Background

Working length have been reported to affect the plate stress and fixation stiffness. However, the results of previous studies have been controversial. The present study was to determine working length effects on different locations of femoral bone gap.

Methods

Five composite femurs with wide bone gaps at five levels (G1, 2, 3, 5, and 7), were fixed with locking plates. G1-3, G5 and G7 represented gaps at distal femur, distal-middle femur and middle femur respectively. Strain gauges were applied near the screw holes. The plate-bone constructs were loaded through a hemicylinder on the femoral head with total constraints at the distal femur. The micro-strains, axial stiffness and interfragmentary motions were recorded. Then the locking screws were removed one by one and the tests were re-run. The working length effects were compared and correlated.

Findings

In distal femurs (G1-3), long working length was negatively correlated with the highest strains (r = −0.97, −0.95 and − 0.95, p < 0.01) and axial stiffness (r = −1, −0.96 and −0.99, p < 0.01). In distal-middle femurs (G5), as the working length increased, the highest strain decreased initially and then increased (r = 0.81, p = 0.026) and the axial stiffness decreased (r = −0.98, p < 0.01). In middle femurs (G7), the highest strain and gap motions were much higher than that in the other groups and not significantly correlated with the working length change.

Interpretation

Long working length could reduce the highest plate strain in distal femurs, but had no significant effects in middle femurs. The working length effects were markedly affected by the loading and boundary conditions.

中文翻译：

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股骨远端和中段骨折锁定钢板中相反的工作长度影响-生物力学研究

背景

据报道工作长度会影响板的应力和固定刚度。但是，先前的研究结果一直存在争议。本研究旨在确定工作长度对股骨骨间隙不同位置的影响。

方法

用锁定板固定五个具有五个水平（G1、2、3、5和7）的宽骨间隙的复合股骨。G1-3，G5和G7分别代表股骨远端，股骨远端-中间和中间股骨的间隙。在螺纹孔附近施加应变计。将板骨构造物通过半圆柱加载到股骨头上，并在股骨远端进行约束。记录了微应变，轴向刚度和片段间运动。然后一一卸下固定螺钉，然后重新进行测试。工作长度的影响进行了比较和关联。

发现

在股骨远端（G1-3），长工作时间与最高应变（r  = -0.97，-0.95和-0.95，p  <0.01）和轴向刚度（r  = -1，-0.96和-0.99 ）呈负相关，p  <0.01）。在中远端股骨（G5）中，随着工作长度的增加，最高应变开始下降，然后上升（r  = 0.81，p  = 0.026），轴向刚度下降（r  = -0.98，p  <0.01）。在股骨中段（G7），最高的应变和间隙运动远高于其他组，并且与工作长度的变化没有显着相关性。

解释

较长的工作时间可以减少股骨远端的最高钢板应变，但对股骨中段没有明显影响。工作长度的影响明显受载荷和边界条件的影响。