Forty-five-degree or higher insertion angles are required to penetrate the opposite cortex in bicortical applications of Kirschner wires: an in vitro study on sheep bones

Abstract

Purpose Slippage of the wires over the opposite cortex from the endosteal side is frequent and can lead to insufficient stability. This in vitro biomechanical study was planned to investigate the angle of wire insertion that leads to trans cortex perforation. Methods Long bones of sheep were cut longitudinally into two pieces and half bones were stabilised on a frame. Three orthopaedic surgeons performed the experiment using ten wires of four different diameters at two different drilling speeds. Each wire was introduced from the endosteal side at angles starting at 30°in 5°i ncrements until perforation. When perforation was achieved, the angle was recorded. To determinate the critical angle of perforation, receiver operating characteristic (ROC) curve analyses was performed. Two-way factorial analysis of variance (ANOVA) and KruskalWallis tests were used for statistical comparisons. Results Kirschner-wire insertion angles of ≥45°provided perforation with a percentage of 83.9 %. Wire diameter, drilling speed and surgeon variables had no effect on perforation angles (p>0.05).Conclusion If preoperative evaluation of fractures to be fixed by K wires reveals the need for oblique wire insertion angle <45°, a standard trocar-tip K wire application would lead to slippage of the wire tip on the endosteal surface of the opposite cortex. According to this study, the operative plan should be changed if such obliquity of the K wire is mandatory during bicortical applications.

Finite element analyses of lateral condyle fracture fixation in paediatrics regarding configuration of Kirschner-wire

“…Cadaver investigations of two divergent 60-degree K-wire configurations showed that it failed to obtain bicortical purchase and bounced off the far cortex [39]. The tendency of bending and skidding over the opposite cortex was observed, resulting in the replacement of K-wire with a thicker fixation material [40]. Although 3 wire fixation showed the best stability, occasionally, fixation of 3 wires can encounter technical difficulty in the real clinical situation because 6 years old children have limited bone area.…”

Intraoperative Kirschner Wire Breakage in a Pediatric Supracondylar Humerus Fracture

“…Also during drilling, if the angle is kept more than 45° measuring from the horizontal articular surface (also called the minimal critical angle), it avoids slippage of the wires over the opposite cortex. The study observed that wires perforate easily and pass opposite cortices when inserted at ≥45° [ 10 ]. Lobst et al have reported that when a smaller diameter wire was used at lower inclinations, the angle of contact with the far cortex may be large causing the wire not to penetrate the cortex and leading to slippage of the wire tip over the endosteal surface of the opposite cortex.…”