Scientists have created medical implants for children which expand in tune with their natural growth.
Until now, children with defects in the heart or other organs have had to undergo numerous heavy-duty operations throughout their lifetime to replace their life-saving implants.
But now, a team of researchers from Boston Children’s Hospital and Brigham and Women’s Hospital has met that unmet need.
The group has developed a growth-accommodating implant designed for use in a cardiac surgical procedure called a valve annuloplasty, which repairs a leaking 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.
A team of researchers from Boston Children’s Hospital and Brigham and Women’s Hospital has developed a growable implant for use in a cardiac procedure called a valve annuloplasty (Pictured: a diagram of the valve from the study)
HOW DOES IT WORK?
It comprises a degrading, biopolymer core and a braided, tubular sleeve.
The sleeve elongates over time in response to the forces exerted by the surrounding growing tissue.
As the inner biopolymer degrades, the tubular sleeve becomes thinner and elongates in response to native tissue growth.
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 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.’
The team took its inspiration from the braided, expanding design of a Chinese finger trap.
‘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, Jeff Karp, PhD, a bioengineer and principal investigator at Brigham and Women’s Hospital, 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.
Now, biomedical device company CryoLife Inc. is 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 implant 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.