title: Thermal osteonecrosis and bone drilling parameters revisited.
abstract: BACKGROUND
  During the drilling of the bone, the temperature could increase above 47 degrees C and cause irreversible osteonecrosis. The result is weakened contact of implants with bone and possible loss of rigid fixation. The aim of this study was to find an optimal condition where the increase in bone temperature during bone drilling process would be minimal.
  
  
  METHODS
  Influence of different drill parameters was evaluated on the increase of bone temperature. Drill diameters were 2.5, 3.2 and 4.5 mm; drill speed 188, 462, 1,140 and 1,820 rpm; feed-rate 24, 56, 84 and 196 mm/min; drill point angle 80 degrees , 100 degrees and 120 degrees and external irrigation with water of 26 degrees C.
  
  
  RESULTS
  Combinations of drill speed and drill diameter with the use of external irrigation produced temperatures far below critical. Without external irrigation, temperature values for the same combination of parameters ranged 31.4-55.5 degrees C. Temperatures above critical were recorded using 4.5 mm drill with higher drill speeds (1,140 and 1,820 rpm). There was no statistical significance of different drill point angles on the increase or decrease of bone temperature. The higher the feed-rate the lower the increase of bone temperature.
  
  
  CONCLUSIONS
  The external irrigation is the most important cooling factor. With all combinations of parameters used, external irrigation maintained the bone temperature below 47 degrees C. The increase in drill diameter and drill speed caused increase in bone temperature. The changes in drill point angle did not show significant influence in the increase of the bone temperature. With the increase in feed-rate, increase in bone temperature is lower.
authors.affiliation: Department of Surgery, University Hospital Center Zagreb, Kispatićeva 12, 10000 Zagreb, Croatia. Augustin.goran@gmail.com
authors.forename: Goran
authors.initials: G
authors.lastname: Augustin
authors.forename: Slavko
authors.initials: S
authors.lastname: Davila
authors.forename: Kristijan
authors.initials: K
authors.lastname: Mihoci
authors.forename: Toma
authors.initials: T
authors.lastname: Udiljak
authors.forename: Denis Stjepan
authors.initials: DS
authors.lastname: Vedrina
authors.forename: Anko
authors.initials: A
authors.lastname: Antabak
mesh_terms: D000818:Animals; D001831:Body Temperature; D001842:Bone and Bones / Q000502:physiology* / Q000601:surgery; D004867:Equipment Design; D005269:Femur / Q000502:physiology / Q000601:surgery; D019637:Orthopedic Procedures / Q000009:adverse effects / Q000295:instrumentation; D010020:Osteonecrosis / Q000517:prevention & control; D013552:Swine; D007507:Therapeutic Irrigation