[Ventral and dorsal correcting and stabilizing methods in idiopathic scoliosis. Long-term outcome]

The age of standardized instrumented scoliosis correction and stabilization began with Harrington instrumentation (HI). With HI, satisfactory long-term correction of the frontal plane averaged approximately 50%, but without notable derotational capabilities. The distraction of the concavity leads to reduction of the sagittal contour of the spine (flat back), which is biomechanically disadvantageous. The newer multisegmentally attached implant systems avoid this disadvantage. The first prototypes of these systems were Luque- (SSI) Cotrel-Dubousset instrumentation. Ideal indications for posterior instrumented curve correction are structural idiopathic double major curves and flexible single curves. However, even with these newer doublerod systems derotation is low, because derotation is, without any doubt, related to anterior release and thus decoupling of the segments by means of disc resection. The optimum method of correction and stabilization of scoliosis using the anterior approach is the ventral derotation spondylodesis (VDS), according to Zielke, who considers it to be a major improvement over Dwyer instrumentation. VDS is the first implant system with which true three-dimensional, segmental curve correction was made possible. Long term correction of the frontal plane and derotation averages approximately 70% and 50%, respectively. Ideal indications are single lumbar, thoracolumbar and thoracic curves. In our experience, the so-called kyphogenic effect of VDS due to anterior convex compression, can be counteracted by derotation and preserving disc space height with weight bearing bone grafts or cages. The low internal stabilizing capabilities with the risk of rod fracture and pseudarthrosis are unfavorable. They make long term cast or brace treatment necessary postoperatively. Meanwhile, the disadvantage of the low internal stabilizing capabilities of VDS has been overcome with the development of the primary stable Halm-Zielke instrumentation and other primary stable anterior fixation systems.