Tool parameters to minimize temperature changes in bone drilling

Drilling is a common technique used in orthopedic surgery procedures but causes increases in temperature that can lead to cell damage and death. The extent of this depends largely on the magnitude of the increase in temperature. The commonly accepted limit to prevent osteonecrosis is less than 47 °C for 60 s. There is controversy when it comes to the optimal drilling parameters that limit temperature increases and cell death. In addition to this, less research has been done on the drilling effects in the osteochondral area of joints. Osteochondral tissue damage can interfere with the daily lives of patients and if severe enough will need to be treated. We hypothesize that increasing tool speed and drill bit size will increase temperature that could be above the osteonecrosis limit.

Ex-vivo experiments were conducted on porcine shoulder joints that tested the thermal effects of different tool speeds and drill bit sizes. A thermal camera was used to record and measure real time temperature changes while drilling. Three drill bit sizes and five tool speeds were used. Statistical analyses includes Welch's ANOVA with Games-Howell Post Hoc analyses, multivariate linear regression, and surface response regression were used to explore the association of tool speeds and drill bit size on temperature.

All the tool speed and drill bit size combinations lead to an increase in temperature that were under the commonly accepted limit. The highest temperature reached was 44 °C with a tool speed of 1150 RPM and 3070 RPM and drill bit size 5.159 mm. It was found that increasing the tool speed increased the temperature change and increasing the drill bit size increased the temperature change.