Kirschner Wires: insertion techniques and bone related consequences

Abstract

The Kirschner (K-) wire was first introduced in 1909 by Martin Kirschner. This is a thin unthreaded wire of surgical steel with a diameter of up to three millimeters and a selection of different tips. The use of K-wires is often promoted as a simple technique because of its easy placement, cost-effectiveness and safety. The most important advantage of K-wires is the ability for percutaneous placement and is especially prevalent in hand surgery as the bones of the hand have suitable access for wire placement. The quality of K-wire fixation after drilling depends on several factors like drilling speed, insertion time and force, irrigation, K-wire diameter and tip configuration. These factors can lead to temperature elevation and subsequent disappearance of osteocytes in the immediate surrounding of the K-wire. In order to find out if hammering K-wires could prevent or lessen the amount of damage to the bone caused by high speed drilling, we analysed the insertion time, degree of temperature development, degree of fixation, histology, the influence of irrigation and the effect of K-wires with different tips. It became clear that there exists a positive correlation between the distance of the empty osteocyte lacunae and the drilling time. In daily practice this means the longer the drilling time, the longer the distance of empty osteocytes surrounding the pin track, i.e. the more osteonecrosis resulting in preterm loosening and pin track infections. We further found that reduced drilling times may prevent the disappearance of osteocytes in the absence of cooling. The use of the pneumatic hammer however prevents for thermal related damage i.e. osteonecrosis without the use of irrigation due to the shorter insertion time and lower temperature elevation compared to the high speed drill. This was confirmed by the osteocytes which were still in the lacunae surrounding the pin track after hammering K-wires. Finally we showed that the fixation of hammered K-wires is at least as good as the drilled ones, especially concerning the hammered sharp trocar tip K-wires. Despite the promising results mentioned above, there does not exist a perfect hammering device at the present time. The pneumatic hammering devices we used in our experimental setting were effective but had some serious disadvantages, like microfractures in the cortex. In order to use the pneumatic hammer in a clinical setting the device has to be further improved and adapted. In conclusion, the pneumatic hammer seems to be an effective K-wire insertion technique. The in vitro and in vivo results we described are promising because they are at least equal and often better compared to drilling concerning insertion time, survival of the osteocytes, heat generation and fixation. However, the golden standard for insertion of K-wires at this moment is still the high speed drill. But more extensive research and the development of a perfect hammering device might probably change the second century of K-wire insertion in the near future.