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

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 clear.

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 patients.7-10 Danielson and Nachemson,11 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 that 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), 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 5- to 9-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 3% to 20% from the pre- to the postoperative period.

Cochrane et al and Hayes et al13 found a high incidence of retrolisthesis in the area of the unfused spine, especially when the lowest fused level was more distal; this retrolisthesis was accompanied by a higher incidence of back pain. Edgar and Mehta reviewed 91 operative scoliosis patients re-examined at least 10 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, were noted. Edwards15 stated that the main thoracic and lumbar curves, main thoracic apical vertebral translation (AVT) 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 5 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 changed included:

  • Main thoracic curve
  • Coronal angulation of the disc below the lowest instrumented vertebra (CAD-LIV)
  • Lowest instrumented vertebra (LIV) angle to the horizontal
  • 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 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 that is basically cosmetic must stand up to long-term scrutiny. Current techniques using multiple screw fixation will present new, important characteristics for study.

References

  1. Parent S., Newton P.O., Wenger D.R. Adolescent idiopathic scoliosis: etiology, anatomy, natural history, and bracing. Instr Course Lect 2005; 54: 529–36
  2. Weinstein S.L., Dolan L.A., Cheng J.C.Y, Danielsson A., Morcuende J.A., Adolescent idiopathic scoliosis. Lancet 2008; 371: 1527–37
  3. Asher M.A., Min L.S., and Burton D.C. Further development and validation of the Scoliosis Research Society (SRS) outcomes instrument. Spine 2000;25:2381-6
  4. Asher M., Min L.S., Burton D., and Manna B. The reliability and concurrent validity of the scoliosis research society-22 patient questionnaire for idiopathic scoliosis. Spine 2003;28:63-9
  5. Loder R.T., Spiegel D., Gutknecht S., Kleist K., Ly T., and Mehbod A. The assessment of intraobserver and interobserver error in the measurement of noncongenital scoliosis in children < or = 10 years of age. Spine 2004;29:2548-53
  6. D’Andrea L.P., Betz R.R., Lenke L.G. et al. Do radiographic parameters correlate with clinical outcomes in adolescent idiopathic scoliosis? Spine 2000;25:1795-802
  7. Cochran T., Irstam L., Nachemson A. Long-term anatomic and functional changes in patients with adolescent idiopathic scoliosis treated by Harrington rod fusion. Spine 1983;8:576-84
  8. Dickson J.H., Erwin W.D., Rossi D. Harrington instrumentation and arthrodesis for idiopathic scoliosis: A twenty-one-year follow-up. J Bone Joint Surg [Am] 1990;72:678-88
  9. Edgar M.A., Mehta M.H. Long-term follow-up of fused and unfused idiopathic scoliosis. J Bone Joint Surg [Br] 1988;70:712-6
  10. Helenius I., Remes V., Yrjoenen T. et al. Comparison of long-term functional and radiologic outcomes after Harrington instrumentation and spondylodesis in adolescent idiopathic scoliosis : A review of 78 patients. Spine 2002; 27(2): 176-80
  11. Danielsson A.J., Nachemson A.L.: Radiologic findings and curve progression 22 Yyears after treatment for adolescent Iidiopathic scoliosis. Spine 2001:26(5): 516-25
  12. O’Brien M.F., Kuklo T.R., Blanke R.N., Lenke L.G. Spinal Deformity Study Group Radiographic Measurement Manual. Medtronic Sofamor Danek
  13. Hayes M.A., Tompkins S.F., Herndon W.A., Gruel C.R., Kopta J.A., Howard T.C. Clinical and radiological evaluation of lumbosacral motion below fusion levels in idiopathic scoliosis. Spine 1988;13:1161-7
  14. Takahashi S., Delecrin J., Passuti N. Changes in the unfused Lumbar Spine in Patients with idiopathic scoliosis: A 5-9 –year assessment after Cotrel-Dubousset instrumentation. Spine 1997: 517-523
  15. Edwards C.C., Lenke L.G., Peelle M. et al. Selective thoracic fusion for adolescent idiopathic scoliosis with C modifier lumbar curves. Spine 2004: 29(5):536-46
  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.

Reprinted with permission from the Summer 2009 issue of COA Bulletin

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