Influence of cervical total disc replacement on motion in the target and adjacent segments.

Autor: Vogt M; Institute of Orthopaedic Research and Biomechanics, Trauma Research Centre Ulm, University of Ulm, Helmholtzstr. 14, 89081 Ulm, Germany., Mehren C; Spine Center, Schoen Clinic Munich-Harlaching, Harlachinger Str. 51, 81547 Munich, Germany; Academic Teaching Hospital of the Ludwig-Maximilians-University (LMU), Marchioninistr. 15, 81377 Munich, Germany; Academic Teaching Hospital of the Paracelsus Medical University (PMU), Strubergasse 21, 5020 Salzburg, Austria., Hackenbroch C; Department of Diagnostic and Interventional Radiology and Neuroradiology, German Armed Forces Hospital of Ulm, Oberer Eselsberg 40, 89081 Ulm, Germany; Department of Diagnostic and Interventional Radiology, University Hospital Ulm, Albert-Einstein-Allee 23, 89081 Ulm, Germany., Wilke HJ; Institute of Orthopaedic Research and Biomechanics, Trauma Research Centre Ulm, University of Ulm, Helmholtzstr. 14, 89081 Ulm, Germany. Electronic address: hans-joachim.wilke@uni-ulm.de.
Jazyk: angličtina
Zdroj: The spine journal : official journal of the North American Spine Society [Spine J] 2024 Jul; Vol. 24 (7), pp. 1313-1322. Date of Electronic Publication: 2024 Jan 30.
DOI: 10.1016/j.spinee.2024.01.018
Abstrakt: Background Context: The motion limitation after cervical discectomy and fusion alters the spine´s kinematics. Unphysiological strains may be the result and possible explanation for adjacent segment degeneration. Alterations to cervical kinematics due to cervical total disc replacement (TDR), especially two-level, are still under investigated.
Purpose: To investigate cervical motion including coupled motions after one-level and two-level TDR in the treated and also the adjacent segments.
Study Design: An in-vitro study using pure moment loading of human donor spines.
Methods: Seven fresh frozen human cervical spine specimens (C4-T1, median age 46 with range 19-60 years, four female) were included in this study. Specimens were tested in the intact condition first, followed by one-level TDR at C5-6 which was subsequently extended one level further caudal (C5-7). Each specimen was quasistatically loaded with pure moments up to 1.5 Nm in flexion/extension (FE), lateral bending (LB), and axial rotation (AR) in a universal spine tester for 3.5 cycles at 1 °/s. During the tests three dimensional motion tracking was performed for each vertebral body individually. From that, the primary and coupled ROM of each spinal level during the third full cycle of motion were evaluated. Nonparametric statistical analysis was performed using a Friedman-test and post hoc correction with Dunn-Bonferroni-tests (p<.05). Ethics approval was obtained in advance.
Results: In FE, one-level TDR (C5-6) moderately increased primary FE in all four segments, but only significantly at the cranial adjacent level C4-5. Additional TDR at C6-7 further increased the ROM at the target segment without much influence on the other levels. Increasing implant height at C6-7 partially counteracted the increased FE. Coupled motions were minimal in all test conditions at all levels. In LB, coupled AR was observed in all test conditions at all levels. One-level TDR decreased primary LB at the target segment C5-6 significantly, without much influence on the other levels. Extending TDR to C6-7 decreased ROM in the target segment but without gaining statistical significance. Increasing implant height at C6-7 further decreased primary LB at the target segment, still without significance. Notably, coupled AR was significantly decreased at the cranial adjacent segment C4-5 compared to the intact condition. In AR, coupled LB was observed in all test conditions at the levels C4-5, C5-6, and C6-7, while the transition level to the thoracic spine C7-T1 showed only little coupled LB. Both one-level and two-level TDR showed little influence on primary AR or coupled motions at any level. Only after increasing implant height at C6-7 was the motion of the caudally adjacent level C7-T1 significantly altered.
Conclusion: Evaluating primary FE, LB, and AR together with the associated coupled motions revealed widespread influence of cervical TDR not only on the motion of the treated level but also at the adjacent segments. The influence of two-level TDR is more widespread and involves more levels than one-level TDR.
Clinical Significance: The prevention of unphysiological strains due to altered kinematics after cervical fusion, which could possibly explain adjacent segment degeneration, were a driving factor in the development of TDR. These experimental findings suggest cervical TDR influences the whole cervical spine, not only the treated segment. The effect becomes more extensive, involving more levels and motion directions, after two-level than after one-level TDR.
Competing Interests: Declaration of competing interest One or more of the authors declare financial or professional relationships on ICMJE-TSJ disclosure forms.
(Copyright © 2024. Published by Elsevier Inc.)
Databáze: MEDLINE
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