Robotic Long Bone Fracture Reduction

Abstract

This research into a medical robot for realigning fractured bones aims to develop the interface, robot, and database technologies to improve the working situation for users and outcome for recipients. Compared with other approaches to fracture reduction, the system being developed here has a number of novel features. The geometric modeling has been effective in allowing a surgeon to visualize the fractured bone and has not been reported elsewhere for fracture reduction to the authors knowledge. By displaying the images to users in this form any mental strain they would face from reconstructing images can be removed. In addition to this, modeling of the forces during reduction has provided a means to determine the requirement for a robotic device. Previously in vivo results had been presented (Maeda et al., 2005; Gösling et al., 2006), however these were limited and suffered from problems associated with taking measurement from living humans. The developed model provides results similar to those measured by Gösling and can be seen to validate these results. This provides a force requirement for the robot to at lest exert around 400 Newton’s of force. The force model also allows the reduction to be planned and verified in 3-D while inspecting the position and expected forces involved. The combined models of bone, force and that of the parallel platform provides a mechanism to rapidly develop control strategies initially without the need for in vivo or phantom testing and will aid in achieving an algorithm design that provides both position accuracy and gentle reduction force. The model itself does also have limitations though. The interface between the platform and leg is assumed rigid which is not strictly true for the use of a foot holster, but if the reduction technique consisting of a pin through the femur is used this becomes more valid. Also the parameters used to develop the model are based on those of averaged cadavers taken from literature so force requirements of very athletic, young or old people need to be treated with caution. Values can be adjusted, however currently what these are is unknown. The parallel design of the robot is inherently safer than a serial mechanism and still allows the user to be distant from the fluoroscopy machine preventing the harmful radiation exposure. Although the use of parallel mechanism in the general medical robotics is not new (Jakopec et al., 2003; Brandt et al., 1999) its application to fracture reduction is. As a replacement for the existing manual traction device and using legacy imaging technology it integrates into the