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Features Departments Information |
 Erik C. King, MD  John F. Sarwark, MD |
A Look at Scoliosis Erik C. King, MD and John F. Sarwark, MD Scoliosis is the most common disorder of the spine that is encountered by pediatricians and pediatric orthopaedic surgeons. Scoliosis can alter the physical appearance of the affected individual dramatically, and it has both physiological and psychological impact. Depending on its severity and on the skeletal age of the child, scoliosis is managed by close observation, bracing, and/or surgery. Although it is common to speak of scoliosis in terms of spinal curvature in the coronal (frontal) plane, it is actually a three-dimensional problem composed of torsion, angulation, and translation simultaneously occurring in the transverse, coronal, and sagittal planes. In order to merit the diagnosis of scoliosis, the coronal curvature (Cobb angle) measured on a posterior-anterior radiograph must be greater than 10°. Curves less than 10° are considered minor asymmetry and are not at risk of progression after skeletal maturity. Scoliosis in skeletally immature individuals is classified by age: infantile (0 to 3 years); juvenile (3 to 10 years); and adolescent (over 11 years, or from onset of puberty until skeletal maturity). In addition, scoliosis is classified by etiology: congenital, neuromuscular or idiopathic. Idiopathic scoliosis is a diagnosis of exclusion, but it comprises the vast majority of cases presenting during the pubertal growth spurt. This article primarily focuses on the current concepts regarding the etiology, natural history, evaluation, and treatment of idiopathic scoliosis in children and adolescents. CONGENITAL SCOLIOSIS Congenital scoliosis results from embryological malformation of one or more vertebrae and may occur in any location of the spine. The vertebral anomalies cause curvature and other deformities of the spine because they lead to differential growth, i.e., one area of the spinal column lengthens at a slower rate than the remainder. The geometry and location of the anomalies determine the rate at which the scoliosis progresses in magnitude during growth. Because these anomalies are present at birth, congenital scoliosis is usually detected at a younger age than is idiopathic scoliosis. In children with congenital scoliosis, there is a known increased incidence of other congenital anomalies. The most common associated anomalies affect the spinal cord (20%), the genitourinary system (20% to 33%), and the heart (10% to 15%). Therefore, evaluation of the neurologic, genitourinary, and cardiovascular systems should be considered when congenital scoliosis is diagnosed. NEUROMUSCULAR SCOLIOSIS Neuromuscular scoliosis encompasses scoliotic spine deformities that are secondary to neurologic or muscular diseases. Etiologies of this type of scoliosis include cerebral palsy, spinal cord trauma, muscular dystrophy, spinal muscular atrophy, and myelomeningocele. Spinal deformities that result from neuromuscular etiologies generally progress more rapidly than idiopathic scoliosis and are more difficult to manage non-surgically. IDIOPATHIC SCOLIOSIS Etiology Idiopathic scoliosis refers to a spinal curve for which there is no discernible cause, and it typically occurs in children and adolescents who are otherwise healthy. In the last ten years, we have developed a better understanding of the causes of idiopathic scoliosis. The consensus at this time is that the etiology is multifactorial.[1] The importance of genetic factors in the development of idiopathic scoliosis has been widely accepted. Multiple epidemiological studies have shown that the prevalence of scoliosis is higher among individuals whose relatives have scoliosis than among the general population. A family history of scoliosis is identified in approximately 30% of patients diagnosed with idiopathic scoliosis. Monozygotic twins show a concordance rate of 73%, whereas dizygotic twins have a concordance rate of 36%. These findings suggest a single-gene disorder, but one that has variable penetrance and genetic heterogeneity. The identity of the affected gene in scoliosis is not known, nor do we know the function of the normal gene in unaffected individuals. One current theory suggests that the gene is involved in central nervous system control of spine growth, and that defects in this gene result in disruption of spinal growth. Decreased melatonin production, increased calmodulin activity, and cell membrane defects have been noted in studies on scoliosis patients. Collagen and muscle abnormalities also have been detected, but these are likely secondary degenerative changes. Other factors such as equilibrium dysfunction, proprioceptive dysfunction, and ocular reflex dysfunction may also influence the pathologic process. Epidemiology When curve magnitude of greater than 10° is used as the criterion for the diagnosis of idiopathic scoliosis, reported prevalence rates range from 1.9% to 3%. The prevalence drops to 0.3% for curves greater than 20°. In addition, there is an overall female predominance, which increases substantially for larger curves. For mild curves (11° to 20°) the female-to-male ratio is 1.4 to 1, but for moderate to severe curves (greater than 20°), this ratio is more than 4 to 1. More than 90% of the adolescent idiopathic curves that occur in the thoracic region have curve apices that are to the right. In fact, left thoracic curves are considered "atypical," and there is a 20% incidence of spinal cord abnormalities (such as tumor, syringomyelia, hydromyelia, and tethered cord) in children who have a left thoracic curve. We routinely perform in-depth neurological testing and MRI of the entire spine and spinal cord on every child who presents with a left thoracic curve. In contrast, left curves in the lumbar spine region are common and are not associated with an increased risk of spinal cord abnormality. Natural History The major factors that influence curve progression are skeletal immaturity, curve magnitude, and curve location.[2] Children who are diagnosed between the ages of 10 and 12 years have an 88% risk that their curves will progress at least 5° prior to skeletal maturity. For teenagers aged 12 to 15 years, the risk is 56%, and for those over 15 years, it is 29%. Long-term studies show that scoliotic curves in excess of 50° at skeletal maturity continue to progress throughout the patient’s adult life at a rate of approximately 1° per year. Thus, an important component of the ability to predict worsening of scoliosis is an accurate determination of the amount of growth remaining. Traditionally, a number of parameters have been used to assess growth potential, such as chronological age, age at onset of menstruation, and Tanner stage. Recent studies provide more precise determination of growth potential. Using more detailed growth analyses based on multiple skeletal anatomic landmarks in addition to the above parameters, our ability to predict skeletal maturity has improved.[3] Approximately 23% of idiopathic scoliosis patients report back pain at the time of initial diagnosis. Among these patients, 10% are found to have an underlying associated pathologic condition (spondylolysis, spondylolisthesis, syringomyelia, hydromyelia, tethered cord, herniated intervetebral disc, or intraspinal tumor).[4] Thus, if there is more than mild back discomfort in a patient diagnosed with idiopathic scoliosis, an evaluation for a cause for the pain other than scoliosis should be performed. Parents often inquire whether scoliosis is harmful to the internal organs. Because of changes in the shape and size of the thorax, idiopathic scoliosis may indeed affect pulmonary function. Recent reports on pulmonary function testing in idiopathic scoliosis patients document diminution of pulmonary function in individuals with mild or moderate scoliosis.[5] This decreased function may impact pulmonary function testing during maximal exercise testing but has not been shown to impact routine activities. However, when the Cobb angle in the thoracic spine exceeds 90°, clinically evident restrictive lung disease may occur. In patients with mild to moderate curves, the presence of scoliosis does not have an effect on pregnancy with respect to delivery and well being of the fetus. Furthermore, pregnancy per se does not cause progression of curvature in mothers who have idiopathic scoliosis. This is true both for individuals who have undergone scoliosis corrective surgery and for those who have not. Screening The American Academy of Orthopaedic Surgeons (AAOS) and the Scoliosis Research Society (SRS) endorse school screening for scoliosis. The AAOS position paper on school screening recommends screening for girls between 11 and 13 years and for boys between 13 and 14 years. These individuals who are found to have an angle of trunk rotation (discussed later) equal to or greater than 7° should be referred to a spine surgeon. (Figure 1).  Figure 1 Graph of ATR vs Cobb angle (from JBJS, 1984). Evaluation After a complete general history and physical examination, a focussed musculoskeletal and neurologic spine examination is performed. Particular attention is paid to curve direction, spine flexibility, sagittal kyphosis and lordosis, shoulder symmetry, rib/flank prominence, trunk balance, pelvic obliquity, and the presence or absence of limb length equality (Figure 2). The rotational component of scoliosis is quantified by measuring the angle of trunk rotation (ATR) during the Adams forward bend test. The Adams forward bend test is performed by having the patient bend forward at the waist with knees extended. In doing so, rib and flank prominence caused by the scoliotic rotational deformity is more visible and can be measured with an inclinometer (Scoliometer™).  Figure 2 Comparison of spinal alignment between unaffected teenager and a teenager with right idopathic scoliosis. Radiographic imaging of the entire spine should be performed on individuals who have an angle of trunk rotation equal to or greater than 7°. Standing radiographs of the entire spine remain the standard for diagnosis and treatment. Refinements in radiographic technology have decreased the radiation exposure for routine radiographic procedures. Indications for MRI screening include neurologic deficit, left thoracic curve, male patient, onset before adolescence, unusually rapid curve progression, lower extremity deformity, and the presence of symptoms such as moderate or severe back pain (Figure 3).  Figure 3 Syringomyelia, an example of a spinal cord abnormality that may be associated with scoliosis. Treatment There are three options for management of idiopathic scoliosis: observation, bracing, and surgical correction. Most cases of scoliosis are detected when the curvature is mild or moderate, and are treated successfully with non-operative management alone. Observation. For curves between 10° and 29° and in the absence of progression, observation alone is recommended. Bracing is indicated for skeletally immature patients who have curves greater than 30°. In some smaller curves, we occasionally initiate brace treatment if rapid progression has occurred. Surgery is considered for curves greater than 40° in skeletally immature patients, and for curves greater than 50° in skeletally mature patients. In selected patients with curves of lesser magnitude than these stated criteria, physical deformity may be substantial enough to warrant surgery. These are patients who have large rib prominences, torsal decompensation, shoulder obliquity, or pelvic obliquity. Families frequently inquire as to whether exercise, posture, mattresses, shoes, or backpacks cause or contribute to scoliosis. With a high level of certainty, it appears that there is no relationship between any of these factors and scoliosis incidence or progression. Nonetheless, modifications (e.g., a properly loaded backpack) may improve secondary pain or discomfort. Electrical stimulation therapy has been shown to be ineffective halting or reversing scoliosis, and consequently, it has been abandoned in scoliosis treatment. Bracing. Bracing is recommended for skeletally immature individuals with curves between 30° and 40°. The goal of bracing is to diminish or halt progression of scoliosis, and it is the only accepted non-surgical treatment modality (Figure 4). An underarm thoracolumbosacral orthosis (TLSO) is currently the most commonly prescribed brace for idiopathic scoliosis (Figure 5). This lower profile brace is more easily concealed that the higher profile Milwaukee brace used commonly in the past. The design of the TLSO lessens the negative psychosocial impact of brace wear in adolescents, and consequently it has a higher likelihood of achieving patient compliance.  Figure 4 Response of curves to bracing is dependent on curve type.  Figure 5 An underarm thoracolumbosacral orthosis (TLSO). The efficacy of bracing is difficult to assess because of our limited ability to quantify at-home compliance reliably among adolescents. One study that evaluated bracing compliance found that only 15% of patients wore the brace at least 90% of the recommended time. For the entire group, the average wear was 65% of the recommended time. Among patients who are compliant, bracing was reported to be 40% more effective at halting curve progression than treatment with observation alone.[6] Furthermore, full-brace wear time (23 hours/day) was shown to be significantly more effective than regimens requiring fewer hours of brace wear. Surgery. The goal of surgical intervention is to correct and improve spinal deformity and to reduce the risk of progression. Surgical techniques have evolved considerably over the last 50 years in terms of effectiveness and safety. In the late 1950s and early 1960s, scoliosis surgery was revolutionized by the work of Harrington who developed reliable instrumentation for correcting and fusing the spine. This instrumentation was implanted via posterior exposure of the spine (commonly referred to as posterior spinal fusion and instrumentation). Harrington instrumentation was used extensively from the 1950s until the early 1990s. However, Harrington instrumentation had a uniplanar approach to correcting coronal curvature, and led to unintended unbalancing of the sagittal spinal alignment, iatrogenic flatback, premature degenerative arthritis, and lower back pain. In the early 1980s, Cotrel and Debousset developed segmental instrumentation, which allowed three-dimensional correction. Segmental instrumentation is now the basis of all posterior spinal instrumentation and is the "gold standard" for surgical treatment of scoliosis (Figure 6). Using segmental instrumentation, reduction in curve magnitude by more than 50% can now be achieved routinely. 
 Figure 6 Posterior segmental instrumentation for three-dimensional correction of spinal alignment. Dwyer and coworkers applied instrumentation concepts to surgery of the anterior portion of the spine. The first anterior spinal instrumentation surgery was reported in 1969, and anterior surgery is now routinely performed. Curves that are typically treated with anterior instrumentation systems are those that primarily affect the lumbar or lower thoracic portions of the spine. The primary advantage of anterior surgery and anterior spinal instrumentation systems is greater deformity correction. The disadvantage of anterior surgery is the increased morbidity from the requisite thoracotomy or abdominal approaches to the anterior spine. The morbidity of anterior surgery recently has been lessened by the development of thoracoscopic techniques. Thoracoscopic approaches for anterior spinal release and fusion (video-assisted thoracoscopic surgery, VATS) have been associated with results equivalent to open thoracotomy techniques. With the use of multiple intercostal portals, excellent visualization and often a better approach to the intervetebral spaces are possible (Figure 7). Thoracoscopy is now performed routinely for first stage spinal discectomies, followed by second stage posterior spinal fusion and instrumentation procedures. Techniques have also been developed for implanting spinal instrumentation via thoracoscopic techniques, but the advantages and complications of these techniques are not yet adequately defined.  Figure 7 Video-assisted thorascopic surgery enables a less invasive approach to spine surgery. Another promising advance is the use of modulation of spinal deformity through surgically induced premature closure of selected vertebral growth plates (hemi-epiphyseodesis). Similar surgical techniques are commonly performed on the extremities, but they have been unsuccessful in spinal surgery in the past. Refined techniques of spinal hemi-epiphyseodesis have been attempted recently at a few spine centers, and preliminary results are encouraging. If successful, these techniques could enable the highly desirable outcome of correcting scoliosis while obviating the need for more extensive spinal fusion surgery.
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