[A surgical micromanipulator in ear surgery: potential and comparison to freehand preparation]

Surgical accuracy in microscopic ear surgery is reduced by limited access and tremor. At this point a micromanipulator could have a positive influence. The goal of the study was: 1. To develop a system that would enable measurements of accuracy, time and precision during a manual approach to the middle ear 2. To apply a manipulator that can easily be a compact part of the regular setup in ear surgery 3. To compare the manual results critically considering accuracy and tremor reduction and to compare these results with those of a manipulator A manipulator in ear surgery does not need to be a highly complex structure with force feedback and multiple degrees of freedom. The surgeon's preparation in middle ear surgery is most of the time straight without potentially applying the 15 degrees of freedom the human hand can offer. The micromanipulator in this study was developed in order to serve as a compact, teleoperated instrument without limiting the surgeon's dexterity. The use of standard instruments facilitates the integration of the system in existing surgical procedures and sterilisation concepts.

Ten head and neck surgeons simulated an approach to the stapedial footplate on a modified 3D cast of a realistic human skull in an experimental OR. A perforator was moved to a reference point on the stapedial footplate. The movements were detected by means of an image acquisition system. Each trial was repeated more than 200 times, aiming both manually and with the aid of a micromanipulator (> 4,000 measurements).

Accuracy for the manual and micromanipulator approach revealed no considerable differences. In absolute terms, the manual approach was more accurate. However, the learning curves indicated a stronger decrease in deviation when the micromanipulator was used and also less deviation in scatter plots. At the beginning, the time required for pointing increased when using the micromanipulator, but decreased to a greater extent in the course of the trial when compared to the manual approach. The work strain was distinctively lower when the micromanipulator was applied.

The micromanipulator gave evidence of a stronger effect as regards individual improvement in accuracy and time span. The micromanipulator shows potential for improvements in accuracy as well as compensation for poor ergonomics.