Percutaneous placement of posterior cervical screws using three-dimensional fluoroscopy

Study Design. The placement of percutaneous posterior cervical screws using three-dimensional fluoroscopic guidance was performed in intact human cadaver specimens. Objectives. To determine the accuracy and feasibility of placing entirely percutaneous posterior cervical screws using a novel form of spinal image guidance. Summary of Background Data. Conventional image guidance has been shown to increase the accuracy of many open cervical instrumentation procedures. There are presently no published studies reporting this novel method for guiding the percutaneous placement of posterior cervical screws. Methods. An isocentric C-arm was used to obtain CT images of three intact cadaver specimens. A percutaneous dynamic reference array was attached to the C2 spinous process of each specimen. Light-emitting diodes attached to the C-arm were tracked with an electro-optical camera. The image data set was then transferred to the image-guided workstation, which performed an automated registration. Using the workstation, trajectories were planned for bilateral C1-C2 transarticular, C3-C6 lateral mass, and C7 pedicle screw placement. Through 1.5-cm incisions, a drill guide fitted with light-emitting diodes was used for sequential, image-guided drilling, tapping, and placement of cannulated 4.0 mm screws at each level. Postprocedure, thin-cut CT scanning was used to determine the accuracy of screw placement. Results. A total of 41 of 42 percutaneous screws (97.6%) were accurately placed. All of the transarticular atlantoaxial and subaxial lateral mass screws showed no evidence of foramen transversarium, neural foramen, or facet joint violation. One of the C7 pedicle screws had a minor cortical wall violation. Conclusion. This study demonstrates the feasibility of placing percutaneous posterior cervical screws. Three-dimensional fluoroscopy appears to enable highly accurate, percutaneous three-dimensional cervical spine navigation.