Workspace and trajectory-based experimental validation of a 3-armed 6-DOF parallel robot for femoral fracture surgery

Femur fractures remain a significant occurrence in the general population, requiring immediate medical care (typically surgery) followed by extensive recovery time. Femur fracture reduction, defined as the process of realigning femur bone fragments, is currently performed manually, a task that is physically demanding and associated with high malalignment rates. Our surgical system Robossis, a 3-armed, 6-DOF parallel robot, is aimed at addressing these issues by exerting the necessary forces to eliminate the physical demand while facilitating proper fracture reduction. The new Robossis V2 system demonstrates improvements over our previous V1 system in both clinical usability and movement capabilities. In this work, we present an experimental validation of Robossis V2 through numerical workspace analysis and optical-tracking-based trajectory testing. Workspace evaluation shows that Robossis V2 provides substantial coverage beyond clinically required alignment ranges, with constrained translational and rotational workspace volumes approximately 136 times and 79 times larger than the required range, respectively. Across all collected trajectory data, Robossis V2 achieved consistent sub-millimeter translational and sub-degree rotational performance, with the 75th percentile of absolute errors remaining below 1 mm and 1 $°$ . These results establish the viability of Robossis V2 as a clinically promising platform for high-precision femoral fracture reduction.