Compact Bone Drilling Robotic System with High Rigidity

Abstract

One of the most important and difficult tasks during the bone drilling is to guide the orientation of the drill-ing axis for the target and to maintain the orientation against the reaction force of drilling during the procedure. To assist the drilling task, a remote center of motion (RCM) mechanism is proper for aligning the orientation without changing the entry point. However, existing RCM mechanisms do not provide sufficient resolution and rigidity to deal with hard tissues. We proposed a new type of RCM mechanism which uses two pairs of lin-ear actuators and gearless-arc guide. For the drilling motion, we designed a single motor-based 2-axis control mechanism based on the rolling friction. In addition, a release mechanism for instant stopping of the drilling motion as requested was added. For the automatic control of guiding and drilling, a CT based navigation sys-tem with an optical tracking system was incorporated. The effectiveness of the integrated robotic system was demonstrated in a series of experiments and ex-vivo drilling test on swine femurs. The proposed robotic system withstood an external force of up to 51 N to maintain the joint angle, and an average targeting error was less than 1.2 mm.