Purpopse

Few Cervical Total Disc Replacement (TDR) devices are engineered to address both the Center of Balance (COB) and the Center of Rotation (COR) of the cervical motion segments. The COB is the axis in the intervertebral disc through which the axial compressive load is transmitted. TDRs placed posterior of this point tend to fall into kyphosis while devices placed anterior of this point tend to fall into lordosis. Thus from a “balancing” point of view the ideal placement would be at the COB. However, the COR position has been shown to be posterior and inferior to the disc space. It has also been shown that constrained devices tend to lose motion when there is a mismatch between device and anatomic centers. Mobile core devices may be placed at the COB since their unconstrained rotations and translations allow for the device COR to follow the anatomic COR, but they rely heavily on the facet joints and other anatomic features to resist the paradoxiacal motion.

The TriLobe cervical TDR (Figure 2) was engineered for both the COB and COR. The purpose of this study was to compare the 3D kinematic and biomechanical performance of the TriLobe to a ball and trough(BT) cervical TDR in an augmented pure moment cadaveric study to find the ideal AP implant placement.