Clinical manifestations

Presentation and course

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 in neurofibromatosis; spinal hairy patches, hemangiomas, or sinuses in dysraphism; elongated arms and legs and a sunken chest (pectus excavatum) in Marfan syndrome; short trunk or limbs in dwarfism; and limb-size discrepancy, cavus foot, toe clawing, or equinus contractures in 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 one 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 one 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 (35).

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 (06). 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 two lines.

Formal diagnostic criteria for scoliosis are 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, accounting for 80% of all scoliosis (62). Idiopathic scoliosis is separated into three 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. Infantile scoliosis constitutes 1% of all idiopathic scoliosis, juvenile scoliosis accounts for 10% to 15%, and adolescent scoliosis comprises about 90% of cases of pediatric idiopathic scoliosis (38). 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 patients with both infantile and juvenile scoliosis but not in adolescent idiopathic scoliosis patients, making spinal MRI especially important to obtain in the younger age groups (32; 24).

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 (56). 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 (47). 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 (55).

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 (71; 70). 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 (53). 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) (10). In long-term follow-up of untreated adolescent patients, Weinstein and colleagues found pulmonary failure only in those with thoracic curves over 100 degrees and in smokers, who also fared worse (71). Typical adolescent curves do not markedly affect long-term pulmonary function. However, curves that exceed 70 degrees often do lead to restricted pulmonary function.

Other concerns. Back pain is more prevalent in scoliotic patients (77%) than in controls (37%) but is unrelated to curve type or severity, and there is minimal difference in functional and physical disability between patients and controls (68).

Congenital scoliosis and kyphosis. Congenital malformations of the spine are usually classified into two 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 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 (10).

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 cognitively normal child, there is little debate regarding the value of surgery to maintain proper positioning. However, in children with severe cognitive impairment and physical disability (Gross Motor Function Classification System level V), highly expensive and risky procedures create more ethically difficult decisions. One particularly valuable article discusses the complex ethics of treating severely involved children with scoliosis from cerebral palsy (72).

Muscular dystrophies. Scoliosis is part of the natural history of Duchenne muscular dystrophy (DMD). Once children stop walking, a large proportion begins to develop scoliosis, which relentlessly progresses and makes seating difficult. The etiology of scoliosis in Duchenne muscular dystrophy stems from poor mobility and weakness of paraspinal musculature, resulting in a rapidly progressive spine curve. In particular, the adolescent growth spurt is a time of rapid progression, in which scoliosis angulation often increases between 16° and 24° per year (44). Many children with Duchenne muscular dystrophy ultimately develop pelvic obliquity as the scoliosis progresses, resulting in unequal weight transfer on the wheelchair and secondary skin breakdown. 

Spinal muscular atrophy. Spinal muscular atrophy is associated with earlier onset scoliosis than many other neuromuscular disorders. Almost all children with spinal muscular atrophy type 1, the most severe form, and spinal muscular atrophy type 2 (intermediate- those that achieve sitting abilities) have scoliosis. Nearly half of all children with spinal muscular atrophy type 3 (mild disease with walking abilities) will have scoliosis (12). 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 (66). 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 severe, 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, odontoid hypoplasia, cervical kyphosis, and cervical stenosis. 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 (37); spondylocostal dysplasia (SCD or Jarcho-Levin syndrome) (05), 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 severe scoliosis at a young age. More than half of patients with Marfan syndrome will develop scoliosis (30). It is important to recognize Marfan syndrome because the life-threatening aortic aneurysms that are associated with Marfan syndrome can be readily prevented or treated with early referral (60).

Neurofibromatosis type 1 (NF1) is also a common cause of scoliosis. In fact, nearly 2% of all pediatric scoliosis cases are attributed to neurofibromatosis type 1. Scoliosis in neurofibromatosis type 1 can be either dystrophic or nondystrophic, depending on whether there are radiographic dysplastic changes of the spine, including dural ectasia, vertebral scalloping, vertebral wedging, widening of the spinal canal, or rib penciling (65). The curves in neurofibromatosis type 1 can become severe, with dural ectasia and tumors causing marked bony erosions and aggressive deformities. Children with neurofibromatosis type 1 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 neurofibromatosis type 1, rib heads may dislocate into the spinal canal, a painful condition that can lead to severe neurologic complications (29; 75; 64; 39). A study of neurofibromatosis type 1 patients found that, in a scoliotic curve with three or more dystrophic features, the risk of curve progression was increased in 85% of patients. Rib penciling was identified as the dystrophic feature most strongly influencing the progression of the curve (26). All children with neurofibromatosis type 1 should be screened for penciling and other dysplastic changes because the prognosis of the scoliosis largely depends on the presence or absence of these features.

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 (23).

Prognosis and complications

Depending on its etiology and severity, scoliosis may resolve spontaneously or 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 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, increase the risk of spinal cord compression, which may lead to paraplegia (46; 67).

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 (21). 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 (45).

Clinical vignette

The male patient was diagnosed in infancy with infantile scoliosis, craniosynostosis, bilateral club feet, and renal dysplasia. He was otherwise neurologically and developmentally normal. Due to his constellation of symptoms, he was referred to genetics at 2 years old and received whole exome gene sequencing, which was normal. MRI scan of the brain and spinal cord were also normal. Throughout early childhood, the scoliosis progressed to the point that the right thoracic curve measured 53.7° by age 2 years.

Prior to this progression, the patient underwent two Risser cast placements.

On exam, the patient had a right-sided thoracic curvature, with slight truncal shift to the right. Over the course of the next 3 years, he required 14 Risser casts, followed by full-time bracing. Unfortunately, he continued to have further progression of his scoliosis despite these measures.

Prior to surgical intervention at the age of 5 years, the patient’s scoliosis had progressed to a 67° right thoracic curvature. After discussion with a multidisciplinary team, the patient underwent MAGEC (MAGnetic Expansion Control) rod placement on both the concave and convex sides, spanning from T4 to L3.

Screws were inserted into the vertebral pedicles bilaterally at T4, T5, T6, L2, and L3.

MAGEC rods incorporate adjustable growing rods that are lengthened noninvasively every 3 to 6 months utilizing an external remote control. They are an effective option for children whose curves cannot be controlled with bracing or casting, until the child is old enough for spinal fusion (03).

The patient returned to the office 4 months post-op for his first lengthening and returned every 4 to 6 months thereafter for further lengthening and imaging. The operation was a success. The patient is currently 9 years old. Although he continues to have mild scoliosis, his right-sided thoracic curve has decreased to 19° and has remained stable with no further curve progression.

Biological basis

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 (52). 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 (61). 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 (58). This is sometimes referred to as the “viscous cycle of spinal deformity.”

Etiology and pathogenesis

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 (22). 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 (22).

Regardless of the mechanism, it appears to be strongly familial. Several identified genetic loci appear to be etiologic factors; at least one specific locus was identified in a single family (59). Idiopathic scoliosis likely represents a complex genetic disorder in which genetic factors interact with environmental factors and growth to create spinal deformity.

Researchers have developed several animal models to study the genes and other factors that lead to scoliosis, including the use of mice and rats. However, an animal model that is proving especially useful is the zebrafish (74). Zebrafish models offer several advantages over many other animal model systems. First, the structure and morphology of the zebrafish is very similar to that of the human spine. Second, there is a high degree of genetic conservation between humans and zebrafish. Third, zebrafish embryos are transparent and develop ex utero, thus, allowing spine development to be readily visualized. Finally, the mechanical forces generated in fish during swimming are loaded on the spine in a manner similar to the force of gravity on humans (as opposed to quadruped mice and rats in which gravity acts perpendicular to the direction of the spine.)

Through the use of the zebrafish model, researchers have shown that specific genetic factors can play an important role in the pathogenesis of scoliosis. Zebrafish with specific gene mutations can spontaneously develop spinal curves that mimic congenital scoliosis or idiopathic scoliosis in humans. One set of genes identified in this way are those involved in cilia and ciliary motility. Whereas the products of these ciliary genes play important roles in cerebrospinal fluid flow, perturbations in CSF flow may underlie the generation of scoliosis (43; 20).

Congenital scoliosis and kyphosis. Congenital malformations of the spine are usually classified into two 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 (49). 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 (17). 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 (23).

Epidemiology

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 one 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 (23).

One controversial issue regarding the epidemiology of idiopathic scoliosis is its relationship with body habitus. In particular, some studies have suggested that both underweight and overweight adolescents are at increased risk for onset and progression of scoliosis. One study showed that the prevalence of adolescent idiopathic scoliosis is twice as high in obese patients than in the general population (11). However, not all studies lead to the same conclusion. A different study found no association between body mass index and the odds of undergoing posterior spinal fusion (13).

A retrospective, cross-sectional study identified sociodemographic disparities among patients diagnosed with adolescent idiopathic scoliosis at initial presentation (51). Specifically, socioeconomic status, race/ethnicity, and health insurance provider all had a statistically significant relationship with the age of initial presentation of adolescent idiopathic scoliosis patients and their corresponding Cobb Angle. Black/African American patients had 2.3 times higher odds of presenting with severe scoliosis, compared to White patients, who more often presented with mild to moderate scoliosis. The study also examined COI-N (Child Opportunity Index-National) score, which is a validated composite score that measures resources for a child in a particular geographic area, including education, health, social, and economic factors. The study found that children living in areas with a lower COI initially presented with more severe scoliosis. Finally, patients with public health insurance, compared to private insurance, presented with a higher Cobb Angle, although no clinical significance was found (51).

Prevention

It is unknown how to prevent scoliosis from occurring, and screening for scoliosis, particularly within school systems, is controversial (41). 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 (69). A systematic review of evidence conducted by a U.S. 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 (25). In 2004, the U.S. Preventive Services Task Force recommended stopping screening adolescents for scoliosis in school. Despite this, more than half of U.S. states continued to screen children, as of 2012 (41).

Differential diagnosis

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.

Scoliosis is associated with several additional diseases and comorbidities. However, these associations depend on the age at onset of scoliosis and on its progression. For example, early-onset scoliosis is associated with global developmental delay, developmental dysplasia of the hip, and epilepsy. In contradistinction, adolescent idiopathic scoliosis is not associated with these conditions. Idiopathic scoliosis is associated with musculoskeletal conditions, whereas congenital scoliosis is associated with cardiovascular diseases. Cases of scoliosis that are progressive have more comorbidities, especially in the respiratory, gastrointestinal, and cardiovascular systems (02).

Diagnostic workup

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 (24).

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 (10).

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

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 (57) or in substantially delaying surgery (04; 28). 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 (15). Although magnetic growing rods have obtained good curve correction with fewer surgeries, there have been issues with metallosis from wear of the implant (36). 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 (16).

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.

In patients with juvenile or adolescent idiopathic scoliosis, several studies suggest that participation in nonagonistic sports confers a lower risk of curve progression and need for bracing. In one study, patients with juvenile or adolescent idiopathic scoliosis with Cobb curves 11° to 25° who participated in noncompetitive sports were protected against curve progression at 12 months follow up, compared to those that did not participate in sports. The study further found that, with an increase in sports frequency each week, the risk of curve progression decreased (50).

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 (69).

However, not all patients with scoliosis are compliant with full-time bracing. Many adolescents will accept night-time bracing but are reluctant to wear a brace during the day. A randomized clinical trial investigated whether night-time bracing in combination with scoliosis-specific exercises could prevent curve progression in patients with moderate-grade adolescent idiopathic scoliosis (defined as 35°to 40°) (14). The control group had only daily physical activity and no bracing. The study found that night-time bracing prevented curve progression of more than 6°, whereas scoliosis-specific exercises alone did not prevent curve progression. These results suggest that in patients who are resistant to full time bracing, night-time bracing, in combination with exercise, may be a reasonable alternative (14).

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; 18; 40; 33). 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% (54). 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 system is reliable and effective for the treatment of patients with early onset scoliosis (09).

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 (31; 42). 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 (73). 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 (27; 63).

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 (48). 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 (34).

A 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 (19). 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.

Special considerations

Pregnancy

An extensive review comparing scoliosis patients who had at least one pregnancy with those who had never been pregnant found no increase in curve magnitude, back pain, or obstetrical outcome in scoliosis patients (07).

Anesthesia

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.