#263 Biomechanical Evaluation of a Selectively Constrained Cervical Disc Replacement
Oral Posters: Cervical
Presented by: B. Bucklen
T. Daftari (1)
S.R. Chinthakunta (2)
K. Salloum (2)
M. Moldavsky (2)
B. Bucklen (2)
(1) Resurgens Orthopaedics Spine Center, Orthopaedics, Kennesaw, GA, USA
(2) Globus Medical Inc, Research, Audbon, PA, USA
Purpose of the Study: Despite encouraging outcomes of one-level cervical disc replacements (CTDR) reported in literature, the biomechanical effects of two-level CTDRs and CTDRs adjacent to fusion on adjacent motion segments are not well understood. The primary objectives of the current investigation were to evaluate the operative level range of motion, center of rotation, and adjacent level intradiscal pressure following two-level cervical total disc replacement compared to fusion.
Methods: Five C3-T1 cadaveric spines were tested on a 6 degree of freedom spine simulator. Surgical constructs included:
2) CTDR C5-C7 [SECURE®-C, Globus Medical Inc., Audubon, PA];
3) CTDR C5-C6 + Fusion C6-C7 [COALITION®, Globus Medical Inc.]; and
4) Fusion C5-C7.
Range of motion (ROM), center of rotation (COR) and intradiscal pressure (IDP) were calculated. Load control protocol with ± 2Nm moments was used in flexion-extension (FE), lateral bending (LB) and axial rotation (AR) to establish intact values. Flexibility testing using displacement control was carried for all other surgical constructs.
Summary of Findings: For two-level CTDR, mean ROM decreased by 13% and 24% at the operated levels (C5-C7) in FE and LB, respectively. In AR, mean ROM decreased by 26% at C5-C6 and increased by 10% at C6-C7. Motion at the adjacent levels (C4-C5 and C7-T1) increased following placement of CTDR and fusion device, with fusion resulting in the highest mean adjacent level ROM. The findings also revealed that the two-level fusion construct tended to increase mean ROM at the adjacent level compared to both the two-level disc replacement, and CTDR adjacent to fusion constructs. Following CTDR placement, COR was maintained close to the intact condition for both the levels. Increase in motion corresponded to increased IDP at the adjacent C7-T1 level.
Conclusions: The two-level CTDR tended to reduce the biomechanical motion.Clinical stability of a two-level disc arthroplasty requires additional investigation. The CTDR adjacent to fusion constructs may be considered a viable alternative for treating two-level cervical degenerative disc disease.