The present invention provides a medical device (200) comprising a housing (201, 202), a guide structure (205) arranged stationarily with respect to the housing (201, 202) and ex-tending along a longitudinal axis, the guide structure (205) comprising a helical track (287) and a longitudinal track (289) being connected with the helical track (287) at a transition point (288), and a nut assembly (220) adapted to move along the guide structure (205). The nut assembly (220) comprises a first nut member (221) arranged in engagement with the helical track (287), a second nut member (321) capable of engagement with the helical track (287) and with the longitudinal track (289), the second nut member (321) being rotationally locked to the first nut member (221), and a bias member (296) arranged to bias the first nut member (221) and the second nut member (321) away from one another, such that the first nut member (221) and the second nut member (321) take up a first relative axial position when they are both in engagement with the helical track (287) and a second relative axial position when the second nut member (321) is in engagement with the longitudinal track (289).
