Objective: Two important and difficult tasks during a bone drilling procedure are guiding the orientation of the drilling axis toward the target and maintaining the orientation against the drilling force. To accomplish these tasks, a remote center of motion (RCM) mechanism is adopted to align the orientation of the drilling axis without changing the entry point. However, existing RCM mechanisms do not provide sufficient resolution and rigidity to address hard tissue cases.
Methods: We propose a new type of RCM mechanism that uses two sets of linear actuators and a gearless-arc guide to have a high resolution and rigidity. In addition, we designed a single motor-based drilling mechanism based on rolling friction. To achieve automatic control of the guiding and drilling process, we incorporated a computer-tomography-based navigation system that was equipped with an optical tracking system.
Results: The effectiveness of the integrated robotic system was demonstrated through a series of experiments and ex vivo drilling tests on swine femurs. The proposed robotic system withstood a maximum external force of 51 N to maintain the joint angle, and the average drilling error was less than 1.2 mm.
Conclusion: This study confirms the feasibility of the proposed bone drilling robotic system with a high-resolution and high-rigidity RCM mechanism.
Significance: This drilling system is the first successful trial based on an RCM mechanism and a single motor-based drilling mechanism, reducing the footprint and required motors with respect to previous bone surgical robots.