Adolescent Idiopathic Scoliosis: Fact & Fiction
Adolescent idiopathic scoliosis is the most common type of idiopathic scoliosis, comprising more than 80% of all patients with idiopathic scoliosis. The adolescent age group is defined as ages 10 to18, and typical curve types are C shape or S shape in the coronal plane. The spine rotates as it curves, resulting in rib hump deformity, shoulder imbalance, or waist asymmetry seen on physical examination. Scoliosis affects girls more than boys at a ratio of 8:1.
Idiopathic scoliosis is thought to be present in 2% to 3% of adolescents. One in 500 of these adolescents will require active treatment and only one in 5,000 will progress to the degree that surgery in indicated. Etiology of idiopathic scoliosis is unknown. Approximately 30% of patients have a significant family history of scoliosis. If there is an underlying neurologic cause (cerebral palsy, muscular dystrophy), the condition is termed neuromuscular scoliosis. Congenital scoliosis implies that segments of the spine either fail to segment or parts fail to form in utero. Both neuromuscular and congenital scoliosis are treated very differently than idiopathic scoliosis.
Most of the time, the scoliosis is asymptomatic and is discovered in routine physical examination, school screening, or is noticed by the patient or family. Some curves do, in fact, cause pain. In that situation, other potential causes of pain need to be explored. It can never be assumed that the scoliosis is the cause. Progression of the curve tends to occur in the secondary growth spurt around the time of menarche.
After a thorough examination, standardized 36-inch PA and lateral standing scoliosis films are necessary to evaluate adolescent idiopathic scoliosis. Even the highly trained scoliosis specialist can measure curves differently and arrive at different numbers. The most qualified specialist should determine the actual curve measurement and assess all subsequent radiographs to try to determine whether progression is actually occurring. Radiation exposure is a concern to all females, particularly growing adolescents. Proper imaging minimizes the need to repeat films. It is important to limit the number of films a patient receives over the course of treatment because all x-ray exposure is cumulative. X-rays often show structural changes including asymmetric growth of the apical vertebrae, a keystone feature of idiopathic scoliosis. Structural vertebral changes indicate that the deformity was present prior to cessation of growth.
Bracing is the only proven non-operative treatment that can prevent progression and, in some rare cases, improve the curve. Bracing is only effective if there is growth remaining and in curves between 25 and 40 degrees. Location of the curve can sometimes determine whether a brace is going to be effective. The window of opportunity is lost when growth is completed. There is no scientific proof that alternative treatments, such as, physical therapy, chiropractic or yoga have any value in the treatment of the growing child adolescent. For symptomatic relief after skeletal maturity, alternative treatments can be utilized if so desired by the patients or their families. These techniques should not be used to treat the curvature in the hopes that it will improve the scoliosis.
Surgery is reserved for thoracic curves greater than 50 degrees. Thoracolumbar and lumbar apex curves are sometimes treated when they are less than 50 degrees. Severe hypo-kyphosis or thoracic lordosis also indicate surgery because of their significant affect on pulmonary function.
Current surgical techniques include pedicle screw segmental fixation to straighten and de-rotate the scoliosis. Limiting the fusion levels to the major curve and maintaining the important lumbar spine flexibility is of primary importance. Modern techniques permit aggressive correction and de-rotation of the deformity, often allowing the surgeon to address only the major curve, leaving the compensatory lumbar curves alone and maintaining important lumbar spine flexibility. Historically, several alternatives to posterior approach have been introduced, yet the majority of surgeons around the world migrate back to a standard open posterior approach for treatment of idiopathic scoliosis. The reasons are simple. Posterior correction is well tolerated by patients, has a low complication rate, a high patient satisfaction rate, and a high long-term fusion rate.
A small minority of surgeons are attempting correction through a more minimally invasive (MIS) posture approach through multiple stab incisions. This involves tunneling under the skin to attempt to decorticate and remove the joints in intermediate sections that are not directly exposed. Instrumentation is placed percutaneously with x-ray assist. The MIS approach to adolescent or adult scoliosis has not been proven to be more effective in the treatment of scoliosis and has been linked to poor correction of sagittal balance. With any change in surgical technique, it may take 5 to 10 years to determine if fusion rates and patient outcomes are consistent with the standard approach. While many new surgical techniques are introduced as "the answer" to a problem, longer term experience reveals that these new techniques are only appropriate for very limited indications.
Our major concerns with MIS approach idiopathic scoliosis are two.
- Radiation exposure: No one knows the long term effects of prolonged X-ray exposure to growing children required with MIS techniques.
- It will take years, maybe decades, to know what the fusion rates and re-operation revision rates will be. Current well established posterior fusion techniques result in high fusion rates, low complication, high rates of curve correction with maintenance of sagittal and coronal balance. This is a well tolerated procedure with excellent outcomes in this patient population. It is the technique used worldwide by most physicians specializing in treatment of Scoliosis.
What about Adults?
The major difference in treating an adult and adolescent with idiopathic scoliosis is the degeneration of the compensatory lumbar spine in adulthood. Adult patients often present with painful conditions including disc degeneration, spinal stenosis, and degenerative or rotatory spondylolisthesis, below the major curves. Sometimes, the major curves themselves can cause symptoms with age. Traditionally, age groups are divided as adolescent (10 to 18 years) and adult (18 and older). In the opinion of this author, persons up to age 30 should be classified with the adolescent group because the surgical treatment is nearly identical.
In the adolescent patient, curve progression determines whether surgery is recommended; however, curve progression alone is rarely the indication in adult patients over 30. Why do surgeons operate on scoliosis patients at all? The answer is that adolescents with curves over 50 degrees in the thoracic spine tend to progress at a rate of up to one degree per year. As curves in the thoracic spine approach 80 to 90 degrees, the restrictive lung disease created by the deformity affects pulmonary function. Simple mathematical calculations indicate that a patient at age 15 with a 50 degree curve could develop serious medical conditions in their forties or fifties .The same long-term natural history study shows that curves under 30 degrees in the thoracic spine tend not to progress. A very important point of this study, which is often overlooked, is the fact that curves with thoracolumbar or lumbar apex are unpredictable. Deformity surgeons need follow patients with these types of curves into their twenties and thirties. If over time there is significant curve progression or truncal decomposition associated with pain, they are often treated surgically when their compensatory lumbar discs are still normal.
Adult patients that, over time, experience increasing lower back pain, decreasing ability to stand upright or sit upright unsupported like in bleacher seating, may elect surgical treatment. In this select group, if their disability is progressive, it may be beneficial to treat them at a younger age when there is less risk of complication. Adult spinal deformity surgery for persons age 60 and up has a much higher complication rate and it is clear that the patients with the most significant disabilities and symptomatology are the ones that gain the most benefit.
Idiopathic scoliosis only affects only 2 to 3% of the population. The window of opportunity for nonoperative brace treatment in the growing child is clear and that window of opportunity closes at skeletal maturity. Early diagnosis's the key to successful non operative management.