Excessive Heat Generation by Power-Driven Craniotomy Tools: A Possible Cause of Autologous Bone Flap Resorption Observed in an Ex Vivo Simulation

Abstract

Background: Bone flap resorption is an issue after autologous cranioplasty. Critical temperatures above 50°C generated by power-driven craniotomy tools may lead to thermal osteonecrosis, a possible factor in resorption. This ex vivo study examined whether the tools produced excessive heat resulting in bone flap resorption.

Methods: Using swine scapulae maintained at body temperature, burr holes, straight and curved cuts, and wire-pass holes were made with power-driven craniotomy tools. Drilling was at the conventional feed rate (FR) plus irrigation (FR-I⁺), at a high FR plus irrigation (hFR-I⁺), and at high FR without irrigation (hFR-I^-). The temperature in each trial was recorded by an infrared thermographic camera.

Results: With FR-I⁺, the maximum temperature at the burr holes, the cuts, and the wire-pass holes was 69.0°C, 56.7°C, and 46.2°C, respectively. With hFR-I⁺, these temperatures were 53.1°C, 52.1°C, and 46.0°C, with hFR-I^- they were 56.0°C, 66.5°C, and 50.0°C; hFR-I^- burr hole- and cutting procedures resulted in the highest incidence of bone temperatures above 50°C followed by FR-I⁺, and hFR-I⁺. At the site of wire-pass holes, only hFR-I^- drilling produced this temperature.

Conclusions: Except during prolonged procedures in thick bones, most drilling with irrigation did not reach the critical temperature. Drilling without irrigation risked generating the critical temperature. Knowing those characteristics may be a help to perform craniotomy with less thermal bone damage.

Keywords: Bone flap resorption; Cranioplasty; High-speed drill; Thermal osteonecrosis; Thermography.