Summary/Abstract: Our long-range goal is to develop a novel semi-autonomous, minimally-invasive, image-guided neurosurgical robotic workstation that consists of a robotic positioning mechanism, a continuum manipulator, flexible instruments, and flexible implants (i.e., flexible pedicle screws (FPSs)) to enable the next generation of minimally- and less-invasive spinal interventions. By providing access to regions within vertebral body, which currently are not accessible utilizing conventional rigid surgical instruments, this neurosurgical robotic workstation will enable surgical treatment of various bone defects in spine such as compression on the spinal cord and/or nerve roots, metastatic bone disease, and vertebral compression fractures due to severe osteoporosis. For this project, we mainly will focus on the mechanical design, development, basic control, and assessment of the subsystems of this novel robotic system with the goal of minimally invasive spinal fusion of osteoporotic vertebrae. Approximately 54 million Americans age 50 and older have osteoporosis causing an estimated two million broken bones per year in the US only. Vertebral fractures are the most common type of osteoporotic fractures (about 47%), which can lead to back pain, loss of height, and further vertebral and non-vertebral fractures. Failure of non-surgical treatments often leads to a spinal fusion surgery to restore stability of the spine using Rigid Pedicle Screws (RPSs). However, anatomical constraints and rigidity of instruments and screws force the surgeon to typically implant the screw inside the low bone mineral density (BMD) regions of the vertebrae in an osteoporotic spine. This results in an increased risk of screws loosening, pullout, and subsequently a surgical failure. It is our central hypothesis that utilizing the proposed minimally-invasive robotic system, the success rate of spinal fusions with RPSs can be significantly improved. This improvement will happen by (i) developing a biomechanical analysis module to plan a curved drilling trajectory based on the spatial (3D) BMD in the vertebra obtained by QCT scans; (ii) increasing the reachability of the surgeons and enabling them to drill in high-BMD regions of vertebra using a steerable drilling robot and the curved-drilling technique; (iii) selectively implanting/anchoring the FPSs within the pre-planned drilled curved trajectories inside the high-BMD regions, which can improve the pullout strength and stability of fusion; (iv) Biomechanical analysis of the fusion with FPS and/or bone cemnet to optimize the spine stability, prevent vertebral collapse, and a need for revision surgery. The proposed contribution is significant, high impact, and innovative since it offers to eliminate the aforementioned complications of current spinal fusion surgery by proposing novel and innovative techniques. To our knowledge, robotically-assisted techniques utilizing a steerable drilling robot and FPSs have not been developed for a minimally invasive spinal fusion of osteoporotic vertebrae. Our goal is to demonstrate that the proposed system can significantly improve the current treatment of osteoporotic vertebrae and shift the current clinical paradigm.

PROJECT NARRATIVE This project aims to reduce the surgical complications and improve the outcomes of minimally invasive fusion surgery of osteoporotic vertebrae by developing a novel semi-autonomous, minimally-invasive, image-guided neurosurgical robotic workstation. The proposed surgical system includes a steerable drilling robot, flexible instruments, and a novel fusion mechanism consists of flexible pedicle screws (FPS) and flexible bone cement injection mechanism. This system aims to (1) increase the reachability of the surgeons within vertebral body and enable them to selectively drill in curved trajectories; (2) implant the FPSs within the pre-planned curved trajectories inside the less-osteoporotic regions of the vertebrae and improve the pull out strength and stability of fusion; and (3) biomechanically analyze the fusion outcome with an FPS and bone cement to optimize the spine stability and reduce the risk of failure in an osteoporotic spine.