Medical implants can save lives by correcting structural defects in the heart and other organs. But until now, the use of medical implants in children has been complicated by the fact that fixed-size implants cannot expand in tune with a child's natural growth.

To address this unmet surgical need, a team of researchers from Boston Children's Hospital and Brigham and Women's Hospital have developed a growth-accommodating implant designed for use in a cardiac surgical procedure called a valve annuloplasty, which repairs leaking mitral and tricuspid valves in the heart.

Currently, children who undergo life-saving cardiac surgeries, such as mitral and tricuspid valve repairs, may require several additional surgeries over the course of their childhood to re-repair or replace leaking heart valves. The novel growth-accommodating implant is meant to enhance the durability of pediatric heart valve repairs while also accommodating a child's growth, decreasing the number of heart surgeries a child must endure.
Beyond cardiac repair, the research team says the tubular, expanding implant design used in their proof-of-concept -- reported today in Nature Biomedical Engineering -- could also be adapted for a variety of other growth-accommodating implants throughout the body.

"Medical implants and devices are rarely designed with children in mind, and as a result, they almost never accommodate growth," says Pedro del Nido, MD, co-senior author on the study, who is chief of cardiac surgery at Boston Children's and the William E. Ladd Professor of Child Surgery at Harvard Medical School (HMS). "So, we've created an environment here where individuals with expertise and interest in medical devices can come together and collaborate towards developing materials for pediatric surgery."

By partnering with Jeff Karp, PhD, a bioengineer and principal investigator at Brigham and Women's Hospital (BWH) and an associate professor of medicine at HMS, his laboratory's expertise in chemical engineering and biopolymer materials was brought into the mix for this research. After vetting many different concepts for a growth-accommodating implant, the team took its inspiration from the braided, expanding design of a Chinese finger trap, selecting their first proof-of-concept to be a tricuspid valve annuloplasty ring implant.

"The implant design consists of two components: a degrading, biopolymer core and a braided, tubular sleeve that elongates over time in response to the tensile forces exerted by the surrounding growing tissue," says Eric Feins, MD, co-first author on the paper, who was formerly a research fellow in del Nido's lab and is currently a fellow in cardiothoracic surgery at Massachusetts General Hospital. "As the inner biopolymer degrades, the tubular sleeve is becomes thinner and elongates in response to native tissue growth."

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