Investigating Torque-Speed Relationship of Self-Tapping Screws

Abstract

Correctly torquing bone screws is important to prevent fixation failures and ensure positive patient outcomes. It has been proposed that an automatic model-based method may be able to determine the patient-specific material properties of bone, and provide objective and quantitative torquing recommendations. One major part of developing this system is the modelling of the bone-screwing process, and the self-tapping screwing process in general. In this paper, we investigate the relationship between screw insertion torque (Nm) and speed of insertion (RPM). A weak positive correlation was found below approximately 30 RPM. Further research should focus on increasing the precision of the methodology, and this testing must be extended to ex-vivo animal bone testing in addition to the polyurethane foam substitute used here.Clinical relevance: To maximise the accuracy of torque recommendations, the model should account for all important factors. This study investigates and attempts to quantify the relationship between screw insertion speed and torque for later inclusion in modelling if significant.