An autopsy yesterday revealed that 14-year-old Ashley Burns of Medford died accidentally from a lacerated spleen, suggesting that the cheerleader may have succumbed to an injury inflicted while practicing her favorite sport.
Her death was believed to be the first Massachusetts fatality related to cheerleading, and the nature of the injury baffled a national cheerleading safety specialist.
''That skill has been done for 10 or 15 years," said Jim Lord, executive director for the American Association of Cheerleading Coaches and Advisors, which provides safety training. ''I don't know that anything can be done to prevent something that appears to be a fluke. . . . It's the only time I've ever heard of it happening."
The Medford teen had been vaulted by three teammates practicing at a Tewksbury gym and had failed to complete a second twist, falling into their arms chest-down, instead of on her back. Afterward, she complained of abdominal pain and said she felt like the wind had been knocked out of her; but her condition rapidly deteriorated.
Yesterday, her death was ruled accidental, caused by laceration of the spleen due to blunt abdominal trauma, said John Cronin, a spokesman for the office of the Chief Medical Examiner.
Neither he nor Burns's family would comment on whether any preexisting medical problems may have aggravated her condition. Burns's middle school principal had told the Globe that stomach problems had her in and out of school last year, and a close family friend said she had had an appendectomy in the spring.
Inflammation of the spleen -- often due to mononucleosis -- can cause a greater risk of injury. That's why doctors prohibit teenage patients from participating in sports until they get a clean bill of health.
But there need not be anything wrong for someone to suffer a spleen injury, most commonly inflicted by car crashes or pedestrian accidents, and sometimes a bicycle handlebar poke, said Dr. Richard Bachur, a specialist in the Children's Hospital Boston emergency department. Last fall, a freshman football player at Sandwich High School had his spleen removed after he was knocked down in a hazing incident.
A spleen injury is particularly dangerous because the organ constantly filters blood, which can escape and fill the cavity if the spleen is punctured. ''Some people would die within minutes of their injury," said Bachur, who pointed to Princess Diana's injuries. Others are treated without removing the spleen, which is located in the upper left side of the abdomen.
The medical examiner's office did not say directly whether the cheerleading injury caused the spleen trauma. In the maneuver that Burns was practicing -- a sophisticated but commonplace stunt -- the flier (Burns) is held aloft by one foot, tossed into the air, and spins twice vertically before landing in teammates' arms.
''They're trained to catch them, to absorb the shock," said Lord. ''Landing a little bit short or not completing the rotation is actually pretty common. And this is a unique injury."
Cheerleading injuries have increased over time -- and drawn greater scrutiny -- as the activity has evolved from sideline pompon shaking to a sport.
According to the National Center for Catastrophic Sport Injury Research, high school girls suffered 70 severe injuries between 1982 and 2004 -- half of them in cheerleading. Four other high school cheerleaders have died during that period from injuries related to the sport.
But for all athletes, injury and death rates are very low. More than 126 million high school athletes participated during the 22 years of the center's research, meaning just 1 of every 100,000 suffered a severe injury, and only .39 per 100,000 died.
Yesterday, Burns's friends and family were reeling from the loss.
''Maybe it was the force coming down. She is such a little peanut," said Fallon Johnson, who was Burns's coach at Northeast All-Stars, a competitive cheerleading squad. ''It makes me nauseous to even think about it. This little girl is gone."
Globe correspondent Lisa Fleisher contributed to this report.