Scoliosis Surgery

Surgery is usually indicated on the curves that have a high probability of progression (i.e, a magnitude over 45-50 degrees).  The curves that would be cosmetically unacceptable as an adult are curves in patients with spina bifida and cerebral palsy that interfere with sitting and care, and curves that affect physiological functions such as breathing.

Surgery for scoliosis is done by a surgeon who specializes in spine surgery. For various reasons, usually it is quite impossible to straighten scoliosis, but in most cases the corrections have very good results.
Spinal Fusion with Instrumentation

Spinal fusion surgery is most commonly performed for scoliosis.  In this procedure, bone (either harvested in other parts of the body or a donor graft) is grafted onto the vertebrae so that when cured, it will form a solid bone mass and the vertebral column becomes rigid.

This prevents the worsening of the curve at the expense of some movements of the spine.  This can be done from the anterior (front) aspect of the spine by entering the thoracic or abdominal cavity, or more commonly done from the back (posterior).  A combination is used in severe cases.

Originally, spinal fusions were done without metal implants.  A cast was applied after surgery, usually under traction to pull the curve as straight as possible and to keep it there while fusion takes place.  Unfortunately, there was a relatively high risk of pseudo-arthrosis (non-fusion) and one or more levels of significant correction could not always be achieved.
In 1962, Paul Harrington introduced a system of spinal instrumentation of the metal, which helped to straighten the spine and hold it rigid while fusion took place.  The original, obsolete Harrington rod operated in a ratchet system, attached by hooks in the column on the top and bottom of the curve that, when deprived of crank, straightened the curve.

A major shortcoming of the Harrington method was that it could produce a position in the skull, which would be in proper alignment with the pelvis and not address rotational deformity.  As a result, the unused portion of the column tries to compensate for this in an effort to keep itself upright.  “Flatback” became the medical name for a complication, especially for those who had lumbar scoliosis.
Modern spinal systems try to solve the sagittal imbalance and unresolved defects in rotation by the Harrington rod system.  Involving a combination of rods, screws, hooks and wires fixing the spine, they can apply stronger, safer forces to the backbone of the Harrington rod.

This technique is known as the Cotrel Dubousset instrumentation, currently the most common technique for the procedure.  Modern spinal fusions generally have good results with a high degree of correction and low rates of failure and infection.  Patients with fused spines and permanent implants tend to have normal lives with unrestricted activities when they are younger, but it remains to be seen whether those who have been treated with new surgical techniques will develop problems as they age.

A notable limitation of spinal fusions is that patients undergoing surgery for scoliosis are ineligible for service in the armed forces of countries like the United Kingdom, Sweden and the United States.
Pedicle screw spinal fusion can improve only after the major curve correction 2 years later among patients with adolescent idiopathic scoliosis (AIS), compared to hybrids (proximal hooks distal pedicle screws) (65% versus 46%) according to a retrospective matched cohort study.   The prospective cohort was matched to the retrospective cohort according to patient age, fusion levels, the Lenke curve type and the operating method.

The two groups were not significantly different with regard to age, AIS Lenke curve type, or degree Riser.  The number of fused vertebrae were significantly different (11.7 + / -1.6 for pedicle screw versus 13.0 + / -1.2 for the hybrid group).  Results of this study may be biased due to the pedicle screw group prospectively analyzed against the group retrospective analysis of hybrid instruments.
If the scoliosis has caused a significant deformity resulting in hump ribs, it is often possible to perform a surgery called costoplasty (also called thorocoplasty) to achieve a better cosmetic result.  This procedure can be performed at any time after fusion surgery, either as part of the same operation or several years later.

Usually it is impossible to completely straighten out and unscrew a scoliosis, and it should be noted that the level of aesthetic success will depend on the extent to which the column rotates in the yet merged ribcage.  A rib hump is evidence that there is still some rotational deformity of the spine.