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Adolescent Idiopathic Scoliosis (AIS) develops in approximately 1% to 3% of the population, primarily in minor forms that do not become progressive or problematic in later life. However, a small percentage of curves do progress to a range that warrants treatment with either an orthosis or surgical arthrodesis. Bracing to prevent and /or limit scoliosis progression is an option only in the growing patient with a moderate curve (25º to 45º). Surgical treatment is considered for patients with curves greater than 40º to 50º.

The natural history if AIS indicates the treatment algorithm. Rapid growth during adolescence (fastest for girls in the year before the onset of menses, occurs more in girls than boys) is one of the greatest risk factors for scoliosis progression, at times as much as 10º to 15º per year. Curves that have progressed to more than 25º to 30º during growth are likely to progress with further growth. Therefore, orthoses are suggested in these patients, with the goal of limiting curve progression as adolescent growth finishes. Similarly, the treatment after completion of growth relates to the risk of progression as an adult. In general, thoracic curves less that 50º are at low risk for progression compared to curves greater than 50º. Moreover, progression is much slower (0.5º to 2º per year) in adults than in adolescents. After the completion of growth, bracing is not practical to control the risk of progression, and surgical treatment is the only means of limiting progression and achieving deformity correction.

The orthopaedic evaluation of a patient with scoliosis is critical to avoid a diagnosis of AIS when some other cause of the deformity exists. One of the more commonly missed causes of scoliosis is intraspinal pathology, such as syringomyelia. The proper evaluation and work-up for patients presenting with scoliosis are outlined in the monograph. Neurologic symptoms or signs, as well as an unusual scoliotic curve pattern (left thoracic, hyperkyphotic), are associated frequently enough with intraspinal pathology to warrant MRI evaluation in such patients.

The variety of scoliosis curves seems to infinite but more common patterns of spinal deformity do exist, and treatment is based in part on curve morphology. Several systems of classifying scoliosis have been devised, and the treatment-based approach of Lenke and associates is presented in this text, although the King-Moe system has long been the standard and as such remains relevant.

The surgical treatment of AIS can be complex, both in the aspects of surgical techniques, and more importantly, surgical decision making. These decisions include the approach - anterior, posterior, or both; how much of the spine to fuse - one curve or two; which level to end distally; and the type and position of bone anchors to the spine (hooks, screws, wires). All these details cannot be presented completely in this text; however, the important principles are offered. For example, the advantages and disadvantages of each surgical technique and the appropriate surgical goals are presented.

The outcomes of scoliosis surgical correction are more reliable that in prior eras. Modern correction methods, both anteriorly and posteriorly, now provide more secure fixation with greater construct rigidity. The risk of excessive blood loss common in the past has been reduced with the use of electrocautery dissection and blood salvage/recirculation systems. In addition, the use of spinal cord neurologic monitoring allows reliable early intraoperative warning of spinal cord injury/hypoperfusion. Thus, greater deformity correction is safely achievable with an early return to activity and reduced risk of pseudoarthrosis.

American Academy of Orthopaedic Surgeons

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