The Normal Spine
The human spine is made-up of a series of bone blocks called vertebrae. They are separated by a “cushion” called the intervertebral disk and connected by ligaments and a series of joints called facets. There are 7 cervical (neck) vertebra, 12 thoracic (chest) vertebra, 5 lumbar (lower back) vertebra, and 5 sacral vertebra.
The spine, when viewed from the side has a series of natural curves that maintain the body balance over the pelvis. The cervical and lumbar spine have a “sway-back” curve called lordosis. The thoracic spine has a forward bend called kyphosis.
When viewed from the front the spine should be straight.
What is Scoliosis?
Scoliosis is a medical term used to describe an abnormal curvature of the spine. It is a 3-dimensional deformity of the spine that is most commonly seen as a side-to-side bending of the spine. In addition to this side-to-side bend, the spinal column also rotates, pushing the ribs and muscles higher on one side compared to the other.
Scoliosis greater than 10° is present in 2-3% of the population. For smaller curves, boys are equally as affected as girls. Girls become more prevalent with larger curve sizes.
Scoliosis is divided into 3 general categories:
Etiology: What Causes Scoliosis?
Eighty percent of scoliosis is classified as idiopathic; the cause is unknown. Many different theories have been investigated. These include genetic factors, hormonal factors, spinal growth abnormalities, biomechanical and neuromuscular factors, and tissue abnormalities involving the muscle, ligaments, and bone. No one theory has been shown to be the cause. A great deal of current research has focused on the genetic cause of scoliosis. The exact genes involved, inheritance patterns, and gene products have not been identified yet.
Congenital scoliosis results when the vertebrae do not develop normally or do not separate normally. This type of scoliosis can be rapidly progressive and has an increased association with kidney and heart malformations.
Neuromuscular scoliosis occurs in association with a neuromuscular disorder such as cerebral palsy, polio, spina bifida, or spinal cord injury. Abnormalities with the spinal cord such as an Arnold-Chiari malformation, a tethered spinal cord, or syringomyelia (syrinx or spinal cord cyst) can also be seen with scoliosis.
Treatment decisions for scoliosis are based on the type of scoliosis and the risk of progression. Factors that determine the risk of progression include gender, the amount of skeletal growth remaining, curve location, and curve magnitude.
Treatment options include:
Observation is recommended in curves less than 20° in a growing child. Interval follow-up from 4-12 months may be recommended.
Bracing (Thoracolumbarsacral Orthosis, TLSO):
Bracing is recommended in progressive curves that reach 25° or curves that are 30° at the initial visit and a significant amount of skeletal growth remains. A brace only works in a growing child and is used to stop the curve from progressing. It will not reverse a curve that has developed. Studies have shown that when used appropriately, a brace is effective at preventing curve progression.
The original brace for scoliosis, the Milwaukee brace, was designed by Walter Blount in the 1940’s. This brace used metal uprights with pads to provide correctional forces to the spine. The brace had an extension above the shoulders around the neck. Modern day braces, the “Boston-type” brace, have removed the neck extension and have a less obvious underarm design. They are made of custom molded plastic and add pads to the inner surface to provide the necessary correctional forces to the spine. These braces are designed to be worn 22-23 hours per day.
Another type of brace, the Charleston nighttime bending brace, was designed to reduce the amount of time the brace had to be worn during the day. The brace hyper-corrected the deformity and is designed to be worn only at night. Some studies, however, have shown this brace not to be as effective as the more standard brace.
Surgical treatment for idiopathic scoliosis is recommended when curves reach 40-45° in a growing child and 50° or more in the skeletally mature child. Curves of this magnitude have been shown to continue to progress with the aging.
The goals of surgery are to obtain a solid bone fusion, to improve the magnitude of the curve, and to maintain spinal balance.
The most common procedure used to accomplish these goals is the posterior spinal instrumentation and fusion (PSIF). Dr. Paul Harrington, in the 1960’s, was the first to use instrumentation to treat scoliosis. The original instrumentation, the Harrington Rod, used 2 hooks and a single rod to obtain partial correction of the curve and hold this correction while a bone fusion took place. Patients who underwent this procedure had to spend at least 6 months in a body cast.
Modern instrumentation techniques use a series of hooks, wires, or screws with two rods. This provided stronger fixation and stability and eliminated the need for the body cast. These techniques also improved the surgeon’s ability to restore spinal balance while obtaining improved correction of the scoliotic curve.
Most surgeries take 3-6 hours. A blood transfusion is usually needed during the surgery. Pre-donated blood from the patient and from friends or relatives can be obtained prior to surgery.
The hospital stay for most patients is 5-7 days. If done during the school year, permission is given for homebound schooling for 6 weeks. If the child feels ready, he or she may return to school sooner. Activities are restricted for the first 6 months after surgery. This will allow a bone fusion to start to develop. A solid bone fusion takes a full year to develop. At the end of a year, the child may return to normal activities.
Pediatric Orthopedic Society of North America
Scoliosis Research Society
American Academy of Orthopedic Surgery