Scoliosis

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Articles and graphics courtesy of Medtronic Sofamor Danek, 2002.

Spinal Anatomy

Abnormal Spine Anatomy

Scoliosis is not a disease - it is a descriptive term. All spines have curves. Some curvature in the neck, upper trunk and lower trunk is normal. Humans need these spinal curves to help the upper body maintain proper balance and alignment over the pelvis. However, when there are abnormal side-to-side (lateral) curves in the spinal column, we refer to this as scoliosis.

Congenital Scoliosis
Congenital scoliosis is defined as a curvature of the spine that is the result of malformations of the vertebral elements. The fact that the spine and spinal column ever form correctly is amazing given the complexity of the process from the embryological standpoint. Most of this development happens during the 3rd-6th week in utero (after conception). In spite of the opportunities for error, congenital malformations are relatively rare.

Doctors think about congenital scoliosis in three groups: failures of formation, failures of segmentation, and combinations of these defects. The most common failure of formation is called a hemivertebra. Hemivertebra produce a growth imbalance in the spine and therefore result the spine growing crooked. Failures of segmentation include block vertebra and unilateral bars, which produce a growth tether of the spine. Finally, when these occur in combination, such as a hemivertebra on one side and a bar on the other, the scoliosis can progress in very rapid manner.

Idiopathic
Idiopathic scoliosis is the most common form of scoliosis in North America, affecting up to 2 % of the population. It's usually caused by an adolescent growth spurt. In order for a physician to diagnose and treat idiopathic scoliosis, he or she must first rule out all other causes of scoliosis. Most idiopathic curves present in adolescence are painless, gradual, have a typical curve pattern (for example, a right thoracic curve), and the neurological exam is normal. Idiopathic scoliosis is much more common in females.

Kyphosis
Kyphosis or hunching over is normal in the thoracic spine. If you look at your child from the side, you will notice that there is a curve in the upper back where they are "hunched over", and a curve in the lower spine ("sway back"). Some kyphosis is normal.
When the doctor measures it on an x-ray, the normal range for kyphosis is quite broad, between 20-50 degrees. However, when kyphosis is greater than 50 degrees, it becomes easy to see and is considered abnormal. Most parents will attribute this to "poor posture", but become concerned that despite their persistent reminders, their child will not stand up straight.

There are two common forms of kyphosis encountered in the teenage population: Scheueremann's kyphosis and Postural Roundback. Scheueremann's kyphosis is most common in teenage boys. It is characterized by a short, sharp kyphosis in the middle part of the upper spine, and may be associated with aching back pain. The kyphosis tends to be rigid on clinical examination. There are x-ray criteria that establish a diagnosis of Scheueremann's kyphosis that can be seen on the x-ray. A mild degree of scoliosis is common in adolescents with Scheueremann's kyphosis.

Postural Roundback is noted by a smooth, flexible kyphosis that is not typically associated with pain. The curve is easily corrected by asking the child to stand up straight. Radiographically, the criteria for the diagnosis of postural roundback are kyphosis greater than 50 degrees, but without the other x-ray findings seen with Scheueremann's kyphosis. These curves tend to be mild in severity and extend over a longer number of vertebral segments when compared to Scheueremann's kyphosis.

Neuromuscular Scoliosis
The term "neuromuscular scoliosis" is used to describe curvature of the spine in children with any disorder of the neurological system. Common categories include cerebral palsy, spina bifida, muscular dystrophies, spinal cord injuries and so forth. Most of these children have as a unifying feature weakness of the trunk. As they grow and their trunk gets weaker, there is a progressive, collapsing deformity of the spine producing a long, c-type curve. These curves tend to be progressive, with the rate of progression becoming worse during rapid growth. For children confined to a wheel chair, progressive curves may affect the child's ability to be seated comfortably, thereby affecting their quality of life and function.

Articles and graphics courtesy of Medtronic Sofamor Danek, 2002.

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