Chapter 6 - Alternatives to Conventional UHMWPE for Hip Arthroplasty

Abstract

This chapter discusses several alternatives to conventional ultra-high molecular weight polyethylene (UHMWPE) for hip arthroplasty. Most of the orthopedic research efforts focus on improving UHMWPE for joint replacements, with the goals of reducing wear and improving implant survival, especially for young active patients. More than 90% of total hip replacements (THR) implanted worldwide since the 1990s have incorporated either a conventional or highly cross-linked UHMWPE insert. In addition to highly cross-linked UHMWPE, other alternative bearing solutions incorporating metal-on-metal (MOM) or ceramic-on-ceramic (COC) articulations have received increased attention in the past 10 years because of their ultralow wear rates in hip simulator studies. The first-generation MOM joint replacements fabricated from CoCr alloy. Second-generation MOM designs were clinically introduced during 1988 by Sulzer Orthopedics that incorporate a CoCr articulating surface, but the acetabular component consisted of a modular shell and an UHMWPE liner embedded with a CoCr insert. On the other hand, COC bearings do not share the same potential biological limitations associated with MOM articulations for hip replacement. Modern COC implants are modular, and the articulating surfaces have been fabricated from high-purity alumina. The acetabular insert may be fabricated entirely from alumina, and fitted to the metal shell with a taper junction.