In-vitro kinematic testing of porcine cervical spine: a rotational manipulation model

Although spinal manipulation is widely used in the management of neck and pain, its exact mechanisms and biomechancial effects are not clear. A porcine model was used to study the relative movements of intervertebral joints under spinal rotation maneuvers with different input angular displacements and thrust velocities. Ten porcine spines (C2/4) were fixed and mounted in a material testing machine. Rotational maneuvers with different input angular displacements (0.8, 1.5, 2 and 3 degrees) and thrust velocities (0.1 - 200 degrees/s) were applied to C2 with C4 fixed. Angular displacement induced at the adjacent level was measured and expressed as percentage of the applied angular displacement. For all the tested conditions, angular deformation at the adjacent level could not be avoided when an angular thrust was applied to the target level. The percentage of the angular displacement induced at the adjacent level was found to be dependent on both the input angular displacement and thrust velocity. If rapid thurst of manipulation is used to direct the input energy and motion at the target level with minimal interference at the adjacent levels, the applied angular displacement should not be too large and the thrust velocity should be within a medium velocity range.