AIS more prevalent, progressive in girls
Amy L. McIntosh, MD, and Jennifer M. Weiss, MD
The cause of adolescent idiopathic scoliosis (AIS)—curvature of the spine that measures greater than 10 degrees—is unknown. Although AIS affects both boys and girls older than age 10, AIS is more than 10 times more common in girls than in boys, with an overall ratio of 11:1.
AIS prevalence increases throughout the teenage years due to curve progression that is associated with the adolescent growth spurt. During the adolescent growth spurt, curves can increase up to 20 degrees in a year. For girls, this rapid progression occurs before the onset of the first menses, usually at age 11 or 12 years. In boys, it occurs later, when they are 13 or 14 years old.
Progression of a scoliotic curve is not only associated with growth but also with gender. Progressive curves are more likely to occur in girls than in boys. The curve patterns most likely to progress in girls are a right thoracic curve and a double major curve (Fig. 1). In boys, left lumbar curves are more likely to progress. A curve of greater than 30 degrees is also more likely to progress in girls.
Fig. 1 In girls, curve patterns most likely to progress are a right thoracic curve and a double major curve.
The magnitude of the curve (Cobb angle), timing of the adolescent growth spurt, onset of menses in girls, and ossification of the iliac apophysis (ie, the Risser sign) are used to determine the risk of curve progression and to help guide treatment of AIS. Risser staging ranges from 0 (skeletally immature) to 5 (skeletally mature) and follows the ossification and later closure of the iliac crest apophysis.
Patients who are still growing and whose curves are less than 25 degrees are treated with radiographic observation. Scoliosis radiographs and clinical examinations, performed at 4- to 6-month intervals, can be used to document any increase in height, change in clinical appearance, and the Cobb angle and Risser sign.
Patients who are still growing and whose curves are between 25 degrees and 40 degrees are usually treated with a Boston brace. Brace treatment has been better studied in girls than in boys, perhaps due to the greater numbers.
The effect of brace treatment likely depends on curve pattern and severity. Larger curves are more likely to progress with or without brace treatment. Girls may be at higher risk for progression than boys.
One study that examined bracing and progression of scoliosis used a heat sensor to monitor brace compliance. Results provide evidence that wearing the brace for more than 12 hours per day will control curve progression. Once skeletal maturity (defined as Risser 4-5, 2 years postmenarchal, and no increase in height) is reached, bracing is no longer appropriate, because progression of the curve is unlikely.
Curves greater than 45 degrees to 50 degrees in all patients (male and female, regardless of remaining growth potential) are best treated with surgical intervention, usually in the form of a posterior spinal fusion with instrumentation.
Magnetic resonance imaging (MRI) of the brain stem and entire spinal cord is occasionally indicated in the workup of AIS to look for an underlying etiology of the scoliosis (eg, Chiari malformation, syrinx, spinal cord tumor). Indications for an MRI include left-sided thoracic curve, patient younger than age 10 years, painful curve, and curve demonstrating progression.
Points to remember
- Scoliosis is more prevalent in girls.
- Scoliosis is more likely to progress in girls.
- Bracing is appropriate for curves measuring 25 degrees to 40 degrees in patients with significant growth remaining (Risser 3 or less, and less than 2 years postmenarchal).
- MRI should be considered in the workup of patients who have an abnormal presentation. This includes the following: male sex; first seen with a surgical magnitude curve greater than 45 degrees to 50 degrees; a left-sided thoracic curve; abnormal neurologic exam including asymmetric abdominal reflexes; cutaneous manifestations of neurofibromatosis (café–au-lait spots, axillary or inguinal freckling, cutaneous neurofibromas); back pain or headache that interferes with daily activities.
- Bracing controls progression but does not diminish curvature. Educate patients to understand that the goal of bracing is to halt progression; the brace will not make their curve smaller.
Amy L. McIntosh, MD, and Jennifer M. Weiss, MD, are members of the Women’s Health Issues Advisory Board.
Putting sex in your orthopaedic practice
This quarterly column from the AAOS Women’s Health Issues Advisory Board and the Ruth Jackson Orthopaedic Society provides important information for your practice about issues related to sex (determined by our chromosomes) and gender (how we present ourselves as male or female, which can be influenced by environment, families and peers, and social institutions). It is our mission to promote the philosophy that male and female patients experience and react to musculoskeletal conditions differently; when it comes to patient care, surgeons should not have a one-size-fits-all mentality.
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- Sun X, Wang B, Qiu Y, Zhu ZZ, Zhu F, Yu Y, et al. Outcomes and predictors of brace treatment for girls with adolescent idiopathic scoliosis. Orthop Surg. 2010 Nov;2(4):285-90. doi: 10.1111/j.1757-7861.2010.00101.x.
- Wu H, Ronsky JL, Cheriet F, Harder J, Küpper JC, Zernicke RF.Time series spinal radiographs as prognostic factors for scoliosis and progression of spinal deformities. Eur Spine J. 2011 Jan;20(1):112-117. Epub 2010 Jul 27.
- Katz D, Herring J, Browne R, Kelley D, Birch J. Brace Wear Control of Curve Progression in Adolescent Idiopathic Scoliosis. J Bone Joint Surg Am. 2010; 92(6):1343-1352.
April 2012 Issue
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