Adolescent idiopathic scoliosis (AIS) is a scoliosis that affects children or adolescents from the age of 10 into young adulthood. Typically it is noticed around 11 to 12 years of age in girls and a little later in boys. Like other types of scoliosis it is characterised by an abnormal sideways S or C curve of the spine. Children with AIS are generally otherwise healthy and normal. AIS is the most common type of scoliosis. Approximately 4% of all children between 10 and 18 years old will develop this type of scoliosis. AIS is more commonly seen in girls than boys – 90% of scoliosis cases are girls. AIS often begins to develop at the initial onset of puberty becoming more apparent as is worsens during growth spurts.
AIS has a better prognosis than juvenile scoliosis, but can still progress to become a significant deformity if it is not detected early and properly managed. It is not uncommon for adolescents with large curves or curves that progress quickly to develop some back pain. The most effective non surgical treatment is bracing but for curves under 25 degrees exercise may appropriate.
What causes AIS?
The exact cause of adolescent scoliosis is unknown hence its classification as an “idiopathic” scoliosis. Idiopathic literally means “of unknown cause”. The most widely accepted theory explaining the development of adolescent scoliosis is one involving a genetic trigger. Adolescent scoliosis is often seen occurring in members of the same family, in the same and in past generations. Scientists believe that a set of genes that may trigger scoliosis may be inherited.
However, scoliosis does not always appear in subsequent generations i.e. not every child of parents who have scoliosis will develop the condition. This suggests that individuals are affected by these genes to different degrees and that other factors may be required for a scoliosis to develop. Research at several institutions has uncovered several different genes that appear to be associated with scoliosis and genetic tests that can identify these genes are currently being trialed.
How is AIS diagnosed?
In the absence of school screenings, adolescent scoliosis is usually first noticed by the child or a family member of the child. A common test used to screen for scoliosis is called the “Adams forward bending test”. In this test the child or adolescent, bends forward at the waist until the spine is parallel with the floor. The examiner stands behind the child and observes the shape of the spine as they are bend over. The main feature alerting the examiner to a scoliosis is the presence of a rib hump, which is typically seen in a thoracic scoliosis. A rib hump is where the ribs on one side protrude more compared to the other side when the child is bent forward. A special instrument that looks similar to a spirit level called a scoliometer can be used to measure the extent of the humping. In some cases the scoliosis is not in the upper part of the torso but in the lower back. Therefore screening should also consist of examination of the whole upright posture including the level of the hips as well as the Adams test.
When scoliosis is suspected, a careful neurological exam and MRI should always be carried out to ensure that the scoliosis is not the result of a neurological condition and that the spinal cord is not being affected by another disease. As well as an MRI it is important for x-rays of the spine to be taken. X-ray should be taken standing up to give a true representation of the curve under the load of gravity. X-rays also give clear images of the bones and allow for more precise measurements of the curvature.
How is AIS treated?
There are two key factors that should determine the appropriate treatment for AIS, these are: 1) the physical maturity of the patient and 2) the severity of the spinal curvature. As children grow at different rates and experience growth spurts at different ages, the calendar age of the patient is not as important as the child’s skeletal age. The skeletal age is determined by how completely a child’s bones have undergone a process known as “ossification”. This is a process whereby the cartilage that initially makes up a child’s bones is replaced by hard bone. Scoliosis specialists can assess this process by examining the hand and or pelvis bones on x-rays. When assessing the pelvis, the examiner is looking for a dark line across the top of the pelvis, also known as the Risser sign. This sign is broken up into grades 0 to 5 (0 being no ossification and a sign of a very immature skeleton and 5 being completed ossification and a fully mature skeleton.). When assessing a hand x-ray, a comparison is made to an index of hand x-rays and based on the best match a skeletal age is given. Alternatively, features from the hand x-ray can be used to grade the level of maturity of the skeleton. Also, because growth patterns in girls and boys tend to be different, the sex of the patient plays a role in treatment as well.
As a general rule, the more immature the skeleton, the more growth left and the greater potential for progression. If a large curve (e.g. 40 degrees) is present in an immature Risser 0 patient it would have a very high likelihood of progression and require intervention, compared to the same 40 degree curve which could be present in a skeletally mature Risser 5 adolescent that did not require intervention because the chance of progression is extremely low.
Using curve size as a guide, the below examples of treatment assume that the patient has an immature skeleton Risser 0-3 with significant growth potential.
In adolescent curves between 10 and 20 degrees there is some evidence to suggest that an intensive course of scoliosis specific physiotherapy may be able to make some correction or control the curve. However once the curve is greater than 20 degrees it is usually too large for physiotherapy alone to manage its progression and physio in conjunction with bracing is recommended.
In curves greater than 20 degrees or in curves greater than 15 degrees where there is a family history of scoliosis a dynamic brace is usually recommended to retrain and strengthen the spine. In some situations, a dynamic brace can be used in adolescent cases with curves as large as 45 degrees.
In adolescent curves greater than 45 degrees conservative treatment becomes more difficult. At this point the type of treatment can vary depending on the treatment goal. For example if the patient is Risser 0 with a 50 degree thoracic curve they are entering the surgical zone, but being immature it may be desirable to delay surgery until Risser 3/4. Therefore an aggressive rigid brace and intensive physiotherapy maybe recommended to try and reduce and stabilise the curve until the patient is more mature and ready for surgery. In a more mature patient Risser 4 with the same 50 degree curve the surgeon may feel that the spine is well balanced and if the curve can be maintained at its current position that surgery may not be necessary. In this case, treatment with a dynamic bracing option may be the most suitable treatment.
Generally in large curves with significant growth left, the prognosis for conservative treatment is usually poor and the primary treatment goal becomes to control the curve to slowing progression and delay surgery until suitable maturity.
Specific scoliosis physiotherapy is often prescribed in conjunction with bracing treatment. The goal of these types of programs are to strengthen the back muscles that would otherwise become weak from the immobilisation caused by the brace.
Surgery is usually recommended when a scoliosis rapidly progresses to a point where it unbalances the spine. Surgery is not recommended on the degree of curve alone, there are other important factors to consider such as: the patients age, the balance of the spine, the potential growth and many other factors.
Scoliosis surgery consists of spinal fusion, in which two or more of the vertebrae are fused together with bone bridges made of bone grafts, and/or instrumentation, in which metal rods are attached to the spine to maintain curve correction. Surgeries may be performed through aposterior approach, in which the operation is performed with an incision in the back, or also with an anterior approach, which is a more extensive surgery that requires making an opening in the chest wall to reach the front part of the spinal column. Patients are usually able to walk the day following their surgery, and hospital stays are generally under 1 week. The majority of children or adolescents return to school within 4-6 weeks and can often return to full athletic activity within a year, though contact sports are not recommended.