• Hans Clement, Christoph Zopf, Markus Brandner, Norbert P Tesch, Rudolf Vallant, and Paul Puchwein.
• Department for Traumatology, Medical University of Graz, Auenbruggerplatz 5, 8036, Graz, Austria.
• Arch Orthop Trauma Surg. 2015 Dec 1; 135 (12): 1675-82.

IntroductionDrilling of bones in orthopaedic and trauma surgery is a common procedure. There are yet no recommendations about which drill bits/coating should be preferred and when to change a used drill bit.Materials And MethodsIn preliminary studies typical "drilling patterns" of surgeons concerning used spindle speed and feeding force were recorded. Different feeding forces were tested and abrasion was analysed using magnification and a scanning electron microscope (SEM). Acquired data were used for programming a friction stir welding machine (FSWM). Four drill bits (a default AISI 440A, a HSS, an AISI 440B and a Zirconium-oxide drill bit) were analysed for abrasive wear after 20/40/60 machine-guided and hand-driven drilled holes. Additionally different drill coatings [diamond-like carbon/grafitic (DLC), titanium nitride/carbide (Ti-N)] were tested.ResultsThe mean applied feeding force by surgeons was 45 ± 15.6 Newton (N). HSS bits were still usable after 51 drill holes. Both coated AISI 440A bits showed considerable breakouts of the main cutting edge after 20 hand-driven drilled holes. The coated HSS bit showed very low abrasive wear. The non-coated AISI 440B bit had a similar durability to the HSS bits. The ZrO2 dental drill bit excelled its competitors (no considerable abrasive wear at >100 holes).ConclusionsIf the default AISI 440A drill bit cannot be checked by 20-30× magnification after surgery, it should be replaced after 20 hand-driven drilled holes. Low price coated HSS bits could be a powerful alternative.

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