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Finite element analysis of the effect of cementing concepts on implant stability and cement fatigue failure.

Janssen D, van Aken J, Scheerlinck T, Verdonschot N - Acta Orthop (2009)

Bottom Line: Two contradictory cementing techniques (using an undersized stem versus a canal-filling stem) can both lead to excellent survival rates, a phenomenon known as the "French paradox".The models were subjected to 2 x 106 cycles of an alternating loading pattern of torque and a transverse load.Canal-filling stems produced fewer cement cracks and less rotation than undersized stems.

View Article: PubMed Central - PubMed

Affiliation: Radboud University Nijmegen Medical Centre, Orthopaedic Research Laboratory, Nijmegen, the Netherlands. d.janssen@orthop.umcn.nl

ABSTRACT

Background and purpose: Two contradictory cementing techniques (using an undersized stem versus a canal-filling stem) can both lead to excellent survival rates, a phenomenon known as the "French paradox". Furthermore, previous studies have indicated that the type of bone supporting the cement mantle may affect implant survival. To further evaluate the mechanical consequences of variations in cementing technique, we studied the effect of implant size and type of bone supporting the cement mantle on the mechanical performance of cemented total hip arthroplasty, using finite element analysis.

Methods: In a generic 2-dimensional plane-strain finite element model of a transverse section of a cemented total hip arthroplasty with a Charnley-Kerboull stem, we varied implant size and type of bone supporting the cement mantle. The models were subjected to 2 x 106 cycles of an alternating loading pattern of torque and a transverse load. During this loading history, we simulated cement fatigue crack formation and tracked rotational stability of the implant.

Results: Canal-filling stems produced fewer cement cracks and less rotation than undersized stems. Cement mantles surrounded by trabecular bone produced more cement cracks and implant rotation than cement mantles surrounded by cortical bone.

Interpretation: Our investigation provides a possible explanation for the good clinical results obtained with canal-filling Charnley-Kerboull implants. Our findings also indicate that inferior mechanical properties are obtained with these implants if the cement is supported by trabecular bone, which may be minimized by an optimal cementing technique.

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A. The original CT image of a Charnley-Kerboull stem replica cemented line-to-line into a donor femur is shown, which served as the basis for all FEA models. B. An example of an FEA model with a maximal canal-filling stem is shown. From the center of the image to the outer edge, the implant, cement mantle, trabecular bone, and cortical bone are shown. The loading conditions (arrows) and boundary conditions applied during the simulations are also shown.
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Figure 0001: A. The original CT image of a Charnley-Kerboull stem replica cemented line-to-line into a donor femur is shown, which served as the basis for all FEA models. B. An example of an FEA model with a maximal canal-filling stem is shown. From the center of the image to the outer edge, the implant, cement mantle, trabecular bone, and cortical bone are shown. The loading conditions (arrows) and boundary conditions applied during the simulations are also shown.

Mentions: The model was created from computed tomography (CT) data used previously for geometric analyses of the cement mantle around line-to-line and undersized femoral implants (Scheerlinck et al. 2006). The model was based on a representative example of a Charnley-Kerboull stem implanted in a line-to-line fashion. For the FEA model, an image of the CT data set was taken at the level of the lesser trochanter. In the CT image, the contours of the cortical and trabecular bone, the cement mantle, and the stem were identified as previously described (Scheerlinck et al. 2006). The model was created based on these contours using an automatic mesher (MSC.MARC; MSC Software Corp, Santa Ana, CA). The models had a thickness of 5 mm and consisted of approximately 6,000 8-node brick elements and 12,500 nodal points (Figure 1).


Finite element analysis of the effect of cementing concepts on implant stability and cement fatigue failure.

Janssen D, van Aken J, Scheerlinck T, Verdonschot N - Acta Orthop (2009)

A. The original CT image of a Charnley-Kerboull stem replica cemented line-to-line into a donor femur is shown, which served as the basis for all FEA models. B. An example of an FEA model with a maximal canal-filling stem is shown. From the center of the image to the outer edge, the implant, cement mantle, trabecular bone, and cortical bone are shown. The loading conditions (arrows) and boundary conditions applied during the simulations are also shown.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2823222&req=5

Figure 0001: A. The original CT image of a Charnley-Kerboull stem replica cemented line-to-line into a donor femur is shown, which served as the basis for all FEA models. B. An example of an FEA model with a maximal canal-filling stem is shown. From the center of the image to the outer edge, the implant, cement mantle, trabecular bone, and cortical bone are shown. The loading conditions (arrows) and boundary conditions applied during the simulations are also shown.
Mentions: The model was created from computed tomography (CT) data used previously for geometric analyses of the cement mantle around line-to-line and undersized femoral implants (Scheerlinck et al. 2006). The model was based on a representative example of a Charnley-Kerboull stem implanted in a line-to-line fashion. For the FEA model, an image of the CT data set was taken at the level of the lesser trochanter. In the CT image, the contours of the cortical and trabecular bone, the cement mantle, and the stem were identified as previously described (Scheerlinck et al. 2006). The model was created based on these contours using an automatic mesher (MSC.MARC; MSC Software Corp, Santa Ana, CA). The models had a thickness of 5 mm and consisted of approximately 6,000 8-node brick elements and 12,500 nodal points (Figure 1).

Bottom Line: Two contradictory cementing techniques (using an undersized stem versus a canal-filling stem) can both lead to excellent survival rates, a phenomenon known as the "French paradox".The models were subjected to 2 x 106 cycles of an alternating loading pattern of torque and a transverse load.Canal-filling stems produced fewer cement cracks and less rotation than undersized stems.

View Article: PubMed Central - PubMed

Affiliation: Radboud University Nijmegen Medical Centre, Orthopaedic Research Laboratory, Nijmegen, the Netherlands. d.janssen@orthop.umcn.nl

ABSTRACT

Background and purpose: Two contradictory cementing techniques (using an undersized stem versus a canal-filling stem) can both lead to excellent survival rates, a phenomenon known as the "French paradox". Furthermore, previous studies have indicated that the type of bone supporting the cement mantle may affect implant survival. To further evaluate the mechanical consequences of variations in cementing technique, we studied the effect of implant size and type of bone supporting the cement mantle on the mechanical performance of cemented total hip arthroplasty, using finite element analysis.

Methods: In a generic 2-dimensional plane-strain finite element model of a transverse section of a cemented total hip arthroplasty with a Charnley-Kerboull stem, we varied implant size and type of bone supporting the cement mantle. The models were subjected to 2 x 106 cycles of an alternating loading pattern of torque and a transverse load. During this loading history, we simulated cement fatigue crack formation and tracked rotational stability of the implant.

Results: Canal-filling stems produced fewer cement cracks and less rotation than undersized stems. Cement mantles surrounded by trabecular bone produced more cement cracks and implant rotation than cement mantles surrounded by cortical bone.

Interpretation: Our investigation provides a possible explanation for the good clinical results obtained with canal-filling Charnley-Kerboull implants. Our findings also indicate that inferior mechanical properties are obtained with these implants if the cement is supported by trabecular bone, which may be minimized by an optimal cementing technique.

Show MeSH
Related in: MedlinePlus