Ph.D., Faculty of Health Sciences, University of the Witwatersrand, 2008. / Lumbar disc replacement is a rapidly expanding surgical treatment modality for longstanding
back and leg pain due to intervertebral disc degeneration. Compared to
fusion surgery, it has the advantage of preserving segmental mobility, but convincing
evidence of superiority over fusion surgery is missing.
As part of this research project, I participated in the development of a new
intervertebral disc prosthesis, with several international patents attached to the design
of the prosthesis, the instrumentation and the insertion technique. The Kineflex
(Centurion) lumbar disc is a mechanical, un-constrained, re-centering disc prosthesis
developed in South Africa. After the development and manufacturing of the disc,
prototype test racks were custom-made at the premises of the manufacturer and the
disc was extensively tested for mechanical wear and fatigue. The first implantation
took place in October 2002. I prospectively captured all cases performed by our
centre, with documentation including demographic data, co-morbidities, clinical
history, symptoms and signs. The completed consent forms were filed. The outcome
was monitored, pre-operatively and in follow-up, with complete radiological
documentation of all radiographs on JPEG files. Clinical outcome results were
documented using two different internationally validated questionnaires as well as
our own questionnaire, which expands further on work and demographic details,
previous operative and conservative treatment, and satisfaction with the treatment
outcome.
The aim of the this project was to develop a disc prosthesis that is suitable and safe
for human implantation into the lumbar spine disc space, even in severely advanced
disc degeneration and to verify this in the outcome studies presented in this thesis.
Existing indications and contra-indications for artificial disc replacement were
critically evaluated regarding their validity for this particular implant.
Results:
Chapter 3 elaborates on the extensive pre-clinical mechanical wear and fatigue
testing protocol to which the Centurion (Kineflex) lumbar disc prosthesis was
subjected. The results of this testing protocol, together with our early clinical
outcome results, formed the basis for the awarding of the European quality
recognition (CE-Mark). In these extensive in vitro studies, we were able to show the
durability of the Kineflex disc prosthesis in the long term. This, together with our
initial clinical outcome results, formed the basis for the acceptance into a
“prospective, randomized, multicenter Food and Drug Administration investigational
device exemption study of lumbar total disc replacement with the KINEFLEX
Lumbar Artificial Disc versus the CHARITÉ™ Artificial Disc”.
Chapter 4 is compiled from an invited submission to a new book on motion
preservation surgery in the human spine, edited by leading spine surgeons in the field
(James J. Yue, Rudolf Bertagnoli, Paul McAfee, and Howard An) and published by
Elsevier Publishers: Chapter 42: Kineflex. In this chapter, an overview is given of the
ideas behind the Kineflex disc development, as well as of the insertion
instrumentation used for disc implantation. It further reports on early clinical
outcome results of the first patients implanted with the device in our centre (the first
40 implantations worldwide were all performed by me).
Chapter 5, our first peer reviewed international publication, reports on clinical and
radiological 2-year outcome results of our first 100 patients. With the Kineflex
implant, we could demonstrate equally good radiological placement accuracy in
patients with severe and less severe disc degeneration of the index level, rendering
the implant suitable even in severe degeneration of a spinal motion segment.
Chapter 6 and Chapter 7 of this thesis consist of two further peer-reviewed
publications. They both report on so-called “off-label” patient sub-groups in our disc
replacement series.
In Chapter 6 we present the second published series on a larger group of patients
presenting with adjacent segment disease after previous lumbar fusion surgery as
well as the first publication, which investigated the radiological changes in alignment
parameters secondary to the disc replacement surgery in this patient group.
Chapter 7 consists of the first published series on patients with “degenerative
spondylolisthesis” treated with disc replacement surgery. A detailed description of
the operative reduction technique is provided, which is unique to the Kineflex disc
and its insertion instrumentation. In this pilot study, two-year results on a limited
patient group are presented.
This thesis concludes with the overall discussion in Chapter 8. It outlines the current
knowledge on artificial disc replacement and places my results into perspective with
recent discoveries published in the literature. It finishes with my assessment of what
future research should concentrate on.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:wits/oai:wiredspace.wits.ac.za:10539/7308 |
| Date | 22 September 2009 |
| Creators | Hahnle, Ulrich Reinhard |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | application/pdf |
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