I'm 57-years old and in need of a hip replacement. I've always been active and a rock hound in my spare time. I need a hip that's going to last and allow me to hike (even if I can't climb over boulders and rough terrain any more). I found three kinds of bearings in articles on-line: metal, metal and plastic, and ceramic. Which one do you recommend for a guy like me?
Hip implants have a fairly long history with many changes from the 1960s to the present day. In fact, just like families with multiple generations (great-grandparents, grandparents, parents, children), objects like hip replacements have generations. The first group of hip implants designed in the 1960s are now referred to as first-generation products. Eventually, they gave way to second generation implants in the 1970s and 80s.
Better technology and improved materials led to the switch from cobalt-chromium-molybdenum (CoCrMo) for the bearings used to create motion to cast alloy in the second generation. By the third generation of hip implants (1990s), materials changed again to high- and low-carbon alloys.
With the fast evolving technology today and improved surgical techniques, we expect to see continued changes in the next decade or so. And as you have discovered, there are three choices for bearings: the traditional metal-on-polyethylene (plastic) and two alternatives: metal-on-metal and ceramic-on-ceramic.
Each type of bearing has its own advantages and disadvantages. For example, ceramic materials are at risk for fracture. Metal bearings cannot fracture but they are more likely to loosen requiring a second (revision) surgery.
Metal bearings can release tiny particles of metal into the joint, which does not happen with ceramics. Well, to clarify that last point a bit, ceramic debris is possible -- it's just much less than with metal bearings. And the body does not seem to react to ceramic wear particles like it does to the less biocompatible metal debris.
Current studies suggest that metal-on-metal bearings are more likely to loosen and wear out compared with bearings made of ceramic materials. Therefore metal bearings with polyethylene liners are recommended for older, less active individuals who are going to want this surgery to be their last.
The best bearing surface for younger, active patients will have to be decided on a case by case basis. The surgeon and patient should consider all the pros and cons of the different types of bearings (metal-on-metal, metal-on-polypropylene, ceramic-on-ceramic). The choice of bearings is made according to age, activity level, bone density, and relative risks and advantages of metal-on-metal versus ceramic-on-ceramic bearings. Potential complications must also be examined and every effort made to prevent any anticipated problems.
Ingrid Milosev, PhD, et al. Comparison of Ten-Year Survivorship of Hip Prostheses with Use of Conventional Polyethylene Metal-on-Metal, or Ceramic-on-Ceramic Bearings. In The Journal of Bone and Joint Surgery. October 3, 2012. Vol. 94-A. No. 19. Pp. 1756-1763.
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