The thermal profile of self-tapping screws: The effect of insertion speed, power insertion, and screw geometry on heat production at the bone-screw interface.

Abstract

IntroductionPower insertion of screws using high-speed saves time during operative fixation of fractures compared to manual insertion. Heat production during screw insertion may cause thermal damage at the critical bone-screw interface, reducing fixation strength, delaying healing, or increasing infection risk. Currently, the thermal impact of screw insertion is incompletely understood. This study investigated the thermal profiles of self-tapping screws at varying insertion speeds, utilizing manual versus power insertion, and with differing cutting flute geometries to determine which variables may save time while mitigating thermal injury. MethodsThermal and mechanical force profiles were obtained during insertion of 24 mm length, 3.5 mm stainless steel screws into 50 PCF polyurethane after pre-drilling. Power insertion at low (30RPM) and high (300RPM) speed, manual screwdriver insertion versus high-speed power insertion, and two different cutting flute geometries were compared. Infrared thermography was used to measure maximum surface temperatures and mean temperature change (°C). Time (s) was measured to compare manual and power insertion. Means were compared using a two-tailed independent t-test. ResultsMaximum surface temperature of high-speed insertion (55.42 ± 5.58 °C) was significantly greater (p < 0.001) than low-speed (41.07 ± 2.33 °C). Similarly, mean temperature rise of high-speed insertion (29.52 ± 5.39 °C) was greater than that of low-speed (15.13 ± 2.63 °C) (p < 0.001). There was no statistical difference in maximum surface temperature between manually inserted screws (56.58 ± 5.53 °C) and high-speed power inserted screws (55.42 ± 5.58 °C) (p = 0.155), while insertion speeds were almost 5 times faster with high-speed power insertion (6.75 ± 1.84 s) than with manual insertion (30.3 ± 4.06 s) (p < 0.001). There were no differences detected between the geometry groups in any outcome measure tested. ConclusionHigh speeds for screw insertion generate significantly greater maximum temperatures and greater temperature rise than slower speeds. Surprisingly, the thermal profile of manual insertion was similar to high-speed insertion, while requiring significantly longer for insertion. Low-speed insertion generated significantly lower maximal temperatures and temperature rise. Surgeons could consider utilizing low-speed when inserting orthopaedic screws with a power driver to minimize thermal impact to bone while optimizing efficiency.