Facet Joint Complex Considerations For Biomechanics Of The Lumbar Functional Spinal Unit: An Improved Model Based Method For Investigating Facet Articulation

The biomechanics of facet kinematics is an important consideration for the native and pathologic spine. Moreover when evaluating new implants and techniques designed for motion preservation from either an anterior or posterior approach, the facet joint complex requires measurement techniques that do not violate the joint integrity to accurately characterize the contributions to the overall functional spinal unit response. Three-dimensional modeling of the lumbar spine can be used to derive a wealth of data beyond range of motion without invasive procedures. We have developed a method to apply kinematic data to rigid body models of each vertebral body reconstructed from high resolution CT scans. The method described has been shown to reduce registration errors from previous techniques. To portray the robustness of this method, we have computationally defined the articular surfaces of the L3-14 facet joint and tracked minimum distance (MD) between each surface. The MD between intact and rigid rod instrumented conditions has been compared. The application of the rigid rod construct has shown to constrain the facet surfaces spatially closer than in the intact condition.