Department of Surgery, University Hospital Center Zagreb and School of Medicine, University of Zagreb, Kišpatićeva 12, 10000 Zagreb, Croatia.
Int Orthop. 2012 Jul;36(7):1449-56. doi: 10.1007/s00264-012-1491-z.
Bone drilling causes an increase in bone temperature, and a temperature above 47°C is critical because it causes thermal bone necrosis. Thermal osteonecrosis is common with the drill diameter of ≥4.5 mm without cooling. The aim of this study was to determine the increase of bone temperature during drilling using newly contructed two-step and internally cooled drills.
An experiment was set up according to a central composite design. An internally cooled drill (3.4 mm and 4.5 mm) and a two-step drill (2.5/3.4 and 3.4/4.5 mm) were used in combination with feed rates of (0.02, 0.04, 0.10, 0.16 and 0.18 mm/rev) and cutting speeds (1.18, 10.68, 33.61, 56.55 and 66.05 m/min) with and without cooling with water of 24°C. Bone temperatures were measured with thermocouples. Drilling was performed on pig diaphyses with a three-axis mini milling machine.
Bone temperatures in all combinations of parameters with internal cooling were below the critical 47°C (p=0.05). The highest temperatures were detected using a 4.5-mm drill (40.5°C). A statistically significant effect other than cooling was found with the drill diameter and feed. A drill diameter of 3.4 mm with internal cooling developed a maximum temperature of 38.5°C and without cooling 46.3°C. For the same conditions a drill with diameter of 4.5 mm reached temperatures of 40.5°C and 55.7°C, respectively. The effect of feed rate is inversely proportional to the increase in bone temperature. With the feed rate 0.16 mm/rev, temperature was below critical even using the 4.5-mm drill (46.4°C, p=0.05). Using the 3.4-mm drill all temperatures were below critical (46.2°C, p=0.05). The two-step drill compared to a standard drill with the same diameter did not show statistical differences in maximum bone temperatures for all combinations of parameters (p=0.05).
A two-step drill does not have any advantages over a standard twist drill of the same diameter. An internally cooled drill causes a significantly smaller increase of bone temperature during drilling with water of 24°C. An internally cooled drill is currently the 'ideal' drill for traumatology/orthopaedics because it produces the smallest increase in bone drilling temperature. If internal cooling is used the regulation of other drilling parameters is of no importance.
骨钻会导致骨温升高，当温度超过 47°C 时，就会发生热骨坏死，这是非常关键的。在没有冷却的情况下，直径大于 4.5 毫米的钻头会导致热骨坏死。本研究的目的是使用新构造的两步式和内部冷却式钻头来确定钻孔过程中骨温的升高。
根据中心复合设计进行实验。使用内部冷却钻头（3.4 毫米和 4.5 毫米）和两步式钻头（2.5/3.4 和 3.4/4.5 毫米），结合 24°C 水的进给速度（0.02、0.04、0.10、0.16 和 0.18 毫米/转）和切削速度（1.18、10.68、33.61、56.55 和 66.05 米/分钟），进行有和没有冷却的实验。使用热电偶测量骨温。在三轴微型铣床在猪骨干上进行钻孔。
所有带有内部冷却的参数组合的骨温均低于临界的 47°C（p=0.05）。使用 4.5 毫米钻头时，检测到的温度最高（40.5°C）。除冷却外，钻头直径和进给也有统计学意义的影响。带有内部冷却的 3.4 毫米钻头的最大温度为 38.5°C，没有冷却的温度为 46.3°C。对于相同的条件，直径为 4.5 毫米的钻头达到了 40.5°C 和 55.7°C 的温度。进给速度的影响与骨温的升高成反比。当进给速度为 0.16 毫米/转时，即使使用 4.5 毫米钻头，温度也低于临界值（46.4°C，p=0.05）。使用 3.4 毫米钻头时，所有温度均低于临界值（46.2°C，p=0.05）。对于所有参数组合，两步式钻头与相同直径的标准麻花钻相比，在最大骨温方面没有统计学差异（p=0.05）。
两步式钻头与相同直径的标准麻花钻相比没有任何优势。在使用 24°C 水冷却的情况下，内部冷却钻头会显著降低骨钻过程中的骨温升高。内部冷却钻头目前是创伤学/矫形学的“理想”钻头，因为它产生的骨钻温度升高最小。如果使用内部冷却，那么调节其他钻孔参数就不重要了。
