Image-injected frameless stereotactic approach to the anterior craniovertebral junction.

Transoral odontoidectomy is often performed in the treatment of cervicomedullary junction disease. The operating microscope is frequently used to improve visualization in this narrow field of view. In the setting of complex anatomy or surgical revision the authors hypothesized that combining frameless stereotactic technique with intraoperative microscopy would improve the ability to visualize and identify intraoperative anatomy. In addition they believed that the ability to visualize the targeted region directly in the operating microscope "image injection" would be of particular interest in this setting, provided that sufficient accuracy for use could be obtained in the registration process. The authors assessed the efficacy of this approach in a cadaveric model and obtained sufficient accuracy to warrant use in the operating room. This technique was applied in the surgical management of a 56-year-old woman with rheumatoid arthritis who had undergone a previous decompressive transoral procedure. Subsequently she suffered progressive deterioration and was found to have residual bony compression of the anterior cervicomedullary junction. The authors performed decompressive surgery and obtained satisfactory results by using the image-injected technique, and the patient experienced subsequent clinical improvement. The authors conclude that the image-injected frameless stereotactic technique is of potential benefit, particularly in the narrow window of approach of the transoral odontoidectomy.