Accuracy study of a new assistance system under the application of Navigated Control® for manual milling on a head phantom

In this article, a technical study of a new assistance system to support surgeons in milling on the temporal bone is presented. In particular, the overall accuracy of a new assistance system was investigated experimentally under conditions close to surgical practice. For the experiment, the assistance system has been used with its associated navigation system for ear-nose-throat (ENT) surgery. A specially constructed head phantom allowed the implementation of reproducible experiments. Thereby, N = 10 specimens were milled by three test persons without medical knowledge and the distance between points on the milled surface and the security zone around the planned nerve for each specimen were calculated. The result was as follows: None of the 10 milled specimens overlapped more than 2mm with the security zone, the average distances to the planned surface of the security zone for each specimen were between 0.01mm and 2.23mm, and the corresponding standard deviations varied from 0.41mm to 1.17mm. But it also shows some variation in averages and standard deviations and it was often too little material removed. This deviation is probably caused by the patient registration and the tool calibration.