A handheld flexible manipulator system for frontal sinus surgery

Purpose Draf drainage is the standard treatment procedure for frontal sinus diseases. In this procedure, rigid angled endoscopes and rigid curved instruments are used. However, laterally located pathologies in the frontal sinus cannot be reached with rigid instrumentation. In order to assist surgeons with such complicated cases, we propose a novel handheld flexible manipulator system. Methods A cross section of 3 mm x 4.6 mm enables transnasal guiding of a flexible endoscope with 1.4 mm diameter and a standard flexible surgical instrument with up to 1.8 mm diameter into the frontal sinus with increased reachability. The developed system consists of an electrical discharge-machined flexure hinge-based nitinol manipulator arm and a purely mechanical handheld control unit. The corresponding control unit enables upward and left-right bending of the manipulator arm, translation, rolling, actuation and also quick exchange of the surgical instrument. In order to verify the fulfillment of performance requirements, tests regarding reachability and payload capacity were conducted. Results Reachability tests showed that the manipulator arm can be inserted into the frontal sinus and reach its lateral regions following a Draf IIa procedure. The system can exert forces of at least 2 N in the vertical direction and 1 N in the lateral direction which is sufficient for manipulation of frontal sinus pathologies. Conclusion Considering the fact that the anatomical requirements of the frontal sinus are not addressed satisfactorily in the development of prospective flexible instruments, the proposed system shows great potential in terms of therapeutic use owing to its small cross section and dexterity.