Temperature changes during cortical bone drilling with a newly designed step drill and an internally cooled drill

Area of Science:

• Orthopedic Surgery
• Biomaterials Engineering
• Surgical Technology

Background:

• Bone drilling can elevate bone temperature, potentially causing thermal necrosis above 47°C.
• Larger drill diameters (≥4.5 mm) without cooling are associated with higher risks of thermal osteonecrosis.

Purpose of the Study:

• To evaluate bone temperature increases during drilling with novel two-step and internally cooled drills.
• To compare the thermal effects of different drill designs and parameters.

Main Methods:

• A central composite design experiment was used.
• Internally cooled drills (3.4 mm, 4.5 mm) and two-step drills (2.5/3.4 mm, 3.4/4.5 mm) were tested.
• Drilling parameters included varying feed rates and cutting speeds, with and without 24°C water cooling.

Main Results:

• Internal cooling maintained bone temperatures below the critical 47°C threshold in all tested conditions.
• Drill diameter and feed rate significantly impacted bone temperature, with larger diameters and lower feed rates increasing temperature.
• A 4.5-mm drill with internal cooling reached 40.5°C, while without cooling it reached 55.7°C.
• Two-step drills showed no significant thermal advantage over standard drills of the same diameter.

Conclusions:

• Internally cooled drills are highly effective in minimizing bone temperature rise during drilling.
• Two-step drills offer no thermal benefit compared to standard drills.
• Internal cooling is crucial for preventing thermal bone necrosis in orthopedic and trauma surgery.