The Minnesota Twins and their fans are awaiting the answer to one crucial detail before the launch of the new season -- the status of an elbow ligament just a few inches long.

After injuring his throwing elbow, pitcher Joe Nathan will soon decide whether to opt for the audacious surgery that not only could save his career but also is credited for revolutionizing baseball.

Tommy John surgery has left a telltale scar on the arms of an estimated one in nine major league pitchers, along with many other players. Now the surgery is becoming common even among high school ballplayers, which indicates that many coaches and parents are relying on it as a safety net for kids whose arms are breaking down long before they get to college or the minor leagues, a trend that worries many.

Even more alarming, say surgeons, is that there are players who are so good post-surgery that some of those kids, and their parents, believe it could make them better pitchers.

"Which of course is not the case," said Dr. Terry Michael, an expert on sports orthopedics at Northwestern University in Illinois.

It began with Tommy John, a lefthander for the Los Angeles Dodgers, who was on his way to pitching his team into the pennant race in 1974. He threw one pitch too many and walked off the mound with a "dead arm." The same ailment dogged legendary pitcher Sandy Koufax before he stopped playing in 1966. John had torn his ulnar collateral ligament (UCL), the tiny piece of tissue that acts as a hinge between the two major bones in the arm. It's an injury that occurs almost exclusively in athletes who throw over their heads - javelin throwers, a few football players, squash players and, most of all, baseball players.

But unlike the dozens of pitchers who preceded him, John did not walk away from the game.

"He could not envision himself without baseball," said Tim Wendel, a professor at Johns Hopkins University and the author of a new book on the history of the fast ball called "High Heat." In a now famous story, John instead turned to the team's doctor, Los Angeles surgeon Dr. Frank Jobe, and asked him to come up with something.

Jobe's solution was to make John a new ligament. He cut a tendon from inside John's right wrist, drilled a short tunnel in the lower bone of his arm, and threaded the tendon through it. He sutured the tendon together, and attached it to the upper bone to create a new hinge.

Jobe gave it a 1-in-100 chance of success. The Dodgers kept John through the next year, but during spring training in 1976, Wendel said, the team manager told John, "You better start showing us something soon." He did. With a game against Houston in the balance, he whiffed the last batter with three consecutive fastballs for the victory.

"He never looked back," Wendel said. "He pitched 14 more seasons for the major leagues, and won 164 games."

Great success

Today the surgery, which hasn't changed much in more than three decades, has an 85 to 95 percent success rate, and has saved hundreds of baseball careers. But the key to its success is often a form of slow torture for players -- rehab. It takes 12 to 18 months for the tendon to become a fully functioning ligament.

If he chooses the surgery, Nathan, the Twins' premier closer, would need to take this season off. But he could come back as good as ever.

"You can't rush it, no matter how hard you want to rush it," said Twins pitcher Pat Neshek, who had UCL reconstruction in November 2008. "Mentally it just wore you down, because you never felt like you were getting better," he said.

He worked for a year to rebuild his arm with endless exercises before it started to feel better. "It's just Groundhog Day. It's so repetitive," he said.

Now he's finally back to where he was before the injury.

"They always say you come back throwing harder, and I think that's a bunch of crap," he said. "It wasn't as cake as some people say it is."

The growing demand for the surgery has raised questions about the biomechanics of pitching and the limits of the human body. As a pitcher goes through his windup, he creates a kinetic chain of energy within his body that peaks when his arm is in the fully cocked position behind his head. At that point, the amount of force bearing down on the elbow is the equivalent of a 50-pound weight in his hand, said Glenn Fleisig, an expert in biomechanics at the American Sports Medicine Institute in Birmingham, Ala.

When he throws, the ligament contracts like a snapped rubber band, pulling the arm forward and releasing energy into the ball.

As the UCL is stressed over and over, it develops tiny tears like a fraying rope. That's true for all muscles and ligaments, but with rest, they heal. With repeated stress and rest the body adapts and the ligaments and muscles become stronger.

Terry, the surgeon from Northwestern, said these days professional teams keep precise records of how many times their pitchers throw. They have strength and conditioning routines designed to improve biomechanics and flexibility. Still, they throw the ball thousands of times with enormous velocities, and in some the injury may be unavoidable, he said.

"The season is long in Major League Baseball, and they are out there every day," he said.

Too much on young arms

What worries Terry and Fleisig is the steady increase in the number of teenage ballplayers with the same injury. High school players don't have the skilled coaching and oversight that major leaguers have, and many teens throw far more than they should, they said.

"Their elbows looks like they are 30 years old at the age of 15," said Fleisig.

Many of those young players and their parents come in seeking the career-saving surgery made famous by the professionals. Sometimes that means surgeons such as Terry have to play coach as well as doctor.

He said he'll do the surgery on a teenager only good enough and committed enough to play ball at the next level -- high school for an adolescent, college or the minor leagues for older teens. He also gives them a serious lecture about what they will need to do during their year of rehabilitation. Some go ahead with it, but some change their minds, he said.

But he'd like parents and coaches to back off the amount of playing time they demand for their kids.

"Nobody from the Twins is going to care [about a] record on an all-star team in eighth grade," he said. "The best way to get kids ready to play sports is keep them healthy and injury-free."

Josephine Marcotty • 612-673-7394 Staff writer Joe Christensen contributed to this report.