Is posterior dynamic stabilization an option to avoid adjacent segment decompensation?

Abstract

Degenerative disk disease (DDD) at the level adjacent to an immobilized (fused) spinal segment is a well-recognized condition which is believed to result from the supraphysiological biomechanical stress and increased range of motion (ROM) created by the rigid fixation of the lumbar spine. It is hypothesized that topping a fusion with a posterior dynamic stabilization (PDS) system at the level adjacent to a fusion may diminish these increased stress and ROM, and subsequently, reduce the incidence of adjacent-level disk disease. The objective of this work was therefore to determine the biomechanical effect of PDS by measuring the stress and the ROM on a segment adjacent to a fusion prior and after PDS instrumentation. A three-dimensional nonlinear finite element model (FEM) of the human osseo-ligamentous lumbar spine was developed and validated based on experiments conducted on human cadavers. PDS topping off a fusion was shown in this model to relieve facet loading and reduce intradiscal pressure on adjacent segments. Assuming that these stresses contribute to adjacent-level disk disease, these data may indicate that PDS topping of a fusion may provide some protection against fusion-induced adjacent-level degeneration. In addition, reduced bone screw interface loading further suggests that PDS may be an option to avoid adjacent segment decompensation. © 2010 Springer-Verlag Berlin Heidelberg.