骶2椎弓根钉内进钉固定拧紧力与骶骨的应变分布规律

Fixation tightening force of the second sacral enter pedicle screw and strain distribution of the sacrum

背景:国内外学者对骶骨骨折术式和骶2椎弓根钉固定方法进行了一定的研究,但对于骶2椎弓根钉固定螺钉拧紧力及在最大螺钉拧紧力作用下骶骨不同部位的应变分布规律研究少见报道。目的:研究骶2椎弓根钉固定拧紧力与骶骨应变分布,为临床骶2椎弓根钉固定术提供生物力学参数。设计、时间及地点:观察性实验,于2008-08在吉林大学力学实验中心完成。材料:取自正常国人新鲜尸体4具,均为男性,年龄25～30岁,由白求恩医科大学解剖教研室提供。方法:取正常国人新鲜尸体骶骨标本,以椎弓根钉内进钉方法固定于骶2椎弓根,以小型力传感器与椎弓根钉固定装置连接测量椎弓根钉的拧紧力,同时以动静态电阻应变仪对预先黏贴在4个椎弓根螺栓固定边缘部位和骶骨不同部位的应变片进行应变电测量。1号进钉点位置为左侧第一骶后孔下缘最低点,2号进钉点位置为右侧第一骶后孔下缘最低点,3号进钉点为左侧第一骶后孔连线与骶外侧嵴的交点,4号进钉点为右侧第一骶后孔连线与骶外侧嵴的交点。主要观察指标:椎弓根螺钉最大拧紧力和骶骨各测点应变分布值。结果:内进钉1号螺钉拧紧力为(68.7±7.8)N,2号螺钉拧紧力为(81.1±5.6)N,3号螺钉拧紧力为(56.9±4.6)N,4号螺钉拧紧力为(57.5±6.5)N。应变电测量最小应变发生在1号螺钉8号测点应变为(18.6±2.6)×10-6,最大应变发生在2号螺钉2号测点应变为(92.6±6.4)×10-6。结论:骶2椎弓根钉术式符合生物力学原理。

BACKGROUND： Studies on surgery for sacral fracture and sacral Ⅱ pedicle screw fixation have been conducted. However, the strain distribution rule of sacrum under maximum twisting force of sacral Ⅱ pedicle screw is rarely reported. OBJECTIVE： To explore the fixation tightening force of sacral Ⅱ pedicle screw and the strain distribution of sacrum so as to provide biomechanical parameters for clinical fixation method of sacral Ⅱ. DESIGN, TIME AND SETTING： Observation experiment was performed at Mechanics Experimental Center of Jilin University in August 2008. MATERIALS： Four fresh corpses of normal people, male, aged 20-30 years old, were provided by the Anatomy Department of Norman Bethune Medical University. METHODS： Fresh sacrum specimens from fresh corpses of normal people, were fixed in the second sacral pedicle by the method of enter pedicle screw. The small sensors were connected to fixation device of pedicie screw to measure the tightening force of pedicle screw. At the same time, the electric strain on the strain gauge of different parts which was resistance to static and dynamic strain gauge pre-pasted on the four fixed-site edge of pedicle and the different parts of sacrum was measured using the resistance strain gauge. The entry point of screw 1 was the lowest point of the inferior margin of left first posterior sacral foramina; screw 2 was the lowest point of the inferior margin of right first posterior sacral foramina; screw 3 was the intersection point of left first posterior sacral foramina and lateral sacral crest; screw 4 was the intersection point of right first posterior sacral foramina and lateral sacral crest. MAIN OUTCOME MEASURES： Maximum tightening force of pedicle screw and strain distribution value of the different points of sacrum. RESULTS： The screw tightening force of the screw 1, 2, 3 and 4 was （68.7±7.8） N, （81.1±5.6） N, （56.9±4.6） N, and （57.5±6.5） N, respectively. The minimum strain was found in the 8th measurement point of screw 1 （18.6±2.6）×10^-6, and the maximum strain was found in the 2nd measurement point of screw 2 （92.6±6.4）×10^-6. CONCLUSION： Second sacral pedicle screw procedure accords with the biomechanical principle.