Meeting an unmet need: A surgical implant that grows with a child

October 10, 2017
Credit: Randal McKenzie

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.

Credit: Randal McKenzie

"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 becomes thinner and elongates in response to native tissue growth."

To create the degrading core, Karp's team recommended the use of an extra-stiff, biocompatible polymer that begins to erode on its surface following implantation. The polymer itself is made of components that already exist in the human body.

"By adjusting the polymer's composition, we can tune the core to degrade predictably over a pre-determined amount of time," says Karp, co-senior author on the study.

Based on the promising in vivo experimental data presented by del Nido and Karp's team, the biomedical device company CryoLife Inc., is already developing their concept into a growth-accommodating annuloplasty ring implant for pediatric heart valve repair.

"In combination with the braided sleeve exterior, this two-part concept could have many medical applications beyond the most obvious ones to enhance cardiac valve surgery in children," says del Nido.

The proprietary design of the braided sleeve developed by del Nido and Karp's team doesn't just share resemblance to a Chinese finger trap but also to an organic structure engineered by nature itself.

"We solved this problem of growth accommodation with a concept that already exists in nature: the octopus has a special ability to stretch its arms into confined cracks and spaces between rocks, in search of its prey," says Yuhan Lee, PhD, co-first author on the study and a materials researcher at BWH. "It can do this because of unique, braid-like crossfibers of connective tissue that enable the simultaneous elongation and shrinking diameter of its arms, allowing it to extend its reach two to three times beyond the original arm length."

This type of elongating movement is also found in natural tissue structure of the mammalian intestines and esophagus.

"This concept could be adapted for many different clinical applications, with exciting potential to be converted into an actively—rather than a passively—elongating structure that could act as a tissue scaffold encouraging growth," says Feins.

Explore further: Surgeons pilot expandable prosthetic valves for congenital heart disease

More information: Eric N. Feins et al, A growth-accommodating implant for paediatric applications, Nature Biomedical Engineering (2017). dx.doi.org/10.1038/s41551-017-0142-5

Related Stories

Surgeons pilot expandable prosthetic valves for congenital heart disease

October 3, 2012
(Medical Xpress)—Surgeons at Boston Children's Hospital have successfully implanted a modified version of an expandable prosthetic heart valve in several children with mitral valve disease. Unlike traditional prosthetic ...

Successful transcatheter treatment of severe cardiac failure

September 11, 2017
The Cardiovascular Surgery Group at Osaka University performed a transcatheter mitral valve implantation in dysfunctional artificial valves in severe cardiac failure patients with prosthetic valve dysfunction, which was previously ...

Boston Children's and Edwards Lifesciences launch pulmonary valve replacement trial

March 16, 2016
Surgeons in the Heart Center at Boston Children's Hospital have partnered with Edwards Lifesciences to launch a clinical study of a new prosthetic heart valve for patients born with a congenital heart defect. Called the COMMENCE ...

Medical treatment may prevent, alleviate mitral valve damage after a heart attack

August 28, 2017
A research team led by investigators from Massachusetts General Hospital (MGH) and collaborators has shown, for the first time, that it may be possible to nonsurgically treat or even prevent the damage to a major heart valve ...

Injectable tissue patch could help repair damaged organs

August 14, 2017
A team of U of T Engineering researchers is mending broken hearts with an expanding tissue bandage a little smaller than a postage stamp.

Recommended for you

How genes and environment interact to raise risk of congenital heart defects

October 19, 2017
Infants of mothers with diabetes have a three- to five-fold increased risk of congenital heart defects. Such developmental defects are likely caused by a combination of genetic and environmental factors. However, the molecular ...

Mouse studies shed light on how protein controls heart failure

October 18, 2017
A new study on two specially bred strains of mice has illuminated how abnormal addition of the chemical phosphate to a specific heart muscle protein may sabotage the way the protein behaves in a cell, and may damage the way ...

Newborns with trisomy 13 or 18 benefit from heart surgery, study finds

October 18, 2017
Heart surgery significantly decreases in-hospital mortality among infants with either of two genetic disorders that cause severe physical and intellectual disabilities, according to a new study by a researcher at the Stanford ...

Saving hearts after heart attacks: Overexpression of a gene enhances repair of dead muscle

October 17, 2017
University of Alabama at Birmingham biomedical engineers report a significant advance in efforts to repair a damaged heart after a heart attack, using grafted heart-muscle cells to create a repair patch. The key was overexpressing ...

Physically active white men at high risk for plaque buildup in arteries

October 17, 2017
White men who exercise at high levels are 86 percent more likely than people who exercise at low levels to experience a buildup of plaque in the heart arteries by middle age, a new study suggests.

High blood pressure linked to common heart valve disorder

October 17, 2017
For the first time, a strong link has been established between high blood pressure and the most common heart valve disorder in high-income countries, by new research from The George Institute for Global Health at the University ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.