Biomedical Engineering Reference
In-Depth Information
3
Polymeric joint bearing surfaces for total joint
replacements
E . O R A L , Massachusetts General Hospital/Harvard Medical School,
USA
Abstract: Ultrahigh molecular weight polyethylene (UHMWPE) is the
polymeric component of hard-on-soft joint replacement implants. This
chapter includes an overview of the rationale behind its development, in
vitro and in vivo characterization methods and reasons for failure.
Key words: artificial joints, metal-on-polyethylene, wear, fatigue resistance,
vitamin E.
3.1
Introduction
Ultrahigh molecular weight polyethylene (UHMWPE) has been the material of
choice for total joint replacements as a part of a `hard-on-soft' articulation
couple since its introduction by Sir John Charnley in the 1960s (Charnley,
1961). Total joint replacement is the most common treatment for end-stage
arthritis, which leads to the degradation of bone and cartilage of the joints and
results in severe pain and the loss of function of the joints. In the US alone, 46
million people suffer from arthritis (Helmick et al., 2008), about 80% of which
is osteoarthritis. Techniques to treat cartilage damage in its early stages are
being developed vigorously, including microfracture, osteochondral autograft
transplantation (OATS), autologous cartilage implantation (ACI) and
mosaicplasty (Hunziker, 2002). The goal of these treatments is to minimize
pain, maximize function for the patients and protect undamaged cartilage to
delay the need for more invasive surgery such as total joint replacement.
Nevertheless, the total joint replacement operation is considered one of the
most successful of our time with Kaplan±Meier implant survival rates of over
80% at 10 years (Murray et al., 1993). It is projected that 1.5 million people in
the US alone will undergo hip and knee joint replacement in 2015 (Kurtz et al.,
2007). However, after the first decade of service, the survival rates decline, and
many patients are required to undergo a revision surgery where part or all of the
implant is replaced with a new one. Revision surgery is costly (~50% more than
primary surgery) (Bozic et al., 2009) and often very complicated. There is a
continual need to reduce the number of revision surgeries to improve the
