Multitechnique characterization of articular surfaces of retrieved ultrahigh molecular weight polyethylene acetabular sockets

The articular surfaces of 10 retrieved ultrahigh molecular weight polyethyl ene acetabular sockets were studied by optical microscopy, X-ray fluorescen ce spectrometry, multiple internal reflectance FTIR spectroscopy, scanning electron microscopy, and wavelength dispersive X-ray microanalysis. The res ults revealed characteristic wear patterns including polishing, scratching, pitting, cratering, folding, shredding, burnishing, cracking, embedding of particles, and development of acquired biofilms with various degrees of mi neralization, The biofilms formed were mainly of proteinaceous origin, and mineralized regions were composed of calcium phosphates with carbonate impu rities. The crystallinity of the polyethylene at the articular surfaces was enhanced compared to the bulk, which was possibly due to the cold work pro duced in vivo. The mineralized regions were classified into two groups base d on the grey levels of the backscattered images obtained. The high-contras t regions that were mainly composed of Ca and P with traces of Al and Si we re associated with bone fragments; the low-contrast regions composed of K, Na, Ca, Mg, Si, Al, Fe, Cl, and P were associated with acquired biofilm cal cification, which implies the active engagement of biofilms in the long ter m performance of acetabular sockets in vivo, (C) 1999 John Wiley & Sons, In c.