Musculoskeletal model of hip fracture for safety assurance of reduction path in robot-assisted fracture reduction

Abstract

We have developed a fracture-reduction assisting robotic system for hip fracture. The robotic system provides power assistance to surgeons during the reduction procedure and simulated fracture reduction trials using a polyurethane-made bone model has shown good reduction results. While the system can reduce surgeon's burden, it also has the possibility to damage soft tissues around bone fragments. It is required to predict or monitor forces produced by the reduction procedure from a safety point of view. To this end we have developed a musculoskeletal model of hip fracture that provides the force acting on muscles from the relative position of bone fragments. Though many musculoskeletal models of limbs have reported, there are few studies that apply it to fracture reduction. In addition, the musculoskeletal model allows us to simulate the reduction force acting on muscles, given reduction path. Two usage methods of the reduction force simulation are proposed for safe reductions. One is to find the gentle reduction path that minimizes the reduction force. The reduction force is simulated according to two reduction paths, and the path with lesser reduction force is identified as the gentle path. The other application is to serve as a detection tool where unexpected large reduction forces can be identified by comparing the measured force with the simulated force in real-time. The consideration about personal error of the muscle geometry and parameter is required. At present, the second function of using the developed simulation to detect unexpected large reduction forces has not been integrated to the robotic system. This will be part of our future work. © 2011 Springer-Verlag.