Combining pedicle screw stimulation with spinal navigation, a protocol to maximize the safety of neural elements and minimize radiation exposure in thoracolumbar spine instrumentation.

ABSTRACT

PURPOSE: The O-arm-based navigation increases the accuracy of pedicle screw positioning and offers the possibility of performing a 3D scan before wound closure. However, repeating the 3D scan exposes the patient to additional radiation. We combined O-arm navigation with pedicle screw (PS) stimulation followed by a 3D scan to evaluate their accuracy and aimed for the creation of a protocol that maximizes the safety and minimizes radiation. METHODS: Patients had pedicle screws insertion using O-arm spinal navigation, then had PS triggered electromyography (EMG), and finally a 3D scan to evaluate the accuracy of screw position. RESULTS: 447 screws were inserted in 71 patients. In 10 patients, 11 screws needed repositioning. Comparing results of PS triggered EMG responses to the 3D scan, we found (a) negative stimulation response with negative 3D scan findings, corresponding to 432 acceptable screw position (96.6 %) in 58 patients (81.7 %). In these cases, the redo 3D scan could be avoided. (b) Positive stimulation response with positive 3D scan findings, corresponding to 7 unacceptable screw position (1.5 %) in 6 patients (8.4 %). In these cases, PS stimulation detected malpositioned screws that would be missed without a redo 3D scan. CONCLUSION: We propose a protocol of routinely performing PS stimulation after screw insertion using spinal navigation. In case of positive stimulation, a 3D scan must be performed to rule out a probable screw mal position (6 patients 8.4 %). However, in case of negative stimulation, redo 3D scan can be avoided in 81.7 % of patients.