gms | German Medical Science

56. Jahrestagung der Deutschen Gesellschaft für Neurochirurgie e. V. (DGNC)
3èmes journées françaises de Neurochirurgie (SFNC)

Deutsche Gesellschaft für Neurochirurgie e. V.
Société Française de Neurochirurgie

07. bis 11.05.2005, Strasbourg

Articulated total disc replacement with 3 or 5 degrees of freedom : a cadaveric lumbar spine study

Meeting Abstract

  • corresponding author M.-A. Rousseau - Department of Orthopaedic Surgery, University of California, San Francisco
  • D. S. Bradford - Department of Orthopaedic Surgery, University of California, San Francisco
  • R. Bertagnoli - Department of Orthopaedic Surgery, University of California, San Francisco
  • S. S. Hu - Department of Orthopaedic Surgery, University of California, San Francisco
  • J. C. Lotz - Department of Orthopaedic Surgery, University of California, San Francisco

Deutsche Gesellschaft für Neurochirurgie. Société Française de Neurochirurgie. 56. Jahrestagung der Deutschen Gesellschaft für Neurochirurgie e.V. (DGNC), 3èmes journées françaises de Neurochirurgie (SFNC). Strasbourg, 07.-11.05.2005. Düsseldorf, Köln: German Medical Science; 2005. Doc09.05.-02.04

Die elektronische Version dieses Artikels ist vollständig und ist verfügbar unter: http://www.egms.de/de/meetings/dgnc2005/05dgnc0009.shtml

Veröffentlicht: 4. Mai 2005

© 2005 Rousseau et al.
Dieser Artikel ist ein Open Access-Artikel und steht unter den Creative Commons Lizenzbedingungen (http://creativecommons.org/licenses/by-nc-nd/3.0/deed.de). Er darf vervielf&aauml;ltigt, verbreitet und &oauml;ffentlich zug&aauml;nglich gemacht werden, vorausgesetzt dass Autor und Quelle genannt werden.


Gliederung

Text

Objective

Total disc replacement is a novel approach for dynamically stabilizing a painful intervertebral segment. While this approach is gaining popularity, and several types of implants are used, the effect of disc arthroplasty on lumbar biomechanics has not been widely reported. The goal of this study was to characterize kinematic and load transfer modifications at L5/S1 secondary to joint replacement.

Methods

Twelve human cadaveric L5/S1 joints were tested before and after disc replacement using Prodisc II implants in 6 specimens and SB Charité III in 6 other specimens. Test specimens were subjected to a physiologic combination of compression and anterior shear. The instant axis of rotation (IAR) was calculated for every 3-degree intervals up to 6 degrees of flexion, extension and lateral bending, and the force through the facet joints was simultaneously measured using flexible intra-articular sensors.

Results

During flexion/extension, the IAR was not significantly modified by implantation with the exception that the IAR was higher relative to S1 endplate with the Charite (p=0.028). The facet force significantly decreased 6° extension (27%, p=0.013). In lateral bending, the IAR was significantly modified by Prodisc replacement, with a decreased inclination relative to S1 endplate, (i.e. increased coupled axial rotation).The ipsilateral facet force was significantly increased in 6° lateral bending with the Charite (85%; p=0.001).

Conclusions

The degree of constraint affects post-implantation kinematics and load transfer. With the Prodisc (3 DOF), the facets were partially unloaded, though the IAR did not match the fixed geometrical center of the UHMWPE, suggesting joint surface incongruence. With the Charite (5 DOF), the IAR was less variable, yet the facet forces trended to increase, particularly during lateral bending. These results highlight the important role the facets play in guiding movement, and that implant constraint influences facet/implant synergy. The long-term consequences of the differing kinematics on clinically-important outcomes such as wear and facet arthritis have yet to be determined.