Does Placement of the Axis of Rotation of the Cervical Spine Affect Motion Segment Mechanics During Flexion and Extension?

Current in vitro testing methodologies remain limited in the ability to explore spinal mechanics. The gold standard of flexibility testing has traditionally focused only on evaluating rotational components of motion within a motion segment unit (MSU). While such data may be applied towards evaluation of the Center of Rotation (CoR) of a joint, many systems lack the needed sensitivity. The result is that there is currently no consensus on the location of the CoR of the spine. Further, very limited data or insight can be gathered as to the precise kinematic or dynamic state of the MSU, the influence of surgically implanted motion restoration devices, or the influence of subtle changes to an implanted device.