Scoliosis surgery

Surgery for scoliosis is only recommended for patients with curves that are greater than 40 to 45 degrees and continuing to progress, and for most patients with curves that are greater than 50 degrees. The main objective of scoliosis surgery is to fuse the spine so that the curve will not continue to progress into adulthood.

Only more severe curvatures (greater than 50 degrees) are likely to progress in adulthood. If a curve is allowed to progress to 70 - 90 degrees, it will not only result in a very disfiguring deformity, but will start to result in cardiopulmonary compromise. This happens because the curve in the spine rotates the chest and closes down the space available for the lungs and heart.

Besides preventing further curvature, scoliosis surgery can also reduce the amount of deformity. Usually, about a 50% correction can be obtained with surgery using modern instrumentation systems in which hooks and screws are applied to the spine to anchor long rods. The rods are then used to reduce and hold the spine while bone that is added fuses together (See Figure 3).

Once the bone fuses, the spine does not move and the curve cannot progress. The rods are used as a temporary splint to hold the spine in place while the bone fuses together, and after the spine is fused the bone (not the rods) holds the spine in place. However, the rods are generally not removed since this is a large surgery and it is not necessary to remove them. Occasionally a rod can irritate the soft tissue around the spine, and if this happens the rod can be removed.

There are two general approaches to the scoliosis surgery – a posterior approach (from the back of the spine) or an anterior approach (from the front of the spine).

1. Scoliosis surgery from the back (posterior surgical approach)

This approach to scoliosis surgery is done through a long incision on the back of the spine (the incision goes the entire length of the thoracic spine)

After making the incision, the muscles are then stripped up off the spine to allow the surgeon access to the bony elements in the spine

The spine is then instrumented (screws are inserted) and the rods are used to reduce the amount of the curvature

Bone is then added (either the patient’s own bone, taken from the patient’s hip, or cadaver bone), which in turn incites a reaction that results in the spine fusing together.

This fusion process usually takes about 3 to 6 months, and can continue for up to 12 months.

For patients who have a severe deformity and/or those who have a very rigid curvature, an anterior release of the disc space (removal of the disc from the front) may first be required. This involves approaching the front of the spine either through an open incision or with a scope (thoracoscopic technique) and releasing the disc space. After the discs at the appropriate levels of the spine have been removed, bone (either the patient's own bone and/or cadaver bone) is added to the disc space to allow it to fuse together. After the disc has been released and fused, the posterior portion of the scoliosis surgery described above is performed.

Removing the discs allows for a better reduction of the spine and also results in a better fusion. This is especially important if the patient is a young child and has a lot of growth left. If just the posterior portion of the spine is fused, the anterior column can continue to grow, and loss of reduction can result ("crankshafting"). Fusing the spine anteriorly prevents this process.

2. Scoliosis surgery from the front (anterior surgical approach)

For curves that are mainly at the thoracolumbar junction (T12-L1), the scoliosis surgery can be done entirely as an anterior approach.

This approach to scoliosis surgery requires an open incision and the removal of a rib (usually on the left side). Through this approach the diaphragm can be released from the chest wall and spine, and excellent exposure can be obtained for the thoracic and lumbar spinal vertebral bodies.

The discs are removed and this loosens up the spine.

Screws can then be placed in the vertebral bodies and a reduction of the curvature obtained and held with a rod.

Bone is added to the disc space (either the patient’s own bone, taken from the patient’s hip, or cadaver bone), to allow the spine to fuse together.

This fusion process usually takes about 3 to 6 months, and can continue for up to 12 months.

The advantage of a purely anterior approach to scoliosis surgery in the appropriate curves is that not as many lumbar vertebral bodies will need to be fused and some additional motion segments can be preserved. Saving some of the motion is especially important for lower back curves (lumbar spine), because if the fusion goes below L3 there is a higher risk of later back pain and arthritis. Saving lumbar motion segments helps prevent loading all the stress on just a few motion segments.

Another advantage is that the anterior approach to scoliosis surgery can sometimes allow for a better reduction of the curve and a more favorable cosmetic result.

The major disadvantage of the anterior approach is that it can only be done for thoracolumbar curves, and most scoliotic curves are in the thoracic spine.

Potential risks and complications with scoliosis surgery
The most concerning risk with scoliosis surgery is paraplegia. It is very rare (about 1 in 1,000 to 1 in 10,000 chance) but is a devastating complication. To help manage this risk, the spinal cord can be monitored during surgery through one of two methods:

Somatosensory Evoked Potentials (SSEP's). This test involves small electrical impulses that are given in the legs and then read in the brain. If there is the development of slowing of the signals during surgery this can indicate compromise to the spinal cord or its blood supply. Another way to monitor the cord is with Motor Evoked Potentials (MEP's), and often both are used throughout a surgery.
Stagnara wake up test. This test involves waking the patient during the surgery and asking them to move their feet. The patient does not feel any pain during this procedure and will not remember it afterwards.

If either of these tests indicates spinal cord compromise, the rods can be cut out and the surgery abandoned. Fortunately, this situation is extremely uncommon.

Another risk with scoliosis surgery is excessive blood loss. There is a lot of muscle stripping and exposed area during the surgery. With proper technique the blood loss can usually be kept to a reasonable amount and blood transfusions are rarely needed. As a precaution, many surgeons will ask the patient to donate his or her own blood prior to surgery (autologous blood donation), which can then be given back to the patient after the surgery. Also, during scoliosis surgery the patient's blood can be collected and transfused back to the patient.

Other potential risks and complications include:

The rods breaking or the hooks or screws dislodging (although with modern instrumentation systems, this type of hardware failure is quite uncommon)
Infection (less than 1%)
Cerebrospinal fluid leak (rare)
Failure of the spine to fuse (about 1 to 5%)
Continued progression of the curve after surgery

Postoperative care
Following scoliosis surgery, patients can usually start to move around about 2 to 3 days after the surgery and when they start feeling better, and total hospital stay is usually about 4 to 7 days. Patients can return to school about 2 to 4 weeks after surgery, but their activity needs to be limited while the bone is fusing.

It is important to note that the more immobile the spine is kept the better it will fuse. Bending, lifting, and twisting are all discouraged for the first three months after surgery. For this reason, some surgeons will prescribe wearing a back brace for a period following the surgery. Any physical contact or jarring type activities are restricted for about 6 to 12 months after surgery.

Generally the patient will be monitored with intermittent examinations and x-rays for 1 to 2 years after the surgery. Once the bone is solidly fused no further treatment is required.

For the most part, patients can resume normal activity levels after a thoracic fusion since fusing the thoracic and upper lumbar spine does not change the biomechanics of the spine all that much. Female patients who have had a scoliosis fusion can still become pregnant and deliver babies vaginally.

By: Peter F. Ullrich, Jr., MD
September 17, 2001 (Updated March 30, 2004)