Biomechanical analysis of cervical range of motion and facet contact force after a novel artificial cervical disc replacement

An ideal implantation of artificial cervical disc replacement (ACDR) prosthesis should preserve the cervical biomechanics and maintain normal cervical biomechanics. In this study, we designed a novel prosthesis based on the physiological curvature of the cervical endplate, and conducted an in vitro test with cadaveric cervical specimens to study its effect on cervical range of motion (ROM) and facet contact force. Eighteen cadaveric cervical specimens (C2-C7) were evaluated with a 50 N follower load and a moment of +/- 2.0 N-m. Testing conditions were as follows: control (group 1), C5-C6 ACDR with a novel prosthesis (group 2), C5-C6 ACDR with the Prestige LP prosthesis (group 3) and C5-C6 cervical discectomy and fusion (ACDF) with cage internal fixation (group 4). The range of motion (ROM) of all segments and facet joint contact force were measured and analyzed. The results showed that there was no significant difference among the group 1, 2 and 3 in terms of ROM (P>0.05). The ROM of C5-C6 in the group 4 showed a significant decrease compared with the group 1, 2, and 3 (P<0.05). The group 2 had a similar facet joint force with the group 1, and there is no statistical difference among the group 1, 2 and 3 (P>0.05). The facet joint force of C5-C6 in the group 4 reduced significantly compared with the other groups (P<0.05). In conclusion, both novel cervical prosthesis and Prestige LP could better preserve the normal cervical ROM and maintain facet joint force than ACDF.