Mathematical formulation for computing the performance of self expanding helical stents

Stents are cylindrical devices implanted inside pathologic tubular passages within the body. The stents, which are made of metal or plastic, keep the passage open for flow (of blood, urine, air etc.) by applying radial pressure on the passage walls. In most cases the stents are selected empirically for each application. We introduce here a mathematical formula for computing the radial pressure induced by self expanding helical stents. The formula was verified experimentally for an urological stent using a special device. The results correlate well with the theoretical predictions ( R = 0.997; y = 1.017 × − 0.06 kg; SEE = 0.034, for forces and R = 0.9988; y = 1.04 × + 8.7 mmHg; SEE = 25.3 for pressures). This formula can potentially serve as an analytical tool for selecting the most suitable stent for a given application.