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Five years ago Sunday, Gillian Reny was an 18-year-old high school senior standing with her parents at the Boston Marathon waiting for her sister to cross the finish line.

Then the bombs went off, killing three people and injuring hundreds, including Reny.

Gillian Reny during recovery after being injured in the 2013 Boston Marathon bombing. Courtesy of Audrey Reny

The blasts sent shrapnel tearing into her right leg, and she was rushed to Brigham and Women's Hospital, where doctors and nurses fought to save the limb. They used tissue from her abdomen to keep blood flowing to her leg, and they used a stabilizing rod to hold the bone in place.

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It was far from a sure thing at first, but as the months passed, it became clear that they could keep her leg intact.

Grateful as she began to recover, Reny and her family asked how they could thank the doctors.

Their answer was to establish the Gillian Reny Stepping Strong Fund, which has raised $13.5 million since 2014 to support trauma research. That research got a physical home last year when the Stepping Strong Center for Trauma Innovation opened at Brigham and Women’s Hospital.

“We wanted to do something to show our gratitude to the hospital and the doctors,” Reny, now 23, said in a recent interview. “How could we possibly thank them for all that they had done for us and our family?"

The fund has given $2.9 million in grants so far, including $100,000 to Dr. Matthew J. Carty, a reconstructive plastic surgeon. Carty, who is working in conjunction with the Massachusetts Institute of Technology, is looking to improve the way amputations are done, so surgery patients are left with a "smarter stump" that is capable of greater sensory feedback, which would improve feeling and movement.

"We're trying to develop a system-based approach to taking care of people with limb loss," said Carty, who has treated Reny.

Other doctors who have received grants are searching for new ways to heal wounds and exploring how stem cells could help regrow bone, according to the hospital.

Reny, who studied the sociology of health and medicine at the University of Pennsylvania and now lives in New York City, working as an assistant buyer for Bloomingdale's, is encouraged to see how the research funded by the center is beginning to help people.

Gillian Reny, who was injured in the Boston Marathon bombing, with her family. Courtesy of Audrey Reny

Still, the anniversary of the bombing each April 15 can be difficult. She plans to spend the day with her family, after running in the Boston Athletic Association's annual 5K on Saturday. And on Monday, she'll be cheering on Brigham and Women's Hospital's Stepping Strong Boston Marathon Team.

“This time of year can be a little more challenging than other times,” Reny said. “My family has done a really good job of turning what happened, and all of the anniversaries, into something positive.”