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Idiopathic Scoliosis

Scoliosis can be identified by the Adam's forward bend test during physical examination. Severe pain, a left thoracic curve or an abnormal neurologic examination are red flags that point to a secondary cause for spinal deformity.

Specialty consultation and magnetic resonance imaging are needed if red flags are present. Of adolescents diagnosed with Scoliosis, only 10 percent have curves that progress and require medical intervention. The main risk factors for curve progression are a large curve magnitude, skeletal immaturity and female gender. The likelihood of curve progression can be estimated by measuring the curve magnitude using the Cobb method on radiographs and by assessing skeletal growth potential using Tanner staging and Risser grading.

Patient Presenting with Idiopathic Scoliosis
Patient Presenting with Idiopathic Scoliosis
This treatment algortihm outlines the decisions made regarding treatment of adolescent idiopathic scoliosis based on curve magnitude at presentation. A variety of variables needs to be considered in each individual patient. Note that this algorithm is meant only to be an initial guideline.

The Scoliosis Research Society has defined Scoliosis as a lateral curvature of the spine greater than 10 degrees as measured using the Cobb method on a standing radiograph. Idiopathic Scoliosis is a structural curve with no clear underlying cause. Secondary causes for scoliosis can usually be identified by radiography and clinical examination.

Scoliosis is present in 2 to 4 percent of children between 10 and 16 years of age. The ratio of girls to boys with small curves of 10 degrees is equal but increases to a ratio of 10 girls for every one boy with curves greater than 30 degrees. Scoliosis in girls tends to progress more often and, therefore, girls more commonly need treatment than boys. The prevalence of curves greater than 30 degrees is approximately 0.2 percent, and the prevalence for curves greater than 40 degrees is approximately 0.1 percent. Improved understanding of the natural history and prognosis of this disease can help the physician predict the patients with Scoliosis who need treatment.

Classification of Adolescent Idiopathic Scoliosis

Since the early 1980s, the King Moe system has been the mainstay worldwide for classifying adolescent idiopathic scolisois (AIS) with respect to its surgical treatment. However, several short-comings in the reliability and clinical applications of the system were elucidated. Therefore, a new, comprehensive system of classifying AIS, the Lenke and associates system, recently has been developed and promoted. This triad classification system, consisting of a curve type, (1 through 6) a lumbar spine modifier, (A, B, C) and a sagittal thoracic modifier (-, N, +), attempts to provide a more systematic and treatment-directed approach to all curve types encountered in the AIS population requiring surgery. Classification of the radiographic parameters of AIS is important as

  1. A means of categorising similar types of curve patterns
  2. A communication tool enabling various practitioners specialising in scoliosis to compare different treatments of similar curve patterns
  3. A tool for comparing various reports in the literature describing new and potentially better ways of treating AIS
  4. A teaching tool for trainees
  5. A potential means of helping select surgical treatment that will obtain optimum results for specific curve patterns, if possible.

Classification systems are most helpful when they not only categorise various parameters of a disease process but also provide specific treatment paradigms to improve the results of both surgical and nonsurgical treatment.

The King Moe System

Although several systems were promoted for classifying AIS in the distant past, the King More system has been the gold standard for classifying thoracic AIS curves. This system, consisitng of five curve types (I through V) has several important features. First it promotes the use of selective thoracic fusion in false double major "thoracic and lumbar" scoliosis curve patterns, whereby only the larger thoracic would be fused, leaving the lesser lumbar curve unfused and mobile. This feature is important because traditionally most double thoracic and lumbar curves had been treated with routine T4 to L4 fusion with Harrington rod instrumentation (bear in mind that the Harrington rod is no longer in use in majority of countries). However, the King More system recommends selective fusion of the thoracic curve only when it is the larger curve and the lumbar curve is more flexible than the thoracic curve, even when it deviates substantially from the middle (i.e, the King Moe II curve pattern).

Second, the important term, stable vertebra, was coined to provide a safe distal end point for instrumentation and fusion in all curve types; this term is especially helpful in the overhang thoracic King-Moe III (L3 or above stable) and the King-Moe IV (overhang curve of L4 stable and tilted into the thoracic curve) curve patterns. The King-Moe I curve pattern is a true double major curve with a larger stiffer lumbar curve. Rounding out the five curve types is the King-Moe V curve, which is a double thoracic curve pattern that has a preoperative positive T1 tilt. For a right main thoracic curve, this pattern is characterised by elevation of the upper left end plate of the T1 vertebral body and usually the first rib, which usually correlates with a high left shoulder preoperatively. Identification of this curve pattern is important to minimise shoulder imbalance postoperatively when treating only a main thoracic curve. In these respects, each of these curve types provides important radiographic information for the clinical and surgical treatment of AIS when using Harrington rod instrumentation and can be somewhat extraordinary when using more modern segmental instrumentation systems.

However, the King Moe system has limitations, particularly whe other investigators, using more modern instrumentation systems and concepts, attempted to classify and then treat various surgical AIS curve patterns. Specific issues that led to fair to poor inter - and intraobserver reliability in two recent studies published consecutively included difficulties distinguishing between the King-Moe type II and type III curves based on the amount of lateral translation at the apex of the lumbar curve. In many curve patterns the lumbar curve almost but not completely deviated from the midline, and rotation was present in the lumbar spine contralateral to that found in the thoracic spine.

These curves often were classified as either King-Moe type II or type III by various investigators. Next, the King-Moe type V pattern, with a structural proximal thoracic curve, can occur in conjunction with any other curve pattern. Thus, combinations of King-Moe type I and type V, type II and type V, and type III or IV and type V curves are possible, making it difficult to select one classification system for each curve. In addition, the King-Moe system, as the name of the article implied, concentrated primarily on thoracic curves, the most common curve pattern set.

However, the other curves based in the thoracolumbar/lumbar spine could not be classified by the system, not could uncommon curve patterns, such as triple major curves. Thus, although the King-Moe system has proved extremely beneficial to the understanding of the surgical treatment of thoracic AIS, it appeared that a new approach was needed in an attempt to remediate some of the short-comings and also to integrate the sagittal plane into the system if possible because the King-Moe system was a coronal plane-only system, ignoring the three-dimensional nature of AIS.