Idiopathic Scoliosis: Long-term Outcomes Following Fusion for Scoliosis Deformity 

Marc J. Moreau, M.D., FRCSC
Edmonton, AB 

Epidemiological studies estimate that 1-3% of the at-risk population (children aged 10-16 years) will have some degree of spinal curvature, although most curves will need no intervention1,2. Progressive scoliosis can affect self-image, mental health, produce pain and limit function3,4. The most common outcome used in scoliosis management is a measure of the severity of the internal spinal deformity5 (Cobb angle), but it is not necessarily the patient's primary concern6.


With respect to surgical management, although technology has greatly increased the safety with which we can correct spinal deformity and preserve spinal balance, long-term results of these changing methods of management are absent. Surgery can reduce deformity and prevent further progression, but its role in the prevention of other negative long-term effects of scoliosis is not clear1.

The word "outcomes" implies more than one facet when addressing the issue of the postoperative scoliosis patient. The first is stability of the spine: does the fusion hold itself over the decades following surgery? The second refers to the unfused lumbar segments below a long spinal fusion and degeneration of the spine in relation to the level of fusion, presence of symptoms over the long term, and ultimate radiographic degeneration of the unfused lumbar spine. The third is outcome qualifiers, which refers to quality of life indices - how well do these operated patients do in terms of pain, self-consciousness and function? We will deal with the first two.

There is a paucity of information describing curve decompensation after fusion in patients treated by modern instrumentation techniques. There is, however, a body of literature in reference to follow-up of Harrington instrumentation patients7,8,9,10. Danielson and Nachemson11, in a study of 156 patients who had undergone Harrington instrumentation and fusion and had been followed for a minimum of 22 years, found an insignificant change in Cobb angle with time. A manual was developed by the Spinal Deformity Study Group12 which defined more specific spinal descriptors other than the Cobb angle to examine postoperative changes in operated curves. Takahashi et al13 analyzed modern internal fixation techniques and also measured thoracic apical vertebral translation (AVT) (Figure 1), the angle from the horizontal of the most instrumented vertebra and coronal decompensation (CD) and sagittal balance from C7-S1 to name a few. Careful analysis of the spinal descriptors revealed changes in curves that were more significant than one was led to believe when compared to analysis of the Cobb angle only.



Modern day surgical procedures used to treat idiopathic scoliosis address the cosmetic deformity linked to the disease, but largely do not take into consideration any long-term life restricting outcomes. Potential consequences such as disc degeneration below the instrumented spine take many years to develop. In Danielson and Nachemson's11 series of patients followed after Harrington instrumentation, they determined that the curves did not increase over time, but that disc degeneration was more common than in a non-operated control group. Takahashi14, in his five to nine year postop follow-up of 30 patients, showed slight loss of correction in the first year after surgery, but stability thereafter; however, he reported that the incidence of back pain increased from three to 20% from the pre to the postoperative period. Cochrane7 et al, Hayes et al13 found a high incidence of retrolisthesis in the unfused spine especially when the fusion level was more distal; along with this retrolisthesis, came a higher incidence of back pain. Edgar and Mehta9 reviewed 91 operative scoliosis patients re-examined at least ten years after surgery and found that although the Cobb angle measurements did not change significantly, sagittal plane deformities as well as an increase in vertebral rotation was noted. Edwards15 stated that the main thoracic and lumbar curves, main thoracic AVT (apical vertebral translation) and sagittal T2-T12 thoracic kyphosis deteriorated with time.

In a small unpublished study16 of 14 patients from the Glenrose Hospital in Edmonton, Alberta with a five to 12 year follow-up, changes were found in all cases; however, these changes varied with each case. The data supported the statement that the spine deteriorates with time in the postoperative period. Parameters that change include the main thoracic curve, coronal angulation of the disc below the lowest instrumented vertebra (CAD-LIV), the lowest instrumented vertebra (LIV) angle to the horizontal and the sagittal T2-S1 alignment. These changes were found to be statistically significant. Also studied were the central sacral vertebral line (CSVL) to LIV, thoracolumbar or lumbar curve coronal decompensation, thoracic apical vertebral translation (AVT), thoracolumbar or lumbar AVT and T1 tilt. Each patient showed a change, but all in a unique manner.

Long-term analysis of the instrumented scoliotic spine presents many facets for examination and study. A procedure which is basically cosmetic must stand up to long-term scrutiny. Current techniques using multiple screw fixation will present new, important characteristics for study.


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  16. Dang N.R., Moreau K.A., Moreau M.J., Hill D.L., Mahood J.K., Raso J. Long-term follow-up of operative adolescent idiopathic (AIS) patients: Unpublished maunuscript

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