Abstract
Background
Studies delineating the adjacent level effect of single level disc replacement systems
have been reported in literature. The aim of this study was to compare the adjacent
level biomechanics of bi-level disc replacement, bi-level fusion and a construct having
adjoining level disc replacement and fusion system.
Methods
In total, biomechanics of four models- intact, bi level disc replacement, bi level
fusion and fusion plus disc replacement at adjoining levels- was studied to gain insight
into the effects of various instrumentation systems on cranial and caudal adjacent
levels using finite element analysis (73.6 N+varying moment).
Findings
The bi-level fusion models are more than twice as stiff as compared to the intact
model during flexion-extension, lateral bending and axial rotation. Bi-level disc
replacement model required moments lower than intact model (1.5 Nm). Fusion plus disc replacement model required moment 10–25% more than intact model,
except in extension. Adjacent level motions, facet loads and endplate stresses increased
substantially in the bi-level fusion model. On the other hand, adjacent level motions,
facet loads and endplate stresses were similar to intact for the bi-level disc replacement
model. For the fusion plus disc replacement model, adjacent level motions, facet loads
and endplate stresses were closer to intact model rather than the bi-level fusion
model, except in extension.
Interpretation
Based on our finite element analysis, fusion plus disc replacement procedure has less
severe biomechanical effects on adjacent levels when compared to bi-level fusion procedure.
Bi-level disc replacement procedure did not have any adverse mechanical effects on
adjacent levels.
Keywords
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Article info
Publication history
Published online: October 24, 2011
Accepted:
September 29,
2011
Received:
May 26,
2011
Identification
Copyright
© 2011 Elsevier Ltd. Published by Elsevier Inc. All rights reserved.
