Ultrasound-Based Robot-Assisted Drilling for Minimally Invasive Pedicle Screw Placement

Minimally invasive pedicle screw placement (MIPSP) is a widely used treatment for spine diseases. When coupled with intraoperative navigation modalities, robots may help improve surgical outcomes and reduce complications. With such a system, the application of pedicle screws has been expanded from needle insertion to the spine surgery. This paper investigates the possibility and feasibility of robot-assisted MIPSP based on ultrasound (US) guidance. The proposed system is non-radiative and fiducial-free, using purely image information to close the registration loop. Then the system automatically positions the drill tip to a planned screw trajectory and executes the drilling operation. Experiments were conducted on both ex-vivo lamb and human cadaver spines. An entry point accuracy of $2.39\pm 1.41$ mm, and orientation accuracy of $2.82\pm 1.85^{\circ }$ was found for 24 drilled trajectories on three lamb spines. On the ex-vivo human spine, the position error averaged $3.08\pm 2.43$ mm at the entry point and $4.05\pm 2.62$ mm at the stop point across 16 drilling instances. Moreover, a $87.5\%$ success rate was reported by using Gertzbein-Robbins grade. The experimental results demonstrate the potential for offering a radiation-free alternative. Although restricted to cadaver trials, this work encourages further exploration of this technology to assist surgeons in maximizing performance in clinical practice.