Classification

The classification of neuromuscular scoliosis can be based on the underlying disorder: neurologic (e.g., cerebral palsy) or muscular (e.g., muscular dystrophy). Neurologic deficiencies can be broken down further into upper motor neuron dysfunction, as seen in myelomeningocele, or lower motor neuron dysfunction, as seen in spinal muscular atrophy (SMA).

Natural History and Associated Complications

Neuromuscular scoliosis generally begins early in life, is rapidly progressive, and causes significant morbidity. Some patients are capable of ambulation, although many lose their ability to walk early in life or never achieve ambulatory status at all. The use of a wheelchair affords these patients educational and social opportunities that enrich their lives. Spinal deformity can impair comfortable sitting and dramatically reduce the individual’s quality of life. Unbalanced curves and significant pelvic obliquity make wheelchair positioning difficult and may cause uneven distribution of weight that may lead to pressure sores (Fig. 24–1). Prominences created by the convexity of a curve may result in skin breakdown; creases within the concavity of the trunk deformity are susceptible to skin maceration and infection (Fig. 24–2). Majd and colleagues¹ showed a correlation between deformity size, functional decline, and decubitus. Large rigid curves restrict lung volume and impair respiration in patients who often already have limited pulmonary capacity. Treatment of neuromuscular scoliosis can also help the caretakers of these patients, improving the ease of transfers, positioning, feeding, and hygiene. The ultimate goal of treatment of patients with neuromuscular scoliosis is the maintenance of as much independence and function as possible. When patients with neuromuscular scoliosis lose the ability to sit comfortably, their quality of life is dramatically decreased. The natural history for a given patient is largely determined by the specific underlying neuromuscular condition and the degree of involvement.

FIGURE 24–1 Progression of scoliosis after skeletal maturity in a patient with cerebral palsy. A, At age 15, curve measures 75 degrees. B, At age 18, curve measures 115 degrees. C, Age 23, curve measures 143 degrees. D, The patient is unable to be comfortably positioned in her wheelchair.

FIGURE 24–2 Severe spinal deformity can lead to skin maceration on concave side of curvature and pressure sores on convex side.

Treatment Principles

The basic principles of observing or bracing smaller, flexible curves and surgically fusing larger, more rigid curves in adolescent idiopathic scoliosis apply to the treatment of neuromuscular scoliosis, although with less aggressive parameters. Observation alone is employed until curves begin to cause functional impairment. Bracing can be a temporizing measure, used primarily to provide sitting support while the patient grows. Eventually, many of these patients require surgical stabilization with a spinal instrumentation and fusion procedure.

Medical Treatment

Genetic and Family Counseling

Because of the complexity of the medical and psychosocial issues associated with neuromuscular disorders and spinal deformity, care needs to be coordinated with a multidisciplinary team. The primary care physician should be well informed of all orthopaedic issues and play a central role in managing care. Psychosocial support for patients and parents is also vital. Patient advocacy groups have proved to be very useful in helping families cope with the illness and associated surgical care. Physicians may wish to provide information regarding clinical trials or refer families to clinical trial websites (www.clinicaltrials.gov provides a current listing of open clinical trials). Patients and parents may need to be referred for genetic counseling to confirm the patient’s diagnosis and aid in family planning.

Bracing

Bracing is a controversial treatment method in idiopathic and neuromuscular scoliosis. Bracing in neuromuscular scoliosis may be used for postural support, although there is incomplete evidence of its efficacy in limiting curve progression (Fig. 24–3). The etiology of the patient’s scoliosis and the patient’s muscle tone have an impact on the practicality of brace treatment. Patients with spastic disorders generally do not tolerate rigid brace treatment, whereas patients with flaccid paresis are more apt to be compliant with brace treatment. The type of orthoses may play a role in the outcome of the treatment.

FIGURE 24–3 A and B, Bracing in neuromuscular scoliosis is often poorly tolerated. Although it provides modest correction as shown in these radiographs, rigid bracing may lead to excessive skin pressure in patients, who cannot actively pull away from brace.

Kotwicki and colleagues¹⁵ followed 45 nonambulatory patients with neuromuscular scoliosis treated with a suspension trunk orthosis (STO) and found that the STO slowed curve progression in 23 patients. The STO construction functions contrary to the classic thoracolumbosacral orthosis (TLSO), with the STO not resting against the patient’s pelvis but rather directly against the seat. The evidence supporting STO use to prevent curve progression is limited, however, and skin intolerance found in 36 patients complicates its clinical practicality. Although there is limited research on the results of the STO brace, there are numerous studies investigating the TLSO brace. In a study of 15 patients, Shoham and colleagues¹⁶ found that a TLSO reduced scoliotic deformity and pelvic obliquity leading to reduced sitting pressure. These results are contrary to other studies reported in the literature. In a study of 23 patients, Miller and colleagues¹⁷ followed 23 patients with cerebral palsy who wore a rigid Wilmington TLSO for an average of 67 months and concluded that the bracing did not slow progression of their deformity. Olafsson and colleagues¹⁸ followed 90 patients with various neuromuscular conditions treated with a soft Boston orthosis for an average of 3 years after brace treatment. They concluded that brace wear was indicated only in a limited subset of patients—ambulatory patients with hypotonia and short thoracolumbar curves (<40 degrees). In all other patients, brace wear was ineffectual in altering progression but did provide assistance in sitting.

Patients with neuromuscular scoliosis may lack sensate skin to feel pressure from the brace or the muscular control to pull away from the sides of the brace. These patients rarely tolerate the rigid braces often used in idiopathic scoliosis. Patients tend to tolerate soft TLSOs designed to provide improved sitting stability and head and trunk control, while limiting discomfort and skin breakdown (Fig. 24–4).¹⁹

FIGURE 24–4 A and B, Soft total-contact TLSO in an older child. Less rigid forms of bracing are better tolerated but do not seem to alter the natural history of curve progression.

The impact of the orthosis on pulmonary function is another important factor to consider when contemplating a TLSO for patients with neuromuscular scoliosis. The effect of bracing on pulmonary dysfunction seems to depend on the level of muscle spasticity. Flaccid patients are more amenable to rigid bracing, although this bracing may significantly decrease chest expansion leading to compromised pulmonary function.²⁰ Spastic patients seem to be more amenable to soft bracing, which does not seem to compromise pulmonary function,²¹ although this bracing has been shown only to enhance seating comfort.¹⁷ Olafsson and colleagues¹⁸ and Bunnell and MacEwen²² suggested that a subset of patients with minimum deformity and muscle hypotonia or mild spasticity may experience slowing of curve progression by bracing without a negative impact on pulmonary function.

Other factors to evaluate when choosing orthotic treatment for neuromuscular scoliosis include ease of application and obstructions. A bivalved brace may be easier for a caregiver to place, although it cannot provide as much corrective strength as a single opening brace. Winter and Carlson²³ found the two-piece bivalved brace to be a useful support in children with myelomeningocele and SMA. Patients with a stoma or gastrostomy tube require modification of the brace to accommodate these features.

If a patient is not a candidate for bracing or surgery, wheelchair modifications can aid in providing a more comfortable seating position. Modular seating systems can be configured for optimal support of an individual patient (Fig. 24–5). A biomechanical evaluation of seating insert configurations by Holmes and colleagues²⁴ concluded that three-point force application provides significant sitting support and static correction of scoliosis. Patients with more severe deformity may benefit from custom-molded seatbacks, although these items are expensive, and younger patients may outgrow them quickly.

FIGURE 24–5 A and B, Wheelchair systems can provide sitting support for patients who are not good candidates for bracing. Custom-molded seatbacks can be made to accommodate substantial spinal deformities.

Operative Treatment

The timing for operative treatment is influenced by curve severity, underlying neuromuscular pathology, and other factors. The curve severity guidelines are loosely based on, but less aggressive than, the guidelines used in idiopathic scoliosis. Fusion should be considered as coronal deformity approaches 40 to 60 degrees. DMD may be an important exception to this concept: Surgery has been advocated when the deformity reaches 20 degrees because of pulmonary considerations.²⁵ Patients with severely limited respiratory function have been shown to have good outcomes in spinal surgery, however. The sagittal profile is another important consideration because lordotic and kyphotic deformities can also impair sitting balance and pulmonary capacity (Fig. 24–6). Other factors that play a role in the decision to operate include patient age, nutritional status, cardiac function, curve progression, patient comorbidities, and family and caretaker support.

FIGURE 24–6 A and B, Clinical photograph (A) and lateral radiograph (B) of a child with severe kyphosis that impedes balanced sitting.

The benefit of scoliosis surgery in this population is a topic of much debate. Many of these patients are poor operative candidates and risk much undergoing involved corrective surgery. Preoperatively, patients may have compromised pulmonary function, limited cardiac capacity, poor bone stock, and high risk for aspiration, which put them in danger of intraoperative or postoperative complications. Correction of large deformities requires extensive exposures and long procedures that can lead to blood loss greater than one to two patient blood volumes. Although many patients already have neurologic compromise, they are still at risk for further compromise because of intraoperative spinal column manipulation. More powerful instrumentation systems have led to less postoperative decompensation and pseudarthrosis; however, there remains a considerable risk of curve progression, sometimes necessitating revision surgery.^26–28

Despite the risk of surgery, the benefits of corrective scoliosis surgery for many of these patients are substantial. Halting or slowing curve progression has a positive impact on the functional ability, comfort, and overall quality of life of these patients. Lonstein and Akbarnia²⁹ reported that more than 50% of patients treated had functional improvement after surgery. In a study of 79 patients with total body spastic cerebral palsy, Comstock and colleagues²⁷ found that 85% of caretakers surveyed were satisfied with the surgery, reporting improved comfort, sitting ability, and cosmesis for the patients. Bridwell and colleagues²⁶ found similar trends in a study of 54 patients with neuromuscular disorders with all caretakers reporting benefit from the surgery, specifically in the areas of ease of patient care, skin breakdown, patient comfort, pulmonary complications, and quality of life. Askin and colleagues³⁰ evaluated 20 patients with neuromuscular scoliosis preoperatively and 6, 12, and 24 months after corrective spinal surgery. The authors noted decreased physical ability at the 6-month time point followed by a return to preoperative function by 12 months and concluded that scoliosis surgery in these patients can stabilize, but not improve, function; however, 75% of patients or caregivers were extremely pleased with the cosmetic results of the surgery. Although most of these patients have deteriorating courses, the correction of spinal deformity seems to improve their function and quality of life.

Although these positive results make a strong case for spine surgery in patients with neuromuscular scoliosis, several review studies have been unable to show a clear benefit of surgical intervention for the patient. Mercado and colleagues³¹ evaluated 198 publications and graded their results on the concept of Grades of Recommendation introduced in the Journal of Bone and Joint Surgery.³² These authors concluded that the current literature shows there is poor-quality evidence that spinal fusion improves the quality of life in patients with cerebral palsy or DMD.³¹ In a Cochrane Collaboration review, Cheuk and colleagues³³ found that there were no randomized controlled clinical trials available to evaluate the effectiveness of scoliosis surgery in patients with DMD, and so no evidence-based recommendations could be made. Although the practicality of conducting a randomized controlled trial of this nature is questionable, the literature does not provide sufficient evidence to support the role of spinal surgical treatment in patients with neuromuscular scoliosis. It is recommended that the decision for surgical intervention be made based on the needs of the individual patient in consultation with the multidisciplinary neuromuscular care team.

The goal of treatment is preservation of function, which may entail maintaining ambulatory status, maintaining sitting without upper extremity support, or simply allowing assisted comfortable sitting. The decision to operate on a patient with neuromuscular scoliosis is a highly individualized process that should involve a frank and open discussion with the family and patient about the risks and expectations of such a procedure.

Preoperative Considerations

Radiographic Assessment

Patients should have a preoperative anteroposterior and lateral film taken of the entire spine preferably in an upright (sitting or standing) position. For assessment of skeletal maturity, a separate anteroposterior radiograph of the pelvis should be considered because scoliosis films often truncate the anatomy necessary to determine skeletal maturity. To assess spinal flexibility, supine bending films or traction films are used. Accurate measurements of the coronal Cobb angle, sagittal Cobb angle, and pelvic obliquity are crucial for complete preoperative planning and postoperative evaluations. In a more recent analysis of the interobserver and intraobserver variability of radiographic measurements of patients with neuromuscular scoliosis, Gupta and colleagues⁵³ found that neuromuscular radiographs can be reliably analyzed with the use of coronal Cobb angle. Patients who may have congenital spinal anomalies or spinal tethering, such as patients with myelomeningocele, should undergo magnetic resonance imaging (MRI) to evaluate the neural elements fully before surgery. Computed tomography (CT) may also be useful in some patients with severe deformity or in patients with a congenital malformation of the vertebrae.

History of Instrumentation in Neuromuscular Scoliosis

In 1942, Haas⁴⁷ published one of the first references to surgical intervention in neuromuscular scoliosis: a case report describing muscle and fascial transfers to obtain complete and permanent correction in one patient. With the introduction of the Harrington rod in 1962, use of this instrumentation with fusion of the spine in patients with neuromuscular scoliosis became the standard. Series using only Harrington rods and posterior spinal fusion have been associated with high incidences of pseudarthrosis (19% to 40%), moderate initial correction (20% to 57%), and loss of correction ranging from 14% to 28%.^29,48 After Harrington rod instrumentation, most patients required bed rest and bracing or casting for up to 1 year.

The introduction of segmental spinal instrumentation by Luque⁴⁹ in 1976 led to major advances in the biomechanical stability and correction of these very deformed spines (Fig. 24–7). Several studies revealed that Luque segmental sublaminar wire fixation had fewer complications than Harrington instrumentation and was stable enough so that most patients required no brace or cast postoperatively.^48,50,51 Using the Luque method, the only patients with cerebral palsy requiring postoperative bracing may be patients with athetosis or poor fixation because of severe osteopenia. This is a tremendous advantage because postoperative casting carries the potential for skin and pulmonary complications. Because of these attributes, the Luque technique became the standard method for posterior spinal instrumentation in patients with neuromuscular spinal deformities.

FIGURE 24–7 This one-piece Luque “box” is a modification of the original double Luque rod technique and is a more rigid construct.

Contouring Luque spinal rods after the technique introduced by Allen and Ferguson⁵² (Galveston technique) allowed the rods to be fixed to the pelvis, providing surgeons with a more effective method of controlling pelvic obliquity. Bell, Moseley, and Koreska developed the unit rod, a precontoured U-shaped rod that includes the Galveston portion for pelvic fixation (Fig. 24–8). Studies of patient outcomes with unit rod fixation have revealed excellent correction and maintenance of correction.^54–56 Bulman and colleagues⁵⁷ compared the unit rod with double Luque rods and reported superior correction of sagittal and coronal alignment and pelvic obliquity with the unit rod constructs. Tsirikos and colleagues⁵⁶ evaluated 287 children treated with unit rod instrumentation to the pelvis with 2-year follow-up and concluded that it offers the advantages of good correction of deformity and pelvic obliquity, a low complication rate, and a 96% caretakers’ survey satisfaction rate. Unit rod instrumentation has also been shown to have good results in ambulatory patients, with excellent deformity correction and preservation of ambulatory function at 2.9-year follow-up in 24 patients.⁵⁸ Additionally, biomechanical studies have shown that the addition of an L5 pedicle screw increases the construct stiffness and the strength-reducing complications associated with the loss of fixation.⁵⁹

FIGURE 24–8 A and B, Unit rod, as shown here in a patient with cerebral palsy, provides a method for obtaining fixation to pelvis and correction of pelvic obliquity.

Through a desire to achieve similar correction as the unit rod construct, without the need for pelvic fixation, the U-rod was investigated by McCall and Hayes.⁶⁰ This rod is an outgrowth of the unit rod concept except the rod terminates in pedicle screws at the L5 level relying on the iliolumbar ligaments to achieve correction of the pelvic obliquity. In their comparison study of 30 patients with unit rod instrumentation and sacral fusion and 25 patients with U-rod instrumentation and L5 fusion, McCall and Hayes⁶⁰ found that the U-rod provided comparable correction of scoliosis and pelvic obliquity in curves with less than 15 degrees L5 tilt at 4 years of follow-up. Regardless of whether the precontoured unit rod or double Luque rods are used, segmental sublaminar wire instrumentation provides simple, inexpensive, and fairly powerful correction of coronal plane deformity. Segmental sublaminar wire instrumentation has limitations in the maintenance of sagittal plane alignment, however, because the sublaminar wiring fails to fix spinal length, and the vertebrae can slide along the smooth rod construct, particularly during trunk flexion (Fig. 24–9A).

FIGURE 24–9 A, Failure of proximal sublaminar wiring in this construct resulted in increased kyphosis and prominent hardware necessitating revision surgery 3 years after primary procedure. B, After proximal revision, the patient developed pullout of the Galveston portion of his construct. This clinical course emphasizes that fixation challenges are present in patients with neuromuscular deformity, particular hyperkyphosis.

Multihook segmental systems such as Cotrel-Dubousset (CD) and Isola have also been shown to be efficacious in patients with neuromuscular scoliosis.^61–63 The comparative efficacy of these two different constructs is inconclusive. In a study of 47 patients with neuromuscular scoliosis, Yazici and colleagues⁶⁴ concluded that the Isola instrumentation combined with Galveston pelvic fixation provided correction and maintenance of pelvic obliquity superior to Luque Galveston, unit rod, or CD instrumentation. The results of this study are in contrast to the work of Wimmer and colleagues,⁶³ who found that there was no difference between Luque Galveston and Isola instrumentation in radiographic outcomes, patient satisfaction, or complication rate. The selection of either of these two instrumentation systems is a choice that relies on surgeon experience and the needs of the individual patient.

In some circumstances, a hybrid system with a combination of hooks, pedicle screws, and sublaminar wires may provide optimal fixation with maximal correction. A biomechanical study conducted at the authors’ institution showed that the addition of bilateral L1 pedicle screws to a Luque-Galveston construct on a cadaveric axial skeleton increased construct stiffness by greater than 60%. The addition of selective hooks or screws or both to an otherwise sublaminar wire construct allows use of compressive and distractive force to address the coronal and the sagittal deformities. Additionally, proximal fixation with sublaminar wires compromises the ligaments above, making junctional kyphosis more likely. Hooks (transverse process) or pedicle screws or both may limit this complication in kyphotic patients at greatest risk.

Pelvic and Sacral Fixation

Severe pelvic obliquity secondary to unbalanced scoliotic curves and lower extremity contractures is common and progressive in patients with neuromuscular scoliosis. A solid spinal fusion to the pelvis aids in sitting comfort and balance^1,65; however, achieving this goal can be troublesome (Fig. 24–9B). Controlling the motion across the lumbosacral joint requires secure fixation to the pelvis to prevent a pseudarthrosis.

Various systems have been proposed to provide fixation to the pelvis. The Galveston technique was the first advancement to improve fusion rates and clinical success in long fusions to the sacrum.^52,53 When paired with either contoured Luque rods or unit rods, it provides powerful coronal correction of pelvic obliquity. This technique places greater forces, however, on the lumbrosacral junction, and proper contouring of the rods may be difficult. The initial concern regarding the association between radiolucency around the screw tips (“windshield wiper” sign) and an increased incidence of complications is of little clinical significance (Fig. 24–10).^66,67 Although a biomechanical evaluation of the Galveston technique by Sink and colleagues²⁸ showed that this construct creates a long lever arm that places considerable cantilever forces at the lumbrosacral junction, these forces lead to a high incidence of proximal fixation pullout and distal migration of Galveston rods. The rods also require three-dimensional bending that makes it difficult to contour the rod properly.⁶⁸

FIGURE 24–10 Radiolucency around rod tip in ilium (windshield wiper effect) suggests lumbosacral pseudarthrosis, which may remain asymptomatic and resolve spontaneously.

Other systems of sacropelvic fixation use an “S” bend (Dunn-McCarthy), which hooks distally over the sacral alae, while the more proximal portion is secured to the lumbar spine at L4 or above with a pedicle screw or infralaminar hook. Reviewing the results of 67 patients, McCarthy and colleagues⁶⁹ found that this technique had decreased operative time compared with Galveston fixation and excellent clinical results, although in 2 of the 67 constructs there was migration of the rods into the pelvis. Other techniques of rod contouring to fix to the pelvis include the Warner-Fackler and McCall techniques, both commonly used in the treatment of myelomeningocele-associated kyphosis in which posterior elements of the lumbar or sacral spine may be absent. In the Warner-Fackler technique,⁷⁰ Luque rods are bent to 90 degrees in two places at the distal end, allowing the rods to pass through the S1 foramina and lever against the front of the sacrum to provide sagittal correction (Fig. 24–11). In a slight variation of this technique, McCall⁷¹ described bending Luque rods to 20 to 40 degrees, passing them through the S1 foramina and bending the protruding portion according to the contour of the anterior sacrum. In 16 myelomeningocele patients with hyperkyphosis, McCall⁷¹ found satisfactory correction and maintenance of correction after 5 years of follow-up.

FIGURE 24–11 A and B, Warner-Fackler method of pelvic fixation was used after kyphectomy in this patient with myelodysplasia.

Improvement on the Galveston concept has been the focus of many clinical studies.^69,72–74 The use of S1 screws alone was investigated, but bone quality is generally not substantial enough for successful use in patients with neuromuscular scoliosis. Early and colleagues⁷² compared the biomechanical properties of Galveston sacropelvic fixation versus Colorado II sacropelvic plates using S1 screws, S2 alar screws, and iliac screws and found that both methods provided similar construct stiffness with the Colorado II plate limiting L5-S1 motion in flexion-extension. These authors found that addition of a pair of L1 screws increased the construct stiffness by approximately 50% in both fixation techniques.

The use of iliac screw fixation has become a subject of several more recent articles because of its ease of implantation, avoiding the complex lumbosacral three-dimensional Galveston rod contouring. Clinical and biomechanical studies have shown an improved fusion rate and high pullout strengths after the use of iliac screws for caudad lumbosacral fixation.^73,74 In a review of 50 patients treated with one or two bilateral iliac screws, Phillips and colleagues⁷⁵ concluded that iliac screws provide a safe and effective means to treat neuromuscular scoliosis at 21 months of follow-up. These authors also noted that two screws in each iliac wing provided a more stable fixation with fewer implant-related complications than using a single screw. In a direct comparison of 20 patients with Galveston rod fixation versus 20 patients with iliac screw fixation, Peelle and colleagues⁷⁶ found that both techniques offer similar pelvic fixation with the iliac screw construct allowing additional screw fixation points to the sacrum and lower lumbar vertebrae. The long-term impact of these screws on the sacroiliac joint was investigated in 67 adult patients by Tsuchiya and colleagues,⁷⁴ and no evidence of degeneration was observed at 5- to 10-year follow-up.

Although iliac screws provide a promising alternative to Galveston fixation, several studies have shown difficulty with implant prominence causing skin irriation.⁷⁷ Peelle and colleagues⁷⁶ did not observe this complication in their patient series, however, because they countersunk the screws below the superficial portion of the posterior iliac crest. The patient’s body habitus must be considered when selecting the means of sacropelvic fixation. In very small or thin patients, the authors continue to prefer a Galveston rod construct for pelvic fixation. Screw fixation is used when possible, especially in cases with a kyphotic deformity, where the Galveston rod may not optimally resist pelvic flexion (Fig. 24–12).

FIGURE 24–12 A and B, Fixation to pelvis in this patient with cerebral palsy was provided by iliac screws connected to 5.5-mm posterior rod system.

When patients with neuromuscular scoliosis are instrumented because of the severe obliquity of the pelvis, intraoperative halo-femoral traction may also be beneficial. Previous studies on this traction technique have been described for patients with idiopathic and congenital scoliosis. In nonambulatory patients with neuromuscular scoliosis, surgeons have relied on rods or screws inserted into the iliac wings by a cantilever method to level the pelvis. This method has the potential to weaken the bone-construct connection in patients with poor bone stock. In a study of 20 nonambulatory patients with neuromuscular scoliosis with halo-femoral traction and 20 matched patients without halo-femoral traction, Takeshita and colleagues⁷⁸ found that halo-femoral traction provided significantly improved lumbar curve and pelvic obliquity correction at 2-year follow-up. These authors had no associated perioperative complications with this technique and found that unilateral femoral traction with corresponding halo traction was able to level the pelvis to an acceptable position before the surgery was begun. When a significant hip flexion contracture exists, traction results in an increase in lumbar lordosis, however, that may be undesirable.

Some authors have argued that the pelvis can be left unfused in patients with slight pelvic obliquity, mild contractures, and little pelvic deformity in the sagittal plane, whereas others have argued that an ambulatory patient should never be fused to the pelvis.^69,79 McCall and colleagues⁶⁰ advocated that patients with less than 15 degrees of L5 tilt should be considered for a fusion to L5. These authors believed that this fusion allows greater mobility and improves the patients’ ability to carry out activities of daily living. Other studies promote fusion to the pelvis in all patients regardless of ambulatory status. A study by Tsirikos and colleagues⁵⁸ of ambulatory cerebral palsy patients with severe pelvic obliquity who were treated with fusion to the pelvis by Luque-Galveston instrumentation found that 23 of 24 patients maintained their ambulatory status. Given the progressive nature of this deformity and the fragility of these patients as operative candidates, the authors generally recommend including the pelvis in the fusion mass for most neuromuscular deformities.

Anterior Spinal Release and Fusion

Indications

The addition of an anterior procedure can assist in the correction of neuromuscular spinal deformity and may be justified in several situations (Fig. 24–13). Anterior release and fusion has generally been indicated in patients with rigid scoliosis, patients with rigid kyphosis, immature patients at risk for the development of crankshaft growth, and patients at risk for pseudarthrosis owing to incompetent posterior elements (myelomeningocele or severe osteopenia).⁸⁰ In assessing the rigidity of the deformity, traction and supine bending films are useful but may underrepresent the available flexibility. An anterior release of a large rigid curve increases the overall spine mobility and makes the posterior correction easier with a relatively high fusion rate. In a study by Newton and colleagues,⁸⁰ the fusion rate achieved with anterior release combined with posterior corrective instrumentation and fusion was found to be comparable between adolescent patients with neuromuscular scoliosis and idiopathic scoliosis at 3-year follow-up.

FIGURE 24–13 A, This severe thoracolumbar curve has preoperative Cobb angle of 136 degrees. B, Owing to inflexibility, anterior disc excision and anterior instrumentation was used as the first stage of this procedure. C and D, Posterior instrumentation T2 to pelvis was used in this spastic quadriplegic patient.

Anterior instrumentation and spinal fusion alone and in combination with posterior instrumentation have also been shown to be successful techniques in a subset of patients with neuromuscular scoliosis. The authors’ current algorithm indicates an anterior procedure for “severe” curves (most often thoracolumbar). If a near-complete correction of the major curve can be predicted with anterior instrumentation after an aggressive multilevel discectomy, a single rod anterior system is included. If the curve remains rigid after an anterior release, the anterior instrumentation is skipped, and either an apical vertebrectomy is performed, or the correction is achieved after posterior osteotomies (Fig. 24–14). It is important to avoid “locking in” a poor correction with anterior instrumentation in rigid curves. The goals of achieving a level pelvis and balanced spine must be weighed against the added morbidity of an anterior release or instrumentation procedures or both.

Figure 24–14 A and B, This severe 140-degree lumbar curve was upsetting wheelchair sitting balance in this spastic quadriplegic patient. C and D, This curve was treated with a staged procedure. Anterior release did not provide sufficient flexibility, and anterior L1 and L2 corpectomy was performed. This procedure was followed by T2 to pelvis posterior instrumentation with completion of L1 and L2 corpectomy posteriorly.

In skeletally immature patients with idiopathic scoliosis, anterior release and fusion reduces anterior overgrowth that results in crankshaft deformity; however, whether this principle can be applied in neuromuscular scoliosis is controversial. In a study of 50 skeletally immature patients with neuromuscular scoliosis treated with posterior instrumentation only, Smucker and Miller⁸¹ noted no significant curve progression at an average of 4 years of follow-up. In contrast, Comstock and colleagues,²⁷ after review of 60 skeletally immature patients with cerebral palsy who underwent surgical scoliosis correction, concluded that skeletally immature patients have the best correction and long-term outcomes when treated with anterior and posterior procedures.

Scoliosis in Cerebral Palsy

Scoliosis is common in cerebral palsy with a 25% incidence of spinal deformity in all cerebral palsy patients. The incidence and degree of deformity correlate with the amount of neurologic deficit and ambulatory status. In a study of 272 institutionalized patients, the highest prevalence of scoliosis was found in the most severely affected patients with 75% of spastic quadriplegic and 68% of spastic diplegic patients having at least 10 degrees of spinal deformity. In the above-mentioned study, 44% of patients who could ambulate independently, 54% of patients who could ambulate with assistance, 61% of patients who could sit independently, 75% of patients who could sit with assistance, and 76% of bedridden patients had significant deformity. Although these numbers may be inflated by the fact that the study population was composed entirely of institutionalized patients, they still reveal a trend of increased deformity with increased spasticity and decreased independent mobility.^105,106

The development of scoliosis in cerebral palsy patients is thought to result partly from persistent primitive reflex patterns and asymmetrical tone in the paraspinous and intercostal muscles. Pelvic obliquity from contractures around the hip plays a role in scoliosis development; however, it is often difficult to isolate this as a contributing factor because pelvic obliquity, hip contractures, and scoliosis often develop simultaneously. Placing patients with a weak trunk and total body involvement into artificial upright sitting positions without appropriate spinal support may encourage gravity-related kyphosis and scoliosis. This suspicion was raised by Madigan and Wallace¹⁰⁶ when they found a 75% incidence of scoliosis in a predominantly institutionalized population comprising “prop sitters” but only a 25% incidence in a population of spastic quadriplegics in which prop sitting was not pursued.

Scoliosis in cerebral palsy has been classified into four categories based on curve pattern (single vs. double) and the presence or absence of pelvic obliquity. Long C curves with pelvic obliquity generally occur in more severely involved nonambulatory patients with spasticity. S curves occur more frequently in sitting or walking patients with little spasticity. S curves seem to be more idiopathic in nature, often without associated pelvic obliquity.²⁹ Patients with severe involvement and a developmental level less than 6 months seldom attain independent sitting balance. Lack of neuromuscular control prevents proper alignment of the head, and these patients do not develop compensatory curves to bring the shoulders and head over the pelvis.

Curve progression is related to the above-mentioned risk factors and quadriplegia, poor functional status, and a single thoracolumbar curve.^1,107,108 As in idiopathic scoliosis, risk of progression is also related to curve magnitude and to the amount of remaining spinal growth. Because progression of spinal deformity begins at the onset of the neuromuscular condition, patients with cerebral palsy have a much longer time to progress and have the potential for developing larger curves than patients with adolescent idiopathic scoliosis. This period of potential curve progression is prolonged further because these patients often maintain open growth plates into their late teens or early 20s. In adults, Thometz and Simon¹⁰⁸ found that larger curves progress faster than smaller curves; they noted curve progression of 0.8 degree per year in curves less than 50 degrees and 1.4 degrees per year in curves greater than 50 degrees. Even patients who have completed growth are at risk for scoliosis progression.

Treatment Options

Authors’ Recommendations

For gravity-dependent mild scoliosis or hypotonic kyphosis in children younger than 10 years, the authors recommend a Plastizote body jacket. This body jacket supports the spine, assists head control, and is well tolerated by the patient. The orthosis usually lasts more than 2 years before it is outgrown. For more rigid curves between 30 degrees and 50 degrees or in less rapidly growing patients older than 12 years, a rigid total-contact orthosis may be tried. Although less well tolerated, a total-contact orthosis provides better correction and may delay the need for surgery by providing greater sitting support.

As discussed earlier, defining the precise indications for surgical intervention in patients with scoliosis and cerebral palsy is difficult. The authors recommend that surgery be considered when scoliosis greater than 50 to 70 degrees exists, taking into consideration the patient’s functional, mental, and general health status. The decision to proceed with surgery of this magnitude requires a thoughtful analysis and discussion with the family and caregivers. If Luque instrumentation is used posteriorly, when possible, 5.5- to 6.35-mm rods and a combination of infralaminar hooks, pedicle screws, and double 16- to 18-gauge wires should be used to maximize correction and rigidity. Smaller diameter rods (4.5 to 4.75 mm) should be used only in very small patients for fear of rod breakage. Anterior fusion should be considered in patients with rigid curves greater than 60 to 80 degrees, in skeletally immature patients, or in patients with fixed pelvic obliquity. In severe curves with marked pelvic obliquity, the correction of the pelvic obliquity and the certainty of permanent correction are often enhanced by the addition of anterior lumbar instrumentation.

The use of pedicle screws and aggressive posterior osteotomies has reduced the use of anterior surgery for some patients. For the most flexible cases, an all-posterior hybrid construct is appropriated; the authors prefer pelvic fixation with iliac bolts over Galveston rods. If the curve is more rigid, Ponte-type osteotomies are added, and the density of pedicle screws is increased. Patients with curves that do not correct to less than 70 degrees on side bending are considered for an anterior procedure, most often at the thoracolumbar junction. If, after complete disc excision (including the posterior longitudinal ligament), the spine is now flexible enough for near-complete correction, the correction is achieved with an anterior rod system. If the spine remains rigid after discectomy, performing an apical vertebral excision is considered. In either case, an anterior rod is avoided when residual rigidity remains, and the correction is achieved with the posterior instrumentation.

All cerebral palsy patients with limited ambulatory capacity should be fused inferiorly to include the pelvis, even if their pelvic obliquity is correctable, because of the potential for increased obliquity owing to persistent muscle imbalances (Fig. 24–15). Most patients do not require postoperative immobilization. In patients with poor bone stock or a motion disorder undergoing fusion to the pelvis, a brace is considered for 3 to 6 months after surgery.

FIGURE 24–15 This patient with cerebral palsy presented at age 17 with Harrington-Luque instrumentation from T4 to L4 done 5 years previously. At presentation, the patient had 85-degree C-shaped scoliosis with marked pelvic obliquity, rotational deformity, and resultant sitting difficulties. In most nonambulatory patients who have adequate spinal length, fusion to pelvis is recommended to avoid this dilemma.

Scoliosis in Myelodysplasia

The incidence of scoliosis in patients with myelodysplasia (spina bifida) varies in the literature from 52% to 90%.^112,113 In a more recent study of 141 patients by Trivedi and colleagues,¹¹³ the authors defined scoliosis in myelodysplasia as curvature greater than 20 degrees and concluded that new curvature could develop as late as 15 years of age.¹¹² In this cohort of patients, 89% of patients with the last intact laminar arch located in the thoracic region had scoliosis, whereas 44% and 12% had scoliosis if their last intact laminar arch was in the upper and lower lumbar regions. From this trend, Trivedi and colleagues¹¹³ concluded that the last intact laminar arch was the most useful early predictor of scoliosis risk, although ambulatory status and clinical motor levels were also useful predictors.

Myelodysplastic spine is one of the most difficult treatment dilemmas in scoliosis management. These patients present with congenital malformations (Fig. 24–17), often in the form of severe kyphosis preventing comfortable sitting and causing skin breakdown that may necessitate separate and early intervention. The risk of deformity from weak, spastic paraspinal musculature and asymmetrical hip contractures remains, often requiring more definitive surgical correction in the preteen or teen years. Surgical correction for myelodysplasia presents unique problems because of the absent posterior elements, increasing the dependence on anterior fusion and fixation. In addition, the posterior approach for surgical correction traverses the poor-quality skin and scar tissue that results from the defect and the early neurosurgical repair (Fig. 24–18).

FIGURE 24–17 A and B, Three-dimensional CT scan shows absence of posterior elements and congenital vertebral anomalies that make myelomeningocele spinal deformities challenging treatment dilemmas.

FIGURE 24–18 An infant with severe scarring from original neurosurgical closure of spinal defect.

There may be an association between myelodysplasia patients with a tethered spinal cord and rapidly progressive scoliosis.¹¹⁴ Most of these patients have some variation of cord tethering as a residuum of the defect and its neurosurgical closure. In patients with unexpected rapid curve progression or increased trunk spasticity (hypertonicity), a tethered cord with or without hydromyelia should be considered. Studies such as MRI or myelography may help define the anatomy; however, the literature does not support a causal relationship between scoliosis and Chiari malformation or syringomyelia.¹¹⁴ Thoughtful teamwork with a neuroradiologist, neurologist, and neurosurgeon helps clarify these issues. Surgical release of a tethered cord can result in scoliosis stabilization, maintenance of motor function, and decreased back pain.¹¹⁵ Pierz and colleagues¹¹⁶ evaluated 21 cases of de-tethering, however, and concluded that improvement or stabilization of scoliosis after de-tethering is less likely in patients with curves greater than 40 degrees or thoracic level defects or both. Given the high incidence of scoliosis and the tendency for rapid progression in these patients, annual follow-up evaluations with posteroanterior and lateral radiographs should closely track coronal and sagittal spinal deformity and hip contractures and trunk spasticity.

Treatment Options

Surgical Management

Definitive surgical management need only be delayed until patients reach 10 to 12 years of age because growth hormone deficiency limits their growth, and truncal height has reached its maximum around this time. Indications for operative management are similar to the indications for other neuromuscular disorders, although a curve that is rapidly progressive in a patient with myelodysplasia may be treated earlier at 40 to 50 degrees. Because a significant hip flexion-abduction contracture can produce lumbar lordosis and scoliosis, the hip contracture should be surgically released before any attempt at surgical correction of the spine.

Anterior Fusion

As previously discussed, anterior fusion is very important in myelodysplasia because the anterior spine provides a large surface for bony fusion in the lumbar spine, in contrast to the deficient posterior elements at these levels. A thoracoabdominal retroperitoneal approach from the convex side of the curve and division of the diaphragm allows anterior disc excision and bone grafting; this may be combined with posterior instrumentation to provide curve correction in select patients (Fig. 24–19). Use of anterior instrumentation alone has a specific role in the treatment of myelodysplasia scoliosis. In a study of 14 myelodysplasia patients treated with a Texas Scottish Rite Hospital anterior construct alone, Sponseller and colleagues¹¹⁸ concluded that anterior instrumentation was successful in a select group of patients with thoracolumbar curves less than 75 degrees, compensatory curves less than 40 degrees, no hyperkyphosis, and no syrinx in the spinal cord. Basobas and colleagues⁸² found excellent surgical correction and maintenance with an anterior instrumentation and fusion procedure in their study of 11 myelodysplasia patients at 5-year follow-up. In patients with a lumbar curve and fixed pelvic obliquity, anterior instrumentation provides a powerful means of correcting the deformity (Fig. 24–20).

FIGURE 24–19 A and B, This young patient with myelodysplasia presented with 80 degrees of scoliosis and severe lordosis. C and D, Severe lordosis was treated with anterior instrumentation from T12 to L5 followed by posterior instrumentation from T3 to pelvis.

FIGURE 24–20 A-D, Idiopathic-like lumbar or thoracolumbar curves in patients with myelomeningocele may be successfully treated with anterior instrumentation only.

Posterior Fusion

Although essential to a solid fusion in most myelodysplasia patients, the posterior procedure is difficult because of the poor quality of overlying tissue, decreased paraspinal muscle vascularity, and missing posterior elements. Posterior fusion in combination with anterior fusion is recommended by several authors. In a study of 50 patients, Banit and colleagues¹¹⁹ concluded that posterior fusion alone yielded a much higher pseudarthrosis rate of 16% than rates reported for anterior and posterior fusion combined. Parsch and colleagues¹²⁰ reviewed results of 54 myelomeningocele patients treated surgically and also concluded that anterior and posterior instrumented fusion resulted in the best correction and lowest complication rate.

Luque or unit rods with sublaminar wiring can be used in segments of the spine in which the posterior elements are intact, although supplementation with screws and hooks increases construct stability. In regions in which the posterior elements are missing, pedicle screws are stronger, although the atypical anatomy makes accurate screw placement difficult. In addition, pedicle screws may be prominent particularly in a kyphotic region because the lateral bony columns are often subcutaneous.

Fusion to the Pelvis

There is considerable controversy over whether the pelvis should be included in the fusion mass. Lindseth and colleagues¹²¹ contended that this is necessary only if there is a component of kyphosis in the lumbar spine or if pelvic obliquity is greater than 15 degrees. They noted an increased incidence of ischial ulcers in patients left with residual pelvic obliquity and fusion to the pelvis probably because the rigid, long, curved segment prevents easy shifting of weight between ischial tuberosities. A prospective evaluation of 11 myelomeningocele patients treated with anterior and posterior instrumented fusion to the lumbar spine revealed good correction of coronal and sagittal plane deformities with fair maintenance of correction. From this experience, the authors of the study concluded that, with the advent of more stable segmental instrumentation, the pelvis could be spared to allow more lumbosacral mobility and to avoid the morbidities associated with pelvic fusion.¹²² Similar results have been found in a select group of myelodysplasia patients with anterior-only instrumentation and fusion where pelvic obliquity can be corrected without pelvic fixation.⁸²

The most predictable approach from the standpoint of the spinal deformity is fusion to the pelvis. In patients with limited activity, the authors recommend fusion to the pelvis to ensure a straight spine over a level pelvis. In ambulatory or very active patients who play recreational activities, such as wheelchair basketball, the pelvis may be spared with the knowledge that a later revision may be required.

Various options are available for instrumentation to the pelvis. The Galveston modification of Luque rods is a commonly used system, although it may not provide as much stability as the Warner-Fackler modification in correcting kyphosis. As previously described, the Warner-Fackler method involves two 90-degree bends in the distal end of a Luque rod allowing the rod to pass through the S1 foramina and lever against the anterior aspect of the sacrum (see Fig. 24–11).⁷⁰ In a small series of nine patients treated with kyphectomy and this method of pelvic fixation, Thomsen and colleagues¹²³ reported excellent correction and maintenance of kyphosis correction at an average of 28 months of follow-up. The authors described two instances of complications (loss of rod connection and migration) both at about 32 months after surgery and concluded that this technique, although effective, should be limited to patients weighing less than 30 kg. McCall described a similar technique with Luque rods passed through the S1 foramina and bent once to 20 to 40 degrees depending on sacral inclination. In his series of 16 patients, McCall⁷¹ reported good correction of kyphosis and excellent maintenance after 57 months of follow-up. Iliac screw fixation has also been shown to afford equivalent maintenance of pelvic obliquity and scoliosis correction compared with the Galveston technique.^75,76

True fusion to the pelvis (to the wing of the ilium rather than just to the sacrum) can be achieved by suturing the detached iliac crest apophysis to the transverse process of the spine at L3 or L4 and filling the created triangle with bone graft (Fig. 24–21). Pseudarthrosis is common in fusions to the pelvis, and the authors still advise a conservative immobilization protocol.

FIGURE 24–21 This bone grafting technique increases the chance of stable fusion by including the wing of the ilium and the sacrum.

Major and minor complications are more common in myelomeningocele patients than in other patients with neuromuscular scoliosis. Reports of the incidence of wound infections range from 19% to 43%.¹²⁴ Many patients have minor complications, such as urinary tract infections or minor wound dehiscence. Major complications, including massive blood loss and instrumentation failure, are more common in myelomeningocele scoliosis than in idiopathic scoliosis or other neuromuscular conditions.^119,124 Pseudarthrosis rates range from 16% to 50% in the literature.^119,125 In addition, the proximity of procedures to the dural sac and the abnormal anatomy increase the risk of shunt compromise and failure. By attending to detail and applying all that is currently known about myelomeningocele scoliosis surgery (careful anterior and posterior fusion, segmental attachment, cautious remobilization), the major complication rate can be reduced to 15% or less.

Kyphosis Treatment

As already noted, bracing is extremely difficult in the severe kyphosis associated with myelomeningocele. Kyphosis is relentlessly progressive (3 to 8 degrees per year) and can become pathologic in 20% of patients. Because surgical correction is complex and difficult, many children are left untreated and seem to function reasonably well, although skin breakdown over the kyphosis, pressure on abdominal contents, and loss of trunk height remain problems. Indications for surgery include progressive kyphosis, skin breakdown over the kyphosis, respiratory compromise, and concern regarding the effect of severe trunk shortening (Fig. 24–22).^71,126

FIGURE 24–22 Lumbar gibbus on this patient with thoracic level myelomeningocele was causing sitting difficulties and loss of trunk height before he underwent kyphectomy and spinal fusion.

Kyphosis in myelomeningocele can be corrected, but intraoperative or perioperative death is frequent enough to give pause to all who treat this disorder. Death can occur from uncontrolled bleeding or problems with cerebrospinal fluid dynamics. The advent of segmental spinal instrumentation has made kyphectomy with fusion at least moderately predictable. The segmental attachment must extend well into the thoracic spine to control the large sagittal plane bending moments.

Basic principles include a long midline posterior approach with exposure of five or six levels of normal closed laminae proximally and distal exposure down to the mid-sacral level. The sac and cord are retracted or resected, with care being taken to repair the dura slightly distal to and separate from the cord transection to avoid tying off the central canal and disturbing cerebrospinal fluid dynamics.¹²⁷ In most cases, retracting the scarred thecal sac allows sufficient exposure.¹²⁶ The spine is prepared for segmental attachment by passing laminar wires or hooks through all normal laminae proximally. The distal segments can be attached by pedicle screw fixation or by screws placed directly into the vertebral bodies. Because the bleeding encountered with osteotomy may force a rapid finish, complete preparation is essential for a successful instrumentation.

The vertebral bodies making up the cranial two thirds of the kyphosis are excised, allowing one to “fold in” the remaining proximal and distal spinal segments (Fig. 24–23). Care must be taken when the vertebrectomy is performed because the kidneys may be present in the concavity of the deformity and may sustain inadvertent injury. Often ribs 10 to 12 must be transected bilaterally to free the proximal segment enough so that the spine folds inward. The rods are positioned posterior to the infolded segments and secured in place. Posterolaterally placed polyaxial screws may be used to augment wiring and provide greater construct rigidity (Fig. 24–24). In a study of seven myelomeningocele patients, Kocaoglu and colleagues¹²⁸ found that the addition of polyaxial screws provided greater correction capacity and a low instrumentation profile in patients with a kyphectomy and Luque instrumentation. The excised vertebrae provide adequate bone graft, applied anteriorly and posteriorly.

FIGURE 24–23 Sagittal diagram describing sequence for performing kyphectomy. A, Spine is exposed, dural sac is tied off or retracted, and kyphotic segment of spine is excised. B, To improve mobility of remaining segments, discs can be excised, and lower two or three pairs of ribs can be sectioned from their origins. C, Two segments of spine are “folded inward,“ bone grafted (from the excised segments), and wired to previously contoured rods.

FIGURE 24–24 A and B, This young patient with spina bifida was missing posterior elements from T11 to sacrum with 103-degree focal lumbar kyphosis with no associated scoliosis. C, Kyphectomy was performed with excision of L2 and L3 vertebrae. D and E, Posterior instrumentation and fusion was used from T7 to pelvis.

Spinal Muscular Atrophy Types

SMA is broken down into three types. First described in the 1890s, type I is also known as Werdnig-Hoffman disease or acute infantile SMA. In this form, children are born with a normal appearance but by 6 months begin to show signs of muscle weakness with poor head control, absent reflexes, and respiratory insufficiency, which is the cause of death by 2 to 3 years of age.¹³¹ Children with type II SMA—the chronic infantile or Dubowitz form—experience the onset of muscle weakness between 6 and 19 months of age but do not have the same severity of symptoms. They attain sitting balance but rarely are able to walk independently. Although respiratory impairment is not as severe as in type I, respiratory complications are common. Type III SMA is also termed the chronic juvenile form of the disease or Kugelberg-Welander syndrome and is characterized by onset after 2 years with milder impairment; most children develop the ability to walk at some time, although many lose this ability around puberty.¹³²

Scoliosis in Spinal Muscular Atrophy

The natural history of scoliosis in SMA depends on whether the patient has type I, II, or III; however, these types represent a spectrum of disease, and the distinctions between types may not be absolute. One should be guarded in making unqualified predictions of prognosis based on type.

All patients with type I SMA develop curves greater than15 degrees. Surgical intervention is not warranted in these patients because of their short life span; a body jacket provides good support for balanced and comfortable sitting. Patients with type II also develop curves greater than 15 degrees, although the onset of spinal deformity occurs later, between 2 and 4 years of age. Most of these patients do not ambulate and are likely to experience rapidly progressive scoliosis. The prevalence of spinal deformity in type III patients is varied, but it typically develops in about half of patients.¹³³ Some of these patients are independent walkers and more likely to escape spinal deformity.^131,134,135

Scoliosis in SMA tends to progress. In 52 cases of SMA, Granata and colleagues found an increase in curve magnitude of 8 degrees per year, despite brace use. They likewise showed a significant increase in curve progression when a patient with mild involvement stopped walking. In 13 nonwalking SMA patients, these investigators found a 3-degree per year curve progression. Walking patients with mild involvement showed only a 0.6-degree per year progression.¹³⁶ The curve most often seen with SMA is a C-shaped thoracolumbar curve. Kyphosis can also be seen with these spinal deformities but is typically not severe.

Treatment Options

Scoliosis in Muscular Dystrophy

More than any other form of neuromuscular disorder, pulmonary function and life expectancy are directly correlated with spinal deformity. FVC begins to decline at the age patients stop standing. From that time, the restrictive effects of thoracic cage deformity and loss of respiratory muscle function cause pulmonary function to decline 4% for each 10 degrees of deformity and each year of age (Fig. 24–27).¹⁵³ Smith and colleagues¹⁵⁰ reviewed the natural history of DMD in 51 boys and found that the rate of progression of scoliosis was inversely related to the age of death. Although most studies have failed to identify a protective role of spinal surgery on pulmonary function,^151,152,154 Galasko and colleagues¹⁵⁵ reported a stabilization of pulmonary function at 3-year follow-up. The study by Galasko and colleagues¹⁵⁵ compared 32 patients who underwent spinal fusion and 23 patients who refused surgery; the FVC remained stable for 3 years postoperatively in the fused group compared with an 8% per year average decline in patients not operated on.¹⁵⁵ Although the impact of spinal surgery on pulmonary function is unknown, the relationship between pulmonary decline and progression of scoliosis has been shown by Kennedy and colleagues¹⁵⁴ to be 3% to 5% per year. When scoliosis progression has reached 20 to 30 degrees, many authors recommend surgery (Fig. 24–28).^25,156,157 Glucocorticoid treatment seems to be affecting the natural history of this condition, but it is unclear how the surgical indications for spinal fusion should be modified.

FIGURE 24–27 Percentage of forced vital capacity (FVC) versus age in patients with Duchenne muscular dystrophy. FVC percentage was found to be the parameter of pulmonary function that most strongly correlated with age and thoracic Cobb angle measurement.

(From Kurz LT, Mubarak SJ, Schultz P, et al: Correlation of scoliosis and pulmonary function in Duchenne muscular dystrophy. J Pediatr Orthop 3:347, 1983.)

FIGURE 24–28 A-D, Preoperatively, this boy with Duchenne muscular dystrophy had 20 degrees of scoliosis and 30 degrees of thoracolumbar region kyphosis. He underwent posterior instrumentation and fusion from T3 to L5 at age 13 to retard further progression of spinal deformity. Treating the patient early allowed stopping short of pelvis.

Treatment Options

The preoperative evaluation of DMD patients must take into account other comorbidities of their disease. Pulmonary function testing should be done before surgery to assess the severity of preoperative respiratory compromise. Although more recent studies have reported successful spinal surgery at FVC of less than 35%,¹⁵⁸ previous work associated this lowered FVC value with increased postoperative morbidity.¹⁵⁷ Similar to the progressive decline in pulmonary function over time, the severity of cardiac dysfunction also increases with age. DMD patients are likely to develop cardiomyopathy and arrhythmias in the 2nd decade of life, and an electrocardiogram, a chest radiograph, and an echocardiogram should be done to screen for cardiac problems. Despite the fact that many of these patients are obese, they should be evaluated for malnutrition because wound healing complications and increased infections rates have been reported.¹⁵⁹ DMD is also associated with a tendency for increased blood loss caused by poor vasoconstrictive function owing to a lack of dystrophin in vessel smooth muscle; preparation for major operative blood loss should be made.¹⁶⁰ Additionally, patients with dystrophic myopathies have an increased risk of malignant hyperthermia.¹⁶¹

Scoliosis in Rett Syndrome

The incidence of scoliosis increases as patients get older: 8% of girls with Rett syndrome have scoliosis at age 5, 40% have it by age 11, and 80% have it by age 20. The deformity can be rapidly progressive; Lidstrom and colleagues¹⁶⁷ reported on 78 patients with Rett syndrome and reported progression rates of 20 to 41 degrees per year in the 10 most severe cases. Because scoliosis in Rett syndrome has this potential for progression, yearly evaluation of the spine should be conducted after the age of 5 years.¹⁶⁸

The treatment for Rett syndrome is similar to treatment for cerebral palsy. Bracing has a limited role in treatment, although it may provide support for comfortable sitting until surgery is performed.¹⁶⁹ As with cerebral palsy, the authors recommend that if sitting comfort and balance become compromised, treatment with segmental instrumentation is indicated. Spinal surgery is indicated when the curve exceeds 40 degrees. Long-term outcome of surgery in patients with Rett syndrome has shown good results. In a prospective study of 23 girls with Rett syndrome and neuromuscular scoliosis, Larsson and colleagues¹⁷⁰ found improved seating position and patient satisfaction at 6-year follow-up. These authors reported that all patients who could walk preoperatively maintained ambulation postoperatively. They also noted that patients and parents reported an overall improvement in well-being with better sitting posture and improved breathing. As with all patients with neuromuscular disorders who undergo scoliosis surgery, spinal cord monitoring is advocated.¹⁷¹