Encyclopedia / S / Scoliosis



Article updated and reviewed by Scott J. Luhmann, MD, Instructor in Surgery, Department of Orthopaedic Surgery, Washington University School of Medicine. Editorial review provided by VeriMed Healthcare Network on May 19, 2005.

Scoliosis is a lateral curvature of the spine, occurring in the cervical (neck), thoracic (chest), or in the lumbar spine (low back).


The onset of scoliosis may occur during infancy (birth to three years), the juvenile years (ages four to nine), or in the adolescent years (greater than or equal to 10). The infantile type more commonly affects males and is the least common of the three types. Spontaneous correction may occur, but in the typical case the curve progresses with growth. Occasionally abnormal development of one or more of the vertebrae (i.e., Hemivertebrae) occurs which may affect curve progression. Juvenile scoliosis first appears between three and 10 years of age when a thoracic curve begins to form causing chest asymmetry, prominence of a shoulder blade, vertical elevation of one shoulder, or asymmetric skin folds. Both boys and girls are relatively equally affected in juvenile scoliosis. Some cases of juvenile scoliosis may not be noticeable until the child reaches adolescence as the skeleton grows to maturity. The most common type is the adolescent type in which girls are affected at a ratio of 10:1 relative to boys.

As the curve progresses, the vertebrae rotate toward the concave part of the curve. This causes the ribs to crowd together on the concave side while they are widely separate and project more posteriorly on the convex side. Most noticeable is the rotational chest asymmetry which can be best seen when the affected individual bends forward to touch their toes. When viewed from the side, most patients with scoliosis have fairly normal back contour with a tendency to have a flatter or less rounded back appearance with relatively normal lumbar lordosis (swayback). The curvature may force the spaces between the spinal disks to become asymmetric, while the vertebrae grow thicker on the outer convex side of the curve. Usually the disc spaces between the vertebrae, though asymmetric, do not degenerate in adolescence.

A very small number of cases result from leg-length discrepancy that is produced by one leg being shorter than the other, causing a tilted pelvis and tilted take-off of the spine (think Leaning Tower of Pisa). However, the majority of cases, regardless of age, have an unknown cause and are considered to be genetic in origin.


Most adolescent scoliosis is "idiopathic," which means the cause is unknown. This differentiates it from scoliosis caused by known processes, such as neuromuscular, pathologic, and metabolic diseases. It is also a mystery why some curves increase rapidly while most remain stable or progress slowly. If rapid curve progression occurs further, diagnostic work-up to identify a possible cause may be indicated. A tendency to develop scoliosis can be genetically inherited and the disorder frequently runs in families. If one child is diagnosed, all other growing children in the family should be examined by the primary care physician. Some nonidiopathic cases of scoliosis can be traced to neurological disorders, such as polio, spinal cord injuries, cerebral palsy, and muscular dystrophy.

It is important that scoliosis be identified as early as possible, since prompt treatment of progressing curves provides the best chance of slowing or halting an increasing curvature.


The traditional mode of therapy, the Milwaukee brace, has been largely replaced by thermoplastic thoracolumbar spinal orthoses (TLSO) that are custom-fitted and easily concealed by loose-fitting clothes. Treatment protocols have typically required wearing the brace for 23 hours per day until skeletal maturity is reached, followed by a gradual weaning program. Some recent information indicates that part-time brace wear (16 hours per day) may be sufficient to slow curve progression for some individuals. Night-time braces (Charleston bending brace) have been advocated by some centers; however conflicting reports have limited the acceptance of this bracing system. As cosmetic appearance will not improve with brace treatment, an unacceptable appearance contraindicates brace treatment. Other nonoperative interventions, such as chiropractic treatment, electrical stimulation, and physical therapy have be used but have not been shown to alter the natural history of scoliosis.


Of the approximately 30,000 to 70,000 spinal surgery procedures performed each year, about one-third are for advanced scoliotic curves. Depending on the patient's age, orthopaedic surgeons usually start discussing surgery as a treatment option when a curve approaches 40 degrees. Curves greater than 45 degrees have a high likelihood of progression in adolescence and in adulthood. As the curve size increases, more chest and trunk deformity develop, which reduce surgery’s ability to completely correct the cosmetic appearance. Breathing problems can occur in scoliosis, but usually occur when curves are greater than 90 degrees.

During the scoliosis surgery, the spine is exposed and is made as flexible as possible in order to optimize correction. The surgeon attaches metal rods to vertebrae from the top to the bottom of the curve with hooks, screws, or wires, fusing the vertebrae with bone fragments taken from the pelvis (above the hip joints), or the spine itself. The healed fusion hardens in a straightened position, leaving the remainder of the spine flexible. The more levels fused the less flexibility there will be after surgery, especially when fusing lumbar levels (low back below the chest cage). Afterwards, brace use is dependent upon multiple patient and surgical factors, and with many current implant systems, is not necessary.

It usually takes one year for the fusion to become solid and strong, with most surgeons saying two to five years is necessary to assure solid fusion. When corrective surgery is done before growth is completed, the patient gains height from the straightening of the scoliotic spine and loses height from the fused levels, which stops growth of the fused levels only. These gains and losses tend to cancel each other out.

The introduction of Cotrel-Dubousset (CD) instrumentation has revolutionized scoliosis surgery. This implant system uses two or more interconnected metal rods with segmental screws and hooks which directly attach to the spine. When compared to the older Harrington Rod system, the CD system has less than a two percent loss of correction, compared with a 10 to 25 percent loss. With the CD system and similar systems, the screws and hooks are rigidly fixed to resist rotation, making body cast unnecessary and braces only occasionally necessary. Second and third-generation CD implant systems have demonstrated continued improvement in the surgeon’s ability to correct the scoliosis and to maintain its position until fusion. The latest research has demonstrated anterior spine surgery (through the chest) to “loosen” or increase the flexibility of the spine is not necessary for curves less than 100 degrees.

Fusion of the anterior spine, instead of posterior fusion (from the back), can be an option for selected patients. Prior to the development of third generation implants, anterior spine fusion was able to better correct the scoliosis, especially the rotational component, while fusing fewer overall levels. However, fewer of these anterior procedures are being performed due to the ability of the latest third generation CD instrumentation to correct angulation, translation, and rotation of the scoliotic spine.


What causes the abnormal curvature of the spine?

Is the curvature progressive?

Are there any other imaging tests which may be helpful?

Can the curve progression be slowed?

Can a scoliosis brace be useful?

When should surgery be a treatment option?