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Effects of Surface Modification and Bulk Geometry on the Biotribological Behavior of Cross-Linked Polyethylene: Wear Testing and Finite Element Analysis.

Watanabe K, Kyomoto M, Saiga K, Taketomi S, Inui H, Kadono Y, Takatori Y, Tanaka S, Ishihara K, Moro T - Biomed Res Int (2015)

Bottom Line: Cross-linking and PMPC grafting decreased the gravimetric wear of the PE disks significantly.The geometrical changes induced in the PE disks consisted of creep, because the calculated internal von Mises stress at the bearing side of all disks and that at the backside of the 3-mm thick disks exceeded their actual yield strengths.A highly hydrated bearing surface layer, formed by PMPC grafting, and a cross-linking-strengthened substrate of adequate thickness are essential for increasing the wear and creep deformation resistances.

View Article: PubMed Central - PubMed

Affiliation: Research Department, KYOCERA Medical Corporation, Osaka, Japan ; Division of Science for Joint Reconstruction, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan.

ABSTRACT
The wear and creep deformation resistances of polymeric orthopedic bearing materials are both important for extending their longevity. In this study, we evaluated the wear and creep deformation resistances, including backside damage, of different polyethylene (PE) materials, namely, conventional PE, cross-linked PE (CLPE), and poly(2-methacryloyloxyethyl phosphorylcholine)- (PMPC-) grafted CLPE, through wear tests and finite element analysis. The gravimetric and volumetric degrees of wear of disks (3 or 6 mm in thickness) of these materials against a cobalt-chromium-molybdenum alloy pin were examined using a multidirectional pin-on-disk tester. Cross-linking and PMPC grafting decreased the gravimetric wear of the PE disks significantly. The volumetric wear at the bearing surface and the volumetric penetration in the backside of the 3-mm thick PE disk were higher than those of the 6-mm thick PE disk, regardless of the bearing material. The geometrical changes induced in the PE disks consisted of creep, because the calculated internal von Mises stress at the bearing side of all disks and that at the backside of the 3-mm thick disks exceeded their actual yield strengths. A highly hydrated bearing surface layer, formed by PMPC grafting, and a cross-linking-strengthened substrate of adequate thickness are essential for increasing the wear and creep deformation resistances.

No MeSH data available.


Related in: MedlinePlus

(a) Volumetric wears of the bearing surfaces and (b) volumetric penetration in the backside surfaces of the untreated PE, untreated CLPE, and PMPC-grafted CLPE disks. The bar indicates the standard deviation. ∗∗ indicates p < 0.01 as per Tukey-Kramer's test and †† indicates p < 0.01 as per Student's t-test.
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fig7: (a) Volumetric wears of the bearing surfaces and (b) volumetric penetration in the backside surfaces of the untreated PE, untreated CLPE, and PMPC-grafted CLPE disks. The bar indicates the standard deviation. ∗∗ indicates p < 0.01 as per Tukey-Kramer's test and †† indicates p < 0.01 as per Student's t-test.

Mentions: The 3D profile of the disks showed that all the disks exhibited substantial volumetric wear of the bearing surface, with the backside surface penetrating into the sham screw hole (Figures 5 and 6). The differences in the degrees of volumetric wear for the 3-mm thick disks of the different materials were not significant (Figure 7(a)). On the other hand, the volumetric wear of the 6-mm thick disk of untreated PE was significantly larger (p < 0.01) than those of the disks of untreated CLPE and PMPC-grafted CLPE. For each material group, the volumetric wear of the 3-mm thick disks was significantly larger (p < 0.01) than that of the 6-mm thick disks. The differences in the volumetric penetration for both the 3-mm thick and 6-mm thick disks of the various materials were not significant. For each material group, the volumetric penetration of the 3-mm thick disks was significantly greater (p < 0.01) than that of the 6-mm thick disks (Figure 7(b)).


Effects of Surface Modification and Bulk Geometry on the Biotribological Behavior of Cross-Linked Polyethylene: Wear Testing and Finite Element Analysis.

Watanabe K, Kyomoto M, Saiga K, Taketomi S, Inui H, Kadono Y, Takatori Y, Tanaka S, Ishihara K, Moro T - Biomed Res Int (2015)

(a) Volumetric wears of the bearing surfaces and (b) volumetric penetration in the backside surfaces of the untreated PE, untreated CLPE, and PMPC-grafted CLPE disks. The bar indicates the standard deviation. ∗∗ indicates p < 0.01 as per Tukey-Kramer's test and †† indicates p < 0.01 as per Student's t-test.
© Copyright Policy - open-access
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC4637033&req=5

fig7: (a) Volumetric wears of the bearing surfaces and (b) volumetric penetration in the backside surfaces of the untreated PE, untreated CLPE, and PMPC-grafted CLPE disks. The bar indicates the standard deviation. ∗∗ indicates p < 0.01 as per Tukey-Kramer's test and †† indicates p < 0.01 as per Student's t-test.
Mentions: The 3D profile of the disks showed that all the disks exhibited substantial volumetric wear of the bearing surface, with the backside surface penetrating into the sham screw hole (Figures 5 and 6). The differences in the degrees of volumetric wear for the 3-mm thick disks of the different materials were not significant (Figure 7(a)). On the other hand, the volumetric wear of the 6-mm thick disk of untreated PE was significantly larger (p < 0.01) than those of the disks of untreated CLPE and PMPC-grafted CLPE. For each material group, the volumetric wear of the 3-mm thick disks was significantly larger (p < 0.01) than that of the 6-mm thick disks. The differences in the volumetric penetration for both the 3-mm thick and 6-mm thick disks of the various materials were not significant. For each material group, the volumetric penetration of the 3-mm thick disks was significantly greater (p < 0.01) than that of the 6-mm thick disks (Figure 7(b)).

Bottom Line: Cross-linking and PMPC grafting decreased the gravimetric wear of the PE disks significantly.The geometrical changes induced in the PE disks consisted of creep, because the calculated internal von Mises stress at the bearing side of all disks and that at the backside of the 3-mm thick disks exceeded their actual yield strengths.A highly hydrated bearing surface layer, formed by PMPC grafting, and a cross-linking-strengthened substrate of adequate thickness are essential for increasing the wear and creep deformation resistances.

View Article: PubMed Central - PubMed

Affiliation: Research Department, KYOCERA Medical Corporation, Osaka, Japan ; Division of Science for Joint Reconstruction, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan.

ABSTRACT
The wear and creep deformation resistances of polymeric orthopedic bearing materials are both important for extending their longevity. In this study, we evaluated the wear and creep deformation resistances, including backside damage, of different polyethylene (PE) materials, namely, conventional PE, cross-linked PE (CLPE), and poly(2-methacryloyloxyethyl phosphorylcholine)- (PMPC-) grafted CLPE, through wear tests and finite element analysis. The gravimetric and volumetric degrees of wear of disks (3 or 6 mm in thickness) of these materials against a cobalt-chromium-molybdenum alloy pin were examined using a multidirectional pin-on-disk tester. Cross-linking and PMPC grafting decreased the gravimetric wear of the PE disks significantly. The volumetric wear at the bearing surface and the volumetric penetration in the backside of the 3-mm thick PE disk were higher than those of the 6-mm thick PE disk, regardless of the bearing material. The geometrical changes induced in the PE disks consisted of creep, because the calculated internal von Mises stress at the bearing side of all disks and that at the backside of the 3-mm thick disks exceeded their actual yield strengths. A highly hydrated bearing surface layer, formed by PMPC grafting, and a cross-linking-strengthened substrate of adequate thickness are essential for increasing the wear and creep deformation resistances.

No MeSH data available.


Related in: MedlinePlus