Surgery for adolescents with scoliosis is only recommended when their curves are greater than 40 to 45 degrees and continuing to progress, and for most patients with curves that are greater than 50 degrees.
Unlike back braces, which do not correct spinal curves already present, surgery can correct curvature by about 50%. Furthermore, surgery prevents further progression of the curve.
There are several approaches to scoliosis surgery, but all use 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 with existing bone.
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.
Two Approaches to Scoliosis Surgery
There are two general approaches to the scoliosis surgery – a posterior approach (from the back of the spine) and an anterior approach (from the front of the spine). Specific surgery is recommended based on the type and location of the curve.
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 stripped 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), inciting a reaction in which the bones in the spine begin fusing together
- The bones continue to fuse after surgery is completed. The 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, another procedure may be required prior to this surgery. A surgeon may recommend an anterior release of the disc space (removal of the disc from the front), which 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.
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Removing the discs allows for a better reduction of the spine and also results in a better fusion. These two factors are especially important if the patient is a young child (10 to 12 years old) and has a lot of skeletal growth left.
Without the anterior release procedure, the anterior column (the part of the spine facing the front of the body) can continue to grow, eventually twisting around the fused, non-growing posterior spinal column, forming a new scoliosis curve (called "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 to loosen up the spine.
- Screws are placed in the vertebral bodies and rods are put in place to reduce the curvature.
- 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 begin to fuse together.
- This fusion process usually takes about 3 to 6 months, and can continue for up to 12 months.
If this surgery is applicable because of the type of curvature, the anterior approach to scoliosis surgery has several advantages over the posterior approach.
- Not as many lumbar vertebral bodies will need to be fused and some additional motion segments can be preserved
- Saving motion segments 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 also helps prevent loading all the stress on just a few motion segments
- This approach 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.