Pilot study: Internally cooled orthopedic drills – standard sterilization is not enough?

Bone drilling causes focal temperature rise due to metal-to-bone contact, which may result in thermal osteonecrosis. Newly constructed internally cooled medical drill of an open type decreases temperature rise at a point of metal-to-bone contact although standard sterilization of such a drill could be inadequate due to bacteria retention within the drill lumen. The aim of this pilot study was to examine the effectiveness of sterilization and to propose sterilization recommendations for internally cooled open type bone drills. Unused internally cooled medical steel bone drills were tested. Drills were contaminated with Pseudomonas aeruginosa, Bacillus sp., beta-hemolytic Streptococcus sp., Enterobacter sp. and methicillin-resistant Staphylococcus pseudintermedius and then incubated for 24 hours at 37 °C. Afterwards, drills were autoclaved for 15, 20 and 30 minutes at 132 °C and 2.6 bar. When 15-minute sterilization was used, one out of 16 drills was contaminated with Pseudomonas aeruginosa, while the other 15 drills were sterile. Extended cycle sterilization in autoclave lasting for 20 and 30 minutes resulted in 100% sterility of all drills tested. In conclusion, lumened drills should be exposed to extended sterilization times in autoclave. Minimal recommended time for sterilization of lumened drills is 20 minutes.