Sep. 04, 2022
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Scoliosis and kyphosis are deformities of the spine in the coronal and sagittal planes, respectively. These spinal deformities arise from multiple etiologies and are commonly observed in patients with neurologic and neuromuscular disorders. In this updated article, the authors provide background knowledge helpful to neurologists caring for patients with spinal deformities. The biological basis for spinal deformities is discussed, along with new techniques for surgical and nonsurgical management.
• Scoliosis and kyphosis, which are curvatures of the spine in the coronal and sagittal planes, respectively, are common among patients with neurologic and neuromuscular diseases.
• Idiopathic scoliosis is a diagnosis of exclusion but has stereotypical characteristics distinguishing it from known neuromuscular causes.
• Progression of scoliotic curves occurs most rapidly during phases of rapid linear body growth, particularly during infancy and adolescence.
• Scoliosis during infancy will usually resolve spontaneously.
• In adolescents with idiopathic scoliosis, bracing can substantially decrease the progression of high-risk curves to the threshold for surgery.
• Patients who do not have typical characteristics of idiopathic scoliosis and no known neuromuscular disorder require further evaluation, including spinal MRI.
Scoliosis and kyphosis were recognized by several ancient civilizations and were first described by the Greek physician Hippocrates. It wasn’t until the mid-twentieth century that the first reliable treatments began to emerge, including the Milwaukee brace and Harrington rods. These treatments laid the foundation for modern scoliosis treatments today (30).
• Scoliosis and kyphoscoliosis can have their onset at any age, but most patients present during adolescence.
• Scoliosis and kyphoscoliosis can present as a manifestation of other disorders, including genetic syndromes and neuromuscular diseases, but most cases are not part of another disorder and have an unknown cause, in which case the disorder is idiopathic.
• Most patients come to medical attention due to rib prominence or truncal asymmetry noted by parents or by the patient, or as an incident finding during a school physical examination or on a chest x-ray.
Patient presentation and physical examination. Scoliosis and kyphosis are common deformities in children seen by neurologists. These spinal deformities arise from multiple etiologies and may be idiopathic, congenital, syndromic, or neuromuscular in origin. Patients with spinal deformities usually present in childhood or adolescence due to rib prominence or asymmetry in trunk balance, shoulder height, or extremities. Additional physical examination findings may provide important clues to an underlying diagnosis. These may include cutaneous lesions, such as café au lait spots, or axillary freckling suggestive of neurofibromatosis; spinal hairy patches, hemangiomas, or sinuses suggestive of dysraphism; elongated fingers with the “wrist sign” or “thumb sign” suggestive of Marfan syndrome; short trunk or limbs suggestive of dwarfism; and limb-size discrepancy, cavus foot, toe clawing, or equinus contractures suggestive of a plexopathy or peripheral neuropathy.
The spinal examination should include the Adams Forward Bend Test to assess trunk rotation, limb length inequality, and spinal motion. The Adams Forward Bend Test looks for elevation of 1 side of the spine, relative to the other, as a measure of spinal column rotation. This test is conducted with the patient bending forward while standing, as if to touch his or her toes. Detection is usually by trunk asymmetry on forward bend. Limb length inequality is detected by noting a difference in the height of 1 hemipelvis, compared to the other, while the patient is in the standing position. Motion is assessed by evaluating the ability of the patient to bend forward, backward, and sideways. Forward and sideways bending can be quantified by measuring how far the patient’s hands can reach in each direction (25).
Criteria for diagnosis. In patients with suspected spinal deformity, coronal and sagittal radiographs should be obtained. Many techniques have been described for measuring spinal alignment (04). However, the “Cobb angle” is generally the most clinically relevant. The Cobb angle is a measure of curvature of the spine in degrees and can be used to quantify both scoliosis and kyphosis. It is calculated by locating the most tilted vertebrae above and below the curve and drawing lines parallel to the superior and inferior vertebral end plates, respectively. The Cobb angle is the angle formed between these 2 lines.
Formal diagnostic criteria for scoliosis is lateral curvature of the spine with a Cobb angle greater than 10 degrees. Curves less than 10 degrees are considered a normal variant, and these patients should not be diagnosed with scoliosis. Thoracic kyphosis is generally defined by a Cobb angle greater than 50 degrees, although this is a subject of debate.
Idiopathic scoliosis. Idiopathic scoliosis is the most common spinal deformity in children. Idiopathic scoliosis is separated into 3 categories, based on the age of onset: “infantile” for onset at 0 to 3 years of age, “juvenile” for onset at 4 to 9 years of age, and “adolescent” for onset at 10 years of age and beyond. The Scoliosis Research Society has recommended that all scoliosis in children before 10 years of age be considered “early-onset scoliosis.” Central axis abnormalities exist in approximately 20% of both infantile and juvenile scoliosis patients but not in adolescent idiopathic scoliosis patients, making spinal MRI especially important to obtain in the younger age groups (22; 16).
Natural history. Curve progression occurs most rapidly during phases of rapid linear body growth, particularly during infancy and adolescence. The latter period may be marked by an abrupt acceleration in curve progression, with rapidly progressing curves approaching 2 degrees per month (41). Curve progression significantly slows at the completion of linear body growth.
Infantile and juvenile idiopathic curves. Infantile curves may either resolve or progress, with resolving curves being far more common. Both the rib vertebral angle difference (RVAD) and rib phase are important for predicting which curves will progress (34). The RVAD is the difference of the angles made between the ribs and corresponding vertebrae at the curve apex. The great majority of resolving curves have an RVAD of less than 20 degrees. In contradistinction, most progressing curves have an RVAD of greater than 20 degrees. Rib phase 1 has no overlap of the rib head and the vertebral body, whereas phase 2 overlaps and indicates progressive curves. Double curves usually progress, even if the RVAD is low. Ninety-five percent of juvenile idiopathic scoliosis curves are progressive (40).
Adolescent idiopathic curves. The behavior of adolescent curves depends on curve patterns and magnitude. Known risk factors for rapid curve progression include larger curve magnitude, lesser maturity, and specific curve patterns (54; 53). Larger curves continue to progress in adulthood. In particular, thoracic curves greater than 50 degrees and lumbar curves greater than 30 degrees tend to progress.
Pulmonary issues and mortality. Only infantile and juvenile curves (early onset), or high-degree or severely lordotic thoracic curves, are likely to result in pulmonary problems in untreated scoliosis. Pulmonary failure is more likely with earlier onset and greater curve severity (38). Juvenile, and particularly infantile, curves are much more likely to result in early to mid-adult pulmonary restriction than adolescent curves, which rarely cause pulmonary problems. Due to their association with pulmonary failure, both infantile and juvenile curves have significantly increased mortality compared to the general population. Campbell has termed the pulmonary failure from this condition “thoracic insufficiency syndrome” (TIS) (07). In long-term follow-up of untreated adolescent patients, Weinstein and colleagues found pulmonary function failure only in those with thoracic curves over 100 degrees and in smokers, who also fared worse (54). Typical adolescent curves do not markedly affect long-term pulmonary function, despite some restrictive disease. However, curves that are more than 70 degrees at maturity are most likely to cause pulmonary problems, and adolescents with thoracic curves in the 70 degree range, and especially more than 80 degree range, have worse pulmonary function than do patients with smaller curves.
Other concerns. Back pain is more prevalent in untreated scoliotic patients (77%) relative to controls (37%), but is unrelated to curve type or severity, and there is minimal difference in functional and physical disability between patients and controls (51).
Congenital scoliosis and kyphosis. Congenital malformations of the spine are usually classified into 2 basic types--failure of formation and failure of segmentation--with frequent mixed types. They are often associated with other parts of the VACTERL complex, most importantly cardiac, renal, and spinal cord abnormalities. Congenital spinal deformities worsen through asymmetric growth. In congenital kyphosis, the failures of formation, being acute angular deformities, place the spinal cord at risk whereas the kyphotic failures of segmentation have a more gradual kyphosis at the apex and less paralysis risk. Congenital deformities can pose significant challenges when they become severe at a young age, with cord impingement in kyphosis and pulmonary compromise in scoliosis. Early fusion of the thoracic spine will markedly diminish chest volume and can result in thoracic insufficiency syndrome (07).
Neuromuscular scoliosis. Scoliosis is very common in neuromuscular diseases. When the curves are localized to the lumbar spine, often in association with pelvic obliquity, the major issue is usually proper seating. When the curve is thoracic, the more important issue is pulmonary compromise. In the awake and alert child, there is little debate regarding the value of surgery to maintain proper positioning. However, in children with severe cognitive impairment and severe physical disability (Gross Motor Function Classification System level V), highly expensive and risky procedures are ethically more difficult decisions. One particularly valuable article discusses the complex ethics of treating severely involved children with scoliosis from cerebral palsy (56).
Muscular dystrophies. Scoliosis is part of the natural history of Duchenne muscular dystrophy. Once children stop walking, a large proportion begins to develop scoliosis, which relentlessly progresses and makes seating difficult.
Spinal muscular atrophy. Spinal muscular atrophy is associated with earlier onset scoliosis than many other neuromuscular disorders. Children with spinal muscular atrophy may develop scoliosis during their first years of life and often have very large curves before 8 years of age.
Skeletal dysplasias. A nosology of skeletal dysplasias defined 456 different conditions (49). Although there are some unique spinal features for many of these disorders, there are many common issues as well. Skeletal dysplasias represent some of the most difficult problems for spinal deformity surgeons to treat because the deformities can be very severe, the bony deformity can be marked, the fixation points can be small and difficult to obtain, the bone can be soft, and the deformities can be rigid. In addition, secondary medical issues, such as pulmonary restriction, can make care even more difficult.
The cervical spine is commonly involved in skeletal dysplasias. The most common issues are atlantoaxial instability, often associated with odontoid hypoplasia (spondyloepiphyseal dysplasia, Kniest dysplasia, mucopolysaccharidosis, pseudoachondroplasia, Stickler syndrome, metatropic dysplasia); cervical kyphosis (diastrophic dysplasia, camptomelic dysplasia, Larsen syndrome); and cervical stenosis (achondroplasia, metatropic dysplasia, Jeune syndrome). Cervical kyphosis is often associated with anterior deficiencies, posterior spondylolysis, spondylolisthesis, or ossification defects. Myelopathy from stenosis, kyphosis, or instability can be difficult to detect in infants and young children who have not yet myelinated sufficiently to show spasticity.
Scoliosis and kyphosis. Many patients have juvenile onset of scoliosis, and the curves can become quite severe. Some of these patients start with relatively normal-appearing spines, but as the platyspondyly deformity progresses, it can resemble congenital kyphoscoliosis. Curves can also develop in adolescence, which are usually not as severe as the earlier-onset curves.
Thoracic kyphosis. Several disorders, such as metatropic dwarfism, spondylometaphyseal dysplasia, chondrodysplasia punctata, and diastrophic dysplasia, can develop a very tight kyphosis that leads to progressive myelopathy. Some skeletal dysplasias are associated with small thoraces and respiratory issues from short ribs and spines. They are often not well distinguished and include Jeune syndrome (asphyxiating thoracic dysplasia), with short limbs (symmetric) and constricted thorax (27); spondylocostal dysplasia (SCD or Jarcho-Levin syndrome) (03), with segmentation defects, multiple rib fusions, and association with the notch pathway resulting in moderate respiratory compromise.
The lumbar spine is less commonly involved in kyphosis, except in achondroplasia, in which late adolescent spinal claudication is a frequent problem.
Syndromic scoliosis. Two common syndromes that are often associated with scoliosis and kyphosis are Marfan syndrome and neurofibromatosis.
Marfan syndrome, the result of a fibrillin 1 defect, is characterized by ligamentous laxity, arachnodactyly, dolichostenomelia, lens dislocations, and aortic aneurysm. Patients with Marfan syndrome are frequently found in clinics dedicated to scoliosis because they can develop very severe scoliosis at a young age. It is important to recognize Marfan syndrome in patients with scoliosis because the life-threatening aortic aneurysms that are associated with Marfan syndrome can be readily prevented or treated with early referral (45).
Neurofibromatosis type 1 (NF1) is also a common cause of scoliosis. The curves in NF1 can become very severe, with dural ectasia and tumors causing marked bony erosions and very aggressive deformities. Children with NF1 should regularly be clinically checked for spinal deformities, and radiographs should be obtained if a spinal deformity becomes clinically apparent. Rib penciling, which is an abnormal narrowing of rib diameter, is an early sign of spinal deformities becoming more aggressive. In NF1, rib heads may dislocate into the spinal canal, a painful condition that can lead to severe neurologic complications during surgery (20; 57; 48; 28).
Adult spinal deformity. The previously discussed variants of spinal deformity typically arise in childhood. However, adult spinal deformity is common and can be either residual from childhood or de novo. De novo adult scoliosis and kyphosis generally arise from degenerative disc disease, reduced mobility and balance, neurodegenerative disorders, or osteoporosis. It is particularly important to obtain a dual energy x-ray absorptivity scan to determine bone density in adults undergoing evaluation for spinal surgery (15).
Depending on its etiology and severity, scoliosis may resolve spontaneously or may progress to a severely debilitating state. More severe curves are more likely to progress. Infantile scoliosis can progress but usually resolves without a need for intervention. Juvenile scoliosis is very likely to progress and require surgical intervention. Adolescent scoliosis is often progressive especially during the adolescent growth spurt, but the majority of cases are moderate and do not require surgical intervention.
Common complications associated with scoliosis include poor pulmonary development, back pain, physical disability, and poor self-image. Severe curves, especially those with a kyphotic component, can also cause increased risk of spinal cord compression, which may lead to paraplegia (33; 50).
Patients with scoliosis and kyphoscoliosis generally require frequent full-spine radiographs. This is particularly true in patients who require surgery. A study has shown that the cumulative radiation dose of scoliosis patients requiring surgery is ten-fold higher than those treated without surgery (13). This frequent requirement for radiographic imaging raises concerns regarding the potential long-term harm to the health of children from the x-irradiation. A study has shown that scoliosis patients have substantially increased incidences of cancer, breast cancer, and cancer mortality over controls (32).
A 14-year-old boy was seen by his pediatrician for a routine examination and was found to have a right thoracic prominence. He had some occasional urinary incontinence and was becoming clumsy with his activities. His examination showed a right thoracic scoliosis with increased thoracic kyphosis and slightly increased tone in his lower extremities compared to his upper extremities. Because of the kyphosis and mild lower extremity spasticity, an MRI was obtained, demonstrating a large lower cervical astrocytoma.
• For idiopathic scoliosis, which constitute most cases of scoliosis, the underlying biological basis is unknown.
• Congenital scoliosis can be due to failure of formation or segmentation of vertebral bodies.
• Scoliosis and kyphoscoliosis associated with neuromuscular disorders is due to asymmetric and irregular activation of muscles controlling spine position and configuration.
• Progressive pediatric scoliosis is ultimately due to asymmetric loading on the spine.
• Reduced bone mineralization may contribute to pathogenesis of spinal deformities.
The biological basis for scoliosis is not fully understood. The specific biological mechanisms involved are variable, based on the etiology of disease. The disorders that lead to scoliosis are polygenic with multiple inheritance patterns (37). However, it is likely that all progressive pediatric scoliosis etiologies share a final common pathway of increasing curvature due to asymmetrical loading on the spine. Increased loading on the concave side of the deformity inhibits growth, while, at the same time, decreased loading on the convex side accelerates growth resulting in a progressive deformity. The principle behind these asymmetric growths is referred to as the “Hueter-Volkmann Law,” which states that mechanical force influences longitudinal bone growth and, in particular, that compressive forces inhibit growth whereas distractive forces enhance growth. Compressive loading reduces overall growth plate thickness, especially in the proliferative and hypertrophic zones. Compressive loading reduces chondrocyte number in the proliferative zone, reduces chondrocyte number and size (height and volume) in the hypertrophic zone, and alters chondrocyte column structure. Distraction of the growth plate has the opposite effects (46). This mechanism is partly responsible for the progressive nature of spinal deformity in skeletally immature children and results in vertebral bodies that become more wedged over time (43). This is sometimes referred to as the “viscous cycle of spinal deformity.”
Idiopathic scoliosis and kyphosis. The etiology of idiopathic scoliosis remains unknown. Several theories exist, including exacerbation of right-to-left asymmetries during the growth spurt, anterior overgrowth, and melatonin pathway abnormalities.
One other possibility for the etiology of idiopathic scoliosis is that affected patients may have a reduced bone quality, which allows for asymmetric spine growth (14). To assess the bone health of adolescents with idiopathic scoliosis, measurements of bone mineralization were compared in adolescent patients with idiopathic scoliosis and in age-matched and sex-matched controls. Measurements of bone density were made using dual energy x-ray absorptiometry (DEXA scans) and peripheral quantitative CT (pQCT) in central bone sites (spine and hip) and peripheral bone site (radius and tibia). The study found that patients with scoliosis had significantly lower bone mineral density at central bone sites but had similar bone mineral density at peripheral bone sites. Because it is the central bone sites, such as the hips and spine, that would be most relevant to the generation of scoliosis, the study findings support the notion that a reduction in bone quality might underlie or contribute to scoliosis (14).
Regardless of the mechanism, it appears to be strongly familial. Several identified genetic loci appear to be etiologic factors; at least 1 specific locus was identified in a Dallas family (44). Idiopathic scoliosis likely represents a complex genetic disorder in which genetic factors interact with environmental factors and growth to create spinal deformity.
Congenital scoliosis and kyphosis. Congenital malformations of the spine are usually classified into 2 basic types, failure of formation and failure of segmentation, with frequent mixed types. These malformations occur very early during gestation and are often associated with other parts of the VACTERL complex, most importantly the cardiac, renal, and spinal cord abnormalities.
Neuromuscular scoliosis and kyphosis. Neuromuscular deformity is caused by poor muscle control, weakness, or paralysis of paraspinal muscles and the surrounding musculature (36). This can be due to dysfunction at the level of the brain (eg, cerebral palsy), spinal cord (eg, spina bifida), motor neurons (eg, polio), peripheral motor nerves (eg, Charcot-Marie-Tooth disease), neuromuscular junction (eg, myasthenia gravis), and muscle (eg, Duchenne muscular dystrophy).
Syndromic scoliosis and kyphosis. Syndromic spinal deformity refers to deformity associated with chromosome or gene-based syndromes, such as Marfan syndrome, Ehlers-Danlos syndrome, Prader-Willi syndrome, Down syndrome, achondroplasia, and Prader-Willi syndrome (10). In these syndromes, abnormalities of muscle tone, strength, or structure lead to spinal deformities.
Adult scoliosis and kyphosis. Adult deformity may be either residual from childhood deformity or de novo. De novo deformity is common and results from degenerative changes, including degenerative disc disease, reduced mobility and balance, neurodegenerative disorders, or osteoporosis. Adult de novo scoliosis is most commonly associated with degenerative disc disease whereas de novo kyphosis commonly results from osteoporotic compression fractures or iatrogenic postural changes (15).
• Approximately 3% of all adolescents have idiopathic adolescent scoliosis, with a Cobb angle greater that 10 degrees.
• Only 10% of patients with idiopathic adolescent scoliosis require treatment.
• Boys and girls are equally affected, but the risk of progression to larger angle curves is much greater in girls than in boys.
• Adult spinal deformity is common, but most do not require surgery.
Idiopathic scoliosis is a common spinal deformity. Small curves and mild spinal asymmetries such as scapular winging, shoulder elevation, or rib prominence are found in 3% to 15% of adolescents. Curves less than 10 degrees are considered a normal variant, and these patients should not be diagnosed with scoliosis. The prevalence of curves greater than 10 degrees is approximately 1% to 3% of the population. Larger curves are much rarer, and males have a much lower prevalence than females. Curves over 40 degrees occur in fewer than 1 per 1000 people. Other etiologies of pediatric spinal deformity are not as common as adolescent idiopathic scoliosis but are generally more likely to require surgery. Adult spinal deformity is very common, affecting 32% to 68% of the population aged 65 and older. The vast majority of these cases are managed nonoperatively (15).
• School-based scoliosis screening programs can effectively detect many cases of scoliosis during early stages.
• Bracing can prevent progressive worsening of curves in many cases.
It is unknown how to prevent scoliosis from occurring, and screening for scoliosis, particularly within school systems, is controversial (30). The American Academy of Orthopaedic Surgeons, American Academy of Pediatrics, Scoliosis Research Society, and the Pediatric Orthopaedic Society of North America recommend that screening for scoliosis be instituted because studies have demonstrated that bracing can prevent worsening of the deformity (52). A systematic review of evidence conducted by a US Preventive Services Task Force concluded that screening can detect adolescent idiopathic scoliosis and that bracing can prevent its progression. However, they found no evidence that screening or bracing can improve adult health outcomes (17).
Although idiopathic scoliosis is the most prevalent spinal deformity, common look-a-likes include syringomyelia, neurofibromatosis, and Marfan syndrome. Scoliosis is common in neurologic diseases as disparate as myelomeningocele, polio, cerebral palsy, spinal muscular atrophy, Friedrich ataxia, and Duchenne muscular dystrophy. Less common disorders associated with scoliosis include spinal tumors, polyneuropathies, and myopathies. A history of numbness, weakness, bowel or bladder incontinence, significant pain, severe headaches, or difficulty swallowing should provoke concern that the condition is not idiopathic scoliosis and should prompt further evaluation.
• High-quality radiographs of the spine should be obtained for all patients suspected of having scoliosis or kyphoscoliosis.
• These radiographic images should be used, not just to calculate the Cobb angle, but also to assess for underlying abnormalities.
• If spinal cord pathology is suspected, then an MRI scan of the spinal cord is indicated.
For patients with a known etiology for their scoliosis, the evaluation focuses on identifying any underlying conditions. High-quality radiographic images from the cervicothoracic junction to the pelvis should be obtained for all patients suspected of having scoliosis and scrutinized for any evidence of underlying abnormalities, such as endosteal scalloping, interpedicular widening, rib penciling, enlarged intravertebral foramina, and soft tissue masses. When any type of spinal cord pathology is suspected, MRI is indicated. MRI is indicated for a history or examination suggestive of underlying neurologic problems, congenital deformity, onset less than 10 years of age, kyphosis across the apex, and atypical curve patterns (16).
Congenital scoliosis and kyphosis. These malformations occur very early during gestation and are often associated with other parts of the VACTERL complex, most importantly cardiac, renal, and spinal cord abnormalities. For this reason, chest x-ray, echocardiogram, kidney ultrasound, and MRI scan of the spinal cord should be obtained in all cases of congenital scoliosis and kyphosis. Spinal radiographs can provide clues regarding potential growth asymmetry, with unilateral failures of segmentation (unilateral bars) having a worse prognosis than failures of formation (hemivertebra), and the combination having the worst prognosis. In congenital kyphosis, the failures of formation being acute, angular deformities place the spinal cord at risk, whereas the kyphotic failures of segmentation have a more gradual kyphosis at the apex and less paralysis risk. Congenital deformities can pose significant challenges when they become severe at a young age, with cord impingement in kyphosis and pulmonary compromise in scoliosis. Because of the associated congenital spinal cord abnormalities, an MRI should be obtained in any patient with underlying neurologic findings or who will undergo surgery. Early fusion of the thoracic spine will markedly diminish chest volume and can result in thoracic insufficiency syndrome (07).
Skeletal dysplasia. Because the cervical spine is commonly involved in skeletal dysplasias, cervical spine films should be obtained in children with known or suspected skeletal dysplasias. MRI evaluation of the spine is important before any spinal surgery is conducted. Sleep studies can be helpful in evaluating for brainstem compression from upper cervical abnormalities.
• Management for cases of scoliosis and kyphoscoliosis depends strongly on multiple factors, including age of onset, etiology, curve severity, and rate of curve progression.
• Most spinal curves with onset in infancy will resolve spontaneously without intervention.
• For many juveniles and adolescents with scoliosis, bracing can slow progression of the curve and prevent the need for surgical intervention.
• Surgical correction is indicated for skeletally immature patients with large curves (typically considered Cobb angle greater than 50 degrees).
• Surgical procedures include the implantation of rods, affixed to the spine or ribs, above and below the curve, and spinal fusion.
Infantile curves. Most infantile curves will resolve without intervention. Resolving infantile curves should be observed and followed periodically until maturity. Once a curve is diagnosed as progressive, early treatment with casting for curves less than 60 degrees in children younger than 18 months of age has had good results in resolving the curves (42) or in substantially delaying surgery (02; 19). As the curves become larger and the children older, casting has a role in reducing the curve size and delaying surgery, but it is unlikely to result in a cure. Both nonoperative treatment and surgery in these children should aim to preserve chest growth and to prevent thoracic insufficiency syndrome. Current options include vertical expandable prosthetic titanium rib (VEPTR) and growing rods. Surgical treatment with growing techniques has a high incidence of complications, including spine stiffness, crankshafting (twisting of the growing spine around a rigid fusion or rod), infection, and rod or implant failure. For this reason, delaying surgery by bracing is an important goal. Magnetically-controlled growing rods are now approved by the FDA, and preliminary studies indicate that this technique, which does not require surgery for the lengthening, may avoid some issues, such as infection, and decreases the number of surgeries (08). Although magnetic growing rods have obtained good curve correction with fewer surgeries, there have been issues with metallosis from wear of the implant (26). Long-term assessment of outcome is needed to ensure patient safety. Vertebral body stapling and vertebral body tethering are emerging growth friendly techniques as well. Both have the advantage of being minimally invasive and do not require bulky rods implanted along the spine. Vertebral body staples are made from nitinol and are strategically applied to the vertebral spinal growth plates. This reduces the growth of the convex side of the curve while the concave side grows unimpeded. Vertebral body tethering utilizes a similar concept, but rather than staples, vertebral body screws are used and fastened to a polyethylene-terephthalate flexible cord (09).
Juvenile curves. Juvenile curves usually progress to a surgical range. Typically, however, the curves do not become large until the adolescent growth spurt. Thus, most of these curves can be temporarily stabilized with a brace. Juvenile curves that must undergo surgical treatment are usually treated with growth-sparing methods, such as growing rods and vertical expandable prosthetic titanium rib. The goals in these cases should be full lung development through the chest, appropriate spine growth, and reasonable spinal alignment.
Adolescent idiopathic scoliosis. Treatments for adolescent idiopathic scoliosis revolve around observation, bracing, and surgery, primarily spinal fusion. There is currently no evidence that chiropractic treatment is effective and very limited evidence that exercise can change the natural history of scoliosis, though it is used extensively in some European centers. The traditional approach to adolescent idiopathic scoliosis is to observe curves less than 25 degrees, brace curves over 25 degrees or curves over 20 degrees with 5 degrees documented progression in patients Risser 2 or less, and operate on curves likely to reach 45 or 50 degrees at maturity. This approach is not universally accepted, however.
Bracing. Studies of bracing in patients with adolescent idiopathic scoliosis have demonstrated that bracing can substantially decrease the progression of high-risk curves to the threshold for surgery. In particular, when patients are observed only and not braced, progression of the curve to a point at which surgery is required occurs in approximately 58%. In contrast, when patients are braced, progression of the curve to a surgical threshold drops to approximately 25%. Furthermore, bracing exhibits a dose-response effect, such that the benefit of bracing increases with longer hours of brace wear. Currently, there is little evidence that any particular brace is superior to others. Furthermore, there have been no well-controlled studies comparing nighttime to full-time brace wear. Thus, the strongest evidence suggests that bracing should occur full-time (18 hours per day) with effectiveness increasing particularly beyond 13 hours per day (52).
If bracing is prescribed, it must be done for the proper indications and expertly fabricated by experienced technicians. Patients and their family members must be motivated and compliant to follow through with treatment; otherwise, observation rather than treatment is appropriate because noncompliant bracing is burdensome to families, expensive, and ineffective. Patients treated with scoliosis bracing report good quality of life at least into midlife.
Surgery. Bracing is not usually effective in the treatment of congenital spinal deformities because the external forces of bracing are unlikely to modify the large forces associated with asymmetric spinal structures. Moreover, bracing may also be counterproductive in progressive disorders, such as Duchenne muscular dystrophy, because the bracing may delay curve progression until the children are too pulmonary compromised for safe surgical treatment. Although surgery is effective in restoring alignment, the underlying progressive disease makes these surgeries relatively risky. Luckily, steroids may prevent the need for surgery in many patients with Duchenne muscular dystrophy (01; 11; 29; 23). Both prednisone, used in the United States, and deflazacort, in the United States and used in other countries, have either delayed or eliminated progressive scoliosis in many boys with Duchenne muscular dystrophy. For patients with curves likely to result in pulmonary compromise, surgery remains the best option. Indications for surgery include a curve of 40 degrees in growing adolescents or of 50 to 60 degrees in patients near maturity, as these curves are most likely to progress in adulthood. In disfiguring curves, surgery does an excellent job of restoring symmetry, but patients exchange a curved but flexible spine for a straighter but rigid spine. The incidence of complications in adolescent idiopathic scoliosis surgery, unlike kyphosis or early-onset neuromuscular or congenital scoliosis, is low. Reoperation rates are 5% to 10% and the need for reoperation is usually due to infection or instrumentation failure. Neurologic deficits occur in 0.5% (39). Spinal cord injuries are rare, but can be devastating. Late outcome of segmental instrumentation is favorable at 15 to 20 years of age and at 20 to 25 years of age for Harrington instrumentation.
Treatment of isolated spinal abnormalities is aimed at the local deformity, with short segment spinal fusion, osteotomy, or hemivertebra excision. More extensive deformities in younger children are usually treated with growing rods or vertical expandable prosthetic titanium rib (VEPTR), attempting to retain longitudinal spinal growth and adequate chest volume while controlling the curves. In older adolescents with sufficient lung volume, these deformities are treated with standard instrumentation and fusion techniques.
A recently developed technology for the treatment of children and adolescents with scoliosis is the magnetically controlled growing rod (MCGR) system. In this system, the spine is instrumented with rods attached to the spine, above and below the curve, with screws and hooks. Each MCGR rod contains a magnet. An external remote-control device signals the magnet to alter the size of the rods, thus allowing the rods to lengthen as the child grows. This rod lengthening procedure can be done on an outpatient basis, in the surgeon’s office, with the child fully awake. The advantages of this system over traditional growing rods are the avoidance of a surgical incision and the lack of a need for general anesthesia when the rods require lengthening. A study has demonstrated that this newly developed system is reliable and effective for the treatment of patients with early onset scoliosis (06).
Exercise. Although the shape and positioning of the spine are affected by the strength and action of the paravertebral muscles and other muscles near and around it, the hypothesis has arisen that scoliosis and kyphosis might be amenable to the positive effects of exercise. For this reason, exercise programs have been tested on adolescents with idiopathic scoliosis and kyphosis in an attempt to improve the spinal curve and other aspects of health associated with spinal deformity. Some studies have found that scoliosis-specific exercise programs can control and improve curve progression (21; 31). In addition, one study has found that the combination of aerobic and resistance training can improve functional exercise capacity and respiratory outcomes in adolescents with idiopathic scoliosis (55). However, several meta-analyses found that there is little evidence to prove that scoliosis-specific exercises can reduce Cobb angle, improve trunk balance, or improve quality of life for adolescents with idiopathic scoliosis (18; 47).
Spinal muscular atrophy. Spinal muscular atrophy is associated with early onset of scoliosis. Children with spinal muscular atrophy may develop scoliosis during their first few years of life and have large curves before 8 years of age (35). Spinal fusion in some children with spinal muscular atrophy can limit their ability to push manual wheelchairs or to bend and perform activities of daily living. However, a retrospective review found strong evidence supporting definitive posterior spinal fusion in these patients. The study found that spinal fusion for patients with spinal muscular atrophy can control curve progression and pelvic obliquity without negatively affecting the space available for lung growth, trunk height, or pulmonary function at 10 years follow-up (24).
A new molecular therapy has been FDA-approved for the treatment of spinal muscular atrophy. Nusinersen is an antisense oligonucleotide drug that alters the splicing of the mutated gene that causes spinal muscular atrophy, thus, increasing the amount of functional protein within motor neurons and promoting their survival (12). However, this therapy must be administered by lumbar puncture, and spinal fusion surgery typically precludes the opportunity for lumbar puncture. To allow administration of nusinersen to patients with spinal muscular atrophy, surgeons performing spinal fusion have begun leaving a nonfused level, which the instrumentation bypasses, in order to allow the requisite lumbar punctures. In patients with spinal muscular atrophy who have already undergone spinal fusions, laminectomies are sometimes performed, thus, allowing administration of nusinersen.
An extensive review comparing scoliosis patients who had at least 1 pregnancy with those who had never been pregnant found no increase in curve magnitude, back pain, or obstetrical outcome in scoliosis patients (05).
Anesthesia is no different from anesthesia in other patients with the same underlying disorder. Congenital kyphosis and cervical spine abnormalities can pose a risk with positioning and intubation, making it important for the anesthesiologist to be aware of the abnormality, to obtain any necessary preoperative testing, and, occasionally, to perform fiberoptic intubation or preoperative tracheostomy. Intraoperative spinal cord monitoring must be accommodated and can be adversely affected by inhalation agents. Blood loss can be significant and measures to control blood loss should be considered.
Ann Tilton MD
Dr. Tilton has received honorariums from Allergan and Ipsen as an educator, advisor, and consultant.See Profile
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