Biomedical Engineering Reference
In-Depth Information
remodelling process is calculated with a conventional prosthesis via finite element
method (FEM) coupled with multi-body simulation (MBS). A migration of the
cup in the proximal direction can be suggested. Based on these results an inno-
vative and economic concept for the design and production of patient-individual
hip cups for primary surgery by means of sheet metal forming is developed. In
this two-stage process first standardized titanium sheet metal components are pro-
duced. Then a true-size enlargement of these components is executed by a modi-
fied adaptive rubber-die forming process. The development is accompanied by an
FE simulation-based planning as well as a metal forming adapted design method.
In this study the first part of the design method is demonstrated, which contains
the deduction of a universal acetabular geometry, necessary for the production
of the standardized component. Furthermore, high pressure sheet metal forming
(HPF) will be introduced for the manufacturing of standardized components. There-
fore an FE-simulation of the process is carried out for the design of the forming
tool.
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Keywords
Total hip arthroplasty
Agglomerative clustering
Sheet metal forming
Finite-element-simulation
1 Introduction
One of the most common operations in Germany is the total hip arthroplasty (THA)
with more than 200,000 implantations each year [
1
]. Over 800,000 are even per-
formed in the whole world [
2
]. Considering the steadily growing life expectancy of
the patients, the prostheses have to remain in the body for ever increasing periods of
time. Despite of years of experience and good clinical results, different complications
occur which negatively influence the retention time of the implants in the body. Up
to 7% of all implanted prostheses will be replaced after 10years as a consequence
of the aseptic loosening of one implant component [
3
]. Especially the migration or
loosening of the artificial hip cup due to bone remodelling is still a current prob-
lem [
4
,
5
]. With regard to the ageing population this means an increase in revision
surgeries marked with a higher risk of complications and thus increasing cost for the
health care system.
The migration or loosening may be a result of the changed mechanical conditions
after the implantation of the THA. This change can lead to a bone remodelling caused
by stress shielding [
6
]. Furthermore, for a stable anchoring of the hip cup a high
bone resection is necessary which promotes bone resorption and hampers revision
surgery. A patient-specific solution can be used to counteract these disadvantages
of conventional hip cups. However, individual hip cups are only implanted for the
treatment of great deformations or tumours. This is due to the time- consuming and
cost-intensive production of each components [
7
].
