Correction Appended

At 40, Jeff Gaynor barely resembled the young man who, in his early 20’s, ran half-marathons and performed martial arts.

Mr. Gaynor, who lives in Champaign, Ill., was so sleep deprived from pain in his hip that he had not had one good night’s sleep in seven years, he said. His body was so twisted and his gait so peculiar that children ran in the other direction when they saw him.

Unable to stand and barely able to walk, he resigned from his job as a mathematics professor at the University of Illinois. His young sons became accustomed to a father who could not run, play or even go to the mall without a lot of planning. He gained weight — 70 pounds — because although he was sedentary, he still ate like an athlete.

But Mr. Gaynor, now 45, has been able to resume some of his former activities because of a new surgical implant called the Birmingham Hip Resurfacing System, an alternative to total hip replacement.