Stimulation of Pedicle Screws with Diathermy: Is it a Viable Option to Detect Breaches?

Background: To analyse use of monopolar diathermy stimulation of pedicle screws in order to improve breach detection. Methods: Prospective single-blind study. Patients with preoperative neurological deficit excluded. Pedicle screws inserted freehand into thoracic and lumbar spine. Monopolar diathermy in “cutting” mode at half the strength used for actual cutting purpose was used to stimulate the tap in situ, followed by stimulation of the screw if satisfactory. Elicitation of twitching of local paraspinal muscles and/ or lower limb muscles was considered a positive response, suggestive of pedicle breach. Appropriate revision of screw track was done accordingly. Intraoperative C-arm imaging and postoperative CT scan [blinded evaluation] was done for further verification in all cases. Meticulous clinical assessment was done in the immediate postoperative period to rule out any kind of neurological deterioration. Results: Seventy-eight consecutive patients undergoing surgical stabilization for varied indications such as trauma [n=15], spondylolisthesis [n=53], spinal infection [n=4] and spinal deformity [n=6] were included in the study. Mean age was 42.3+12.3 years. 468 pedicle screws were inserted. Eleven true positive and three false positive cases were noted. Nine false negative cases were detected on postoperative CT. These breaches were however, <2 mm and asymptomatic. Considering this, this method demonstrated sensitivity, specificity, positive predictive value and negative predictive value of 97.63%, 100%, 100% and 21.43%, respectively. No patient had any adverse effect related to the diathermy stimulation. Conclusions and Clinical Relevance: Diathermy stimulation of pedicle screws inserted into spine in conjunction with screw track probing and intraoperative C-arm imaging is a viable option to improve accuracy of screw placement, particularly in a setup where no other advanced electrophysiological tests exist. Level of Evidence: II [diagnostic studies]