股骨自锁髓内钉的设计与生物力学特性

目的设计一种操作简便的新型髓内钉———斜面型自锁髓内钉(SLN),并测试其生物力学特性。方法本型SLN通过斜面结构的原理将轴向推动力转化为横向推动力,从而实现通过髓内钉尾部的运动控制横钉的收缩运动,进一步通过横钉的髓内把持作用实现带锁髓内钉的功能。在制成原型钉后,以10根股骨为标本制造股骨中上端骨折模型的实际操作,验证该结构运动的可行性和可靠性,通过X线片检查髓内固定情况。模拟单腿负重的受力力线,在instron-1342型MTS机测试拉、压、弯、扭等力学指标。结果该结构能够顺利完成设计动作,运动过程稳定、可靠,髓内固定情况满意;横钉与主钉接触面间可提供相当的剪切力切断可能的包绕物。在拉、压、弯、扭四项指标上,本型SLN的性能与G-K型带锁髓内钉接近,较分叉型自锁髓内钉略优,比梅花针和Ender氏髓内钉明显优越。结论本型SLN结构简单,运动可靠,在主要的受力面上无明显的应力集中点;受力合理,生物力学性能满意,基本能够达到设计要求;操作简便。

Biomechanical properties of the newly-designed femoral self-locking nail with bevels

Objective To introduce a new design of interlocking system which is easy in use, makes the distal fracture fragments well aligned and rigidly fixated, reduces exposure to radiation for the surgeon and patient, and allows for a decrease in operating time. Methods The new interlocking system was designed to be a self-locking nail with bevels (b-SLN). According to the bevel principle, the axial force of the nail should be turned into a transverse force so as to control the transverse nail's movement. 10 dry-bone simples were made into the fracture model of the middle-femur to test the prototype nail. The retention of the nail in the intramedullary cavity was evaluated by the radiogram. The mechanical properties of a simulated model of single leg loading were tested on the instron-1342 type MTS. Results The prototype nail performed well as designed. The process was stable and reliable. The retention in the intramedullary cavity was fine. The shearing force between the transverse nail and main nail was enough to cut anything around them. The mechanical properties of b-SLN were similar to those of the Grosse-Kempf nail, better than auto fork compress locked intramedullary nail, and much better than MHUA nail and Ender's nail. Conclusions The structure of b-SLN is simple and reliable. There is no focus-point under stress. Its biomechanic properties are satisfactory. It is easy to use with no need of fluoroscopes in the operating theatre.