数字散斑法加载100 N与500 N测量胫骨干骨折内固定下的位移

背景：以往研究多以传感器研究钢板置入内固定治疗骨折生物力学特点，存在直接接触、精度低等缺点。目的：以数字散斑法测试成人胫骨加压钢板内固定中骨折断端第4颗和第5颗螺钉在不同拉力条件下的平均位移。方法：测试之前在所有成人胫骨标本表面喷涂银漆粉，用于数字散斑测量。横行截断胫骨中点，制造胫骨干中段骨折模型。将加压钢板置入胫骨后外侧骨膜下，骨折端两侧各4枚螺钉穿透4层骨皮质。标本分6个状态：A，8枚螺钉加压胫骨内固定(未锯断，模拟骨愈合状态)；B，在A组的基础上胫骨中点锯断；C，在B组的基础上去掉上面第1颗螺钉；D，在C组的基础上去掉下面第1颗螺钉；E，在D组的基础上去掉上面第2颗螺钉；F，在E组的基础上去掉下面第2颗螺钉，按A~F组测量顺序进行测量。在100，500 N拉力下，用CSS-44100型电子万能试验机进行加载拉力测量骨折断端近侧第4颗与第5螺钉的位移。结果与结论：方差分析显示在100 N拉力下(F=3.107)，A组与F组比较方差的P < 0.05；在500 N拉力下(F=4.719)，A组与F组比较方差的P值< 0.05。说明靠近骨折线的螺钉承受较大的应力，容易断裂，在加压钢板内固定治疗胫骨骨折时，经过推断假定其螺钉直径建议增加1.0~2.0 mm。

Screw displacement following tibial fractures internal fixation under 100 and 500 N forces by digital speckle correlation method

BACKGROUND:Biomechanical features of plate internal fixation for fractures are commonly analyzed utilizing sensor, which presents direct contact and low accuracy.OBJECTIVE:To measure mean displacement of the forth and fifth screws under different tensile forces with internal fixation of compression plate for tibial fracture by digital speckle correlation method. METHODS:The specimens of antisepsis adult tibia were spray with the silver for the digital speckle technique before the experiment. The tibia was desected from the middle point to establish model of middle segmental fracture. The compression plate was implanted below the posterolateral periosteum, and 4 lock screws inserted each from two ends of fracture into 4-layer cortical bone. The specimens included 6 conditions: group A: the tibia was not sawed with the steel, and internally fixed with 8 screws (simulation of bone healing); group B: the tibia was sawed at the middle point of the tibia on the basis of A; group C: the first screw of the upper end was removed on the basis of B; group D: the first screw of the lower end was removed on the basis of C; group E: the second screw of the upper end was removed on the basis of D; group F: the second screw of the upper end was removed on the basis of E. The measurements were performed from A to F. Under the tensile forces of 100 and 500 N, the displacement of the forth and fifth screws were measured with CSS-44100-e-universal test machine.RESULTS AND CONCLUSION:Analysis of variance showed that under 100 N (F=3.107), group A and group F had significant differences (P < 0.05); under 500 N (F=4.719), group A and group F had significant differences (P < 0.05). The screws near the fracture line for tibial compression plate internal fixation were easily broken because of the large displacement. Therefore, the screw diameter is recommended to increase 1.0-2.0 mm following calculation.