Abstract
The first successful direct 3D printing, or additive manufacturing (AM), of heat-cured silicone meniscal implants, using biocompatible and bio-implantable silicone resins is reported. Silicone implants have conventionally been manufactured by indirect silicone casting and molding methods which are expensive and time-consuming. A novel custom-made heat-curing extrusion-based silicone 3D printer which is capable of directly 3D printing medical silicone implants is introduced. The rheological study of silicone resins and the optimization of critical process parameters are described in detail. The surface and cross-sectional morphologies of the printed silicone meniscus implant were also included. A time-lapsed simulation study of the heated silicone resin within the nozzle using computational fluid dynamics (CFD) was done and the results obtained closely resembled real time 3D printing. Solidworks one-convection model simulation, when compared to the on-off model, more closely correlated with the actual probed temperature. Finally, comparative mechanical study between 3D printed and heat-molded meniscus is conducted. The novel 3D printing process opens up the opportunities for rapid 3D printing of various customizable medical silicone implants and devices for patients and fills the current gap in the additive manufacturing industry.
Highlights
The meniscus, which is a pair fibrocartilaginous cushion within the knee joint, acts as a weight bearing cushion, lubricating device and knee stabilizer
The uninterrupted extrusion of silicone is crucial for the 3D printing of the meniscus implants
The rheological fingerprints of both Ecoflex30 and Ecoflex50 silicone samples at the temperature 50 ◦ C are shown in Similar behavior for PDMS solutions is reported [31]
Summary
The meniscus, which is a pair fibrocartilaginous cushion within the knee joint, acts as a weight bearing cushion, lubricating device and knee stabilizer. It is mainly C-shaped and triangular shaped in the horizontal and cross-sectional sections, respectively. Its relatively centralized acellular extracellular matrix and limited peripheral vascular supply from the meniscocapsular plexus severely restricts the meniscus regenerative capability when damaged or torn. Treatment options for meniscus tears include direct repair, replacement with either scaffolds or implants and partial or total meniscectomy (removal of the damaged meniscus tissues). Repair methods for meniscal tears with sutures, pins and fibrin glue were used with limited success due to poor vascular supply. Replacement with meniscus scaffolds made of polycaprolactone (PCL) or collagen
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