Evaluation of the efficiency of the C-ring aiming guide for atlantoaxial transarticular screw fixation in toy breed dogs

The goal of the present study was to evaluate the efficiency and safety of the C-ring aiming guide for the atlantoaxial transarticular screw fixation technique in toy breed dogs. Twenty-one adult canine cadavers of toy breed dogs were used in this study. The left and right sides of the cervical vertebrae were randomly assigned to two implant insertion groups: a C-ring aiming guide group and a drill guide group. A 1.2-mm Kirschner wire was inserted into each side by using either a C-ring aiming guide or a drill guide. CT scans were performed before and after surgery. The optimal safe implantation corridor angle and length, the implant insertion angle and length, the implant insertion time and the proportion of the insertion corridor to the optimal corridor were evaluated. Violations to the alar foramen and the vertebral canal also were evaluated. The implant insertion time was twice as long as that observed in the aiming guide group (P < 0.05). The proportion of the insertion angle and length to the optimal angle were not significantly different between groups (P > 0.05). With respect to precision, there was a trend toward less variability in the aiming guide group; however, this difference was not significant (P = 0.09). The violation of the alar foramen was significantly lower in the aiming guide group than in the drill guide group (P < 0.05). Violation to the vertebral canal was detected in one cadaver in the drill guide group but did not occur in the aiming guide group. The use of a C-ring aiming guide was associated with less damage to the alar foramen and the vertebral canal during atlantoaxial transarticular screw fixation in toy breed dogs.