An assembly for breaking up vascular thrombus or other obstructive material including a motor housing (12, 210) having a motor (14, 214), a motor shaft (15, 222) extending from the motor, a first housing (230, 330, 430) positioned at a distal end of the motor shaft, a rotational thrombectomy wire (30, 130) and a second housing (246, 350, 450) positioned at a proximal end of the wire. The first housing has a first magnet (242, 340, 430) positioned therein and recessed from the distal edge (338, 438) of the first housing which has a first plurality of teeth (337, 437). The second housing has a second magnet (360, 460) positioned therein and recessed from a proximal edge (358, 458) of the second housing which has a second plurality of teeth (357, 457) intermeshing with the first plurality of teeth when the wire is coupled to the motor shaft. The first and second plurality of teeth slip when a torque of the motor shaft exceeds a predetermined value.
