Cartilage-mimicking, high-density brush structure improves wear resistance of crosslinked polyethylene: a pilot study.
BACKGROUND
In natural synovial joints under physiologic conditions, fluid thin-film lubrication by a hydrated layer of the cartilage is essential for the smooth motion of the joints. The considerably less efficient lubrication of artificial joints of polyethylene is prone to wear, leading to osteolysis and aseptic loosening and limiting the longevity of THA. A nanometer-scale layer of poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC) with cartilage-mimicking brushlike structures on a crosslinked polyethylene (CLPE) surface may provide hydrophilicity and lubricity resembling the physiologic joint surface.


OBJECTIVE
We asked whether the photoirradiation time during graft polymerization would affect the density and stability of the PMPC layer and the PMPC-grafted surface would enhance the durability of artificial joints. We investigated the effect of photoirradiation time and the resultant characteristics of the PMPC layer on the durability of the CLPE.


METHODS
For each of the PMPC-grafted CLPE surfaces with various photoirradiation times (six groups: 0 [untreated CLPE], 11, 23, 45, 90, and 180 minutes), 18 sample pieces (total of 108 samples) were evaluated in surface analyses, and four cups (total of 24 samples) were evaluated in a hip simulator test.


RESULTS
The density of the PMPC layer increased with an increase in the photoirradiation time. The hip simulator test confirmed the PMPC-grafted CLPE with a high density of the PMPC layer exhibited minimal wear as compared with the untreated CLPE. High-density PMPC grafting appears essential for maintaining the high wear resistance of the PMPC-grafted CLPE. To obtain a high-density PMPC layer, the photoirradiation time must be greater than 45 minutes.


CONCLUSIONS
The cartilage-mimicking, density brushlike structure of the PMPC-grafted CLPE could extend high durability to acetabular cups in THA.


CONCLUSIONS
Our in vitro findings suggest the wear performance of CLPE acetabular cups in THA can be improved by this approach.
Research Department, Japan Medical Materials Corp, 3-3-31, Miyahara, Yodogawa-ku, Osaka, 532-0003, Japan. kyomotom@jmmc.jp
Masayuki
M
Kyomoto
Toru
T
Moro
Yoshio
Y
Takatori
Hiroshi
H
Kawaguchi
Kazuhiko
K
Ishihara
D019644:Arthroplasty, Replacement, Hip; D001672:Biocompatible Materials / Q000737:chemistry; D003432:Cross-Linking Reagents / Q000737:chemistry; D019544:Equipment Failure Analysis; D005720:Gamma Rays; D006622:Hip Prosthesis; D008422:Materials Testing; D008689:Methacrylates / Q000737:chemistry*; D010767:Phosphorylcholine / Q000031:analogs & derivatives* / Q000737:chemistry; D010865:Pilot Projects; D058105:Polymerization; D011109:Polymethacrylic Acids; D011474:Prosthesis Design; D013499:Surface Properties
D001672:Biocompatible Materials; D003432:Cross-Linking Reagents; D008689:Methacrylates; D011109:Polymethacrylic Acids; C115766:poly(2-methacryloyloxyethyl-phosphorylcholine); D010767:Phosphorylcholine