Collaborative Drill Alignment in Surgical Robotics

TL;DR

The paper addresses the challenge of achieving precise drilling for transcondylar screw placement in veterinary surgery without patient-specific physical guides. It introduces a collaborative robotic system that uses a virtual drill guide implemented via a fast inner-loop virtual mechanism with nonlinear saturating springs and a slower outer-loop vision controller to align with the bone. The authors detail comprehensive calibration procedures (probe, drill tip/axis, bone, hand-eye) and demonstrate through 16 3D-printed bone trials that the system achieves translation comparable to PSGs and improved angular accuracy. The work suggests a practical, reusable alternative to PSGs with potential for minimally invasive, multi-hole drilling and real-time adaptation, while outlining safety, stability, and integration enhancements for future deployment.

Abstract

Robotic assistance allows surgeries to be reliably and accurately executed while still under direct supervision of the surgeon, combining the strengths of robotic technology with the surgeon's expertise. This paper describes a robotic system designed to assist in surgical procedures by implementing a virtual drill guide. The system integrates virtual-fixture functionality using a novel virtual-mechanism controller with additional visual feedback. The controller constrains the tool to the desired axis, while allowing axial motion to remain under the surgeon's control. Compared to prior virtual-fixture approaches -- which primarily perform pure energy-shaping and damping injection with linear springs and dampers -- our controller uses a virtual prismatic joint to which the robot is constrained by nonlinear springs, allowing us to easily shape the dynamics of the system. We detail the calibration procedures required to achieve sufficient precision, and describe the implementation of the controller. We apply this system to a veterinary procedure: drilling for transcondylar screw placement in dogs. The results of the trials on 3D-printed bone models demonstrate sufficient precision to perform the procedure and suggest improved angular accuracy and reduced exit translation errors compared to patient specific guides (PSG). Discussion and future improvements follow.

Figures (12)

• Figure 1: a) Experimental setup in position for drilling, from the perspective of the vision sensor. b) Block diagram of the control architecture, showing inner and outer control loops. More details in Section \ref{['sec:VirtualDrillGuide']}.
• Figure 2: Reference frames and the transformations between them.
• Figure 3: Probe calibration measurements: the probe reference frame is shown in two configurations, pivoting around fixed point $p$.
• Figure 4: Descending: NDI Polaris Vicra sensor; passive probe; tracked drill bit; and tracked Ellis pin.
• Figure 5: Drill geometry. Calibrated point and axis, $\bm{p}_{\text{tip}}$ and $\bm{a}_{\text{bit}}$ are shown, as well as derived point $\bm{p}_{\text{base}}$.

Theorems & Definitions (2)

• Remark 1
• Remark 2