Article

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
(73.6N+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 (1.5Nm). 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.
CI - Copyright (c) 2011 Elsevier Ltd. All rights reserved.

Langue : ANGLAIS