gms | German Medical Science

62nd Annual Meeting of the German Society of Neurosurgery (DGNC)
Joint Meeting with the Polish Society of Neurosurgeons (PNCH)

German Society of Neurosurgery (DGNC)

7 - 11 May 2011, Hamburg

Radiological outcome und intraoperative findings following explantation of 20 cervical disc prostheses

Meeting Abstract

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  • C. Brenke - Department of Neurosurgery, University Medicine Mannheim, Universität Heidelberg, Germany
  • K. Schmieder - Department of Neurosurgery, University Medicine Mannheim, Universität Heidelberg, Germany
  • M. Barth - Department of Neurosurgery, University Medicine Mannheim, Universität Heidelberg, Germany

Deutsche Gesellschaft für Neurochirurgie. Polnische Gesellschaft für Neurochirurgen. 62. Jahrestagung der Deutschen Gesellschaft für Neurochirurgie (DGNC), Joint Meeting mit der Polnischen Gesellschaft für Neurochirurgen (PNCH). Hamburg, 07.-11.05.2011. Düsseldorf: German Medical Science GMS Publishing House; 2011. DocDI.02.09

doi: 10.3205/11dgnc114, urn:nbn:de:0183-11dgnc1142

Published: April 28, 2011

© 2011 Brenke 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: Long-term results following implantation of cervical disc prostheses show a lower rate of adjacent level degeneration compared to fusion procedures. However, heterotopic ossification and spontaneous fusions were observed in up to 66% and 9%, respectively. As these results were obtained only using plain x-ray, exact determination of ossification is not possible. Due to an impending product failure, disc prostheses of 20 patients were re-evaluated radiologically using x-ray and computed tomography (CT) prior to explantation. Aim of the study was to assess function and exact bony configuration of the operated and the adjacent segments. Intraoperative findings were documented

Methods: Plain and function x-ray were available preoperative, 3 and 12 months postoperative and prior to explantation. The range of motion (ROM) has been determined in the operated and the adjacent levels. Using pre- and postoperative ROM’s, a motion-index has been calculated (preOP ROM/postOP ROM). Height of the operated segment and the degree of heterotopic ossification was measured using a preoperative CT and a CT prior to explantation.

Results: The motion index prior to explantation was reduced to 1.2 in the operated segment compared to 1.4 three months postoperative. In the upper segment it increased to 1.3 prior to explantation compared to 0.9 at three moths postoperative. ROM prior to revision was 10.8 ± 7.2, 2 patients (10%) were fused (ROM < 2). The height of the operated segment increased significantly (+1.6 ± 1.1 mm, p = 0.035), left sided lateral osteophytes increased (1.7 ± 2.1 mm, p = 0.009). Despite preserved function in the operated segment in 90%, there were severe lateral osteophytes detectable in 40%. Intraoperatively, mainly the lower part of the prosthesis was not firmly adherent in 7 patients (35%), posterior dislocation occurred in 1 patient. Prevalence of small ventral osteophytes was not predictive for fusion

Conclusions: In spite of preserved function there are radiological signs of spontaneous fusion in a significant number of patients. As mainly left sided lateral osteophytes were observed with the operative approach having been done from the right side, excessive drilling might be the main factor for it. Improved fixation of the implant might prevent its migration in the future.