Wear analysis of retrieved alumina heads and sockets of hip prostheses.
The wear behavior of hip prostheses alumina components was studied on 20 retrieved implants removed for socket loosening. The observed wear takes two forms: a running-in of the mating surfaces and a gross disruption of the surfaces. The running-in is very shallow, in the order of 0.2 micron after 8 years of implantation. This is observed on the load-bearing areas of the components. Gross wear is not material-related but had always been associated to a high contact pressure between the edge of the socket and the femoral head. Such a high contact pressure occurs after the socket had loosened and then tilted or if it was initially positioned too vertically. The long-term success of alumina-alumina THP components depends essentially upon biomechanical considerations and upon the quality of the material. The area of contact between the head and the socket should be large enough to minimize the contact stresses. This can only be achieved by a good positioning of the socket and by a close tolerance fit of the alumina components; any deviation from sphericity should also be avoided. The normal wear behavior of alumina is a running-in process leading to an average wear rate of 0.025 micron/year as compared to 100 microns/year for UHMWPE on metallic heads.
Dorlot
J M
JM
Department of Metallurgical Engineering, Ecole Polytechnique, Montréal, Québec, Canada.
Christel
P
P
Meunier
A
A
D000368:Aged; D000369:Aged, 80 and over; D000535:Aluminum; D000537:Aluminum Oxide; D002516:Ceramics; D005260:Female; D006622:Hip Prosthesis; D006801:Humans; D008297:Male; D008855:Microscopy, Electron, Scanning; D008875:Middle Aged; D011475:Prosthesis Failure; D013499:Surface Properties
D000535:Aluminum; D000537:Aluminum Oxide