The direct anterior approach, created by California surgeon Dr. Joel M. Matta, is not yet widely available. Only as many as 6 percent of orthopedic surgeons nationwide use the new technique, in part because it has a fairly steep learning curve. "That learning curve is its downside. It's painful," said Mariani, who added that it took Matta almost 10 years to perfect the technique before he could start teaching others. "There was a lot to sort out."

"Some procedures are a variation on another," said Bourne. "Not this. It's significantly different," although the components are the same. The angle, the retraction, the X-ray guidance all represent radical change.

Mariani first investigated it, then he and Bourne set about learning to do it. They had to watch the procedure a number of times, then they practiced on cadavers until they were comfortable they could do it in a real patient, working as a team. For the first surgeries they did using this approach they carefully selected patients based on anatomy so they had "lots of room" to work. "Now we do all of them."

Combined, they have decades' experience in hip replacement. The result for the patient, they said, "is not better. It's spectacularly better. Some people are going home on the second day, with little or no restriction. When they return for a two-week checkup, most of the patients don't even need a cane."

Because of the incision location, dislocation is much less of a problem, which eases many of the restrictions placed on patients in terms of initial movement. And they can be up and about much quicker. They've now used the anterior surgery in about 70 patients, implanting a Corail Total Hip System that was made for this approach to hip replacement by DePuy Orthopaedics.

It's used solely for primary hip replacement. "I can't imagine doing a revision this way," Mariani said. And it's not a good approach for people with certain anatomical anomalies, either.

Susan Mulkey has tried hip replacement both ways, with the same surgeon. Mariani replaced her first hip in 2002, and she knew she'd eventually need the other one replaced because of osteoarthritis. When the pain got bad enough to start talking about it, "I didn't want to do it. I knew it was two months of your life, gone. I kept postponing it. And Dr. Mariani was learning a new procedure and told me to hang on a bit."

He was up to speed on the new surgery about the time she couldn't wait any longer, "so I bit the bullet and did it. It was a completely different operation. I was real anxious because I know what I felt like the first time I got out of bed."