Silicone Is Very Hygienic
Other elastomers, such as polyurethane, may be softer and better at cushioning the pressure between the prosthesis and the stump, but they are not as hygienic as silicone. “The choice of material is based on the needs of the amputee,” says Leiniger. “Everyone is different, so you have to come up with a customized solution for each patient.”
Dimensionally Stable under Pressure or Heat
Both the standardized liners and the highly-individualized hand or foot prostheses consist of high-quality, biocompatible silicone that meets specific purity criteria, stresses Leiniger. Ottobock uses two-component silicones for this that cure either at room temperature (RTV-2 silicones) or at elevated temperatures (HTV silicones). The first component comprises the actual silicone and substances that enable the polymers to crosslink. The second contains a catalyst that initiates and accelerates the crosslinking reaction. “When the two components are combined, a vulcanization reaction is triggered, and the material cures,” says Dr. Andreas Bacher, , technical service manager at WACKER SILICONES with responsibility for medical products. This so-called two-component addition-curing has the advantage of not releasing byproducts during curing that would irritate the skin. Furthermore, the material does not shrink. And once it has cured, the silicone remains dimensionally stable even when exposed to heat or pressure, unlike many other plastics that can deform.