Clinical Application of a New Dental Reference System for Computer Assisted Surgery at the Lateral Skull Base

Objective: The safest method for a reliable registration on the lateral skull base is the placement of fiducial markers into the patient’s bone by screws. An alternative method is the use of a resin splint that is fixated to the maxillary dentition, which carries the fiducial markers. Then the invasive fixation using bone screws becomes unnecessary. The aim of this study was to evaluate the accuracy of a new dental reference array (DRA). Methods: The DRA was initially tested in laboratory settings and was then applied to ten patients with surgery on the lateral skull base. An individual formed maxillary dental splint was created out of polymethylmethacrylate. The Vector Vision compact® (BrainLAB, Germany) navigation system measured the deviation on several target markers at the lateral skull base in one phantom trial, one cadaver skull and ten patients. Results: The DRA was perfectly adjusted to the phantom. The average deviation was only 0.5mm. The average deviation on four different target markers in the cadaver trial was 0.6 mm. In five patients the accuracy was acceptable (<1.2mm). But in the other five cases the deviation was more than 10mm due to different problems which were analysed carefully. Discussion: The DRA could resolve the problem of invasive marker fixation with little additional effort and cost. However, the successful use depends on the individually formed dental splint, which has to be perfectly adjusted to the maxilla, because the additional weight of the extraoral part acts as a lever and may dislocate. It is essential that the splint does not cant; the reference extension must not graze the skin of the patient; during surgery no coverage should pull on the DRA, otherwise the repositioning is not accurate. When avoiding all this, the accuracy of the dental reference array is sufficient for image-guided surgery of the lateral skull base.