Factors Predicting Spontaneous Lumbar Curve Correction in Scoliosis

Sometimes fusion surgery is needed to correct scoliosis (curvature of the spine) in adolescents. The goals are to correct deformity and balance the curves of the spine. Another goal is to derotate the segments that have gotten twisted around. The surgeon tries to do all this with the least number of vertebrae fused together as possible. Motion is preserved above and below the fusion sites.

Previous studies have helped surgeons identify which patients can benefit from a selective thoracic fusion. This procedure is for the child who has two curves: one in the thoracic spine and one in the lumbar spine. Only the thoracic curve is fused. The lumbar curve often corrects itself after the thoracic segment is fused.

The question posed in this study by surgeons at Duke University was: does it matter what kind of fusion is done? Are patients more likely to experience spontaneous lumbar curve correction with an anterior or with a posterior fusion?

Two groups of patients were compared. One group had an anterior fusion with instrumentation (hooks, wires, screws). The second group had a posterior fusion with similar instrumentation methods. Patients in both groups were matched as carefully as possible. For example, they were the same ages and having surgery at the same thoracic levels.

X-rays were used to measure before and after results. The authors report no significant difference in spontaneous lumbar correction after anterior or posterior fusion. The main determining factor was the lowest instrumented vertebra(LIV). The greatest amount of spontaneous correction of the lumbar curve occurred in patients with the lowest instrumented vertebra.

Analysis of the results also showed two other important factors. First, the more flexible the lumbar curve is before thoracic fusion, the more likely the lumbar curve will spontaneously correct itself. And second, the amount of correction that can be achieved in the thoracic spine makes a difference. The more the thoracic curve can be safely corrected, the more spontaneous correction occurs in the lumbar spine.

This study does not answer the question: how far down should the spine be fused? At what point does the thoracic fusion prevent correction of the lumbar curve? Future studies are needed to add this piece of information to the puzzle.