110 HAND (2009) 4:108–112 Fig. 2 Temperature elevation during K-wire insertion at 0.5 mm from the K-wire insertion site. Mean value and standard error of mean of the temperature elevation during K-wire insertion. The asterisk (*) indicates statistical significance, p<0.01 (Bonferroni Multiple Comparisons). significantly lower compared to drilling without irrigation (Fig. 2). Hammering further, resulted in a significantly shorter insertion time compared to drilling without irrigation and drilling with irrigation. There was, however, no significant difference between drilling with and drilling without irrigation (Fig. 3). The extraction force of the K-wires inserted by pneumatic hammering and drilling with irrigation was not found to be significantly different. K-wires inserted without irrigation showed significant lower extraction force compared to hammering (Fig. 4). We had to exclude two measurements from the hammering group. The K-wires stuck in the anterior cortex, where after, it was not possible to hammer the K-wire through the posterior cortex. Fig. 3 K-wire insertion time. Mean value and standard error of mean of the Kirschner wire insertion time. The asterisk (*) indicates statistical significance, p <0.01 (Bonferroni Multiple Comparisons). Fig. 4 Extraction force needed to remove the K-wire directly after insertion. Mean value and standard error of mean of the extraction force needed to remove the Kirschner wire. The asterisk (*) indicates statistical significance, p <0.05 (Bonferroni Multiple Comparisons). Discussion Our experiment showed the lowest temperature rise during drilling with irrigation compared to drilling without irrigation and hammering. This can be explained because the denuded cortex was exposed directly to the constantly provided cooling agent at the point of penetration resulting in an optimal irrigation effect. The temperature increase with hammering was not as low as drilling with irrigation, but was significantly lower compared to the temperatures reached with drilling without irrigation. These results confirm the previously reported findings of Zegunis et al., who showed temperatures of 54°C for drilling and 34°C for hammering [25]. The significant lower maximum temper- atures reached using the hammering technique can result in less thermal damage during K-wire insertion without the need for irrigation. In our experiment, we standardized the insertion force for both techniques. Half a kilogram was found to be the optimal weight for forwards movement of the pneumatic hammer. This weight, however, was relatively low for the forward movement of the drill, resulting in relatively long insertion times. Although one would think that this also can lead to an increase in temperature, similar findings were seen in three previous experiments. Zegunis et al. showed a difference of 9 s, needing 41 and 50 s for hammering and drilling, respectively [25]. The measured temperatures were 34°C for hammering and 54°C for drilling. They did not mention standardizing the insertion force. Wassenaar et al. used a variable insertion force of 7 N and 16.9 ± 4.9 N for hammering and drilling respectively, this resulted in insertion times of 18.4 s for hammering and 73.6 s for drilling [23]. Finally, our research group used weights of 1.0 and 1.5 kg for hammering and drilling, respectively. This resulted in insertion times of 13 s for hammering and 142 s for drilling [11]. In our present research using K-wires with