Placement of endosteal implants in the zygoma after maxillectomy: A cadaver study using surgical navigation

Endosteal implants facilitate obturator prosthesis fixation in tumor patien ts after maxillectomy. Previous clinical studies have shown, however, that the survival of implants placed into available bone after maxillectomy is g enerally poor. Nevertheless, implants positioned optimally in residual zygo matic bone provide superior stability from a biomechanical point of view. I n a pilot study, the authors assessed the precision of VISIT, a computer-ai ded surgical navigation system dedicated to the placement of endosteal impl ants in the maxillofacial area. Five cadaver specimens underwent hemimaxill ectomy. The cadaver head was matched to a preoperative high-resolution comp uted tomograph by using implanted surgical microscrews as fiducial markers. The position of a surgical drill relative to the cadaver head was determin ed with an optical tracking system. Implants were place into the zygomatic arch, where maximum bone volume was available. The results were assessed us ing tests for localization accuracy and postoperative computed tomographic scans of the cadaver specimens. The localization accuracy of landmarks on l the bony skull was 0.6 +/- 0.3 mm (average +/- SD), as determined with a 5- df pointer probe; the localization accuracy of the tip of the implant burr was 1.7 +/- 0.4 rnm. The accuracy of the implant position compared with the planned position was 1.3 +/- 0.8 mm for the external perforation of the zy goma and 1.7 +/- 1.3 mm for the internal perforation. Eight of 10 implants were inserted with maximal contact to surrounding bone, and two implants we re located unfavorably. Reliable placement of implants in this region is di fficult to achieve. The technique described in this article may be very hel pful in the management of patients after maxillary resection with poor supp ort for obturator prostheses.