without braces or other protection.
These evaluations may be accomplished with the aid of a nurse, pediatrician, therapist, and orthotist. Periodic radiographic assessment of the spine and hips is often required as well; it is rare that a patient has no evidence of spinal or hip deformity on physical examination.
Surgical Management of Specific Orthopaedic Problems
Foot and Ankle Deformities
Congenital and developmental foot deformities are common in children with myelomeningocele. Calcaneal deformity is the most common, followed by equinus, valgus deformity, clubfoot, and vertical talus. Foot deformities often interfere with effective bracing for ambulation or lead to pressure sores in ambulatory patients. Broughton and colleagues found that acquired deformities could not be accounted for solely by spasticity or muscle imbalance. Even nonambulatory patients have concerns about the cosmetic appearance of the feet and experience difficulty wearing normal shoes.
In general, foot deformities in an infant should undergo a trial of gentle passive manipulation, with care taken to avoid pressure sores and fractures. Even with early correction, recurrence is common, and surgery is ultimately needed on most feet. When required, it is important that surgical correction be delayed until the child is developmentally ready to be in the upright position. Proceeding with surgery for foot deformity before the patient is ready to be fitted with orthoses for standing or walking risks recurrence before the child even begins to walk. Early recurrence of the deformity can be minimized by ensuring that after the removal of postoperative casts, well-fitting orthoses are immediately available for use day and night, and the child should be encouraged to stand or walk in them.
Equinus
Pure equinus contractures in patients with myelomeningocele are common. They are not caused by voluntary muscle imbalance, however, because most patients have flail feet or, in patients with low lumbar lesions, tibialis anterior functioning. Positioning deformity, in utero or postnatally, and gastrocsoleus spasticity account for some of the equinus contractures seen and, in some patients, equinus develops after tibialis anterior tendon transfer to the calcaneus (see later, “Calcaneal Deformity”).
Patients with positional neonatal equinus contractures associated with higher level paralysis can initially be treated with extremely gentle passive manipulation. If the equinus deformity persists when the child is ready for orthoses for standing and ambulation, percutaneous release or open lengthening of the heel cord can be carried out. Percutaneous heel cord lengthening can be performed in the outpatient clinic if the patient is insensate in that area. Some patients have long toe flexor contractures as well, which should be divided. Otherwise, persistent toe flexion deformities can result in pressure sores on the ends of the toes when the child is placed in shoes. Careful postoperative casting for a few weeks should be followed by the fitting of orthoses required for standing or ambulation.
Equinovarus
Clubfoot deformity is a common anomaly in patients with myelomeningocele, irrespective of the level of myelodysplasia. #b
#b References .
This deformity in myelomeningocele patients is truly teratologic in that the deformity is almost always rigid, with less propensity to respond to conservative treatment, requires extensive surgery to correct, and is likely to recur, even after excellent correction combined with resection of the tendons that would presumably be the source of recurrence. * cReferences .
Patients with myelomeningocele and clubfoot deformity can initially be managed in a similar manner as other patients with idiopathic clubfoot deformity (see Chapter 23 ). However, the treating physician should be very experienced and comfortable with manipulation and casting techniques because absence of the pain response or of protective sensation makes it difficult to avoid pressure sores or fractures. One recent report noted favorable results with use of the Ponseti method to treat clubfeet associated with myelomeningocele. However, despite excellent initial correction, the authors noted relapse in 68% of patients with spina bifida and a need for comprehensive soft tissue release in 14% of patients, four times more frequent than idiopathic patients. Because crawling with the feet dragged behind and rotated internally creates a deforming force that promotes recurrence, surgery should not be performed before patients have reached the developmental milestone of pulling to a stand.When nonoperative or minimally invasive techniques fail, extensive release is often required, and ancillary procedures such as lateral column shortening are required much more frequently than in patients with idiopathic clubfeet. In patients with lower lumbar lesions, the tibialis anterior tendon may be lengthened or transferred to the midline or heel (see later, “Calcaneal Deformity”). In patients with upper lumbar or higher lesions, tendons are frequently resected rather than lengthened. Only in patients with almost complete preservation of lower extremity function is typical tendon lengthening performed rather than resection. Furthermore, much as in patients with arthrogryposis, myelomeningocele-related clubfeet may require naviculectomy, talectomy, or talar enucleation (Verebelyi-Ogston procedure) to achieve correction. Infrequently, in the most severe deformities, bringing the foot into a corrected position may cause vascular compromise, requiring combining clubfoot correction and tibial and fibular shortening. Difficulty with wound closure is common, and rotational flaps have been described for primary closure of the surgical incision. I have found, however, that it is most effective to leave the wound open as much as necessary with the foot in the corrected position, provided that circulatory status is not impaired in that position, and to change the cast or window it for dressing changes. An alternative is to close the skin loosely and bring the foot into a corrected position with a few cast changes in the first 2 weeks after surgery. Inadequate skin coverage for surgical correction of recurrent clubfoot deformities has been addressed with the preoperative use of soft tissue expanders, but with only limited success (in two of seven cases).
Postoperative casting must be meticulous, as described earlier. Excessive swelling, erythema, or systemic reaction must be investigated by removing the cast and inspecting the foot. Wound necrosis and pressure sores are frequent, even with casting by the most experienced and attentive of surgeons, and families should be so warned. Bracing of at least the foot is required indefinitely after cast removal, so the surgeon should ensure that the required orthoses are ready to be applied when the cast is removed. The postoperative casting protocol may be shortened in favor of braces compared with that in patients with idiopathic clubfeet.
Recurrence of deformity can be treated by primarily bony procedures, including midfoot and forefoot osteotomies, talectomy, or triple arthrodeses When using these procedures, the surgeon must be careful to obtain even weight-bearing forces to minimize the predisposition to the development of neurotrophic ulcers. A variation of equinovarus deformity may be seen in patients with lower lumbar paralysis with a functioning anterior tibialis. In some of these patients, a deformity consisting of primarily forefoot dorsiflexion and supination gives the impression of a deformity caused solely by the unopposed action of the tibialis anterior or a very mild clubfoot. In infants with such a deformity, posterior or lateral transfer of the tibialis anterior alone may not correct all components of the deformity, and a limited posteromedial release is often required as well.
Calcaneal Deformity
Calcaneal deformity may be seen as a birth contracture or as a delayed deformity secondary to the unopposed action of the tibialis anterior in patients with paralysis at the lower lumbar level. †c
†c References .
Not all developmental calcaneal deformities can be explained solely on the basis of muscle imbalance or spasticity. Calcaneal deformity of the foot may make the fitting of orthoses more difficult and less effective, and it predisposes patients to the development of neurotrophic heel ulcers. The latter can be difficult to eradicate and may progress to recalcitrant calcaneal osteomyelitis ( Fig. 36-7 ). Patients with progressive calcaneal deformity or those with a propensity toward ulcer development can be treated surgically to prevent this from occurring. In one study, a delay in surgical treatment of this deformity resulted in a tenfold increase in the prevalence of calcaneal ulcers, from 3% to 30% of ambulatory patients.
Patients with mild calcaneal deformities from birth, with the possible exception of those with tibialis anterior–sparing involvement, may respond to gentle passive stretching of the foot into plantar flexion and splinting in a neutral, weight-bearing position. Patients with persistent or progressive calcaneal deformities associated with unopposed tibialis anterior function frequently require anterior release of the deformity, usually combined with posterior transfer of the tibialis anterior to the calcaneus to facilitate brace fitting and prevent the development of calcaneal plantar ulcers. ‡c
‡c References .
The transfer is not performed if this muscle is spastic. The tibialis anterior muscle transfer procedure is described in Plate 36-1 . A few important points should be made with regard to this surgery. First, in patients with low lumbar lesions, a posterior transfer performed in the hope of providing enough ankle stability to make braces unnecessary usually does not succeed; AFOs continue to be needed for maximum mobility. Second, the transfer should be positioned with the foot in a neutral position and, postoperatively, the foot should be immobilized in a neutral position in a cast, not in equinus. If the foot is positioned in a plantar-flexed position, the patient may sustain a distal tibial metaphyseal fracture after cast removal when the foot is dorsiflexed with weight bearing. Finally, excessive tightening of the transfer in equinus may result in the development of an equinus deformity that requires release, particularly when the transferred tibialis anterior is not under volitional control.Vertical Talus
Congenital vertical talus occurs with greater frequency in patients with myelomeningocele than in the general population, although it is much less common than clubfoot and other deformities of the foot. The manipulative treatment discussed for the management of vertical talus in Chapter 23 may be used in patients with myelomeningocele. However, the treating surgeon must be cognizant of the increased likelihood of pressure sores and recurrence of deformity. Patients with vertical talus and spina bifida usually require surgical correction, which is the same as for any patient with congenital vertical talus (see Chapter 23 ). The principles of timing and postoperative management raised in the discussion of clubfoot in patients with myelomeningocele apply here as well. Specifically, surgery should be delayed until the patient is neurodevelopmentally ready for orthoses and ambulation. Postoperative casting must be meticulous and hold the foot in a neutral functional position, and bracing and weight bearing should be instituted as soon as the casts are removed.
Valgus Deformity of the Foot and Ankle
Valgus deformity at the ankle is a common deformity in ambulatory patients with myelomeningocele, irrespective of the level of paralysis. §c
§c References .
The deformity may arise from the distal tibia, the subtalar joint, or both and may be compounded by an external rotation deformity of the tibia. The most common sequela of this deformity is skin irritation or breakdown over the medial malleolus from excessive pressure against the orthosis ( Fig. 36-8 ). Important considerations for the orthopaedic surgeon include determining the precise location of the clinical valgus (ankle or subtalar), ascertaining whether the patient is skeletally mature and, if immature, approximately how much growth remains in the distal tibia, and deciding whether the extent of deformity requires immediate correction because it is unbraceable or whether more gradual methods of correction can be used. Thus assessment requires a physical examination of the patient, consultation with an orthotist regarding the interim management of medial malleolar pressure areas, and anteroposterior radiographs of the ankle to determine the source of the valgus and state of the physis. In skeletally immature patients, a scanogram and radiographs of the hand and wrist for estimation of bone age may be necessary to assess how much growth remains in the distal tibia if distal tibial epiphysiodesis techniques are being considered.
Distal Tibia.
Surgical options for the management of distal tibial valgus deformities include distal tibial and fibular osteotomy, distal tibial medial hemiepiphysiodesis or growth tethering with implants such as staples, screws, and plates, and Achilles tendon–distal fibular tenodesis. A distal tibial valgus deformity that causes pressure sores and cannot be corrected by adjustment of orthoses or such a deformity in a skeletally mature patient requires a distal tibial osteotomy and varus realignment ( Fig. 36-9 ). Skeletally immature patients with deformities that are progressive but not in need of immediate correction are candidates for medial tibial hemiepiphysiodesis or Achilles tendon–fibular tenodesis. The medial growth arrest may be affected by direct curettage, stapling of the medial side of the distal tibia, or insertion of a fully threaded screw percutaneously from the medial malleolus proximally across the physis. An Achilles tendon–fibular tenodesis is indicated for young patients with mild distal tibial valgus deformities who are considered too young for an epiphysiodesis of the distal tibia.
Distal Tibial Osteotomy.
Fixation may be done with crossed Steinmann pins, staples, external fixator, or internal fixation with a dynamic compression plate. This osteotomy may be complicated by delayed union, nonunion, or infection, particularly in adolescents. Recurrence of the deformity is also relatively common in skeletally immature patients. Postoperatively, patients should be kept non–weight bearing initially because weight bearing with diminished pain perception can lead to excessive swelling and motion. Patients should also be counseled not to crawl in postoperative casting. If possible, the knees should not be flexed excessively in long-leg casts because this can cause rehabilitation difficulties after cast removal.
Distal Tibial Medial Hemiepiphysiodesis.
If the patient is skeletally immature, with a deformity that does not demand full and immediate correction, a medial hemiepiphysiodesis can be considered. The medial tibial physis can be closed with direct surgical ablation, stapling, or insertion of a medial malleolar screw. The advantages of this technique are that immediate weight bearing is usually allowed and external immobilization is not necessary.
Achilles Tendon–Fibular Tenodesis.
Stevens and Toomey described the tenodesis of a portion of the Achilles tendon to the distal fibula above the distal fibular physis. Their rationale was that the valgus deformity is secondary to lateral compartment paralysis, with subsequent underdevelopment of the fibula, and that this lack of growth stimulation can be compensated for by tenodesis of a slip of the Achilles tendon to the fibula. With weight bearing and ankle dorsiflexion, the tenodesis pulls downward on the fibula, leading to gradual correction of the deformity. The surgical procedure is outlined in Plate 36-2 . Similar to distal tibial hemiepiphysiodesis, this procedure is indicated for skeletally immature patients with progressive deformities that do not yet require complete correction. It is particularly well suited for younger patients in whom hemiepiphysiodesis is not appropriate.
Subtalar Joint.
When radiographs reveal that most of the valgus deformity is in the subtalar region, treatment should consist of subtalar arthrodesis, with internal fixation across the subtalar joint and extraarticular iliac crest bone grafting. Cautioned is advised, however, because fusions in the foot, even when clinically plantigrade, predispose the patient to neurotrophic ulcers over the long term. Thus triple arthrodeses and subtalar fusions should be avoided whenever possible. An alternative to subtalar arthrodesis may be to use a medial displacement osteotomy of the calcaneus.
Rotational Deformities (Internal or External)
Rotational deformities of the lower extremities are frequent in ambulatory and nonambulatory patients. In nonambulatory patients and in most ambulatory patients, the problem is largely cosmetic. Extreme internal rotation may interfere with ambulation if the child is catching his or her foot on the contralateral extremity during swing. Internal rotational deformities are usually dynamic, secondary to medial hamstring dominance, or fixed, secondary to internal tibial torsion. When a dynamic internal rotational deformity is interfering with gait, Dias and associates reported good results with transfer of the semitendinosus to the biceps and head of the fibula, but I have no experience with this procedure. Internal tibial torsion can be treated by rotational osteotomy. I prefer to perform a tibial osteotomy distally with fixation with crossed Steinmann pins or a dynamic compression plate.
Marked external rotation, in addition to being cosmetically displeasing, may indirectly interfere with ambulation by making the fit or function of the AFO component of bracing more difficult. The external rotational deformity places the medial malleolus in the line of progression of the limb and may lead to constant skin breakdown from rubbing against the AFO. This problem is aggravated if there is valgus deformity of the ankle or hindfoot as well. In addition, the calcaneus-preventing action of the orthosis, particularly a ground reaction orthosis, may be rendered ineffective if the external rotational deformity moves the foot sufficiently out of the line of progression of the patient’s gait ( Fig. 36-10 ). An external rotational deformity may come from the hip but is usually found in the tibia. Treatment consists of internal rotational osteotomy of the affected segment (usually the tibia), which Vankoski and co-workers believe should be considered when external torsion exceeds 20 degrees.
The surgeon must carefully assess the nature of the patient’s gait and extent to which the deformity should be corrected before recommending rotational osteotomy. Patients who ambulate with little knee motion—that is, who advance their limbs primarily by hip flexion or adduction with the hip externally rotated (typical of patients with upper lumbar level paralysis)—will have difficulty clearing a foot in swing that points directly in the line of progression. In these patients, the external rotational deformity should not be corrected if no gait or bracing problems are present. If rotational osteotomy is undertaken, the surgeon should aim to have the angle of foot progression in a more acceptable position of external rotation. Satisfactory results with distal tibial osteotomy have been reported in 80% to 90% of cases. However, significant complications have been reported and include delayed union (averaging 6 months to union), wound infection, and persistent swelling. Note that I do not recommend a rotational osteotomy of the tibia in a patient with myelomeningocele without a serious consideration of the potential sequelae weighed against the extent to which the rotational deformity is creating problems for the child.
Knee Deformities
The knee is not prone to many congenital anomalies in patients with myelomeningocele and is a surprisingly hardy joint in these young patients. However, long-term studies in ambulatory patients with low lumbar or sacral lesions suggest that knee instability, with or without pain, is present in about 25%.
Congenital Knee Flexion Contracture.
Patients can be born with flexion contractures of the knee. Flexion contractures of less than 10 degrees resolve by the time the patient is ready for ambulation, spontaneously or with judicious passive stretching, even when the patient has no motor function across the knee. Knee flexion deformity may recur, particularly in patients with higher levels of paralysis.
Congenital Knee Hyperextension or Dislocation.
Congenital knee hyperextension or dislocation may also occur in patients with myelomeningocele, usually in those carried in the full breech position. Simple hyperextension deformity may respond to careful passive stretching and splinting. Congenital knee dislocation requires surgical treatment. This should be performed well before the child reaches walking age so that the postoperative knee-flexed position can be resolved before orthoses are required for ambulation. In patients with myelomeningocele, treatment of congenital knee dislocation usually results in some extension contracture, persistent hyperextension at the knee, or multiplanar instability. The treatment of congenital knee dislocation is discussed further in Chapter 21 .
Developmental Knee Flexion Contracture.
In ambulatory and nonambulatory patients, knee flexion contractures can occur during growth. The development of these contractures does not appear to correlate with ambulatory status, level of paralysis, or presence of spasticity. Normally, knee flexion deformities of 20 degrees or less are well tolerated in ambulatory patients, with or without bracing across the knee; nonambulatory patients can usually tolerate even more flexion contracture without interference in mobility status or transfers. If greater deformity is present, careful thought must be given to the patient’s ambulation level and extent to which ambulation is being impeded by the flexion contracture. Contractures that interfere with ambulation or transfers may be treated with radical knee flexor release or anterior distal femoral hemiepiphysiodesis.
Knee Extension Contracture.
Another common problem is extension contracture, although it is not as common as one might expect based on the number of patients with at least some quadriceps function but no hamstring function. The deformity is most often a consequence of quadriceps spasticity but may also be seen following extensive bracing or other immobilization in extension, surgical treatment for flexion contractures, or congenital knee dislocation. Extension contractures generally do not interfere with bracing or ambulation, but are difficult for patients to cope with in the sitting position and can impede independent sit to stand transfers. In ambulatory patients, observation is usually the wisest course. When extension contractures are problematic in ambulatory patients, a V- Y quadricepsplasty is effective. In nonambulatory patients, adequate flexion can usually be gained by simple transection of the patellar tendon. Intraarticular release is generally not required. With either procedure, the patient should be immobilized in knee flexion only as long as necessary for the soft tissues to heal. This should be followed by a program of daily gentle passive and, if possible, active range-of-motion exercises of the knee.
Knee Instability or Internal Derangement.
Patients with myelomeningocele frequently present with unexplained swelling of the knee. The surgeon must first ascertain that there is no infection or intraarticular fracture. If these conditions are excluded, the precise cause of the effusion may be difficult to determine. Usually, the problem is synovial irritation from multiplanar instability or excessive movement of the knee, which frequently develops in adult patients. Patients who are ambulatory with AFOs should probably be converted to KAFOs, at least temporarily, to protect the knee. The physician and parents should also review the patient’s activities, looking for those that might be placing undue stress on the knee (e.g., incautious transfers, aggressive activities out of orthoses). One study found that the use of KAFOs did not provide protective benefit to the knee in patients who were able to ambulate effectively in AFOs alone. Thus, in general, patients who ambulate effectively in AFOs should not be prescribed KAFOs solely in the hope of preventing long-term instability of the knee.
Hip Deformities
No aspect of the orthopaedic management of patients with myelomeningocele is more controversial than the proper management of the hip joint. ‖c
‖c References .
Specific deformities encountered include abduction or external rotation contractures, hip flexion contractures, developmental dysplasia of the hip present at birth, and progressive paralytic subluxation and dislocation of the hip, usually with attendant hip flexion and adduction contractures.Abduction or External Rotation Contracture.
This deformity, which may be congenital or developmental, is typically seen in patients with thoracic and upper lumbar lesions. Occasionally, it develops from poor positioning and passive manipulation of the lower extremities, with the patient’s limbs always remaining in a position of flexion, abduction, and external rotation. Initial management consists of gentle passive manipulation that draws the limbs into a position of neutral hip flexion, adduction, and internal rotation. A deformity that persists when the child is neurodevelopmentally ready for upright positioning with braces should be treated surgically. Release of the tensor fasciae latae, rectus femoris, sartorius, and anterior fibers of the gluteus medius and minimus muscles from the anterior and lateral pelvis usually achieves neutral positioning of the hips. Postoperatively, the lower limbs are maintained in a neutral position with a removable, narrow, foam adduction splint or by wrapping the legs together in elastic bandages. The parents are taught how to perform gentle passive manipulation of the hips to maintain the child’s ability to bring the hips into neutral adduction, extension, and internal rotation as soon as the wound has healed adequately. Although uncommon, infection, heterotopic bone formation, hip subluxation or dislocation, femoral fracture, and recurrence of deformity are complications associated with this procedure. Parents and therapists should have a clear understanding that the purpose of this release is to achieve upright positioning and ambulation with hip-knee-ankle-foot orthoses (HKAFOs) and upper extremity aids. These patients typically choose wheelchairs as their predominant method of mobility in adolescence and adulthood.
Flexion Deformity.
Pure hip flexion deformity is usually seen in conjunction with hip subluxation or dislocation (see later), secondary to involuntary hip flexion or spasticity (often with knee flexion contracture as well), or as a simple contracture from unopposed preserved hip flexor power. In an ambulatory patient who requires only KAFOs, the contracture usually does not require release or extension osteotomy for its own sake. However, if the patient also has a troublesome knee flexion contracture, greater hip extension may be desirable to aid in the patient’s postoperative management. Nonambulatory patients usually are not troubled by hip flexion contractures. Patients who remain good walkers with HKAFOs are the main candidates for treatment. Usually, a patient in a brace can accommodate 20 to 30 degrees of contracture, with the necessary modifications made by the orthotist. When the deformity is greater than this, hip flexor release or, rarely, extension osteotomy of the proximal femur, should be carried out. Frawley and colleagues achieved good outcomes in 43 of 57 hips after hip flexor release at 9-year follow-up; in this study, 10 had a poor outcome (>30-degree flexion contracture) and 4 had contracture recurrence. The success of the procedure was not correlated with the patient’s age or neurologic level, but did correlate with walking ability. A subluxated or dislocated hip does not seem to influence the final outcome.
Paralytic Hip Subluxation or Dislocation.
The most frequent and vexing hip deformity is paralytic subluxation and dislocation of the hip. The presence of unopposed hip flexor and adductor muscle function in a growing child, as seen in patients with upper lumbar lesions and, to a lesser extent, in those with lower lumbar lesions, leads almost inevitably to progressive hip subluxation and dislocation.
Controversies in Treatment.
The nature of the problem is perhaps best understood by comparing the treatment of developmental dysplasia of the hip in patients with myelomeningocele with its treatment in neuromuscularly intact patients. In the latter, a Pavlik harness and closed reduction are the mainstays of treatment in patients before walking age. In patients with myelomeningocele, however, because of the associated muscle imbalance, such reduction is inevitably followed by recurrence of the dislocation because there is no spontaneous improvement in the structural femoral and acetabular deformities that contribute to the dislocation. In myelomeningocele, the muscle imbalance between intact flexors and adductors and weak or absent extensors and abductors drives the hip back into a dislocated position, with accentuation of the structural deformity. Therefore, in the rare patient with myelomeningocele in whom reconstruction of a dislocated or subluxated hip is considered, all the principles of paralytic hip dislocation treatment must be followed: (1) obtain a concentric reduction, usually by means of an open reduction; (2) correct the bony abnormality (femoral anteversion and valgus, and acetabular insufficiency, usually posterior) because there is no propensity for spontaneous correction; and (3) seek to balance the flexor-adductor, extensor-abductor imbalance muscle release.
Paralytic hip surgery in myelomeningocele patients is extensive and involves transfers or muscle releases, which by their nature result in diminished muscle strength, even though balance may be achieved. Given the higher incidence of surgical complications in patients with myelomeningocele, such as hip stiffness, fracture, and heterotopic bone formation, along with the natural history of diminishing mobility in these partially paralyzed patients, the reason for controversy in the treatment of myelomeningocele-related hip abnormalities is apparent.
Reduction.
Based on gait analysis in lumbar myelomeningocele patients with hip dislocation or subluxation, reduction of the dislocated hip is thought to be unnecessary. The exception may be children with sacral level lesions and near-normal function. Gabrieli and associates assessed pelvic and hip kinematics in community ambulators with unilateral hip dislocation or subluxation and found that gait symmetry corresponded to the absence of hip contractures or presence of bilateral symmetric hip contractures, but not to the presence of hip dislocation. They concluded that hip reduction was unnecessary. An evidence-based review also showed that surgery for hip dislocation did not improve walking ability.
An increasing number of pediatric orthopaedists who care for children with myelomeningocele believe that the indication for surgical treatment of hip dysplasia in patients with myelomeningocele is progressive subluxation in an ambulatory patient. For the few patients in whom reduction is considered, it almost always requires anterior open reduction with capsulorrhaphy, appropriate muscle releases (usually psoas and frequently adductors), and femoral and acetabular osteotomies.
Correction of Bony Abnormality.
Correcting the femoral bony deformity requires a proximal femoral varus osteotomy, often with external rotation to correct the associated femoral anteversion. Acetabular deformity can be corrected by the Pemberton osteotomy, Dega osteotomy, shelf procedure, Steel triple innominate osteotomy, or Chiari osteotomy. Most surgeons believe that a Salter innominate osteotomy is not indicated for myelomeningocele patients because this osteotomy redirects the acetabulum to face posteriorly, which is the direction of hip dislocation initially, and may thus result in recurrent posterior instability. I prefer to use the Dega or periacetabular osteotomy to correct deficient acetabular coverage in patients with myelomeningocele.
Muscle Balancing Procedures.
Broughton and colleagues reviewed the natural history of hip deformity in 802 children with myelomeningocele. Hip dislocation had occurred by age 11 years in 28% of thoracic level patients, in 30% of upper lumbar level patients, in 36% of patients with L4 functioning, in 7% of patients with L5 functioning, and in 1% of patients with sacral level lesions. Hip dislocation was not inevitable, even with maximal muscle imbalance about the hip. Hip flexion contractures were much more common in patients with thoracic and upper lumbar paralysis than in those with lesions at other levels. This challenges the concept of muscle balance restoration as a principal aim in children with myelomeningocele because the presence and extent of imbalance are so variable.
Muscle balancing procedures include the following: (1) simple release of the iliopsoas tendon with adductor release; (2) posterior transfer of the adductor muscle mass on the ischium to convert it into more of a hip extensor; (3) transfer of the iliopsoas tendon posterolaterally to convert it to a hip abductor (Sharrard procedure); and (4) transfer of the external oblique to the trochanter to recruit a hip abductor from the anterior abdominal wall. ¶c
¶c References .
We have not found that muscle transfers about the hip result in improved function and believe that the rare patients with myelomeningocele who require hip reconstruction can be treated successfully with capsulorrhaphy and muscle release combined with appropriate femoral and acetabular procedures.Surgical Complications.
One of the complications of extensive hip surgery is loss of mobility. This may be exacerbated if heterotopic bone formation occurs. In nonfunctional or nonambulatory patients, this loss of mobility can create significant morbidity; after surgery, they may be unable to sit comfortably because of inadequate hip flexion or fixed pelvic obliquity. Taylor reported that resection of the proximal femur failed in most cases and recommended repositional osteotomy (i.e., flexion osteotomy) as an alternative when improved hip positioning is required.
Summary: Management of Paralytic Hip Subluxation and Dislocation.
The indications for the surgical treatment of paralytic hip subluxation and dislocation remain controversial and the effectiveness of such surgery is debatable. #c
#c References .
Applying the relatively successful surgical techniques used in patients with poliomyelitis without an adequate understanding of the confounding variables in patients with myelomeningocele has resulted in excessive hip surgery in the latter group of patients. Nevertheless, a few select patients with myelomeningocele may gain from the added stability of successful hip surgery. One of the problems is that successful surgery of the hip may be difficult to accomplish; redislocation, hip stiffness, and loss of active hip flexion are common complications, and these may actually make the patient worse. * dReferences .
Unfortunately, a review of the literature does not clarify the indications for surgery, even in good ambulators. Some authors contend that the patient who is most likely to benefit from hip stabilization procedures has a low lumbar lesion, is neurologically stable, and has proved to be an excellent ambulator. Others have found no difference in function between low lumbar level patients with dislocated hips and those with surgically stabilized hips. Some authors believe that unilateral dislocation in an excellent ambulator strengthens the indications for hip stabilization to prevent limb length inequality, pelvic obliquity, and scoliosis. Others have found no such benefit. Fortunately, hip pain is unusual in myelomeningocele patients, so its prevention cannot be used to justify surgical reduction or stabilization of the hip.Issues that are not controversial are that the primary goal of the orthopaedic surgeon is to maintain flexibility in the hip, and patients with thoracic and upper lumbar lesions do not benefit from hip stabilization. Furthermore, there is rarely, if ever, an indication to perform iliopsoas transfer in patients with myelomeningocele; those with higher lesions will not benefit, and those with lower lesions risk the loss of active and passive hip flexion. I perform surgical treatment of hip dysplasia in patients with myelomeningocele only when there is progressive subluxation in an ambulatory patient. Gait analysis studies support this conservative approach in other patients, noting that surgical reduction of myelomeningocele-related hip dislocation does not result in better ambulatory potential than leaving the hips dislocated. In addition, the numerous potential surgery-related complications can be avoided.
Spinal Deformities
Spinal deformity in patients with myelomeningocele occurs frequently, can be complex, and often requires treatment. †d
†d References .
Deformities can be congenital or acquired, specific to myelomeningocele or similar to deformities seen in other conditions. Congenital spinal anomalies include scoliosis secondary to vertebral malformations, congenital kyphosis related to posterior dysplasia, and intrathecal anomalies such as diastematomyelia. Acquired deformities include idiopathic-like scoliosis, pelvic obliquity–related scoliosis, and neuromuscular curves secondary to spinal muscle asymmetry, hydrocephalus, or tethered cord from any cause ( Fig. 36-11 ). Deformities occur with any level of paralysis and without regard to ambulation ability or history. Problems created by spinal deformity include unstable skin over the deformity in the case of kyphosis, pressure sores or interference with sitting balance in wheelchair-bound patients, and pulmonary compromise secondary to compression from the diaphragm or rib deformity. Although generalizations can be made, treatment must be individualized, based on the cause, severity, and risk of progression of the deformity, the patient’s age and ambulatory status, and the impact of the deformity on the patient’s well-being.
General Management of the Spine
Radiographic evaluation of the entire spinal column should be carried out in infants with myelomeningocele, looking specifically for the presence, location, and severity of kyphosis, the last level of posterior element closure, and any evidence of congenital spinal deformity ( Fig. 36-12 ). The last includes failures of formation or segmentation, as with any congenital spinal anomaly (see Chapter 12 ), and pedicular widening or secondary posterior element incompleteness, which may indicate the presence of diastematomyelia. Routine physical examination and periodic radiographic screening for evidence of scoliosis should be performed in all patients with spina bifida because the prevalence of this deformity is so high.
Congenital spinal deformities are managed as in any other patient; if the deformity is progressive, local anterior and posterior spinal fusion is carried out (see Chapter 12 ). Progressive neuromuscular (noncongenital) curves are treated according to their severity, evidence of progression, and the patient’s skeletal maturity. First, the overall health of the patient’s neurologic system should be evaluated, particularly in those with newly evident or rapidly progressive deformities. Shunt function should be assessed and the spinal cord evaluated for evidence of tethering, hydromyelia, or diastematomyelia. Curves between 25 and 45 degrees in skeletally immature patients may be considered for total-contact orthoses. Bracing in ambulatory patients dependent on extensive lower extremity braces, particularly HKAFOs, can be challenging, but because spinal orthoses can at least delay the rate of progression of deformity, they should always be considered; bracing should probably be recommended for young patients in whom deferral of spinal fusion is warranted. As for patients with idiopathic scoliosis, spinal fusion should be considered for curves greater than 55 degrees unless the patient is a community ambulator. In this case, spinal fusion to the pelvis should be delayed until the patient becomes largely wheelchair-reliant or the curve becomes significantly worse.
Patients with myelomeningocele who undergo spinal surgery are particularly likely to experience peri- and postoperative complications, making attentive treatment by an expert health care team essential. Even with such care, pressure sores, urinary tract infections, wound breakdown, deep infections, pseudarthrosis, and progression of the deformity are more frequent than in all other patient populations with spinal deformities.
Preoperatively, the treating surgeon must ensure that the patient’s shunt function is stable, there is no ongoing urinary tract infection, the weight-bearing skin of the pelvis and upper thighs is free of pressure sores, and the skin over the portion of the spine to be operated on is healthy. Preoperative assessment should include careful assessment and neurosurgical consultation to assess the potential need for prior or concurrent detethering of the spinal cord.
Postoperatively, the wound must be carefully monitored and promptly attended to if there is evidence of superficial or deep infection or tissue necrosis. The patient’s urinary tract must be kept clean. The patient’s perineal skin must be carefully monitored when the patient resumes sitting—the load of weight bearing will have changed anatomically because of the deformity correction, and there is always some loss of lumbopelvic movement with fixation to the pelvis, which likely increases the pressure in load-bearing areas in a sitting patient. Wheelchair seating modifications should be made in the early postoperative period, prior to initial postoperative discharge, to lessen the likelihood of skin problems associated with the change in posture. Finally, if a patient performs independent transfers with flail or almost flail extremities, the surgeon must observe these transfers preoperatively to determine whether fixation to the pelvis will allow these movements postoperatively. I encourage one- or two-person assisted transfers for 6 to 8 weeks postoperatively to prevent excessive lumbopelvic movement through the limbs, which can occur with independent transfers. Rarely, a spine-thigh orthosis may be needed to protect the lumbopelvic junction from excessive movement during this period.
Kyphosis
Kyphosis of the lumbar spine is a common deformity in myelomeningocele patients (20% to 46%; Fig. 36-13 ). They have been described as paralytic, sharp-angled, and congenital. Carstens and co-workers found paralytic kyphosis (<90 degrees at birth) to be most common (44%), followed by sharp-angled kyphosis (≥90 degrees at birth; 38%). Both types of kyphotic curves progress during growth at a rate of 2 to 6 degrees/year. The progression of true congenital kyphosis was the least common (14%) in Carstens and colleagues’ series, and progression was variable during growth. Kyphosis is usually seen in patients with thoracic and upper lumbar levels of paralysis. Progressive kyphosis is usually associated with a compensatory thoracic lordosis ( Fig. 36-14 ). Mintz and co-workers noted that progressive kyphosis was associated with the loss of any previously preserved lower extremity function.
Management of Skin Breakdown.
The treatment of myelomeningocele-related kyphosis is always challenging. Lumbar kyphosis can be problematic from birth, causing difficulty closing the skin and the meningeal defect. Later difficulties include skin breakdown with sitting, sitting balance problems, and even pulmonary compromise caused by pressure on the thoracic cavity from the collapsing abdomen and diaphragm. Chronic skin breakdown can leave the neural elements and the spinal column exposed and at risk for infection ( Fig. 36-15 ).
If the kyphosis prevents adequate skin closure at birth, one or two largely cartilaginous vertebral bodies can be enucleated and the remaining spine held together with sutures or cerclage wire ( Fig. 36-16 ). Excellent initial correction can be achieved, but eventual recurrence of the kyphosis should be expected. However, recurrence takes the form of a more rounded deformity, which may require a less technically demanding correction in the future.
Patients with skin breakdown over a stable kyphosis that does not need treatment should have their wheelchair supports and activities carefully evaluated and any irritants causing the breakdown removed. If these efforts are unsuccessful, rotational or free flaps can be used to cover the kyphotic area with thicker, more stable skin. Soft tissue expanders have been used for this purpose as well, independently and in conjunction with spinal deformity correction.
Definitive Management.
There appears to be little, if any, role for bracing in an attempt to control or correct the deformity. Definitive management of kyphosis consists of kyphectomy and posterior spinal fusion and instrumentation. ‡d
‡d References .
This is one of the most challenging procedures in orthopaedics. Patients in whom the apex of the deformity lies below the level of neurologic function are typically treated by cordectomy, vertebral body resection, and instrumentation.Preoperative Preparation.
Careful preoperative assessment is necessary. The function of the shunt must be determined and, if it is nonfunctioning in a patient who is shunt-dependent, it must be replaced before surgical treatment of the kyphosis. The skin over the kyphosis must be as stable as possible and, if it is of poor quality, a plastic surgeon should be consulted to assess the use of tissue expanders or rotational flaps. Patients should have careful nutritional assessment and their nutritional status maximized prior to surgery. The patient should be treated for any urinary tract infection preoperatively, and renal function should be evaluated. The aorta typically bridges the area of kyphosis and thus is not at great risk during vertebrectomy; however, the kidneys are often nestled within the kyphotic area and may be inadvertently injured during surgery. Cordectomy may result in improved bladder function, as evidenced by increased bladder compliance and capacity. Rarely, a patient has neurologic function below the apex of the kyphotic deformity, in which case the spinal sac must be carefully protected from injury or devascularization.
Kyphectomy
Technique.
Sharrard was the first to describe the technique of vertebrectomy in the management of kyphotic deformity in newborns and later in older children, as described by Sharrard and Drennan. At surgery, the neural elements are dissected away from the posterior spinal elements (see Plate 36-3 ). In patients with no function below the level of resection, the nerve roots and cauda equina remnants can be resected by tying the roots, elevating the distal cord, and transecting it. The meninges should be dissected free of the neural elements, resected distal to the elements, and sutured closed. The spinal cord should not be tied because acute hydrocephalus may result, possibly causing sudden death. After resection of the cord, the lumbar spine is dissected extraperiosteally from the posterior approach to the anterior aspect of the vertebral bodies. Two or more vertebral bodies are resected through their midportions so that the kyphosis can be reduced. Fixation to the pelvis is then carried out. A number of instrumentation techniques have been described, including fixation with Harrington compression instrumentation, Luque-Galveston instrumentation to the iliac crests, the Dunn-McCarthy modification of Luque instrumentation to the sacral alae, Luque rods contoured to fit through the first sacral foramen per the Fackler technique (a modification of the Dunn-McCarthy technique), vertebral body plates, and figure-eight wire loops around the pedicular remnants, with immobilization in a cast or brace ( Fig. 36-17 ). §d
§d References .
My preferred technique is to use Dunn-McCarthy rods over the sacral alae in older children, with posterior pedicular wire loops or vertebral body screws, and to use pedicle screws from the lowest level at which they are intact to the T2 or T3 level proximally. In young patients (6 to 10 years), I prefer the Fackler technique, in which a contour rod is placed anterior to the sacrum through the first sacral foramen. In younger patients, I have also used sublaminar wires without fusion in the upper thoracic spine to allow for growth. There have been recent reports of using the vertical expandable prosthetic titanium rib (VEPTR) to treat young patients with severe kyphotic deformity. The high rate of complications in patients undergoing one-stage, definitive spine surgery has resulted in bias against the use of so-called growing techniques, which require multiple planned operations in patients with myelomeningocele; I prefer to use nonoperative delaying tactics (i.e., casts and braces) in very young patients and perform single-stage definitive surgery after the age of 6 years.Results.
Martin and co-workers reported improved skin condition and sitting posture in all 10 patients treated by vertebrectomy, figure-eight wire fixation, and postoperative cast immobilization at an average age of 5 years. However, lower extremity fractures, delayed wound healing, and pseudarthroses occurred. The average degree of deformity was 90 degrees preoperatively, 40 degrees postoperatively, and 60 degrees at an average follow-up of 5 years.
Warner and Fackler found that 8 of 21 patients in whom kyphosis was stabilized with Harrington compression instrumentation, but none of 12 patients treated by fixation anterior to the sacrum (modified Dunn-McCarthy technique) and instrumentation, had recurrence of kyphosis on follow-up. Improved deformity correction using the Dunn modification of segmental fixation also has been reported by others. McCall reported that preoperative deformity averaged 110 degrees, postoperative deformity averaged only 15 degrees, and loss of correction averaged only 5 degrees on follow-up. Of 16 patients, 8 had complications, and blood loss averaged 1100 mL.
Garg and colleagues achieved improved seating balance and skin conditions in 17 of 18 patients undergoing kyphectomy. Seven patients required reoperation and three developed deep infection. One patient who had removal of implants following deep infection developed recurrent deformity. As a result of this experience, anterior fusion prior to implant removal is now recommended for patients who develop deep infection.
Odent and associates reported nine patients who underwent a two-stage procedure consisting of a posterior kyphectomy using lumbar pedicle screws and long, S -shaped rods buttressing the anterior sacrum and a thoracoabdominal approach to the spine, with an inlay strut graft from T10 to S1 as a second operation several weeks later. Kyphosis was corrected from a mean of 110 degrees before surgery to 15 degrees afterward, with no instrumentation failure, loss of correction, or pseudarthrosis. The authors believe that this technique improves biomechanical and biologic fusion mass anteriorly and should prevent late instrumentation failure and loss of correction. Caution is advised, however. It is generally agreed that kyphectomy with instrumentation is a major surgical procedure, intraoperative blood loss is usually well in excess of 1000 mL, perioperative deaths have occurred, and postoperative complications, including skin breakdown, infection, loss of fixation, and recurrence of deformity, occur more frequently than after most other orthopaedic procedures. ‖d
‖d References .
Scoliosis
Scoliosis in patients with myelomeningocele may be congenital, idiopathic-like, or related directly or indirectly to the spinal dysraphism and associated paralysis (associated intrathecal anomalies such as tethered cord, hydromyelia, or diastematomyelia; paralytic pelvic obliquity; asymmetric paralysis). Scoliosis is one of the most common musculoskeletal deformities requiring treatment in patients with myelomeningocele (52% to 70%, most by 6 years of age), and 50% of them will require surgery. ¶d
¶d References .
Muller and Nordwall found scoliosis in 94% of patients with thoracic level lesions and 20% with sacral level lesions. Ambulatory status also correlated strongly with the development of scoliosis, which was more likely in nonambulatory patients and in those with limited ambulation.Noncongenital scoliosis in young myelomeningocele patients is highly likely to progress by an average of 5 degrees/year. The severity of the curve and age of the patient are risk factors for progression—curves of more than 40 degrees are much more likely to progress, and curves continue to develop until age 15 and progress only slightly thereafter. Curves less than 20 degrees often resolve. The clinical motor level, ambulatory status, and last intact laminar arch are all predictive factors for the development of scoliosis.
Orthotic Treatment.
Spinal orthoses such as the Boston brace may have a role in the management of noncongenital scoliosis in patients with myelomeningocele. Practically speaking, however, spinal orthoses such as the Boston brace may be difficult to incorporate into the overall management of a child with myelomeningocele, especially one who is ambulatory, because the spinal orthosis may be hot, uncomfortable, and cumbersome. In patients who require a pelvic band for lower extremity bracing, the band must accommodate the brace; those who sit exclusively may have pressure problems under the brace or over the anterior thigh.
Spinal Fusion.
Several aspects of myelomeningocele make scoliosis surgery unique in these patients. Foremost among these is the presence of a posteriorly deficient spinal column, presenting challenges to fixation and fusion. Second, because the curves are neuromuscular, treatment often entails fusion to the pelvis, which requires fusing across the posterior deficiency and may negatively affect mobility and self-care. There is invariably significant scarring around the neural elements, and distraction correction in patients with useful lower extremity function must be done carefully to avoid the potential loss of neurologic function. Finally, these challenges, combined with the scarring of posterior soft tissues, result in a much higher than average incidence of wound healing and deep infectious complications. #d
#d References .
Spinal fusion with correction of the scoliotic deformity can have a positive effect on pulmonary function in myelomeningocele patients. This may be secondary to improved thoracic mechanics after stabilization.In many patients, the combination of posterior element deficiency and relative skeletal immaturity mandates anterior or combined anterior and posterior spinal fusion. * e
References .
Internal fixation may be anterior, with vertebral body screws and rods, or posterior, with rods, hooks, wires, and pedicle bone screws, with fixation to the pelvis. †e†e References .
Technique.
My preferred surgical treatment for scoliosis in patients with myelomeningocele is a single-stage combined anterior spinal release and fusion, followed by posterior spinal fusion with instrumentation to the pelvis. I use pedicle screws when possible, pedicle wires or screws in the area of posterior element insufficiency, and Luque-Galveston or Dunn-McCarthy fixation to the pelvis (see Plate 36-3 ).
Postoperative Management.
Urinary tract infection, which threatens the urinary tract and posterior spinal fusion site, wound infection, pressure sores, implant failure, and pseudarthrosis are all postoperative problems unique to or more frequent in myelomeningocele patients after extensive spinal fusion, particularly with instrumentation. To minimize the possibility of a potential urinary tract infection leading to a bacteremia-induced spinal wound infection, I treat patients the evening before surgery with parenteral gentamicin.
Postoperatively, the patient’s urinary management routine should return to the preoperative technique, usually clean intermittent catheterization, as soon as possible, with postoperative urine cultures and prompt aggressive treatment of any early urinary tract infection. The surgical wound must be kept covered with a sterile dressing until healed and should be inspected regularly for evidence of inflammation, necrosis, hematoma, CSF collection, or drainage. If present, these conditions should be managed aggressively with surgical débridement, as indicated. Increasingly, I have been using an impermeable, negative-pressure (vacuum-assisted closure [VAC]) dressing to cover the wound for several weeks following the surgery.
Fusions to the pelvis with instrumentation must be carefully protected during the early postoperative period (6 to 12 weeks). During this time, I do not allow independent transfers by the patient and teach the parents and other caretakers to move the patient’s spine, pelvis, and lower extremities as a unit to prevent excessive force on the instrumentation at the lumbosacral junction. If necessary, a spinal orthosis with thigh extensions is fabricated to protect these areas. The patient’s skin must be carefully monitored for evidence of irritation or impending breakdown in the new weight-bearing areas of the sacrum, buttocks, and thighs. Sitting should be resumed gradually, with assessment of these areas after the initial 20 minutes of sitting and periodically thereafter. Adjustments to the wheelchair cushion and back support are almost always necessary. Finally, the surgeon must monitor for evidence of deep infection or pseudarthrosis, as indicated by implant failure or progressive deformity.
Results.
Extensive spinal fusion such as that necessary to treat progressive noncongenital scoliosis in myelomeningocele patients can have a negative impact on the child’s overall mobility. Although sitting balance was shown to improve, ambulatory ability was adversely affected in 67%, unchanged in 33%, and improved in none in one study. Thus the decision to perform anterior and posterior fusion, especially to the pelvis, must be carefully weighed against the potential impact on the child’s mobility and independence.
ADLs, including self-dressing and self-catheterization, may also be adversely affected by extensive spinal fusion. Thus the wise orthopaedic surgeon seeks the counsel of therapists and a urologist regarding the potential impact of spinal fusion on these activities before proceeding with surgery. Finally, the incidence of pressure sores in sitting position, weight-bearing areas may actually be increased by spinal fusion to the pelvis, regardless of whether there is residual pelvic obliquity. Presumably, the loss of flexibility of the lumbar spine and lumbosacral junction, combined with altered areas of weight bearing in the sitting position, causes this increased incidence of pressure sores. Wheelchair modifications, including cushions, must be made in the early postoperative period.
A review of early reports of spinal fusion in myelomeningocele patients is instructive; one simultaneously realizes the impact that experienced multidisciplinary care and improved surgical techniques and instrumentation have had on the results of spinal fusion but is sobered by the frequency and gravity of postoperative complications in this patient population. Postoperative complications, including deep wound infection, pseudarthrosis, fracture, worsening of neurologic deficits, or pressure sores have been reported in more than 50% of these patients, regardless of the surgical technique.
With rare exceptions, posterior or anterior fusion alone is inadequate for myelomeningocele patients with paralytic scoliosis; progressive spinal deformity above the area of anterior surgery that required further posterior surgery, despite solid fusion from the first procedure, has been reported. Pseudarthrosis rates have been reduced by 50% using combined anterior and posterior fusion with a variety of instrumentation systems. McMaster noted improved posture and function in 21 of 23 patients treated by staged anterior spinal fusion with Dwyer instrumentation followed by posterior spinal fusion with Harrington instrumentation. However, one patient died of cardiorespiratory failure, four had wound necroses, two had deep wound infections, and one had a lumbosacral pseudarthrosis.
The best results of spinal fusion for paralytic scoliosis in myelomeningocele patients occur in those treated by combined anterior and posterior fusion, with stable segmental fixation achieved by a combination of sublaminar wires, pedicular remnant wires, and pedicle screws. Banta reported that, overall, the addition of anterior fusion to posterior fusion and instrumentation resulted in greater correction of spinal deformity and pelvic obliquity and an improved fusion mass over that achieved with posterior fusion alone. Parsch and colleagues and Stella and associates reported similar results.
Hyperlordosis
A less common spinal deformity in patients with myelomeningocele is hyperlordosis, with or without associated scoliosis. Hyperlordosis can lead to difficulty sitting, intertriginous skin breakdown, and difficulty with self-catheterization in females because of the posterior rotation of the perineum ( Fig. 36-18 ). In the past, this deformity was associated with lumboperitoneal shunting, but this method of shunting is rarely used today. Treatment, when required, is by a combination of anterior and posterior spinal release and posterior instrumentation; in severe rigid deformities, postural reduction in traction after spinal release, before definitive instrumentation, may improve the deformity.
