Posterior lumbar spinal dynamic stabilisation devices are intended to relieve the pain of spinal
segments while prolonging the lifespan of adjacent intervertebral discs. This study focuses on the
design of such a device, one that has the correct stiffness to stabilise the spinal segment by the correct
amount.
An initial literature survey covers contemporary topics related to the lumbar spine. Included topics are
lumbar anatomy and kinematics, pathology of degenerative disc disease and treatment thereof, other
spinal disorders such as spondylolisthesis and spinal stenosis, as well as the complications associated
with lumbar dynamic stabilisation. The influence of factors such as fatigue and wear, as well as the
properties of appropriate biomaterials are considered when determining the basis of the device design
and development.
Stabilising the spinal segment begins with correct material selection and design. Various designs and
biomaterials are evaluated for their stiffness values and other user requirements. The simplest design,
a U-shaped spring composed of carbon fibre-reinforced poly-ether-ether-ketone (CFR-PEEK) and
anchored by polyaxial titanium pedicle screws, satisfies the most critical user requirements.
Acceptable stiffness is achieved, fatigue life of the material is excellent and the device is very
imaging-friendly. Due to financial constraints, however, a simpler concept that is cheaper and easier
to rapid prototype was chosen. This concept involves a construct primarily manufactured from the
titanium alloy Ti6Al4V extra-low interstitial (ELI) and cobalt-chrome-molybdenum (CCM) alloys.
The first rapid prototype was manufactured using an additive manufacturing process (3D-printing).
The development of the device was performed in three main stages: design, verification and
validation. The main goal of the design was to achieve an acceptable stiffness to limit the spinal
segmental range of motion (ROM) by a determined amount. The device stiffness was verified through
simple calculations. The first prototype’s stiffness was validated in force-displacement tests. Further
validation, beyond the scope of this study, will include fatigue tests to validate the fatigue life of the
production-ready device. / MIng (Mechanical Engineering), North-West University, Potchefstroom Campus, 2014
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:nwu/oai:dspace.nwu.ac.za:10394/12254 |
| Date | January 2013 |
| Creators | Parker, Christopher Daniel |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
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