Only a few studies have been done to look at age differences with total hip replacements. Since most patients do wait until age 50 or older, finding out how younger patients fare isn't easy.

Doctors at the Anderson Orthopaedic Research Institute in Virginia have given us some answers. They looked at 561 hip replacements done over a period of 20 years. All patients were 50 years old or younger. This group included 256 hips in patients who were 40 years old and younger.

The authors were surprised to find no difference in wear rates between the two groups. They followed the patients for five, 10, and 15 years. Wear rates were calculated using repeated X-rays over the years. They found implants lasted five years in 97 percent of patients under 40. This is called the five-year survivorship rate.

The 10-year survivorship rate in the same group was 85 percent. And at 15 years the survivorship rate was 54 percent overall. That last figure means about half the implants had failed by 15 years, but the researchers found only part of the implant failed. The whole implant didn't need to be replaced. Revision surgery could be done just to replace the worn part.

Studies like this are very encouraging. Your chances of an earlier operation may improve as more information is reported.