A cooperatively controlled robotic system with active constraints for enhancing efficacy in bilateral sagittal split osteotomy.

Purpose: Precise osteotomies are vital in maxillofacial procedures such as the bilateral sagittal split osteotomy (BSSO) where surgical accuracy and precision directly impacts patient outcomes. Conventional freehand drilling can lead to unfavorable splits, negatively impacting surgical outcome.

Methods: This paper presents the development work of a cooperatively controlled robot system designed to enhance the efficacy of osteotomies during BSSO. The system features two assistive modes for the execution of a patient-specific surgical plan: (1) a Haptic guidance mode that helps the surgeon align the surgical drill with the planned cutting plane to improve surgical accuracy of the cut and (2) an Active constraint mode that restricts deviations from the cutting plane to enhance surgical precision during drilling. We validated the system through feasibility experiments involving 36 mandible phantoms and a cadaveric specimen, with a surgeon, a surgical resident, and a medical student performing osteotomies freehand and with robotic assistance. Additionally, NASA TLX surveys were conducted to assess the perceived ease of use of the robotic system.

Results: Compared to freehand methods, the robotic system improved the efficacy of the cut from $2.16\pm 0.98$ to $0.71\pm 0.53$  mm for the med student, $1.74\pm 0.95$ to $0.53\pm 0.35$  mm for the resident, and $1.64\pm 0.85$ to $0.63\pm 0.24$  mm for the surgeon while reducing the task load.

Conclusion: Our experimental results demonstrate that the proposed robotic system can enhance the precision of surgical drilling in the BSSO compared to a freehand approach. These findings indicate the potential of robotic systems to reduce errors and enhance patient outcomes in maxillofacial surgery.