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Cemented tibial tray fixation
Citation Link: https://doi.org/10.15480/882.1526
Publikationstyp
Doctoral Thesis
Publikationsdatum
2017-03
Sprache
English
Author
Advisor
Referee
Title Granting Institution
Technische Universität Hamburg-Harburg
Place of Title Granting Institution
Hamburg
Examination Date
2016-08-29
Institut
First published in
Biomechanik;
Publisher
Shaker
Although a successful surgical intervention, total knee arthroplasty resulted in about 25 000 revision procedures in 2013 (Germany). The majority of cases concern the tibial component of the prosthesis. Avoidance or at least postponement of revision surgery is desirable in order to decrease infection risk and bone loss related to implant extraction. In up to one third of the cases the reason for revision is aseptic loosening, which is caused by poor implant fixation. Fixation is typically performed using bone cement that forms an interlock with the trabecular bone. An indicator for the fixation strength is pull-out strength, which has been shown to correlate to penetration depth of the cement into the bone. Considering the interlock connection, the architecture of trabecular bone may play a role in fixation strength. The trabecular architecture is patient- and location-dependent, requiring patient-specific analysis.
The aim of this thesis was to improve interlock between cement and bone. This goal was achieved by investigation of cement layer morphology in cadaveric specimens. The influence of cement penetration depth, cementation technique, as well as of bone density and porosity on fixation strength was analysed using computed tomography (CT) image analysis, mechanical pull-out testing and statistical modelling of fixation strength by regression. Investigated cementation techniques were gun and manual application, full and plateau-only cementation, two-layered cementation and bone cleansing using pulsatile or syringe lavage.
A procedure was developed that enabled 3D reconstruction of the cement layer from the CT images of cemented tibial implants within cadaveric specimens. Clinical CT imaging offers insufficient resolution for the accurate representation of trabecular architecture, limiting the analysis of the role of trabecular architecture in fixation strength. Micro-CT was used to characterise the trabecular architecture in samples obtained from below the tibial plateau of native tibias. The results were related to the bone density as determined in normal CT. The cement-bone contact area within the loaded interlock was determined and shown to be crucial for fixation strength. The cement penetration depth indicates the area available to transfer the applied load to the bulk bone of the tibial head. Cement penetration depth below a critical value leads to deformation of cement and pore-forming trabeculae close to the surface. The few existing interlocking trabeculae are overloaded and fail, so that the cement pulls out of the pores. Above the critical value, load acts on a larger contact area, stress and strain are lower and load can be transferred to the bone below the cement mantle. The available load-transfer area depends on the cement penetration depth and the porosity of the trabecular bone.
The results of this thesis show that from the investigated cementation techniques only cement application using a cement gun had an improving effect on the cement layer, but only, if the resection surface underwent pulsatile lavage cleansing preceding cement application. However, regardless of the cement application technique, the critical cement penetration depth was always exceeded after thorough cleansing.
The statistical model for estimating fixation strength allows patient-specific determination of the penetration depth that is necessary to obtain the critical load-transfer area. These findings should be applied in pre-operative planning to identify extreme cases and select cementation technique accordingly, as well as in postoperative risk assessment with regard to aseptic loosening.
The aim of this thesis was to improve interlock between cement and bone. This goal was achieved by investigation of cement layer morphology in cadaveric specimens. The influence of cement penetration depth, cementation technique, as well as of bone density and porosity on fixation strength was analysed using computed tomography (CT) image analysis, mechanical pull-out testing and statistical modelling of fixation strength by regression. Investigated cementation techniques were gun and manual application, full and plateau-only cementation, two-layered cementation and bone cleansing using pulsatile or syringe lavage.
A procedure was developed that enabled 3D reconstruction of the cement layer from the CT images of cemented tibial implants within cadaveric specimens. Clinical CT imaging offers insufficient resolution for the accurate representation of trabecular architecture, limiting the analysis of the role of trabecular architecture in fixation strength. Micro-CT was used to characterise the trabecular architecture in samples obtained from below the tibial plateau of native tibias. The results were related to the bone density as determined in normal CT. The cement-bone contact area within the loaded interlock was determined and shown to be crucial for fixation strength. The cement penetration depth indicates the area available to transfer the applied load to the bulk bone of the tibial head. Cement penetration depth below a critical value leads to deformation of cement and pore-forming trabeculae close to the surface. The few existing interlocking trabeculae are overloaded and fail, so that the cement pulls out of the pores. Above the critical value, load acts on a larger contact area, stress and strain are lower and load can be transferred to the bone below the cement mantle. The available load-transfer area depends on the cement penetration depth and the porosity of the trabecular bone.
The results of this thesis show that from the investigated cementation techniques only cement application using a cement gun had an improving effect on the cement layer, but only, if the resection surface underwent pulsatile lavage cleansing preceding cement application. However, regardless of the cement application technique, the critical cement penetration depth was always exceeded after thorough cleansing.
The statistical model for estimating fixation strength allows patient-specific determination of the penetration depth that is necessary to obtain the critical load-transfer area. These findings should be applied in pre-operative planning to identify extreme cases and select cementation technique accordingly, as well as in postoperative risk assessment with regard to aseptic loosening.
Schlagworte
knee arthroplasty
cement-bone interface
cement mantle morphology
cementation techniques
DDC Class
610: Medizin
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Dissertation Katrin Nagel tub.pdf
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