| Popis: |
Dynamic stabilization may provide a more physiologic alternative to fusion for patients suffering from low back pain. A validated 3-D nonlinear finite element model of the intact L3-S1 lumbar spine was used to evaluate the biomechanics of various dynamic stabilization systems in comparison with rigid screw rod system that is used in conventional fusion. The intact model was modified at L4-L5 to simulate stabilization with, rigid screw-rod system, rigid screw flexible rod system, Dynesys system, Cosmic system, and Wallis system. These devices were also simulated in decompression surgery to evaluate the stability. The load control and hybrid protocols were used to evaluate these devices. Various biomechanically relevant parameters like range of motion, facet loading, disc stresses, implant stresses, instantaneous axis of rotation and load sharing were evaluated. Results show that the flexible rod system does not vary much in terms of stiffness and load sharing capabilities from the rigid screw rod system. Dynesys, Cosmic and Wallis systems are more flexible than rigid systems but not flexible enough to say that they preserve motion. However, they have the ability to allow for loading through the intervertebral disc. All the flexible stabilization systems were capable of stabilizing the decompression surgery in flexion and extension and lateral bending. Dynesys and Cosmic systems do not restore stability in axial rotation. |
