Drilling, not a benign procedure: laboratory simulation of true drilling depth. 
Drilling is an integral part of almost all boney operations.  Various anatomical structures coursing close to the bone are at risk if the drill bit projects beyond the far cortex.  Aim of this study was to evaluate and quantify the depth to which surgeons over drill beyond the far cortex.  During an AO course 153 (41 females, 112 males) surgeons and physicians were invited to participate in this study.  Each participant performed 3 bicortical drillings on generic artificial bone.  Polystyrene plates were mounted on the far cortex of the bone to allow for exact measurement of the over penetration of the drill bit.  A total of 462 bicortical drilling manoeuvres were analysed.  The average projection of the drill bit beyond the far cortex was 6.31 mm.  No significant statistical correlation was noted between the specialty or the experience of the participant and depth of over drilling.  It is remarkable that the mean and the range of far cortex over-penetration was quite similar amongst surgeons of differing grades and experience.  The results of this study should return to mind to pay attention when drilling particularly in anatomical sites where nerve and vessels coursing close to the far cortex.