Medical implants of fixed size cannot accommodate normal tissue growth in children and often require eventual replacement or—in some cases—removal, leading to repeated interventions, increased complication rates and worse outcomes. Implants that can correct anatomical deformities and accommodate tissue growth remain an unmet need. Here, we report the design and use of a growth-accommodating device for paediatric applications that consists of a biodegradable core and a tubular braided sleeve, with inversely related sleeve length and diameter. The biodegradable core constrains the diameter of the sleeve, and gradual core degradation following implantation enables sleeve and overall device elongation to accommodate tissue growth. By means of mathematical modelling and ex vivo experiments using harvested swine hearts, we demonstrate the predictability and tunability of the behaviour of the device for disease- and patient-specific needs. We also used the rat tibia and the piglet heart valve as two models of tissue growth to demonstrate that polymer degradation enables device expansion and growth accommodation in vivo.
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The authors are grateful to the Animal Research Children’s Hospital staff (A. Nedder (head veterinarian) and veterinary technicians) and the Boston Children’s Hospital perfusion team for their overwhelming support and assistance in this project. This work was also supported by the National Institutes of Health (grant GM086433 to J.M.K.) and the Basic Science Research Program through the National Research Foundation of Korea funded by the Ministry of Education of Korea (2012R1A6A3A03041166) and the Korea Institute for Advancement of Technology (N0002123) to Y.L.
E.N.F., Y.L., E.D.O., N.V.V., D.P., P.E.H., H.Y., V.A., J.M.K. and P.J.d.N. have a provisional patent application entitled ‘Autonomously growing implantable device’ (USSN 62/295,768).
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Supplementary figures, tables and methods.
Representative video of a growth-accommodating annuloplasty ring in an ex vivo swine-heart preparation. The video is en face view of the tricuspid valve, with the ring in place. 100× normal speed
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Feins, E.N., Lee, Y., O’Cearbhaill, E.D. et al. A growth-accommodating implant for paediatric applications. Nat Biomed Eng 1, 818–825 (2017). https://doi.org/10.1038/s41551-017-0142-5