Temperature and force generation in surgical bone drilling

Abstract

High heat generation in surgical bone drilling causes thermal necrosis, thus impairing bone healing and implant reliability. Surgeons are often unaware of such in-situ drilling characteristics. Prediction and control of temperature is thus crucial for improved patient outcome. As a first step to this regard, the current paper aims to comprehensively explore the effect of the key parameters on bone drilling performance. Drilling tests were performed on Sawbone and bovine bone with the change of rotational speed (1000 – 2500 rpm), feedrate (30 – 60 mm/min) and drill bit (Ø3 and 4 mm). Drilling temperature, force, thermal necrosis exposure probability and chip formation were analyzed. Sawbone was found to reveal significantly less temperature and force generation than bovine bone, and hence the analysis presented was focused on bovine bone. Rotational speed and feedrate showed an opposing effect. Higher speed increased temperature but decreased force, while higher feedrate reduced temperature but increased force. Drilling with lower spindle speed and intermediate feedrate was shown to have a low chance for thermal necrosis. Bone chip formation changed from continuous (shearing) to broken type (fracturing) when the speed was increased from 1000 to 2500 rpm. If not necessary, smaller drill bit was suggested to minimize the underlying effect. These preliminary findings appeared to guide one to develop and optimize a prediction model for surgeons to estimate and control temperature and force for a safe bone drilling, which is the key focus of the author’s future work.