(Inside Science) -- It's the first week of the baseball season and therefore a time for optimism, spring and rebirth. But during this year's spring training at least five pitchers expected to play major roles with their respective teams were diagnosed with a damaged part of the elbow known as the ulnar collateral ligament, or UCL, in their throwing arms. The surgery designed to repair this injury borrows a tendon from elsewhere in the body to stand in for the damaged part. It is known as Tommy John surgery and is named after the pitcher who first had the repair in 1974 and then went on to win 146 more games before retiring in 1989.
The damage to the UCL is thought to come from the stress created by throwing a ball at high speeds, and the Tommy John surgery is becoming common among major league pitchers and young players alike. As Glenn Fleisig, a biomechanics expert, told me in 2009, building up the ability to throw a ball faster is not the same process as increasing strength to lift heavier weights or jump higher. You can't just build bigger muscles and expect the pieces that connect them to withstand more and more stress. When they throw, pitchers are so close to the limits of the human body that if they add muscles to get stronger, then "ligaments and tendons won't be able to take it," Fleisig said.
As the surgery became more popular and star pitchers returned to form or became stars only after getting the fix, people began to think that the surgery makes a pitcher better.
So, do pitchers actually improve after having elbow surgery?
There are numerous studies of this and related issues. Many of them show conflicting results. Notably, two press releases from the same day promised the exact opposite findings -- one implied that performance increased after surgery, and another implied that performance declined after the surgery. This begs the question: why are the surgery's effects so hard to sort out?
Study #1: This study, from researchers at Rush University Medical Center, in Chicago, found that pitchers win more games after the surgery.
Study #2: This study, from researchers at Detroit's Henry Ford Hospital, found that Major League Baseball pitchers don't regain their performance level after the surgery.
That seems pretty confusing. Both showed that over 80 percent of MLB pitchers do return to the major leagues, but study #1 showed improved performance in multiple categories, including allowing fewer hits and walks per inning pitched, and lower earned run averages. Study #2 showed increases in both of those categories.
Both studies covered similar time periods (study #1: 1986-2012, study #2: 1982-2010).
It's important to note that Tommy John surgeries are skyrocketing among MLB pitchers. According to study #1 about 20 players underwent the surgery in the whole of the 1990s. Nowadays, about 15 pitchers go under the knife every year.
But wait, there are two more recent studies. In study #3, doctors at the University of Chicago, publishing in February in the American Journal of Sports Medicine, found that there was no significant difference in a pitcher's velocity before and after a Tommy John surgery. That study only looked at the years 2008-2010.
A fourth study, presented in March at a meeting of the American Academy of Orthopaedic Surgeons, by Christopher Ahmad, the head team physician for the New York Yankees, and others, looked at every major league pitcher to have received the surgery before 2011 -- beginning with Tommy John in 1974. They showed a decline in ERA, walks and hits per inning, the percentage of fastballs thrown and fastball velocity.
An NBC News story from March mentioned three of these studies. The writer, Brian Alexander, mentioned that the authors from studies #2 and #4 said study #1 used a different and perhaps easily misinterpreted approach. Study #1 looked at the pitcher's stats from the year before the injury only, and compared those to the pitcher's post-surgery stats. The other authors told NBC that "often, pitchers begin to break down — and show poor results — in the year prior to surgery. That’s why they get it." In other words, if a pitcher were hurt and still pitching, then his stats might decline as compared to his ability when healthy. Then, when he recovered from the surgery, even if he wasn't quite back to his original 100 percent, he might still be better than he was the year before his surgery, which is the comparison period used in study #1.
That's still valuable information. It means that when the pitcher has severe elbow damage, it's worth fixing. And that Tommy John surgery is effective. But -- it illustrates the problem with headlines and how they can lack nuance. It can be true that the surgery doesn't return a pitcher to his peak success, and also that the surgery does make the pitcher better than he was immediately before the surgery. All the studies indicate that greater than 80 percent of MLB pitchers return to the majors after Tommy John surgery. The issue of defining what constitutes positive and negative outcomes is tricky in medical studies. It gets even more complicated if you try to use certain statistics, such as a pitcher's wins, to evaluate his effectiveness. Success on a baseball field isn't just about one person's performance. The defense and the hitter influence the pitcher's statistics. So does random chance. Even if fastball velocity does decrease after the surgery, it's also pretty common for pitchers to lose fastball velocity as they age.
As with many science topics, the issue is complicated, and easy to misinterpret. It remains pretty neat that surgeons figured out how to fix a career-ending injury by harvesting a tendon from elsewhere in the pitcher's body in order to rebuild his elbow -- and that pitchers can go on to perform at elite, Major League levels.