Position Height Mobile Core ADR Biomechanical Lumbar Spine, 2008 J. Engineering Med.

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PubMed: 18441758
Proceedings Part H: Link
Charite' Institue: Link

Proceedings of the Institution of Mechanical Engineers, Part H: Journal of Engineering in Medicine
© 2008 Professional Engineering Publishing
Issue Volume 222, Number 2 / 2008 Pages 229-239

Effect of Position and Height of a Mobile Core Type Artificial Disc on the Biomechanical Behaviour of the Lumbar Spine
A Rohlmann1, T Zander1, B Bock1, G Bergmann1
1 Biomechanics Laboratory, Charite´ Campus Benjamin Franklin, Berlin, Germany

Abstract

The extent of natural disc removal and the implant position and height of an artificial disc with a mobile core were studied for their effects on intersegmental rotation, intradiscal pressure, and facet joint force. A validated finite element model of the lumbar spine was used. The model was loaded with the upper body weight, a follower load, and muscle forces to simulate standing, flexion, extension, lateral bending, and axial rotation. The implant position was varied up to 2 mm in an anterior and posterior direction and up to 3 mm in a lateral direction. Three different implant heights were simulated. The effect of removing the lateral parts of the annulus was also studied. The implant position and height markedly affect intersegmental rotation and facet joint forces but have hardly any influence on intradiscal pressure in the adjacent discs.

Removing the lateral parts of the annulus increases intersegmental rotation and facet joint force mainly for lateral bending and axial rotation. The calculated translation of the mobile implant core is about 1 mm at most, and thus its effect is often overestimated. Great care should be taken to choose the optimal implant height and to insert the implant in the best position for each individual patient.


Keywords: lumbar spine , artificial disc, finite element analysis, implant position, implant height


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