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  4. Primärstabilität von unzementierten Press-FitImplantaten am Anwendungsfall des Oberflächenersatzes im Hüftgelenk
 
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Primärstabilität von unzementierten Press-FitImplantaten am Anwendungsfall des Oberflächenersatzes im Hüftgelenk

Citation Link: https://doi.org/10.15480/882.1008
Other Titles
Primary stability of uncemented press-fit hip implants
Publikationstyp
Doctoral Thesis
Date Issued
2011
Sprache
German
Author(s)
Rothstock, Stephan  
Advisor
Morlock, Michael  
Title Granting Institution
Technische Universität Hamburg
Place of Title Granting Institution
Hamburg
Examination Date
2011-02-14
Institut
Biomechanik M-3  
TORE-DOI
10.15480/882.1008
TORE-URI
http://tubdok.tub.tuhh.de/handle/11420/1010
In comparison to cemented hip implants which offer a form closure (interdigitation) with the bone, uncemented implants based on a force closure (Press-Fit) with frictional contact show a reduced primary stability. With a sufficient anchorage at the bone in order to minimize relative motions at the bone-implant interface, which could inhibit bone ingrowth, these prosthesis have the potential for a superior secondary stability compared to cemented versions which could suffer from cement failure. Clinically uncemented versions of total hip prosthesis for the femur and the acetabulum are used for a longer period of time. For modern bone preserving surface replacements the uncemented Press-Fit anchorage has not become widely accepted yet, due to an increased postoperative failure rate. The aim of this work was therefore the identification of crucial parameters and optimal parameter ranges for clinical practice, which provoke a successful primary stability and allow optimizing the implant design. To investigate these problems a patient specific numerical model of the proximal human femur including the implant was developed and validated. Based on this model an extensive parameter study with varying interference between bone and implant (Press-Fit), interface friction coefficient, bone quality as well as implantation method (axial impaction, radial expansion) was performed. The used continuum bone model was also accounting for the post-yield bone deformation which is introduced during ‘Press-Fitting’ but not for the trabecular micro architecture of cancellous bone and the abrasion of single trabeculars. Due to this limitation an experimental set-up based on µCT measurements was developed in order to analyse the plastic bone deformation during implantation for a wide variation of parameters (friction coefficient, interference, bone architecture). The amount of Press-Fit and bone quality were identified as important parameters affecting the primary stability. Additionally the implantation method and implant design showed a strong influence on the bone loading and damage. Especially for high friction coefficients at the interface the amount of unnecessary shear forces increases to values similar as the normal forces which are predominantly influencing primary stability. With moderate radial interferences of 50µm the micro motion was stabilized at values allowing bone ingrowth without overloading the bone. A promising future option might be an implantation method using the radial shrinking technique of the prosthesis onto the bone in order to avoid abrasion processes at the interface.

The fulltext of this thesis has been replaced after publication on 2011/06/20 with a corrected version.
Subjects
unzementierter Hüftgelenksersatz
Primärstabilität
Press-Fit
numerische Modellierung
uncemented hip replacement
primary stability
press-fit
numerical modeling
Lizenz
http://doku.b.tu-harburg.de/doku/lic_ohne_pod.php
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