No matter what form of anterior scoliosis instrumentation a spinal surgeon chooses to use it is generally accepted that complete clearance of the intervertebral discs over the levels being instrumented should be undertaken. This improves the flexibility of the curve, potentially enhancing the correction that can be achieved but, perhaps more importantly, reduces the forces that must be exerted on the spine through the instrumentation, particularly at the upper and lower levels. Complete disc clearance may also facilitate intervertebral fusion.

The most challenging aspect of disc clearance is removal of the posterior aspect of the annulus and the posterior longitudinal ligament The standard surgical technique involves initial excision of the convex lateral and anterior annulus, followed by the gelatinous nuclear material. This is relatively easily and quickly achieved. However, careful, patient and painstaking piecemeal removal of the posterior annulus is then necessary and this is more time consuming. Care is clearly required to avoid injury to the adjacent dura and neurological structures. Access to the posterior annulus with a ronger becomes more difficult towards the far concave aspect of the disc.

Little information is published concerning the time required for standard disc clearance. However, in the author's experience, and from personal information provided by other surgeons, 30 minutes per level is generally required.

Coblation is a relatively new surgical technology by which tissue is removed by vaporisation achieved through the production of an ionized plasma vapour. The depth of vaporisation is very limited and is achieved with virtually no heat production, resulting in minimal thermal damage to adjacent tissue.

The author has used coblation in anterior correction of scoliosis, and in his view the technique allows simpler, more controlled and thus ultimately safer clearance of the posterior annulus. Clearance is also achieved more quickly, the time required for each level undertaken being reduced to approximately 15 minutes.