Abstract
Background
In selected cases, en-bloc spondylectomy is the only option to reach wide resection
margins for patients with malignant tumours of the thoracolumbar spine. These patients
must be also provided a secure initial stabilization of the spine and this is the
role of vertebral body replacements employed with posterior fixation systems. The
aim of this study was to determine the postimplantation stiffness of a connected vertebral
body replacement pedicle screw system in different implantation scenarios following
an en-bloc spondylectomy. Reconstruction was varied by posterior fixation lengths
and axial compression forces during implantation.
Methods
Three-dimensional stiffness was assessed in 6 fresh frozen human spinal specimens
(Th11-L3) using a six degree of freedom spine simulator. Following en-bloc spondylectomy
reconstruction was performed using a carbon composite fibre vertebral body replacement
connected to a posterior fixation system by two artificial pedicles. The spines were
loaded with pure moments (7.5 Nm) in the three main motion planes. The intersegmental rotations were measured between
Th12 and L2.
Findings
Reconstructions using long posterior fixation modes demonstrated significant (P < 0.05) higher stiffness compared to short posterior fixations in all motion planes.
In axial rotation short posterior fixation modes failed to reach the values of the
intact state. Neither high nor low axial compression force during implantation showed
a significant impact on postfusional stiffness.
Interpretation
In this biomechanical model, the employed system should be implanted with a posterior
fixation of two adjacent segments to the lesion in order to achieve a secure stabilization
of the treated segment.
Keywords
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Article info
Publication history
Published online: September 13, 2007
Accepted:
July 3,
2007
Received:
November 15,
2006
Identification
Copyright
© 2007 Elsevier Ltd. Published by Elsevier Inc. All rights reserved.
