Effect of a semiconstrained elastic integrated cervical artificial disc on the cervical motion

Background and Objectives: Cervical total disc replacement (TDR) is a novel dynamically stabilizing technique for the symptomatic cervical intervertebral segment. While the long-term effect of mainstream cervical nonconstrained artificial disc group (CNAD) does not match the theoretical effects of mobility preserving and neural decompression. The cervical semiconstrained elastic integrated artificial disc (CSID) may be a more reasonable design. However, beneficial or adverse effects of this design have not been measured and data for biomechanical effect are unavailable. The aim of this study is to assess the biomechanical effect of CSID on the segmental motion at implanted and adjacent levels. Methods: This study was supported by medical science developmental funding of Nanjing (20,000 dollars). Eight cadaveric C3–T1 specimens were loaded in flexion/extension (F/E), axial rotation (AR), and lateral bending (LB) with CSID, CNAD, and anterior fusion (AF) implanted at C5–C6 level alternatively. The range of motion (ROM), neutral zone (NZ), and elastic zone (EZ) at implanted and adjacent levels were measured. The mean values of parameters in the intact specimen group (INT), CSID group, CNAD group, and AF group were compared statistically (n = 8). Results: There was no significant difference of ROM, NZ, and EZ at implanted and adjacent levels between CSID and INT in F/E, AR, and LB (P > 0.05). CNAD caused a significant change of EZ in F/E and LB and ROM in LB at implanted level. Meantime, CNAD caused ROM increasing at adjacent levels (P