ASMI’s Glenn Fleisig talks about Tommy John Surgeries, Wearable Sensors at Sloan Conference

For such a small piece of tissue, the ulnar collateral ligament can do a lot of damage when it tears. According to Jon Roegele, 90 professional baseball players underwent Tommy John surgery to repair a damaged UCL in the last calendar year, costing teams tens of millions of dollars and months of lost service time. Young prospects, grizzled veterans, pitchers, catchers, outfielders, flamethrowers and junkballers: all went under the knife and emerged with the infamous long, curved scar.

The high stakes go a long way to explain why Glenn Fleisig, Ph.D., research director at the American Sports Medicine Institute, was invited to speak on the epidemic at last weekend’s Sloan Sports Analytics Conference. Fleisig — who also serves as chairman of USA Baseball’s Medical and Safety Committee, an advisor for Little League Baseball, and on Major League Baseball’s Elbow Task Force — presented “Analytics of the Tommy John Injury Epidemic” Saturday morning to discuss the ASMI’s research, dispel some common myths, and talk about the “Pitch Smart” guidelines he helped develop.

Even in the few months since the Pitch Smart guidelines were released, Fleisig said he was “blown away” by the amount of positive feedback he’s received.

“For 20 years, Dr. [James] Andrews and myself have been giving guidelines that have been pretty well received in general by those in medicine,” he said in an interview. “Since the Pitch Smart guidelines came out, we’ve seen the same kind of response from coaches and parents across baseball.”

But Fleisig still devoted a significant amount of time to clearing up misconceptions about the surgery’s success rate (only two-thirds of MLB pitchers who underwent Tommy John surgery made it back to the majors and stayed there) and effect on pitchers (pitchers do not see a bump in performance immediately after the surgery).

The highlight of Fleisig’s talk was a discussion of the risk factors associated with UCL injuries. Fleisig reported the results of a recent study into the biomechanics of 80 minor league pitchers — 40 of whom had returned from Tommy John surgery, and 40 healthy controls. The paper looked at a number of potential risk factors (including amount of arm abduction, stride length, and the infamous “inverted W“), but found no difference between the mechanics of the previously injured and healthy pitchers. Fleisig admitted, however, that the study was not predictive: by looking at the biomechanics of only those pitchers who successfully returned to pitching, the study overlooked any mechanical flaws that had since been corrected, as well as any biomechanical issues in those pitchers who were unable to make a successful comeback.

A better predictor of UCL injuries, Fleisig said, was overuse. A recent ten-year study of 476 adolescent baseball pitchers found that pitchers who threw over 100 innings in a year were three times more likely to be injured; those who regularly threw over 80 pitches in a year more than four times; those who pitched for at least eight consecutive months five times; and those who regularly pitched fatigued 36 times more likely to suffer a UCL injury.

“I hear people say that throwing isn’t a natural motion,” Fleisig said during his presentation. “Throwing is natural. Pitching at max effort, 100 or more times in a game, that’s what’s not natural.”

Fleisig believes overuse of young pitchers is largely responsible for the rise in professional pitchers getting Tommy John surgery, even as organizations are placing increasingly strict limits on prized prospects like Dylan Bundy and Joba Chamberlain.

“A lot of the time, the damage has already been done by the time they get to pro ball,” Fleisig said. “When you pitch, you produce lots of microscopic tears that can heal with rest, but if you pitch too much, then [the UCL] is like a frayed rope, and there’s not much you can do.”

Fleisig’s group has calculated that a 90-mph fastball puts as much as 100 newton meters (N-m) of torque on the elbow. Fortunately, this force is instantaneous or UCLs would be tearing on virtually every pitch. But the ligament still absorbs a significant part of that force; as muscles tire, the amount absorbed by the UCL can increase, leading to the dramatic increase of UCL injuries in pitchers who regularly throw when fatigued. Fleisig said that strength and conditioning can help reduce the risk of injury, but stressed the importance of the entire kinetic chain, from legs to trunk to arm muscles.

“I wish I could say there was one key to avoiding injuries — and that would make a good article — but that’s not reality,” Fleisig said. “The secret isn’t the legs, the secret isn’t the arms, the secret isn’t the trunk, it’s the whole body.”

In addition to his work with ASMI and the sport’s governing bodies, Fleisig also serves as a consultant for Motus Global, a movement analysis company whose mThrow sleeve for pitchers will be available to the public this spring. The headline number produced by the system will be a measurement of workload, derived from the sum of the torque put on the elbow across all throws a player makes, including pitching in game situations, warmups, and drills such as long toss. The sleeve (and the metrics it provides) are still in the early stages, but Fleisig is confident that it represents an improvement in teams’ understanding of workload.

“We don’t know what the right exact formula [for workload] is,” Fleisig said. “For instance, if you throw two throws at 50 N-m, is that the same amount of danger to your elbow as one throw at 100 N-m? Probably not. But before the Motus sleeve, workload was just added up by people counting how many throws someone did.”

Fleisig admits, however, that users will rely too heavily on the system’s workload calculation, especially at the amateur level where coaches, trainers, and players may lack the rapport to establish when a pitcher is truly fatigued.

“The potential customers for the Motus sleeve are not only pro pitchers but also high school kids,” Fleisig said. “I would hope that the pro teams would click through to see the extra data the sleeve produces, whereas I think the summarized information might be the best for many of the amateurs.”

A number of companies aim to improve further on Motus Global’s innovation, and are working on systems that can automatically capture full-body kinematic data without markers. Fleisig does not consult on any of these projects, but has seen some of them in action. Most, including the system Sportvision presented at Saberseminar last summer, require manual digitization, where a human observer annotates the location of the pitcher’s joints at every frame. But despite the demand for automated systems, Fleisig stressed that these technologies are only a tool in the arsenal of coaches, trainers, and pitchers to prevent injuries and improve performance.

“Biomechanics experts and technology are not the keys to optimizing pitcher safety and performance,” he said. “The key will be the expertise of coaches to use this new information.”