Adolescent Idiopathic Scoliosis (AIS)

Adolescent idiopathic scoliosis, also called AIS, is a condition that affects children from 10 years old to young adulthood and is characterized by an abnormal curve of the spine to the right or left in the shape of an S or a C. Adolescents with scoliosis are generally healthy. Most are completely active, despite the curvature in the spine.

AIS is by far the most common type of scoliosis, and up to 4 percent of children aged 9 to 14 have detectable scoliosis. Girls, or young women, are at higher risk than boys, or young men, with 60 to 80 percent of all cases occurring in females. AIS is often seen by the pediatrician or during a school screening at the beginning of puberty or during a growth spurt. AIS is also the type of scoliosis with the best chance of not worsening, which is why treatment usually begins with observation only.

Some Basic Facts About AIS

• Scoliosis is technically defined by the presence of a curve in the spine to the right or left of >10 degrees.
• While AIS is more common in adolescent girls than boys, the presence of small curves is actually equally common in boys and girls. However, many more adolescent girls than adolescent boys have severe curves, suggesting that the condition may be more likely to progress in girls.
• The incidence of AIS is higher in children with a positive family history (i.e., a family relative also had/has scoliosis).
• Adolescents with small curves usually do not experience pain from AIS.  When curves become larger or progress quickly, it can cause some back pain for patients. If back pain is present, additional tests may be performed to rule out other spinal conditions or other possible causes of the pain. We may also prescribe physical therapy to help with the back pain. Most of the time, back pain is due to other factors, such as heavy backpacks, bending over books/computers/gaming systems, or other activities.

What Causes AIS?

The exact cause of AIS is unknown (idiopathic). There has been considerable medical research into understanding scoliosis, which has led to the acceptance of several hypotheses for how AIS may develop.

One possible cause of developing AIS is simply inheritance from a relative who carries the gene. The extent to which genes affect an individual is highly unpredictable. Research suggests that multiple sites on multiple chromosomes may be involved in the development of scoliosis. Another hypothesis gaining greater acceptance is that scoliosis is not one condition but rather a number of distinct conditions with the same clinical presentation. Each of these conditions may also have a different prognosis. This might explain the wide range in curve severity and rates of curve progression among patients.

Much about AIS remains to be discovered and fully understood. As a result, ongoing research at a number of academic medical centers throughout the U.S. is attempting to further unlock these medical mysteries and improve the treatment and prevention of scoliosis.

How Is AIS Diagnosed?

Adolescent idiopathic scoliosis is usually first suspected during a standard physical examination by a pediatrician or primary care physician, or during a school screening test. Such examinations have the child or adolescent bend forward at the waist until the spine is parallel with the floor, while the physician observes the shape of the spine as it bends. If scoliosis is present, when the child or adolescent bends forward, the abnormal rotation of the spine creates a rib hump, with the ribs on one side sticking out slightly. If a rib hump or sign of scoliosis is found, then a standing x-ray series is recommended to make a definitive diagnosis of scoliosis. As mentioned before, this requires a curvature angle of at least 10 degrees.

If scoliosis is found, your child will be referred to a Pediatric Orthopaedic Surgeon to discuss the available treatment options.

A neurologic exam of the back and extremities will be performed during the physical exam and, if indicated, with additional diagnostic testing to ensure that no other spinal conditions are present and that the spinal cord is not affected by the abnormal curvature.

How Is AIS Treated?

Decisions regarding the appropriate treatment for AIS depend primarily on 2 factors: the severity of the spinal curvature and the patient's physical maturity. Because children grow at different rates and experience growth spurts at different ages, the patient's age is less important than the child’s bone age.  Bone age and the amount of growth left can be determined from pelvic X-rays (Risser grade) and hand X-rays (Sanders Score). Also, because growth patterns in girls and boys differ, the patient's sex plays a role in treatment.

Nonsurgical Treatment

The majority of children or adolescents will have mild curves (10-25 degrees) when AIS is first diagnosed, and will therefore be treated with observation only in most cases. This means that the child will be seen regularly by a Pediatric Orthopedic Surgeon, who will monitor the possible progression of the curve with several standing X-rays over time. The spinal curves of most children do not progress, and no further treatment is needed. However, if the curve becomes more severe, the patient may require bracing treatment.

There is a type of scoliosis-specific physical therapy called Schroth physical therapy or Physiotherapeutic Scoliosis-Specific Exercise (PSSE). This may be started prior to or in conjunction with bracing.

Physically immature patients with moderate curves (25-40 degrees) generally require treatment with a brace. Girls are physically immature if they are premenarchal (i.e., have not had their first period). Boys will usually receive bracing at slightly older ages than girls, because their spine continues to grow longer than girls' spines do. One goal of bracing is to begin treatment before the spinal growth period is completed. There are different types of braces, and you can find more information in our Scoliosis Bracing section.

With adherence to the bracing schedule, the bracing treatment is extremely successful. However, in some patients, the curve worsens, and surgery becomes the best treatment option.

Surgical Treatment

In very specific situations, vertebral stapling is an option for patients. This is a surgical intervention to try to prevent the need for a full spinal fusion and instrumentation.

Physically immature patients with severe curves (>40 degrees) are at high risk of further progression and therefore usually require surgical treatment after the curve reaches 50 degrees. Curve progression is more unpredictable in physically mature patients, but if the curve exceeds 50 degrees, surgery is also recommended.

Scoliosis surgery in adolescents/adults typically involves spinal fusion, in which vertebrae are fused with bone grafts and instrumentation. The instrumentation consists of metal rods that are attached to the spine to maintain curve correction. Most spinal fusions are performed through a posterior approach, in which the operation is performed with an incision in the back.

The alternative is an anterior approach, which is done in certain situations. This requires making an opening in the chest wall to reach the front part of the spinal column. Surgeries utilizing the anterior approach have changed in the last decade or so with the advent of thoroscopic spine surgery, in which smaller openings are made, and special cameras are used to visualize the spine. This minimizes scars and recovery time.

Because of the stability and effectiveness of the devices used in these spine operations today, patients are usually able to walk the day after surgery, and hospital stays are generally 3-5 days. The majority of adolescents return to school within 4 weeks and can often return to full athletic activity within 6 months.