New perceptions of shoulder injuries
Hub scientists close in on muscle, bone
Talk about a dead arm.
Using a computer-controlled cadaver to simulate a pitcher on the mound, Boston researchers are gaining insights into the causes of baseball shoulder problems — which derail more major leaguers than just about any other injury.
In the study, the reanimated bodies duplicate the throwing motions of actual pitchers, but the Beth Israel Deaconess Medical Center scientists say their findings reach beyond professional baseball and may help countless weekend warriors, as well as high school and college athletes, recover from similar injuries or prevent them altogether.
Working in the shadow of Fenway Park, and with a grant from Major League Baseball, the researchers have found a common denominator that, they say, is a likely culprit in some of the most common shoulder injuries among pitchers — a misaligned scapula, better known as the shoulder blade.
“When pitchers experience a ‘dead arm,’ unable to achieve the velocity, the scapula malposition is a major cause of this,’’ said Dr. Arun Ramappa, a co-leader of the research team and the chief of sports medicine and shoulder surgery at Beth Israel Deaconess.
While other scientists have traced various shoulder problems to an out-of-whack scapula, the Beth Israel Deaconess team is believed to be the first to demonstrate, down to the muscle and bone level, precisely how the injuries occur through the use of mechanized cadavers. That, Ramappa said, will help them better understand which treatments, including surgery and physical therapy, are most effective at restoring shoulder mobility.
The researchers began by programming a computer with millions of bits of data captured by a high-speed camera, which snapped 120 frames a second of MLB pitchers who were tagged with small infrared markers attached to their arms and torso. The computer then directed a mechanized scaffold to move the cadaver’s arm, exactly duplicating each pitcher’s motion, albeit much slower.
Practicing first with skeleton models, and then on the cadavers, the team documented a normal range of motion for a pitcher’s shoulder. Then the researchers created various “injuries’’ to the cadavers, such as cartilage tears and misaligned shoulder blades, problems commonly suffered by pitchers, to see how that affected the shoulder. It would be unethical to purposely injure a person, but the donors consented while still alive to use of their bodies in medical research.
The researchers found that when the scapula was out of line, it increased the stress on the shoulder joint, where the arm joins the shoulder. This can impinge the movement of the rotator cuff, which is the group of muscles, tendons, and ligaments that connect the upper arm bone with the shoulder blade, and is pivotal to shoulder mobility.
Baseball pitchers, and other athletes such as tennis and volleyball players, are especially vulnerable to misaligned shoulder blades because their repetitive, overhead arm movements create an imbalance, overdeveloping some muscles at the expense of others, particularly the ones that support the shoulder blade, Ramappa said.
Last season, shoulder problems accounted for 17.4 percent of the injuries among players on the disabled list, second only to elbow issues at 17.9 percent, according to MLB.
Pitching exerts such a powerful, wrenching force on a player’s body, “it’s incredible they last so long,’’ said Ara Nazarian, a researcher in orthopedic biomechanics at Beth Israel Deaconess and another leader of the study.
“The torque is two to three thousand times what you would see in a normal motion,’’ Nazarian said.
The study has not yet been published, making it hard for other shoulder specialists to assess its value. But some who were briefed on the preliminary findings said the work is likely to help athletic trainers refine techniques, especially for younger athletes.
Dr. Paul Weitzel, an orthopedic surgeon who specializes in sports medicine at New England Baptist Hospital, said he often encounters aspiring pitchers who have not received proper training, which would help them ward off injuries by strengthening the muscles that support their shoulder blades.
“We see kids from programs where you would think they would have knowledge of this, and you are surprised that no one has talked to them about a shoulder strengthening program,’’ said Weitzel, who also is the team physician for Tufts University and Wellesley High School.
Brigham and Women’s Hospital orthopedic surgeon Scott Martin said the Beth Israel Deaconess work may also help specialists understand how to better adapt physical therapy aimed at the injured, elite athlete to a wider circle of patients.
“There are always limitations in studies’’ that use cadaver models “because it’s not living tissue and it changes dramatically, so you have to be careful about how much information you glean from this type of study and apply it,’’ said Martin, who also is an associate professor at Harvard Medical School.
“The proof is with living patients, but you have to start somewhere,’’ Martin said, “and this study is where it starts.’’
For Cambridge painter Joshua Meyer, the proof has come after months of physical therapy. The 37-year-old father of two fell on the ice three years ago and dislocated his right shoulder. He managed to pop it back in place and figured that was the end of the problem.
But things only got worse, to the point that Meyer said his shoulder would pop out of place “like a Barbie doll.’’
It turned out he had torn cartilage in his shoulder joint. Ramappa repaired it in September and then sent Meyer to physical therapy. Much of that time was spent building up the muscles that support his shoulder blade because a misalignment there, as Ramappa’s study found, increases the stress on the shoulder joint and the likelihood of another injury.
“I haven’t tested it yet, playing baseball with my kids,’’ Meyer said. “But I don’t have that paranoia about using my arm anymore.’’
Kay Lazar can be reached at firstname.lastname@example.org.