A Pre-Operative Planning Tool for Patient Specific Guide Stability Assessment: An Experimental Validation

This work describes the development and experimental evaluation of a software tool (OrthoGrasp) to predict the stability of patient specific guide (PSG) designs. The tool assists in the design of PSGs to ensure that they will provide the high level of stability required to achieve successful and accurate surgical drilling tasks. OrthoGrasps adapts robotic grasping theory to analyse potential PSG designs by treating each point of contact between the guide and the host bone as a force-torque wrench that can be used to calculate stability metrics. The efficacy of OrthoGrasp was evaluated in this study by conducting a series of force-to-dislocation experiments for a range of glenoid anatomies and associated PSG designs that were analysed using OrthoGrasp. The OrthoGrasp derived Least Resisted Wrench (LRW) and Volume Of the Polytope (VOP) metrics, adapted from the robotic grasping literature were then compared to the experimental results through the use of Spearman Rank Correlation analysis. The results demonstrated that the VOP metric was in good agreement with experimental results and thus could be used to predict the overall stability of a PSG design, but the LRW metric had poorer predictive value. In summary, this work demonstrated the potential of the OrthoGrasp pre-operative planning tool to objectively analyse and rank potential PSG designs to ensure that surgeons are provided with guides that stably fit their patients to assist in achieving optimal surgical accuracy.