THE EFFECT OF A DYNAMIC STABILIZATION DEVICE ON DISC LOADING UNDER COMPRESSION

In the current study, finite element analyses were conducted to examine the biomechanical capability of a new designed dynamic stabilization system, FlexPLUS, to restore the load transmission of nucleotomized intervertebral L4-L5 lumbar motion segment spine under compression. To fulfill the purpose, detailed three-dimensional FE models of L4-L5 motion segment and the FlexPLUS were developed. Compressive loading up to 3,000N was applied to the intact L4-L5 model (to simulate healthy condition), the L4-L5 model without nucleus (to simulate nucleotomized condition), and the implanted nucleotomized L4-L5 model (to simulate surgical treated condition). The predicted axial displacement of L4 against applied compressive force of the intact L4-L5 model agreed well with experimental data. The predicted overall stiffness of the nucleotomized L4-L5 model was nearly 41 % lower than that of the intact model, while the implanted model was only 24 % lower. Under 3,000N compressive force, the predicted percentage of load shared by the annulus for the healthy, nucleotomized and implanted nucleotomized models were 53%, 84 % and 60%, respectively. The results showed that FlexPLUS can effectively reduce the load shared by the annulus of the nucleotomized segment, which further help to decompress the degenerated segment, to restore intervertebral disc height and yet permit segmental motions