Title: Multi-Directional Mechanics of the Spine
Summary:This work currently in progress is unique in that we have now been able to measure the bending properties of the human intervertebral disc about 13 axes rather than the traditional 3 axes.

Using our technologies that were developed for measuring the in vivo motion of the wrist, we can visualize 3-D motion spinal segments tested in vitro.
Funding: Departmental

This mechanical testing apparatus illustrates a test along the combined axis of left axial rotation and left lateral bending. The ACU (A) is potted in urethane and then assembled in cylindrical specimen holders (B) that are indexed in 45° increments. The holders attach to plates that are indexed with three sets of holes (C1, C2, and C3) at 45° increments. Two zero-backlash universal joints (D), the vertical load control of the actuator (E), and two perpendicular linear bearing tables (F) allow pure bending moments to be applied to the ACU. Load and moment data along three orthogonal axes are acquired with a six axis load cell (G). The entire apparatus fits within a servohydraulic load frame (H).

• Coordinate system showing various moment axes