title: Performance test of different 3.5 mm drill bits and consequences for orthopaedic surgery.
abstract: BACKGROUND
  Drilling 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.
  
  
  METHODS
  In 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.
  
  
  RESULTS
  The 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).
  
  
  CONCLUSIONS
  If 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.
authors.affiliation: Department for Traumatology, Medical University of Graz, Auenbruggerplatz 5, 8036, Graz, Austria.
authors.forename: Hans
authors.initials: H
authors.lastname: Clement
authors.affiliation: Institute for Materials Science and Welding, Technical University of Graz, Kopernikusgasse 24, 8010, Graz, Austria.
authors.forename: Christoph
authors.initials: C
authors.lastname: Zopf
authors.affiliation: Institute of Electrical Measurement and Measurement Signal Processing, Technical University of Graz, Kopernikusgasse 24/IV, 8010, Graz, Austria.
authors.forename: Markus
authors.initials: M
authors.lastname: Brandner
authors.affiliation: Institute of Anatomy, Medical University of Graz, Harrachgasse 21, 8010, Graz, Austria.
authors.forename: Norbert P
authors.initials: NP
authors.lastname: Tesch
authors.affiliation: Institute for Materials Science and Welding, Technical University of Graz, Kopernikusgasse 24, 8010, Graz, Austria.
authors.forename: Rudolf
authors.initials: R
authors.lastname: Vallant
authors.affiliation: Department for Traumatology, Medical University of Graz, Auenbruggerplatz 5, 8036, Graz, Austria. paul.puchwein@medunigraz.at.
authors.forename: Paul
authors.initials: P
authors.lastname: Puchwein
mesh_terms: D001842:Bone and Bones / Q000601:surgery*; D002102:Cadaver; D004867:Equipment Design; D019544:Equipment Failure Analysis; D006801:Humans; D008422:Materials Testing / Q000379:methods*; D019637:Orthopedic Procedures / Q000295:instrumentation*; D013525:Surgical Instruments
keywords: AISI 440A; AISI 440B; Coatings; Drill bit; Drill feeding; Drilling cortical bone; Feeding force; Peak forces