gms | German Medical Science

59th Annual Meeting of the German Society of Neurosurgery (DGNC)
3rd Joint Meeting with the Italian Neurosurgical Society (SINch)

German Society of Neurosurgery (DGNC)

1 - 4 June 2008, Würzburg

Restoration of mean center of rotation helps recover physiologic kinematics in cervical disc arthroplasty

Die Bedeutung des physiologischen Rotationszentrums für eine natürliche Bewegungskinematik bei Bandscheibenendoprothesen in der Halswirbelsäule

Meeting Abstract

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  • corresponding author J. Herdmann - Zentrum für Orthopädie und Wirbelsäulenchirurgie Düsseldorf, St. Vinzenz-Krankenhaus
  • S. Rhee - Zentrum für Orthopädie und Wirbelsäulenchirurgie Düsseldorf, St. Vinzenz-Krankenhaus
  • A. Pilz - Zentrum für Orthopädie und Wirbelsäulenchirurgie Düsseldorf, St. Vinzenz-Krankenhaus
  • F. Floeth - Zentrum für Orthopädie und Wirbelsäulenchirurgie Düsseldorf, St. Vinzenz-Krankenhaus

Deutsche Gesellschaft für Neurochirurgie. Società Italiana di Neurochirurgia. 59. Jahrestagung der Deutschen Gesellschaft für Neurochirurgie e.V. (DGNC), 3. Joint Meeting mit der Italienischen Gesellschaft für Neurochirurgie (SINch). Würzburg, 01.-04.06.2008. Düsseldorf: German Medical Science GMS Publishing House; 2008. DocSO.03.08

The electronic version of this article is the complete one and can be found online at:

Published: May 30, 2008

© 2008 Herdmann et al.
This is an Open Access article distributed under the terms of the Creative Commons Attribution License ( You are free: to Share – to copy, distribute and transmit the work, provided the original author and source are credited.



Objective: The design of a cervical disc prosthesis not only influences the ease of implantation and its range of motion but also the kinematics of movement of the spinal segment. In cervical disc arthroplasty kinematics and tissue balancing play a major role for long-term outcome. The mean centre of rotation (MCR) is a well-defined parameter in the description of movement kinematics. It allows for comparison of quality of motion in healthy segments and in degenerated segments before and after disc arthroplasty.

Methods: Between May 2004 and April 2007 65 patients (49 women and 16 men) aged 24 to 53 years were selected for disc arthroplasty at either one or two levels (8 patients) using PCM prosthesis (Cervitech Inc.). Indications were radiculopathies (n=51), axial pain (n=11) or myelopathy (n=3) due to disc hernia or degeneration. Hypermobility was an exclusion criterion. Flexion/extension radiographs were obtained before treatment, at dismissal, and at 3, 6, 12 and 24 months after surgery. Digitized radiographs were analyzed with SpineView software. In 46 patients a full 24 months radiographic follow-up could be obtained for analysis.

Results: Disc arthroplasty was performed at C4/5 (n=15), at C5/6 (n=36) and at C6/7 (n=22). Only two of 73 treated levels were fused (seen at 12/24 months). In flexion/extension radiographs immediately before surgery, the total range of motion was reduced, especially in the affected segment: in 28 of 73 segments motion was so little that it was not possible to calculate the MCR. After surgery motion rapidly increased and reached normal values after 12 months. At 24 months, total motion was slightly less than at 12 months (not significant) with an equal contribution of non-treated and treated levels to the changes. In all but 5 (3) treated segments, the MCR at the segment treated with a prosthesis could be calculated after 3 (6) months. Initially the MCR was shifted anteriorly and downward compared to the findings of Dvorák et al (1991). After 12 months MCR was congruent with the in vivo flexion/extension findings in normal cervical spine in 64 of 73 treated segments and in 160 of 187 healthy segments. 6 of 7 patients with a non-satisfying clinical result showed non-congruent MCR-findings at the treated segment.

Conclusions: These results strongly support the hypothesis that quality of motion is of major importance. Disc arthroplasty with PCM/PCM-VTM prosthesis allows for an advantageous motion path. This results in physiologic movement kinematics in 88% of the treated segments.