A screw-moving assembly (100) for a screw assembly (903), the screw-moving assembly (100) comprising: a screw-moving actuator (102); and a bias-adjustment mechanism (104); wherein the screw-moving actuator (102) and the bias-adjustment mechanism (104) are configured to connect to the screw assembly (903); the screw-moving actuator (102) is configured to transmit, in use, a screw-translation force (112) to a longitudinal central axis (905) of the screw assembly (903); and the bias-adjustment mechanism (104) is configured to transmit, in use, a biasing force (114) to the longitudinal central axis (905) of the screw assembly (903).