First hip replacement uses novel material

BOSTON, July 24 (UPI) -- Massachusetts General Hospital surgeons did the first total hip replacement using a joint socket lined with a novel material invented at the hospital.

Total replacements for hips and other joints were developed in the late 1960s, but it soon became apparent that hip implants could start loosening about five years after surgery and would eventually fail completely.

A team at Massachusetts General Hospital led by Dr. William Harris investigated this complication and found that long-term friction of the implant's head against the polyethylene-lined joint socket would break off small particles of polyethylene. The body's immune system reacted against these foreign particles, eventually destroying adjacent bone tissue and causing the implant to loosen -- a condition called periprosthetic osteolysis.

The researchers found that high doses of radiation would "crosslink" the polyethylene, bonding molecules together to produce a much more durable material.

However, the MGH researchers knew that the first-generation material had limitations, and the researchers found that oxidation could be blocked by diffusing vitamin E throughout the polyethylene material. Vitamin-E-stabilized, highly crosslinked polyethylene has received U.S. Food and Drug Administration approval for use in joint implants and was used in the first surgical procedure last week, according to Dr. Andrew A. Freiber, who preformed the procedure.