Musculoskeletal Biomechanics Laboratory, Edward Hines, Jr. VA Hospital, Hines, IL, USA.
Department of Orthopedic Surgery and Rehabilitation, Loyola University Medical Center, 2160 S. First Avenue, Maywood, IL, 60153, USA.
Eur Spine J. 2020 Nov;29(11):2713-2721. doi: 10.1007/s00586-019-06064-4. Epub 2019 Jul 15.
We investigated a new metric for assessing the quality of motion of the cervical segments over the arc of extension-to-flexion motion after cervical disc arthroplasty (CDA). We quantified: (1) the amount of motion contributed by individual spinal segments to the total cervical spine motion, termed segmental motion fraction, and its variation throughout the arc of extension-to-flexion motion and (2) how cervical disc arthroplasty using two distinct prosthesis designs may influence the segmental motion contributions.
We tested 16 human C3-T1 spine specimens under physiologic loads; first intact, after CDA at C5-C6, and then at C5-C6 and C6-C7. The M6-C (Orthofix, USA) and Mobi-C (Zimmer, USA) disc prostheses were used in eight specimens each.
The designs of the cervical disc prostheses tested significantly influenced the variation in segmental motion fraction as the spine underwent motion between the endpoints of extension and flexion. While the mean segmental motion contribution to the total cervical motion was not influenced by prosthesis design, the way the motion took place between the extension and flexion endpoints was significantly influenced. The M6-C artificial disc restored physiologic motion quality such that implanted segments continued to function in harmony with other segments of the cervical spine as measured before arthroplasty. Conversely, the Mobi-C prosthesis, while maintaining average motion contributions similar to the pre-implantation values, demonstrated large deviations in motion contribution over the extension-to-flexion arc motion in ten of 16 implanted segments. Such non-physiologic implant kinematics could cause excessive prosthesis wear and motion and stress shielding at adjacent segments. These slides can be retrieved under Electronic Supplementary Material.
我们研究了一种新的指标，用于评估颈椎间盘置换术后颈椎屈伸运动弧中颈椎各节段运动质量。我们量化了：（1）每个脊柱节段对颈椎总运动的贡献量，称为节段运动分数，以及其在屈伸运动弧中的变化；（2）两种不同假体设计的颈椎间盘置换术如何影响节段运动的贡献。
我们在生理负荷下测试了 16 个人的 C3-T1 脊柱标本；首先是完整的，然后是 C5-C6 颈椎间盘置换术后，然后是 C5-C6 和 C6-C7 颈椎间盘置换术后。在 8 个标本中使用了 M6-C（Orthofix，美国）和 Mobi-C（Zimmer，美国）椎间盘假体。
测试的颈椎间盘假体设计显著影响了节段运动分数在屈伸运动终点之间的变化。虽然假体设计对节段运动对颈椎总运动的平均贡献没有影响，但运动在屈伸运动终点之间发生的方式受到了显著影响。M6-C 人工椎间盘恢复了生理运动质量，使得植入节段继续与颈椎的其他节段和谐地发挥功能，就像在置换前一样。相反，Mobi-C 假体虽然保持了与植入前相似的平均运动贡献，但在 16 个植入节段中有 10 个节段的运动贡献在屈伸运动弧中出现了较大的偏差。这种非生理的植入体运动学可能会导致假体过度磨损和运动，以及相邻节段的应力遮挡。这些幻灯片可以在电子补充材料中检索到。
