Objective: To investigate the effect of ultrasonic parameter settings on maximum temperatures in the drilling site and penetration time and determine the most suitable parameters for efficient and safe robot-based ultrasonic bone drilling in spinal surgery. Methods: Five adult bovine thoracic and lumbar vertebrae specimens (T10-L6) were cut into 10 mm thick slices. A total of 50 slices were obtained. Among them, 30 and 20 slices were used for cancellous bone experiments and cortical bone experiments, respectively. In the cancellous bone experiment, the slices were randomly divided into three groups, corresponding to different feed rates of 0.8 mm/s, 1.6 mm/s, and 2.4 mm/s, respectively, with 10 slices in each group. The cancellous part of each slice was drilled 9 times with different output powers from 20% (48 W) to 100% (120 W). In the cortical bone experiment, the slices were randomly assigned into two groups, corresponding to a different feed rate (0.8 mm/s and 1.6 mm/s). Drilling was performed on the cortical part of each slice 4 times with different output power, which increased from 70% (84W) to 100% (120 W). All experiments were conducted at room temperature of 25 ℃. Maximum temperature and penetration time were recorded. The maximum grinding temperature and penetration time of cancellous bone and cortical bone under different output power and feed rate were compared. Results: At the same feed rate, the maximum temperature of the cancellous bone decreased as output power increased. There were statistically significant differences in the maximum temperature between the output powers of 120 W and 24 W under different feed rates(61.2 ℃±9.4 ℃ vs 70.9 ℃±5.7 ℃, 59.2 ℃±7.1 ℃ vs 69.5 ℃±10.7 ℃, 55.5 ℃±5.5 ℃ vs 69.2 ℃±9.3 ℃, all P<0.05). At the premise of the same output power, there was no significant difference in the maximum temperature among different feed rates (all P>0.05). At the feed rate of 0.8 mm/s, the maximum temperature of cortical bone decreased as the output power increased. The maximum temperature at the output power of 120 W was significantly lower than that of 84 W (P=0.048). However, at the feed rate of 1.6 mm/s, the maximum temperature could not be significantly lowered by the increase in output power (P>0.05). Under the same output power, the maximum temperature at the feed rate of 1.6 mm/s were all significantly lower than those of 0.8 mm/s (all P<0.05). The penetration time of cancellous bone did not decrease significantly with the increase in the output power (all P>0.05) while it decreased significantly as the feed rate increased (all P<0.05). Regarding cortical bone at the feed rate of 0.8 mm/s, the increase in output power could not shorten the penetration time (P>0.05); at the feed rate of 1.6 mm/s, the penetration time at the output power of 120 W was significantly shorter than that of 96 W (P=0.008). With the same output power, the penetration time at the feed rate of 1.6 mm/s were significantly shorter than those at 0.8 mm/s (all P<0.05). There was no statistical difference in the penetration failure rate among different feed rates with the same output power (all P>0.05). The penetration failure rate was 0 when the output power of cancellous bone was 48 W and above and the output power of cortical bone were 108 W and 120 W. Conclusions: The maximum temperature of vertebral cancellous bone and the cortical bone is primarily influenced by the output power and the feed rate, respectively; the penetration time of cancellous bone and the cortical bone is affected by the feed rate and both of feed rate and output power, respectively. The most suitable parameters are output power of 120 W and feed rate of 2.4 mm/s for cancellous bone and output power of 120 W and feed rate of 1.6 mm/s for cortical bone.
目的： 研究超声磨钻参数设置对牛椎体磨削部位最高温度和穿透时间的影响，确定最佳参数，实现脊柱手术中基于机器人辅助的高效安全的超声磨钻磨削。 方法： 将5头成年牛胸腰椎标本（T10-L6）用切割机切成10 mm厚切片，共获得50个切片，其中30个切片用于松质骨实验，20个切片用于皮质骨实验。松质骨实验中，将切片随机分为3组，每组10个切片，对应不同的进给速率（0.8、1.6和2.4 mm/s）。在切片的松质骨部位用不同的输出功率进行9次磨削，输出功率从20%（48 W）增加到100%（120 W）。皮质骨实验中，将切片随机分为2组，每组对应不同的进给速率（0.8 mm/s和1.6 mm/s）。在切片皮质骨部位进行4次磨削，分别对应输出功率从70%（84 W）增加到100%（120 W）。实验在室温25 ℃下进行，用红外热像仪记录磨削部位的最高温度，并记录穿透时间。比较松质骨及皮质骨在不同输出功率和不同进给速率下磨削最高温度及穿透时间的变化情况。 结果： 相同进给速率时松质骨磨削部位的最高温度随着输出功率的增加而降低，输出功率120 W时最高温度同24 W时差异有统计学意义（61.2 ℃±9.4 ℃比70.9 ℃±5.7 ℃、59.2 ℃±7.1 ℃比69.5 ℃±10.7 ℃、55.5 ℃±5.5 ℃比69.2 ℃±9.3 ℃，均P<0.05）。在相同输出功率下，不同进给速率的最高温度差异均无统计学意义（均P>0.05）。皮质骨在0.8 mm/s进给速率下，最高温度随输出功率增加而降低，输出功率120 W时最高温度显著低于84 W时（P=0.048）；但在1.6 mm/s进给速率下，增加输出功率不能显著降低最高温度（P>0.05）。在相同输出功率情况下，进给速率1.6 mm/s时的最高温度比0.8 mm/s时均显显降低（均P<0.05）。松质骨磨削穿透时间不随输出功率增加而显著缩短（均P>0.05），但随进给速率增加而减少（均P<0.05）。皮质骨在0.8 mm/s进给速率下，输出功率增加不能使穿透时间缩短（P>0.05）；1.6 mm/s进给速率下，输出功率120 W时穿透时间最短，显著低于96 W时（P=0.008）。在相同输出功率下，进给速率1.6 mm/s时的穿透时间比0.8 mm/s时缩短（均P<0.05）。无论松质骨还是皮质骨，在相同输出功率下，不同进给速率的穿透失败率差异均无统计学意义（均P>0.05）。松质骨在输出功率48 W及以上时，皮质骨在输出功率108 W和120 W时，穿透失败率均为0。 结论： 磨削最高温度椎体松质骨受输出功率影响，皮质骨受进给速率影响；穿透时间松质骨受进给速率影响，皮质骨同时受进给速率和输出功率影响。松质骨最佳磨削参数为输出功率120 W，进给速率2.4 mm/s；皮质骨为输出功率120 W，进给速率1.6 mm/s。.