Kyle R F, Wright T M, Burstein A H
J Bone Joint Surg Am. 1980 Dec;62(8):1308-14.
We examined the effect of screw-plate angle on the sliding characteristics and jamming potential of four popularly used stainless-steel and cobalt-chromium-molybdenum compression hip screws. The actual coefficient of sliding friction for these alloys was measured in each device. The force on the screw required to overcome the static frictional force also was determined, by varying the lengths of screw engaged in the barrel under conditions of static equilibrium representing 130-degree and 150-degree screw-plate angles. For the 130-degree loading configuration, this force was significantly (p < 0.001) higher than that required for the 150-degree loading configuration for all four screw types. The actual coefficient of friction was relatively constant for each material, although slight variations due to differences in design between screw types were found. A positive correlation (p < 0.01) was seen between the apparent coefficient of friction (the ratio of sliding force to normal force) and the length of the screw extending from the barrel. All stainless-steel screws jammed in the 130-degree tests when not completely engaged in the barrel. None of the 150-degree tests produced jamming and none of the cobalt-chromium-molybdenum screws jammed in either the 130-degree or the 150-degree test. Examination of jammed devices by scanning electron microscopy showed galling on the superior surface of both the screw and the barrel.
Understanding the conditions that facilitate sliding of hip screws aids in ensuring their proper use. The higher the nail-plate angle, the easier it is to impact the hip-fixation device and thus allow bone impaction and stability at the fracture site. The potential for jamming a sliding hip screw is decreased by maximum engagement of the screw in the barrel. Differences in the material and design of sliding hip-fixation devices have relatively little effect on the sliding characteristics compared with the nail-plate angle and the engagement of the screw in the barrel.
我们研究了螺钉 - 钢板角度对四种常用不锈钢和钴铬钼加压髋螺钉滑动特性和卡塞可能性的影响。在每个装置中测量了这些合金的实际滑动摩擦系数。在代表130度和150度螺钉 - 钢板角度的静态平衡条件下，通过改变拧入套筒的螺钉长度，还确定了克服静摩擦力所需的螺钉上的力。对于130度加载配置，对于所有四种螺钉类型，该力均显著（p <0.001）高于150度加载配置所需的力。每种材料的实际摩擦系数相对恒定，尽管发现由于螺钉类型之间设计差异存在轻微变化。表观摩擦系数（滑动力与法向力之比）与从套筒伸出的螺钉长度之间存在正相关（p <0.01）。在130度测试中，所有未完全拧入套筒的不锈钢螺钉都会卡塞。150度测试均未产生卡塞，并且钴铬钼螺钉在130度或150度测试中均未卡塞。通过扫描电子显微镜检查卡塞的装置显示，螺钉和套筒的上表面均出现擦伤。
了解有助于髋螺钉滑动的条件有助于确保其正确使用。钉 - 板角度越高，越容易打入髋固定装置，从而在骨折部位实现骨压紧和稳定性。通过使螺钉最大程度地拧入套筒，可降低滑动髋螺钉卡塞的可能性。与钉 - 板角度和螺钉在套筒中的拧入情况相比，滑动髋固定装置的材料和设计差异对滑动特性的影响相对较小。
