NiTi based stent for the treatment of acute urinary retention due to benign prostatic hyperplasia: a preliminary study on NiTi wires and tubes under pure bending.

Benign prostatic hyperplasia (BPH) remains an incompletely understood disease, mostly striking old men. In fact, 40% of men over 50 show evidence of BPH [1]. The main consequence of BPH is an uncontrolled growth of prostate epithelial and stromal tissues. Eventually, this may lead to an acute urinary retention (AUR) [2], calling for an emergency treatment. Today, the first line treatment consists in emergency catheterization. However, catheterization is responsible for 80% of nosocomial urinary tract infections (NUTIs); with NUTI risk increasing by 3%-10% a day [3]. As an alternative to catheterization, an innovative NiTi shape memory alloy (SMA) based stent, made of a helical wire inserted into a helical tube was developed. In particular, this stent presents at least two distinct successive shape memories during heating, allowing an extension phase to release the urethra, and a contraction phase for an easy removal. This paper presents the stent mechanism, and the first mechanical characterization of the NiTi wires and tubes, under pure bending.