Biomechanical evaluation of a new pedicle screw-based posterior dynamic stabilization device (Awesome Rod System) - a finite element analysis

Abstract

BackgroundPedicle-screw-based posterior dynamic stabilization devices are designed to alleviate the rate of accelerated degeneration of the vertebral level adjacent to the level of spinal fusion. A new pedicle- screw-based posterior dynamic stabilization device- the Awesome Dynamic Rod System was designed with curve cuts on the rods to provide flexibility. The current study was conducted to evaluate the biomechanical properties of this new device.MethodsFinite element models were developed for the intact spine (INT), the Awesome Dynamic Rod Implanted at L4-L5 (AWE), a traditional rigid rod system implanted at L4-L5 along with an interbody cage (FUS), and the Awesome Dynamic Rod System implanted at L4-L5 along with an interbody cage as an adjunct to fusion procedures and extension of dynamic fixation to L3-L4 (AWEFUS). The models were subjected to axial loads and pure moments and evaluated by a hybrid method on range of motion (ROM)s, disc stresses, pedicle screws stresses, and facet joint contact forces.ResultsFUS sustained the lowest L4-L5 ROM decrement in flexion and torsion. AWE demonstrated the lowest adjacent level ROM increment in all moments except for extension at L3-L4, and AWEFUS showed the greatest ROM increment at L2-L3. AWE demonstrated lowest adjacent segment disc stress in flexion, lateral bending and torsion at L3-L4. AWEFUS showed the highest disc stress increment in flexion, extension, and lateral bending, and the lowest disc stress decrement in torsion at L2-L3. AWE sustained greater adjacent facet joint contact forces than did FUS in extension and lateral bending at L3-L4, and AWEFUS demonstrated the greatest contact forces concentrating at L2-L3.ConclusionThe results demonstrate that the Awesome Dynamic Rod System preserved more bridged segment motion than did the traditional rigid rod fixation system except in extension. However, the Awesome Dynamic Rod System bore a greater facet joint contact force in extension. The Awesome Dynamic Rod System did protect the adjacent level of fusion segments, but led to much greater ROM, disc stresses, and facet joint contact forces increasing at the adjacent level of instrumented segments.

Finite element modelling of hybrid stabilization systems for the human lumbar spine

“…Screw lengths were 45 mm. The thread on the pedicle screws was underestimated [29][30][31][32] to reduce the computational weight of the models. The 'tie' constraint was created between the pedicle screws and the vertebraes to be permanently bonded together by full constraint.…”

Comparison of Biomechanical Performance of Five Different Treatment Approaches for Fixing Posterior Pelvic Ring Injury

“…e finite element (FE) modeling technique enables the exploration of different scenarios using computer models, and once validated, it can serve as an effective tool in biomechanics. erefore, in recent years, the FE technique has been widely used to investigate the biomechanical performance of different techniques [16][17][18][19][20][21][22], including analyzing different types of S1 screw fixation [22] and evaluating different fixation techniques for the treatment of sacroiliac joint injuries [18]. However, only a few studies have investigated the biomechanical stability of different fixation techniques for posterior pelvic ring fractures.…”

Prediction of biomechanical behavior of lumbar vertebrae using a novel semi-rigid stabilization device

“…Dynamic stabilization (DS) devices are mostly preferred in the cases of minor degeneracy in order to preserve motion and to improve physiological load transmission so as to relieve pain. [5][6][7][8][9] Spinal fusion having rigid instrumentation accelerates the degeneracy of adjacent FSUs, stress concentration and morbidity complications. [10][11][12][13] The clinical efficacy and the biomechanical aspects of such implants are to be evaluated through long-term follow-up observational study, in vitro/in vivo experiments and numerical simulations.…”

“…It was mentioned that Dynesys behaved stiffer as compared to TOPS system and better load sharing was observed at reduced load resulting in minimization of screw loosening at bone-screw interface. Chen et al 9 have performed biomechanical study of a new posterior DS device named ''Awesome Rod System (AWE)'' located at L4-L5 considering a FE model of lumbar segment (L1-L5). Authors concluded that AWE shields the fusion segments with increase in ROM, facet contact forces and disc stresses at the adjacent level of instrumented segments.…”