Nobuhiro Kaku, Hiroshi Tsumura and Takehiko Torisu
Department of Orthopaedeic Surgery, Oita Medical University, Oita, Japan

We researched the qualitative changes in the polyethylene of a bipolar head retrieved at revision occurring in vivo using optical microscopy and Fourier transform infrared spectroscopy. The bearing surface of the outer head was smooth with no definable scratches delamination. However, the evidence of delamination of the beveled throat region and cracking at the base of the leaf was noticed. The degree of oxidation was different in each area of the polyethylene in the bearing component and that of the rim was shown to be higher than that of the bearing surface. Comparing the rate of ketone and ester, ketone binding was frequently found around the prosthetic rim rather that at the bearing surface. However, the ratio of ester at the surface was higher than that at the deep area of the same rim. We considered these results showed local environmental effects in vivo play a significant role in dictating the response.

Key words: bipolar hip arthroplasty; polyethylene; wear debris; oxidation; Fourier transform infrared spectroscopy