加压螺丝钉内固定股骨颈骨折的蠕变实验

Creep following compression screw fixation for femoral neck fracture

背景:弄清模拟股骨颈骨折单头加压螺丝钉单钉固定,双钉固定,双钉固定植骨后对股骨蠕变力学性质影响对于新型股骨颈骨折内固定器械的研究和股骨颈骨折内固定术式的选择都具有一定的参考价值。目的:观察加压螺丝钉单钉固定、双钉固定、双钉固定后在骨折区植骨3种方法对股骨颈骨折蠕变特性的影响。设计、时间及地点:随机对照观察,于2006-08/09在吉林大学力学实验中心完成。材料:取正常国人急性头部创伤致死的新鲜尸体股骨标本24个,由白求恩医科大学解剖教研室提供。方法:24个标本随机分为3组,单钉固定组:单钉固定位于模拟骨折面中部;双钉固定组:2枚钉分别位于颈部张力侧;双钉固定植骨组:在双钉固定基础上于骨折线前部垂直骨折线开槽,每组8个标本。以0.5GPa/min的应力增加速度对标本施加应力,设定时间7200s,采集100个实验数据,以回归分析的方法计算归一化蠕变方程。主要观察指标:各组标本蠕变数据和曲线,蠕变与时间的变化规律。结果:①蠕变实验结果表明,单钉固定组初始蠕变量为0.4937%,双钉固定组初始蠕变量为0.4023%,双钉固定植骨组初始蠕变量为0.3821%,初始蠕变量大说明其初始位移大,稳定性不好。②单钉固定组7200s蠕变量为0.226%,双钉固定组为0.212%,双钉固定植骨组为0.219%。③各组蠕变曲线是以指数关系变化的,在最初600s变化较快,随时间延长应变缓慢上升,最后进入平衡阶段。结论:单钉固定、双钉固定和双钉固定植骨3种方法对股骨颈骨折蠕变的影响无明显差异。

BACKGROUND： The influence of creep mechanical properties after simulation of femoral neck fracture to compression screw fixation, single screw fixation, double screw fixation, and double screw-bone grafting in bone fracture zone is valuable for studies on novel fixator for femoral neck fracture and selection of internal fixation patterns. OBJECTIVE： To observe the effects of three types of compression screw fixation （single screw fixation, double screw fixation, and double screw-bone grafting） of femoral neck fracture on creep characteristics. DESIGN, TIME AND SETTING： Randomized, controlled experiment was performed at the Mechanics Experiment Center of Jilin University from August to September 2006. MATERIALS： Twenty-four fresh femur specimens from corpses of acute head trauma were provided by Department of Anatomy, Norman Bethune Medical University. METHODS： Twenty-four specimens were randomly divided into three groups （n=8）. In single screw fixation group, the screw was fixed on the middle of fracture site; in double screw fixation group, two screws were fixed at tension sides of the neck; in double screw-bone grafting group, slotting was performed vertically to the fracture line in front of the fracture line besides double screw fixation. Stress was imposed on specimens by 0.5 GPa/min stress increase for 7 200 seconds. 100 experimental data were collected. Normalized creep equation was calculated with regression analysis method. MAIN OUTCOME MEASURES： Creep data and curves as well as change rules of creep and time of specimens. RESULTS： The initial creep capacity was 0.493 7% in single-screw fixation group, 0.402 3% in double screw fixation group, and 0.382 1% in double screw-bone grafting group; great initial creep capacity represents great initial displacement and poor stability. 7 200 s creep was 0.226% in single-screw fixation group, 0.212% in double screw fixation group, and 0.219% in double screw-bone grafting group. Creep curves altered with index relationship： rapid changes occurred in the initial 600 seconds; as time went up, the strain slowly elevated and entered the balance. CONCLUSION： No significant difference was found in the influence of three types of compression screw fixation （single screw fixation, double screw fixation, and double screw-bone grafting） on creep characteristics.