Abstract
Introduction
There are various choices to fix up Atlanto-Axial dislocation (AAD) and Basilar invagination (BI), it may be Posterior only, Anterior only or Combined. Many surgeons refrain from “posterior only” approach of C1-C2 distraction (as described by Atul Goel and Lahiri) because of the fear of Vertebral artery (VA) injury and it's poorly understood course between C1, C2, and Occipital condyles. We describe details of preoperative work and subsequently adopted, customized surgical plans, as per VA configuration to distract & fix the C1-C2 joint to achieve reduction in AAD and BI without harming the Vertebral artery. This case series covers most of the variations of VA around C1-C2 for learning purpose. After seeing this work up, many surgeons may allay their anxieties and take up this single stage corrective measure to achieve correction of deformities in cases of AAD & BI. In the due course author will also explain different variations of Vertebral artery not only in different individuals, but also in same subject on either sides. We describe the adaptive surgical methods taken based on these data to avoid injury to VA, and still achieve a firm distraction and fixation at C1-C2 with this single stage. The technique can thus be extrapolated in various other cases of AAD and BI with hardly any exception.
Material and Methods
Three serial patients with an established diagnosis of Atlanto-axial dislocation and Basilar invagination are described. All three were evaluated with 3-D MPR CT with vertebral artery angiography (CTA-VA), and MRI at Cervico-medullary junction (MRI-CMJ). The VA in one subject was going through pedicle on one side and in another subject, it was going around the C1-C2 facet joint, while in another case it was entirely intra-spinal. The radiological evaluation was done in both pre and post operative period to describe anomalies of CVJ, different courses of VA and vectors thus used for potential instrumentation. Postoperative scans were used to see adequacy of fixation.
Results
There was a clear evidence of highly variable course in VA of all three subjects. There were different courses in right and left VAs as well, commanding different choices of instrumentation on both sides in a single individual. All patients achieved reduction of AAD & BI and there was no injury to the vascular structure in question. They all improved in clinical signs and symptoms in the due course.
Conclusion
Authors conclude that it's mandatory to subject all patients to CT angiography in an order to view the Vertebral artery course wrt C1-C2 facets, which is not only variable in different individuals but also, on both sides in same individual, hence even in a single patient we may need different instrumentation to achieve the same goal. The authors also conclude that instrumentation at C1-C2 without CTA-VA is not only dangerous but can be fatal as well, hence instrumentation done without the above mentioned study should be considered a mandatory practice in the safest interest of patients and to achieve optimum and customized instrumentation.