Background

Screws are the most commonly inserted orthopaedic implants. However, several variables related to screw insertion and tightening have not been evaluated. This study aimed firstly to assess the effect of insertion variables on screw tightness, secondly to improve methodologies used by researchers when testing screw insertion techniques and thirdly to assess for any learning or fatigue effects when inserting screws.

Methods

Two surgeons tightened a total of 2280 non-locking, 3.5 mm cortical screws, with 120 screws inserted to what they felt to be optimum tightness whilst varying each of the following factors: different screwdrivers for measuring torque, screwdriver orientation, gloves usage, dominant/non-dominant hand usage, awareness to the applied torque (blinded, unblinded and re-blinded), four bone densities and seven cortical thicknesses. Screws were tightened to failure to determine stripping torque, which was used to calculate screw tightness – ratio between stopping and stripping torque.

Findings

Screw tightness increased with glove usage, being blinded to the applied torque and with denser artificial bone and with thinner cortices. Considering all the insertions performed, the two surgeons stopped tightening screws at difference values of tightness ((77% versus 66% (p < 0.001)). A learning effect was observed with some parameters including sterile gloves usage and non-dominant hand application.

Interpretation

Different insertion conditions frequently changed screw tightness for both surgeons. Given the influence of screw tightness on fixation stability, the variables investigated within this study should be carefully reported and controlled when performing biomechanical testing alongside practicing screw insertion under different conditions during surgical training.

中文翻译：

---

非锁定螺钉插入条件的变化会导致无法预测的变化，从而导致固定紧密度和脱模率下降

背景

螺钉是最常见的骨科植入物。但是，尚未评估与螺钉插入和拧紧有关的几个变量。这项研究的目的首先是评估插入变量对螺钉紧固度的影响，其次是改进研究人员在测试螺钉插入技术时使用的方法，其次是评估在插入螺钉时是否有学习或疲劳影响。

方法

两名外科医生总共拧紧了2280个3.5 mm的非锁定皮质螺钉，并在他们认为最佳的紧固度下插入了120个螺钉，同时改变了以下每个因素：用于测量扭矩的不同螺丝刀，螺丝起子的方向，手套的使用，主要/非主要的手部使用情况，对施加的扭矩（盲目，非盲目和重新盲目）的意识，四个骨密度和七个皮质厚度。将螺钉拧紧至无法确定剥脱扭矩，该扭矩用于计算螺钉的紧固度-止动扭矩与剥脱扭矩之间的比率。

发现

螺丝紧度随着手套的使用，对施加的扭矩不敏感，人造骨密度更高和皮层更薄而增加。考虑到所有插入操作，两位医生以不同的紧度值（（77％比66％，p  <0.001））停止拧紧螺丝，并在某些参数下观察到了学习效果，包括无菌手套的使用和不占优势的手部使用。

解释

不同的插入条件经常改变两位医生的螺钉紧固度。考虑到螺丝紧固度对固定稳定性的影响，在进行生物力学测试以及在外科手术训练期间在不同条件下练习螺丝插入时，应仔细报告和控制本研究中研究的变量。