Adolescent idiopathic scoliosis (AIS) is the most common form of idiopathic scoliosis. Routine well-child examinations and sports physicals are an optimal time to evaluate for AIS in the clinical setting and can be done quickly and easily.
Scoliosis is defined as a lateral curvature of the spine greater than 10 degrees on radiography that is typically associated with trunk rotation. The three major types of scoliosis are congenital, idiopathic, and neuromuscular. Idiopathic scoliosis is divided into three subcategories based on the age of onset. Infantile idiopathic scoliosis affects patients younger than 3 years, juvenile idiopathic scoliosis appears in children aged 3 to 10 years, and AIS occurs in skeletally immature patients older than 10 years.
Approximately 2% to 4% of children aged 10 to 16 years have some degree of spinal curvature.1,2 The prevalence of curves greater than 30 degrees is about 0.2%, and it is less than 0.1% for curves greater than 40 degrees.3 Small magnitude curves have an equal prevalence between girls and boys; however, as the curve magnitude increases, girls show a clear predominance over boys of about 4:1.
The cause of AIS is likely multifactorial. Genetics are thought to play a role in scoliosis; however, the specific mode of inheritance remains undetermined.3 Twin studies show a high concordance rate of about 73% in monozygous twins and 36% in dizygous twins.4 Current research is underway to identify a panel of genetic markers that may help predict the risk of curve progression to an extent that surgical intervention is required. Other areas, including connective tissue, neuromotor system, biomechanics, and hormonal system, have been investigated; however, they have not shown a definitive causative effect.
Curve Progression and Growth Potential
An understanding of the natural history of AIS is helpful for making treatment recommendations. Curve progression is related to future growth potential, gender, curvature severity, and curve pattern.1,3,5,6
Curve progression is most likely to occur during periods of skeletal growth. The remaining growth potential is determined by a combination of factors including menarcheal status, age of patient at onset, and Risser sign. The Risser sign is a measure of skeletal maturity determined by the amount of ossification of the iliac crest apophysis, which begins anterolaterally and progresses posteromedially with maturity (see Figure 1).
The Risser sign.
Image courtesy of Kimberly Burton-Laurance.
The grade is determined by dividing the iliac crest into the following quadrants: Risser 0 = no ossification, Risser 1 = up to 25%, Risser 2 = up to 50%, Risser 3 = up to 75%, Risser 4 = 100%, and Risser 5 = complete bony ossification of the iliac crest. Patients with a Risser sign of 2 or less have three times the risk of curve progression than patients beyond this.1
The use of menarcheal status in conjunction with the Risser grade is helpful in assessing the risk for curvature progression. Risser stage 2 patients have a 50% risk of progression before menarche, whereas postmenarcheal patient risk is reduced to less than 20%.1
The severity of curvature in conjunction with skeletal maturity helps assess the risk of progression as well. Skeletally immature patients have a risk of curvature progression of about 20% for curvatures of 20 degrees, 60% for curvatures of 30 degrees, and 90% for curvatures of 50 degrees.1 At skeletal maturity, curves less than 30 degrees are less likely to progress into adulthood,7 whereas curves between 30 and 50 degrees are at risk to progress about 10 to 15 degrees over a lifetime and curves greater than 50 degrees progress 1 to 2 degrees annually. 3 Curve magnitudes of 20 to 29 degrees in immature patients have a 68% probability of progression opposed to those closer to maturity (Risser 2–4) with a 23% chance of progression.8
Thoracic curves and double curves have the largest risk of progression. The risk is lower with thoracolumbar curves, and lumbar curves have the lowest risk.1
Routine screening for AIS is controversial. Many states mandate scoliosis screening; however, the efficacy of these programs is unproven.9 In 1996, the United States Preventive Services Task Force concluded there was insufficient evidence to make a recommendation for or against screening. In 2004, the United States Preventive Services Task Force recommended against screening of asymptomatic adolescents.
In 2008, the American Academy of Orthopaedic Surgeons, the Scoliosis Research Society, the Pediatric Orthopaedic Society of North America, and the American Academy of Pediatrics convened a task force to review the issues related to scoliosis screening and issued an information statement concluding that although screening has limitations, the potential benefits that patients with idiopathic scoliosis receive from early treatment can be substantial. They recommend that females are screened twice, at age 10 and 12 years, and males once at age 13 or 14 years.9 Screening methods include the Adam’s forward bend test, scoliometer measurements, and measuring the Cobb angle (described in further detail below) on radiography.
Patients may present to the office for the evaluation of scoliosis in many different ways, including: as school-based screening referrals; as a complaint of deformity noted by themselves, family, or friends; or as an incidental finding on a routine well-child examination. A focused history should include the age of onset of curvature, family history of scoliosis, menarcheal status, complaints of pain, and neurologic changes including bowel or bladder dysfunction and weakness. AIS is a diagnosis of exclusion, and, therefore, secondary causes of scoliosis need to be ruled out.
Although back discomfort may be reported, significant back pain is an atypical finding. If back pain is the presenting complaint, a thorough examination should be performed to rule out possible underlying etiologies other than scoliosis. In a study of 2,442 patients with idiopathic scoliosis, 23% had back pain at presentation and an additional 9% during the period of observation. Nine percent of patients with back pain were found to have an underlying condition including spondylolysis, spondylolithesis, Scheuermann kyphosis, syrinx, herniated disc, hydromyelia, tethered cord, or intraspinal tumor.10
Physical examination should include the patient’s height plotted on a growth curve chart standardized for age and sex. Skin should be evaluated for midline abnormalities, such as hemangiomas, hair tufts, and lumbosacral dimpling, which can indicate an underlying spinal cord abnormality. A visual inspection of alignment includes observation for both obvious and subtle asymmetry of shoulder height, scapulae, flank creases, iliac crests, and breasts. If a leg length discrepancy is detected, a lift beneath the shorter leg is helpful to account for compensatory scoliosis. Tanner stage determination may be helpful because peak curve progression occurs during the pubertal growth spurt (Tanner stage 2–3).
A thorough neurologic examination should be performed to rule out underlying neurologic causes. Reflexes including abdominal reflex, balance, and lower-extremity strength should be assessed. The abdominal reflex can help rule out subtle intraspinal pathology. It is performed with the patient supine as the examiner gently strokes the skin on either side of the midline above, at, and below the level of the umbilicus. Contraction of the muscle toward the stimulated side is a normal response.
The Adam’s forward bend test is a useful screening method both in the office and as part of school-based screening. The patient bends forward at his/her waist until the spine is horizontal with the floor, the palms are placed together, and the arms are extended toward the ground. The provider evaluates the patient from behind for the presence of asymmetry in contour, noted as one side of the back higher than the other.
A scoliometer or inclinometer (similar to a standard carpenter’s level) is used to measure the angle of vertebral rotation. With the patient bending forward (as in the Adam’s forward bend test), the scoliometer is placed perpendicularly to the long axis of the body and then moved along the spine. The location of maximal asymmetric prominence and the corresponding angle (ie, the amount central ball moves from the midline) on the scoliometer should be noted. This angle is useful to determine if radiographs may be indicated. Of note, this number does not correlate to the Cobb angle degrees on radiography.
Radiographs are not necessary in every patient referred for a scoliosis evaluation. Indications for radiographs include obvious significant curvatures on examination, scoliometer measurements of 7 degrees or greater, or progressive monitoring in previously diagnosed patients with AIS (see Sidebar).
Indications for Radiographs in Patients with AIS
- Obvious significant curvatures on examination
- Scoliometer measurements of ≥7 degrees
- Progression monitoring in previously diagnosed patients with AIS
AIS = adolescent idiopathic scoliosis.
Data from Bunnel11 and Skaggs12
Standard images include upright standing posteroanterior (PA) and lateral views. PA radiographs minimize radiation exposure to the breast and thyroid. When imaging, leg length discrepancies should be corrected by placing wooden blocks under the shorter leg until the hips are level.
Radiographs should be viewed with the heart on the left, as if looking at the patient from behind. Curves are described by the direction the convexity points and the location of the apex vertebrae (the one most deviated from the midline). The most common type of curve in AIS is a right thoracic, left lumbar double curve. Leftward curves are uncommon and need further attention because they may be associated with nonidiopathic causes. The Risser sign, as described previously, should be determined as well. Radiographs should also be reviewed for other possible underlying etiologies, such as soft-tissue masses, wedged vertebrae or hemivertebrae, vertebral body lucencies, and widening of the interpedicular space.
The Cobb method is used to determine the degree of scoliosis curvature. The most tilted vertebrae above and below the apex on the PA radiograph are identified. The angle between intersecting lines drawn perpendicular to the superior endplate of the top vertebrae and inferior endplate of the bottom vertebrae form the Cobb angle. Intra- and interobserver reliability is about 5 degrees (see Figure 2).
Image courtesy of Kimberly Burton-Laurance.
Additional imaging, such as magnetic resonance imaging, is reserved for patients with an atypical presentation of AIS, such as a left thoracic curve, significant or unusual pain, abnormal neurologic findings, concerning radiographic findings, or other red flags from history and the physical examination.
Management of AIS
The goal of scoliosis management is to prevent further progression of the curvature. Management decisions are made based on the curve severity at presentation, pattern and location of curvature, and growth potential of the patient (chronologic age, menarche status, and Risser sign). The majority of adolescents will not require intervention; fewer than 10% require active treatment.3 Management options include observation and nonsurgical or surgical treatment.
Skeletally immature patients have the greatest risk for curve progression (see Figure 3). Patients with scoliometer measurements less than 7 degrees are monitored clinically every 6 months. If this angle increases to more than 7 degrees, radiographs should be performed. Patients with a Risser grade of 0 to 2 with curves less than 25 degrees can be observed every 3 to 6 months or until curvature progresses more than 5 degrees between visits or becomes greater than 25 degrees. Curves between 25 and 40 degrees should be considered for brace therapy, and curves greater than 45 or 50 degrees should be evaluated for possible surgery.
A flowchart showing adolescent idiopathic scoliosis management. PA = posteroanterior.
Figure courtesy of Monique S. Burton, MD.
In patients approaching skeletal maturity (Risser 3 and higher), curves less than 25 degrees can be followed every 6 to 9 months. Patients should be monitored for at least a year past skeletal maturity (girls Risser 4 and boys Risser 5). After skeletal maturity, patients with curves less than 30 degrees can be discharged from care. Curves less than 30 degrees at skeletal maturity are not likely to progress. Those with curves greater than 50 degrees have potential for progression into adulthood and should continue to be observed.
Brace therapy is the most common form of nonoperative treatment. Bracing is typically recommended in skeletally immature patients with curves between 25 and 40 degrees or curve progression of more than 5 degrees at consecutive follow-up appointments.
The goal of bracing is to prevent curve progression, not to correct curvature. It is not indicated in skeletally mature patients or in patients with a Cobb angle greater than 50 degrees.
Patients treated with a brace should be monitored approximately every 6 months. Bracing is continued until the peak growth spurt has concluded (about Risser 4 or 2 years after menarche for girls and Risser 5 for boys). Bracing is considered successful when the curve does not progress more than 5 degrees.13
The underarm, thoraco-lumbo-sacral orthosis, known as the Boston brace, is most commonly used and well tolerated because it is easily camouflaged beneath clothing. The Milwaukee brace (cervico-thoraco-lumbo-sacral orthosis), which includes cervical extension, is difficult to hide, less tolerable, and typically reserved for patients with thoracic curves with an apex above T8 or double thoracic curves.
Braces are typically worn 16 to 23 hours per day, with removal for sports activities as needed. Nighttime braces (Charleston, Providence) provide a maximal side bending corrective force, are worn 8 to 10 hours during the night, and may be considered in skeletally immature patients with single major curves of 25 to 35 degrees with an apex below T8.14,15
Bracing therapy remains controversial with advocates for both beneficial use and those indicating no difference from observation.15–19 Patient compliance likely plays a role in the efficacy of use.15 Recently, a multicenter prospective study concluded that bracing significantly decreased the risk of progression of high-risk curvatures of 20 to 40 degrees in skeletally immature patients.20
Other nonsurgical treatments include electrical stimulation, physical therapy, chiropractic treatments, and biofeedback. Currently, these methods remain controversial in their efficacy.
The goals of surgical treatment are to prevent progression, achieve maximal permanent correction of deformity, improve appearance, and keep short-term and long-term complications minimal. Surgery is typically indicated in patients with Cobb angles greater than 45 degrees; however, additional factors including age, curve progression, and symptoms such as pulmonary compromise are important factors to be considered. 13,20 Adolescents may choose to delay surgery until adulthood; however, adults tend to have less flexible curves and higher rates of complications.21
AIS is the most common form of idiopathic scoliosis. The causes appear to be multifactorial in nature. Screening during routine well-child examinations and/or school-based evaluations will help identify patients who need ongoing monitoring. The evaluation of curvatures in conjunction with the level of skeletal maturity will help to guide the management of the curvature.
- Bunnell WP. The natural history of idiopathic scoliosis. Clin Orthop Relat Res. 1988;229:20–25.
- Roach JW. Adolescent idiopathic scoliosis. Orthop Clin North Am. 1999;30(3):353–365. doi:10.1016/S0030-5898(05)70092-4 [CrossRef]
- Miller NH. Cause and natural history of adolescent idiopathic scoliosis. Orthop Clin North Am. 1999;30(3):343–352. doi:10.1016/S0030-5898(05)70091-2 [CrossRef]
- Kesling KL, Reinker KA. Scoliosis in twins: a meta analysis of the literature and report of six cases. Spine. 1997;22:2009–2014. doi:10.1097/00007632-199709010-00014 [CrossRef]
- Lonstein JE, Carlson JM. The prediction of curve progression in untreated idiopathic scoliosis during growth. J Bone Joint Surg Am. 1984;66:1061–1071.
- Tan KJ, Moe MM, Vaithinathan R, Wong HK. Curve progression in idiopathic scoliosis: Follow-up study to skeletal maturity. Spine. 2009;34(7):697–700. doi:10.1097/BRS.0b013e31819c9431 [CrossRef]
- Weinstein SL, Ponseti IV. Curve progression in idiopathic scoliosis. J Bone Joint Surg Am. 1983;65:447–455.
- Lonstein JE. Scoliosis: surgical versus nonsurgical treatment. Clin Orthop Relat Res. 2006;443:248–259. doi:10.1097/01.blo.0000198725.54891.73 [CrossRef]
- Richards BS, Vitale MG. Screening for idiopathic scoliosis: an information statement. J Bone Joint Surg Am. 2008;90(1):195–198. doi:10.2106/JBJS.G.01276 [CrossRef]
- Ramirez N, Johnston CE, Browne RH. The prevalence of back pain in children who have idiopathic scoliosis. J Bone Joint Surg Am. 1997;79:364–368.
- Bunnell WP. Outcome of spinal screening. Spine (Phila PA 1976). 1993Sep15;18(12):1572–1580. doi:10.1097/00007632-199309000-00001 [CrossRef]
- Skaggs DL. Referrals from scoliosis screening. Am Fam Physician. 2001Jul1;64(1):32. 34–35.
- Kim HJ, Blanco JS, Wildmann RF. Update on the management of idiopathic scoliosis. Curr Opin Pediatr. 2009;21:55–64. doi:10.1097/MOP.0b013e328320a929 [CrossRef]
- Grivas TB, Rodopoulos GI, Bardakos NV. Night-time braces for treatment of adolescent idiopathic scoliosis. Disabil Rehabil. 2008;3(3):120–129.
- Schiller JR, Thakur NA, Eberson CP. Brace management in adolescent idiopathic scoliosis. Clin Orthop Relat Res. 2010;468(3):670–678. doi:10.1007/s11999-009-0884-9 [CrossRef]
- Danielsson AJ, Hasserius R, Ohlin A, Nachemson AL. A prospective study of brace treatment versus observation alone in adolescent idiopathic scoliosis: a followup mean of 16 years after maturity. Spine (Phila PA 1976). 2007;32(20):2198–2207. doi:10.1097/BRS.0b013e31814b851f [CrossRef]
- Dolan LA, Weinstein SL. Surgical rates after observation and bracing for adolescent idiopathic scoliosis: an evidence based review. Spine (Phila PA 1976). 2007;32(19S) S91–S100. doi:10.1097/BRS.0b013e318134ead9 [CrossRef]
- Maruyama T.Bracing adolescent idiopathic scoliosis: a systematic review of the literature of effective conservative treatment looking for end results 5 years after weaning. Disabil Rehabil. 2008;30(10):786–791. doi:10.1080/09638280801889782 [CrossRef]
- Nachemson AL. Peterson LE. Effectiveness of treatment with a brace in girls who have adolescent idiopathic scoliosis. A prospective, controlled study based on data from the Brace Study of the Scoliosis Research Society. J Bone Joint Surg Am. 1995;77:815–822.
- Weinstein SL, Dolan LA. Effects of bracing in adolescent with idiopathic scoliosis. N Engl J Med. 2013Sept.19 [Epub ahead of print]. doi:10.1056/NEJMoa1307337 [CrossRef]
- Weinstein SL, Dolan LA, Cheng JCY, et al. Adolescent idiopathic scoliosis. Lancet. 2008;371:1527–1537. doi:10.1016/S0140-6736(08)60658-3 [CrossRef]