滑丝空心取钉器的研制及临床应用

Development and clinical application of screw remover for the skidded screws

目的 研制用于拆除骨科滑丝空心螺钉拆除的EZ取钉器,探讨其结构特点和生物力学特性,并通过临床应用来验证取出效果. 方法 采用新鲜尸骨标本,股骨、胫骨、尺桡骨各3具,按临床要求固定螺钉,骨髓腔内灌注骨水泥,并以随机数字表法分为三个生物力学测试模型组：A组为起子取螺钉打滑时最大扭力组；B组为EZ取钉器一个手柄时最大扭力组；C组为EZ取钉器两个手柄时最大扭力组.固定螺钉为直径4.5 mm和直径3.5 mm两种.在万能材料试验机上测试实验标本扭转旋出螺钉时的最大扭矩值、扭角及螺钉旋出时的功耗大小和效率.应用EZ取钉器拆除临床上遇到的滑丝螺钉,验证其取钉效果. 结果 A组拔出扭矩为2.87～3.27 N.m,B组为3.06～4.83 N·m,C组为4.12 ～8.36 N·m（P ＜0.05）；三组相应的扭角均值分别为0.77°、0.28°、0.16°（P＜0.05）.螺钉旋出时各组的功耗均值分别为21 J、32J、45 J,对应各组间的功率（机械效率）分别为0.35 J/s、0.53 J/s、0.75 J/s（P ＜0.05）.应用EZ取钉器拆除临床上遇到的直径7.3 mm滑丝空心钉7例（17枚）,均顺利取出. 结论 EZ取钉器具有足够的抗扭强度和刚度,夹持力大,临床应用效果好,是骨科拆除滑丝空心钉较理想的工具.

Objective To develop an EZ screw remover for screwing out the skidded screws,discuss its design features and biomechanical characteristics and verify its extracting effect by clinical applications. Methods Fresh skeleton specimens were used in the study,including the femur （n =3）,tibia （ n =3 ）,radius and ulna （ n =3 ）.The screws were fixed to the specimens according to clinical requirements and bone cement was filled into the medullary cavity.The specimens were randomized into three biomechanical test model groups,ie,Group A （measuring the skidded screws with the biggest torsion when the screws were taken out by screwdriver）,Group B （measuring the skidded screws with the biggest torsion when the screws were taken out by one handle of EZ screw remover） and Group C （ measuring the skidded screws with the biggest torsion when the screws were taken out by two handles）.The fixed screws were divided into two types of φ4.5 mm and φ3.5 mm.The experimental specimens were tested on the universal testing machines to measure the maximum torque,torsion angle,power consumption value and efficiency when drawing out the screws. The experimental data were compared between groups.The skidded screws encountered in clinical were taken out with EZ screw remover to verify the extracting effect. Results The pullout torque in Groups A,B and C was 2.87-3.27 N · m,3.06-4.83N · m and 4.12-8.36 N · m respectively （ P 〈 0.05 ）.The average torsion angle value in each corresponding group was 0.77°,0.28°,0.16° respectively （P 〈 0.05 ）.When the screws were screwed out,the average power consumption was 21 J,32 J and 45 J in Groups A,B and C respectively and power （ mechanical efficiency） was 0.35 J/s,0.53 J/s and 0.75J/s in Groups A,B and C respectively,with significant differences （ P 〈 0.05 ）.Seventeen pieces of the cannulated skidded screws of φ7.3 mm in seven patients were successfully taken out by using the EZ screw remover. Conclusion EZ screw removerhas enough resistance strength and rigidity to torsion as well as powerful clamping force and hence is an ideal tool for screwing out the skidded screw in orthopedics