Comparing the Kinematics of Lumbar Spine: Anatomic Facet Replacement System (AFRS™) vs. Rigid Fixation System

Problems associated with spinal fusion such as adjacent level degeneration and donor site pain have shifted the focus to motion preservation technologies. The Anatomic Facet Replacement System (AFRS^™) (Facet Solutions, Inc., Logan, Utah) attempts to address posterior lumbar spine pathologies while preserving stability and natural biomechanics thereby mitigating any potential adjacent level effects resulting from the reduction or elimination of motion as seen in semi-constrained dynamic stabilization and fusion devices. The AFRS^™ is comprised of a precision instrumentation set whose design is based upon a comprehensive CT morphology study of the facet joint. It utilizes traditional pedicle screw fixation of its superior and inferior facet implants and is manufactured from a wear resistant alloy called cobalt-chromium-molybdenum. An experimentally validated finite element model was used for the quantification of facet loads and stresses in various components of the facet replacement system and also in the model stabilized using a pedicle screw rigid rod fixation system.