A device for cutting tissue including (a) an elongated shaft body defining a drive lumen, (b) a cutting head extending from a distal end of the elongated shaft body and being rotatable via a drive shaft disposed within the drive lumen, and (c) a retainer for keeping the cutting head attached to the shaft body if the cutting head becomes detached from the drive shaft or if the drive shaft breaks. A flexible drive shaft including (i) a core configured for resisting helixing, and (ii) at least one outer layer configured for transferring torque. A method of producing a flexible drive shaft including providing a core configured for resisting helixing, and wrapping the core with at least one outer layer of wires configured for maintaining high torsional rigidity. Related apparatus and methods are also described.
