[Dynamic instrumentation of the lumbar spine. Clinical and biomechanical analysis of success factors].

Total disc replacement and posterior dynamic stabilization represent alternatives to lumbar spinal fusion which should reduce the risk of adjacent segment degeneration. Disc replacement is indicated for pure discopathy without facet joint degeneration. Spinopelvic balance influences the implant's biomechanics. Therefore pelvic incidence, sacral slope, segmental lordosis and the mean axis of rotation need to be considered. Dynamic stabilization is indicated in moderate discopathy and facet joint degeneration, in degenerative spondylolisthesis grade I with a hypermobile segment and in dynamic lumbar stenosis. The combination of caudal fusion and cranial dynamic stabilization allows a better maintenance of lordosis with multiple level instrumentation and prevents adjacent segment degeneration. If pelvic incidence and sacral slope are high, L5-S1 should be fused because of elevated shear forces.