title: Can a surgeon drill accurately at a specified angle?
abstract: OBJECTIVE
  To investigate whether a surgeon can drill accurately a specified angle and whether surgeon experience, task repetition, drill bit size and perceived difficulty influence drilling angle accuracy.
  
  
  METHODS
  The sample population consisted of final-year students (n=25), non-specialist veterinarians (n=22) and board-certified orthopaedic surgeons (n=8). Each participant drilled a hole twice in a horizontal oak plank at 30°, 45°, 60°, 80°, 85° and 90° angles with either a 2.5  or a 3.5 mm drill bit. Participants then rated the perceived difficulty to drill each angle. The true angle of each hole was measured using a digital goniometer.
  
  
  RESULTS
  Greater drilling accuracy was achieved at angles closer to 90°. An error of ≤±4° was achieved by 84.5 per cent of participants drilling a 90° angle compared with approximately 20 per cent of participants drilling a 30-45° angle. There was no effect of surgeon experience, task repetition or drill bit size on the mean error for intended versus achieved angle. Increased perception of difficulty was associated with the more acute angles and decreased accuracy, but not experience level.
  
  
  CONCLUSIONS
  This study shows that surgeon ability to drill accurately (within ±4° error) is limited, particularly at angles ≤60°. In situations where drill angle is critical, use of computer-assisted navigation or custom-made drill guides may be preferable.
authors.affiliation: Department of Veterinary Medicine , University of Cambridge , Cambridge , UK.
authors.forename: Valentina
authors.initials: V
authors.lastname: Brioschi
authors.affiliation: Vets4Pets , Ipswich , UK.
authors.forename: Jodie
authors.initials: J
authors.lastname: Cook
authors.affiliation: Department of Veterinary Medicine , University of Cambridge , Cambridge , UK.
authors.forename: Gareth I
authors.initials: GI
authors.lastname: Arthurs
keywords: bone drilling; drill angle; drilling accuracy