HOUSTON - America's chances for an Olympic medal in men's gymnastics took a severe hit yesterday when X-rays revealed that Paul Hamm suffered a broken hand in a parallel-bar mishap the previous night.

Hamm, the only American man to win the all-around gold at a world championships and an Olympics, fractured the fourth metacarpal bone in his right hand near the end of the opening night of competition at the 2008 Visa Championships.

Hamm was examined by James Bicos, an orthopedic sports-medicine surgeon at St. Vincent's Performance Center in Indianapolis. Bicos said Hamm likely would have a pin inserted in the hand and would be unable to practice for four to six weeks.

That means Hamm won't be able to compete at the Olympic trials, June 19-22 at the Wachovia Center in Philadelphia. The men's gymnastics competition in Beijing will begin on Aug. 9, the day after the opening ceremonies.

If Hamm is healthy enough, however, he would be able to petition the selection committee for a spot on the Olympic team, a request that almost certainly would be granted.

"The team has to be named by July 1, and at that time, he would have to show that there's a reasonable expectation he would be able to participate at a high level," said Dennis McIntyre, director of the men's program for USA Gymnastics. "Obviously, Paul is a prime candidate for the Olympic team. I don't think anybody doubts that."

If the petition were granted, Hamm would be invited to the team's pre-Olympic camp in Colorado Springs, July 13-22, at which time he would again have to prove he was physically ready.

Team members who are injured can be replaced by an alternate - McIntyre said two would be named - up to 24 hours before competition in Beijing begins.

Hamm had been expected to battle China's Yang Wei for the all-around gold medal at the Games.

His coach, Miles Avery, said the gymnast would return home to Columbus, Ohio, today. He will consult a hand specialist next week. Avery said they were considering doctors in Columbus, Indianapolis and Baltimore.

"We are working to get Paul home to see a hand specialist," Avery said. "We need to find out what the best course of action is to get it taken care of, and to develop a strategy for getting him back to this level as quickly and safely as possible."

Despite the fall, Hamm finished with the highest all-around score on the first of two nights of performances at these championships, accumulating the top point total in three of the six events.

Hamm sat out 21/2 years after winning gold and silver medals in Athens in 2004, so Thursday night was the clearest indication yet that his comeback might be successful.

He was hurt near the end of the sixth and final discipline, when he failed to catch the bar on a flip and jammed the hand. He briefly went to the sideline and then returned to finish his performance, grimacing as he did so.

Afterward, holding an icepack on the hand, he noted that he was in pain, had heard something pop, and would get X-rays in the morning.

Those X-rays, taken at Memorial Hermann Sports Medicine and Rehabilitation Center, confirmed the fracture.

USA Gymnastics president Steve Penny described the injury to perhaps the top American male gymnast ever as "an unfortunate development."

Assuming no complications with the surgery, Bicos said, Hamm has "an excellent chance of being 100 percent" for the Summer Games.

"For someone who is not an elite athlete like him, it's hard," Bicos added. "But given his motivation, he should definitely be ready for the Olympics."

The Phillies' Chase Utley had a pin inserted in his hand after breaking the same bone in July 2007. He sat out a month.