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

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

Background

This study aimed to discover the most stable outcome among different Kirschner-wire (K-wire) configurations for fixation of a lateral condyle fracture (Milch type II) in different loads of stress by using finite element analyses (FEA).

Methods

The right humerus of a 6-year-old boy with a lateral condyle fracture (Milch type II), was modelled with a computer aided engineering. Using FEA, peak von Mises stress and stiffness were evaluated first for a single K-wire fixation by varying the angle (0, 5, 10, 15, 20, 25, 30 degrees). Then, based on the single K-wire result, assessment of peak von Mises stress and stiffness were evaluated via FEA for two- or three-wire fixation under various configurations (two convergent, two parallel, three divergent).

Results

Single K-wire fixation by 5 and 25 degrees had the lowest peak von Mises stress. The fracture site showed higher stiffness at 0, 5 and 15 degrees. Considering the collected results and clinical situation, 5 degree K-wire was selected for the FEA of multiple K-wire fixation. For multiple K-wire fixation, three divergent (5–20-35 degrees) K-wires showed better stability, both in peak von Mises stress and stiffness, than any two-K-wire configurations. Among two K-wire fixations, two divergent (5–50 degrees) K-wires provided the lowest von Mises stress in varus and valgus while two divergent (5–65 degrees) K-wires showed better results in flexion, extension, internal and external rotation, and both configurations showed similar results in stiffness.

Conclusions

We successfully created a paediatric lateral condyle fracture (Milch type II) model which was used to conduct FEA on different K-wire configurations to achieve stability of the fracture. Our results show that an initial K-wire inserted at 5 degrees, followed by the insertion of a second divergent wire at either 45 or 60 degrees provides the most stability in two K-wire fixations in this type of fracture repair.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12891-022-05897-3.

Intraoperative Kirschner Wire Breakage in a Pediatric Supracondylar Humerus Fracture

A displaced supracondylar humerus in a child is usually treated with closed reduction and percutaneous Kirschner (K)-wire fixation. The procedure is straightforward and usually yields excellent outcomes. In general, intraoperative complications are uncommon and intraoperative complications related to K-wires are exceedingly rare. We present the case of intraoperative K-wire breakage while performing closed reduction and K-wire fixation for a pediatric supracondylar humerus fracture. This unusual complication occurred while drilling through the medial cortex and the broken end of the K-wire disappeared under the skin in the cartilaginous distal humerus. The broken wire was removed by making an incision over the broken end. This report serves as a reminder to follow principles of drilling and avoid K-wire-related complications while performing percutaneous fixation of the pediatric supracondylar humerus fracture.

How to Prevent K-Wire Bounce in Oblique Supracondylar Humerus Fractures

Supracondylar humerus fractures with an obliquely oriented fracture pattern can pose a clinical challenge in obtaining adequate fixation. Traditionally, 1.6-mm Kirchner wires are used for fracture fixation when pinning pediatric supracondylar humerus fractures. However, when pinning across obliquely oriented fractures, the angle of pin inclination may increase to the point where the 1.6-mm k-wire cannot penetrate the far cortex. We have found that, when pinning oblique supracondylar humerus fractures, utilization of a 2.0-mm k-wire can assist the surgeon in obtaining bicortical purchase. We present a cadaveric study demonstrating the maximal angles at which both 1.6-mm and 2.0-mm k-wires will penetrate the far cortex. This technical trick can give surgeons a relatively simple solution to treat these difficult fractures.