A variety of bearing surfaces are available for use in hip replacement surgery. The most commonly used articulation is a metal ball against polyethylene (a type of plastic) liner. This represents approximately 80% of the bearing surface market in the United States as of 2005.
The next most common bearing combination is a metal ball against a metal liner. This offers the benefit of excellent wear and large head size to promote better range of motion and a lower dislocation rate. The potential drawbacks of metal-on-metal articulations are the risk of elevated metal ion levels which result from metal articulating against metal. The long-term consequences of elevated metal ion levels have yet to be completely determined.
The third most common articulation is ceramic against ceramic. This allows the benefit of excellent wear but because of the ceramic material currently available, head sizes are limited in the most commonly used range for total hip replacement in the United States.
There has been recent increased interested in large head total hips because of the advantage of excellent range of motion and decreased dislocation rate. There are ongoing clinical studies comparing large head total hips to more traditional sized total hip replacements.
When considering hip replacement, it is important for patients to discuss bearing surface materials as well as head sizes and the implications that they have on wear and function.