Control of Fracture Reduction Robot based on Biomechanical Property of Human Leg

For femoral fracture reduction, we have developed a surgical robotic system. Indirect traction is employed in our system. Indirect traction in fracture reduction is a generally used surgical method for preventing complications such as bone splits caused by high stress on bones. For traction, a patient's foot is gripped by a jig and pulled to the distal side. Indirect traction has the advantage of distributing bone stress by utilizing a strong traction force; however, this procedure does not accurately control the proper positioning of fractured fragments when a surgical robot is used. The human leg has knee and an ankle joints, and thus robotic motion presents problems in not being able to directly propagate reduction motion to a fractured femoral fragment, rendering control of bone position difficult. We propose two control methods for fracture reduction robots using external force/torque measurements of the human leg. First proposed method is using a transform function which transform from a force/torque space to a position space. Second is using a simple ligament model. Results showed that the first proposed method reduced repositioning error from 6.8 mm and 15.9 degrees to 0.7 mm and 5.3 degrees and second reduced from 2.1 mm to 0.9 mm.