ARUP; ISBN: 978-0-9562121-5-3 - CMBBE 2012 - Cardiff University

EOS. Among these options, VEPTR has recently been used to treat EOS. The first
use relates complications such as deep infections and wound breakdown due to
significant soft tissue dissection needed for the insertion of the device and its rather
prominent size under the subcutaneous tissues. This study aimed at evaluating different
design of the VEPTR in order to decrease its dimensions. In order to do this, finite
element analysis was carried out four VEPTR design subjected to a compressive load:
the standard dimension, one design with a decrease from 6mm to 5mm of the rod
diameter, another one with a decrease of the width of the distal extension and finally a
design with a decrease of the height from 6mm to 5mm.
Results show that the rod of the proximal extension (where the load is applied) is more
solicited than the distal extension. The lower side of the rectangular cross section of the
proximal extension is overall more stressed than the upper side. However, Von Mises
stress decreases within the proximal extension with increasing distance from the area of
load application. The decrease of the rod diameter (from 6mm to 5mm) increases
mainly the stress within the rod of the proximal extension and in a small area on the rod
of the distal extension. The decrease of the height (from 6mm to 5mm) shows an
increase of the stress in the upper part of the proximal extension. The stress within the
distal extension as well as the distraction lock remains the same. The same observation
can be made for the decreasing width (from 6.7mm to 5.7mm) design. The stress within
the distal extension as well as the distraction lock remains the same as in the standard
design and increased in the upper part of the proximal extension.
To conclude, this study shows that the VEPTR design, mainly the distal extension,
could be downsized in order to avoid complications such as wound breakdown and deep
infections.
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