Heat generation during bone drilling operations is a serious challenge for the internal fixation surgery of bone fracture. Indeed, the heat generated at the drilling site causes complications including local temperature rise, thermal necrosis, irreversible damages to the bone tissue, and possible failure of orthopedic surgery. High-speed machining is an advanced method which has achieved remarkable results in some cases of reducing the temperature rise of the tool or workpiece. The present research examines high-speed drilling (HSD) of the bone using theoretical (based on Orthogonal Cutting theory and High-Speed Cutting model) and experimental (based on infrared thermography) approaches. The thrust force and temperature changes of the bone and drill bit have been measured at different rotational speeds. The drilling tests have been performed under a constant feed rate of 100 mm min-1, hole depth of 8 mm, and 18 rotational speeds of 1000-18,000 r min-1 (with 1000 r min-1 intervals) on a bovine femur. The results indicated that application of high rotational speeds in most cases caused increased temperature rise of the bone; only the rotational speed of 7000 r min-1 (which is associated with dramatic force reduction) and speed of 11,000 r min-1 (which is associated with alteration of the chip formation mechanism and its nature) resulted in the minimum extent of temperature rise in the bone. It was also observed that the High-Speed Cutting model was able to correctly estimate the threshold of high-speed machining range for the bone (5000 r min-1) and was also valid for the bone drilling operation.
Keywords: Bone fracture; High-speed drilling; Infrared thermography; Internal fixation; Temperature rise; Thermal necrosis.