Tuesday, April 5, 2011

Now What? If you remove the Depuy implant and replace it, what goes in its place? What are the alternatives and risks associated with them? (2 of 4 in a series)

Hip Replacement Implants
Your surgeon will select the design of the hip replacement and size of femoral ball to give you the range of motion and stability that you need to function. There are several different choices of hip implants to consider, each using varying materials and having different pros and cons:
  • Metal Ball and Polyethylene Liners
  • Ceramic Ball and Polyethylene Liner
  • Metal Ball and Metal Liner
  • Ceramic Ball and Ceramic Liner
Nice videos of each type can be found on this site:  http://bonesmart.org/hip/total-hip-replacement-implants/

Ceramic Ball and Polyethylene (Plastic) Liner

Ceramic heads are harder than metal and are the most scratch resistant implant material. The hard, scratch resistant, ultra-smooth surface can greatly reduce the wear rate on the polyethylene bearing. The potential wear rate for this type of implant is less than Metal-on-Polyethylene.

Ceramic-on-Polyethylene is more expensive than Metal-on-Polyethylene, but less than Ceramic-on-Ceramic. In the past, there had been incidents of fractures, but newer, stronger ceramics have resulted in considerable reduction of fracture rates (0.01%) compared to the original brittle ceramics.

Some ceramic-on-polyethylene implants utilize a vitamin E-stabilized, highly crosslinked polyethylene bearing material. Vitamin E, a natural antioxidant, is expected to improve the longevity of the implant bearings used in total joint replacements. In laboratory testing, these liners have demonstrated 95-99% less wear than some other highly crosslinked polyethylene liners.

Ceramic-on-Polyethylene implants have a potential wear at a rate of about 0.05 millimeters each year, i.e. 50% less than Metal-on-Polyethylene. The newer, highly crosslinked polyethylene liners have shown potential wear rates as little as 0.01 millimeters each year.

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