Effects of Dynamic Forces in Robotic Fracture Reduction

Biological systems are often difficult to understand from experimental research, and those results that are obtained need to be interpreted carefully when being used for new surgical methods. Using medical robotics for long bone reduction introduces new challenges and the possible side effects need to be carefully considered. One such effect is the possibility of oscillation during the reduction process and this research aimed to understand the magnitude of dynamic terms and what the implications are. Modeling and simulation was used to represent the salient features of reducing a fractured bone and estimate the additional dynamic force that could be produced. It was found that if oscillation occurs especially at higher frequencies, force can be increased to 20 times the value of pure muscle stretch. To keep additional force components magnitudes less than 5 N accelerations should be smaller than plusmn 0.2 m/s². This means that caution needs to be observed when designing a robot control system and special care given to mitigating oscillation or similarly high accelerations and velocities.