Navigated anterior approach to the upper cervical spine after occipitocervical fusion
Technical note. To introduce the application of navigation system with software for brain surgery to the upper cervical spine of patients who have previously had occipitocervical (O-C) fusion. The anterior approach to the spine using a navigation system with software for spine surgery is difficult because the registration tends to be inaccurate. However, after O-C fusion, the upper cervical spine is considered part of the skull, and a navigation system with software for brain surgery in which the registration is performed using the head with several markers attached to it can be applied. Three patients with previous O-C fusion-2 with upper cervical chordoma and 1 with a disc herniation at C2/3-were treated using this technique. In the first case, with a huge retropharyngeal C1 chordoma, this technique was very helpful in blindly dissecting the nonvisible parts of the tumor. In the second case, with a C2 chordoma, the vertebral arteries were successfully exposed under the guidance of the navigation system at both primary and revision surgery. In the third case, with disc herniation at C2/3, the herniated disc was removed successfully with the totally fused spine. In this application, computed tomography images can be merged freely with magnetic resonance images, which is helpful to clarify the soft tissues such as tumor, disc herniation, or the dural tube. This technique greatly supports surgeons inexperienced in the anterior approach to the upper cervical spine or surgeons at revision surgery who may be lost in and daunted by an unfamiliar operation field surrounded by important structures. Although an anterior approach to the upper cervical spine in the patient with O-C fusion may rarely be required, this application should be considered.