Drilling of bone: Effect of drill bit geometries on thermal osteonecrosis risk regions

Abstract

Bone-drilling operation necessitates an accurate and efficient surgical drill bit to minimize thermal damage to the bone. This article provides a methodology for predicting the bone temperature elevation during surgical bone drilling and to gain a better understanding on the influences of the point angle, helix angle and web thickness of the drill bit. The proposed approach utilized the normalized Cockroft-Latham damage criterion to predict material cracking in the drilling process. Drilling simulation software DEFORM-3D is used to approximate the bone temperature elevation corresponding to different drill bit geometries. To validate the simulation results, bone temperature elevations were evaluated by comparison with ex vivo bone-drilling process using bovine femurs. The computational results fit well with the ex vivo experiments with respect to different drill geometries. All the investigated drill bit geometries significantly affect bone temperature rise. It is discovered that the thermal osteonecrosis risk regions could be reduced with a point angle of 110°to 140°, a helix angle of 5°to 30°and a web thickness of 5% to 40%. The drilling simulation could accurately estimate the maximum bone temperature elevation for various surgical drill bit point angles, web thickness and helix angles. Looking into the future, this work will lead to the research and redesign of the optimum surgical drill bit to minimize thermal insult during bone-drilling surgeries.

An Experimental Investigation of Forces on Cortical Bone in Deep-Hole Bone Drilling

“…In deep-hole bone drilling, this study observed that the bonedrilling forces increased abruptly once the drill-bit moved deeper into the bone than its ability to evacuate bone chips. As reported in previous studies [10,13,17], this force increase can lead to mechanical and thermal complications such as drill-bit breakage and thermal necrosis. Our findings can be used to improve the deep-hole bone-drilling process, reducing those unwanted complications.…”

“…Despite extensive research on bone-drilling processes with shallow drilling depths (5-7 mm) [10][11][12][13][14][15][16][17][18][19], few studies have investigated the deep-hole bone-drilling process. Considering the similarity of cutting mechanics of bone drilling to those of metal drilling, diverse studies on metals can be relevant in the understanding of deep-hole bone-drilling processes.…”

Surgical Drill Bit Design and Thermomechanical Damage in Bone Drilling: A Review

“…This suggestion seems applicable because a light web thickness produces not only low torque 167,174 but also bone temperature. 13,167,175,176 Moreover, Akhbar and Yusoff 5, 13 discovered minimum osteonecrosis regions with a light web thickness. Two methods have been integrated to achieve appropriate web thickness, i.e., web thinning (S, X, N, and R methods) 173,190 and split point drill.…”

“…90,95,133 A narrower point angle has longer cutting lips and, thus, produces wider chips. 13 A different point angle serves a different type of material. For example, a point angle of 118°is used for generalpurpose drilling, 74,104,153 whereas a narrower point angle is applied for drilling of the soft non-ferrous material (e.g., bone, fiber, and wood).…”

“…25 To drill a harder material (e.g., high alloyed steel, hardened steel, and mild steel), a higher point angle (130°and above) is preferred because the cutting edges are more durable. 5,13 In bone drilling, the point angle in the range of 60-160°is adopted. 5,13 However, the 60°p oint angle produces an ellipsoidal hole, which prevents the placing of the screws in the hole.…”