A medical device has an artificial contractile structure including at least one contractile element adapted to contract a hollow body organ in such a way that said contractile element is adapted to be in a resting position or in an activated position, the activated position being defined with the contractile element constricting the hollow body organ and the resting position being defined with the contractile element not constricting the hollow body organ. The medical device further includes a tensioning device adapted to apply a force so as to tighten the contractile element around the hollow body organ, the tensioning device having a flexible transmission with a tensioning element arranged in a sheath. The sheath has an inner coiled wire coiled in a first direction, and an outer coiled wire surrounding the inner coiled wire and coiled in a second direction opposite to said first direction.
