Virtual-Fixtures Based Shared Control Method for Curve-Cutting with a Reciprocating Saw in Robot-Assisted Osteotomy

In mandibular angle split osteotomy (MASO), prominent mandibular angles need to be cut off with saws such as reciprocating saws. Compared to traditional-freehand methods, robot-assisted methods provide potentials for better cutting performance. In the robot-assisted mandibular angle split osteotomy (RAMASO), a cutting method based on shared control is proposed along with an optimization-planned osteotomy curve. Experimental verification using planes and skull phantoms were conducted and discussed for evaluation of accuracy and safety. The results in 7 cutting experiments for the following error were mainly within 0.76mm and -1.00mm (Q3±1.5∗IQR), peaking at 1.80 mm. The maximum of time-consuming was 304.0s, with the average human robot interactive force reaching around 3.3 N. Experiments indicate the proposed method achieves better performance in accuracy and efficiency compared with the free hand. Note to Practitioners - This paper is inspired by the curve-cutting osteotomy task under the combination of pre-defined virtual fixtures and the kinematic constraint of the reciprocating saw. The motions of current surgical osteotomy robots are mostly generated by either of virtual fixtures and kinematic constraints, which is representing less autonomy on surgery. The introduction of autonomy in surgical robotics can greatly increase the surgeon's performance in efficiency, accuracy, and safety. The technique of shared control is capable of achieving the semi-autonomy task to significantly improve the accuracy with feedback mechanisms in control science. Thus, the advanced control strategies are required into the process of surgical osteotomy operation. In this article, we proposed a novel methodology to control the hands-on robot executing a curve path. The developed control scheme has the following functionalities: 1) it enables the lateral control for the cutting task for the hands-on robot system. 2) it maintains the pre-defined path-generated virtual fixtures and finds the optimal-parameters of the virtual fixtures. For the convenience of presentation, the mandibular angle split osteotomy is chosen as the background, but in fact this method can be extended to more surgical and even industrial applications with a similar scenario.