Scoliosis (> 40 degrees)
Objectives- Discuss indications for surgery for thoracic, thoracolumbar, and lumbar curves larger than 40 degrees
- Discuss the effect of surgery in altering the natural history of scoliosis
- Describe, in general terms, the differences in the newer instrumentation systems from Harrington instrumentation, including versatility, cost, incidence of complications, and effect on sagital alignment
Discussion points
- What is the role of the thoracoscopic approach to treatment of spinal deformity?
- Does spinal cord monitoring decrease the incidence of neurologic complications?
Discussion
The changes in the operative approach to spinal deformity in the last generation are huge. The Harrington rod was the only system used until the 1970's when interest in segmental instrumentation began to revolutionize the field. The Harrington rod is a pure distraction system, and earlier writings ignored its effect on sagital alignment. As followup studies documented the deleterious effects of fusion into the lower lumbar spine, and the "flat back syndrome" resulting from use of distraction rods only, other methods of management were developed. These include segmental wires first promulgated by Luque, the Cotrel-Dubousset system which does not use wires, and the Isola system which uses features of both. Subsequent refinements have led to the present plethora of available systems. Anterior instrumentation has also undergone major advances; disc excision accompanied by segmental anterior instrumentation reliably produces superior correction to posterior systems. The recent addition of pedicle screws has provided better capablilty of applying corrective forces to posterior systems. The thoracoscpic approach to anterior surgery is presently becoming more popular, and thoracoscopic anterior instrumentation is presently being used in some centers. It is too early to determine the place of thoracoscopic instrumentation in the total picture of deformity correction.
The most significant complications after deformity correction are neurologic (paralysis), pseudoarthrosis, and infection. The newer systems rely on translation or rotational correction more than distraction, which lessens the vascular insult to the spinal cord. However, they are more invasive, with multiple sites of insertion into the spinal canal, which allows more opportunity for neurologic damage. This was especially problematic after the introduction of segmental wires. Ligation of segmental vessels via anterior approaches is generally safe, but paralysis has been reported. Spinal cord monitoring, both sensory and motor have been effective in providing intraoperative warning of potential neurologic catastrophe, and some type of monitoring is presently considered state of the art. Bonegraft substitutes may reduce the morbidity from autogenous iliac crest grafting.
In general, surgery appears to have a favorable effect on the natural history of spinal deformity, although the age group of patients studied to date had Harrington instrumentation. The longterm effects of newer instrumentation systems obviously have yet to be studied. Emphasis at present is on trying to determine the effect of fusion and instrumentation on the unfused portion of the spine and maximize overall balance and mobility.
Indications for fusion are thus still relative. Most patients with deformity desire correction, and the patient's desire for correction is still the major indication for surgery. In heavier patients, the cosmetic effect of the curve is lessened. Double curves also have less cosmetic effect than single. Thus a single "threshold" figure for surgical correction is unrealistic. Finally, lesser degrees of thoracolumbar curves can produce greater amounts of deformity and place the patient at greater risk for subsequent vertebral translational shift than higher curves.
The field of surgical correction of spinal deformity is very fluid at present. Frequent updating of the data base can be expected.
References
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- Asher MA, Burton DC. A concept of idiopathic scoliosis deformities as imperfect torsion(s). Clinical Orthopaedics & Related Research 1999(364):11-25.
- Betz RR, Harms J, Clements DH, 3rd, Lenke LG, Lowe TG, Shufflebarger HL, et al. Comparison of anterior and posterior instrumentation for correction of adolescent thoracic idiopathic scoliosis [see comments]. Spine 1999;24(3):225-39.
- Bridwell KH. Surgical treatment of idiopathic adolescent scoliosis. Spine 1999;24(24):2607-16.
- Edgar M, Mehta M. Lon-term followup of fused and unfused idiopathic scoliosis. J Bone Joint Surg(Br) 1988;70:712-16.
- Grogan DP, Kalen V, Ross TI, Guidera KJ, Pugh li. Use of allograft bone for posterior spinal fusion in idiopathic scoliosis. Clinical Orthopaedics & Related Research 1999(369):273-8.
- Haher TR, Gorup JM, Shin TM, Homel P, Merola AA, Grogan DP, et al. Results of the Scoliosis Research Society instrument for evaluation of surgical outcome in adolescent idiopathic scoliosis. A multicenter study of 244 patients. Spine 1999;24(14):1435-40.
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- Muschik M, Schlenzka D, Robinson PN, Kupferschmidt C. Dorsal instrumentation for idiopathic adolescent thoracic scoliosis: rod rotation versus translation. European Spine Journal 1999;8(2):93-9.
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- Sweet FA, Lenke LG, Bridwell KH, Blanke KM. Maintaining lumbar lordosis with anterior single solid-rod instrumentation in thoracolumbar and lumbar adolescent idiopathic scoliosis. Spine 1999;24(16):1655-62.
- Wattenbarger JM, Richards BS, Herring JA. A comparison of single-rod instrumentation with double-rod instrumentation in adolescent idiopathic scoliosis. Spine 2000;25(13):1680-8.
- White SF, Asher MA, Lai SM, Burton DC. Patients' perceptions of overall function, pain, and appearance after primary posterior instrumentation and fusion for idiopathic scoliosis. Spine 1999;24(16):1693-9; discussion 9-700.
May 16-19, 2012 in Denver, CO
