Implantable biocompatible expander suitable for treatment of constrictions of body lumen

An implantable biocompatible expander suitable for treatment of benign prostatic hyperplasia (BPH), the expander comprising:

• a single elongated undulating ring having a proximal end comprising three proximal prongs, each proximal prong having a respective apex, and a distal end comprising three distal prongs, each distal prong having a respective distal apex, wherein the expander is resiliently deformable from a relaxed radially expanded configuration to a radially contracted configuration suitable for transluminal delivery through the urethra, respective longitudinal struts connecting each of the proximal apices to two of the distal apices and each of the distal apices to two of the proximal apices, whereby the expander is configured to span a substantial section of the prostatic urethra between the bladder neck and external sphincter and cause in-situ expansion of the substantial section of the prostatic urethra and whereby the expander has a triangular cross-sectional shape configured to match the triangular cross section of the prostatic urethra such that, in-situ, the proximal prongs are configured to sit in the most lateral triangular recesses of the prostatic urethra and the longitudinal struts are configured to engage the wall of the prostatic urethra.