Neuromonitoring with pulse-train stimulation for implantation of thoracic pedicle screws: a blinded and randomized clinical study. Part 2. The role of feedback

Abstract

Object The authors have reported in Part 1 of this study on a novel neuromonitoring test for the prevention of medial malpositioning of thoracic pedicle screws. In the present paper they examine the impact of providing the results of the test as intraoperative feedback to the surgical team. Methods This is the second part of a 2-part report of a prospective, blinded and randomized neuromonitoring study designed to lower the incidence of medially malpositioned thoracic pedicle screws. Details of the neuromonitoring technique and data supporting the alarm criteria used are contained in the companion article (Part 1). For the majority of pedicle screw placements, intraoperative test results were withheld from the study team (that is, the team members were blinded to the test results). However, for a limited number of pedicle sites the authors provided one of 2 forms of testing feedback to the surgical team: 1) “break the blind” feedback, if testing suggested that screw placement would result in direct contact between screw and the dura mater; and 2) “planned” feedback, beginning during the later stages of the study and provided for 50% of pedicle sites. Feedback gave the surgeon the opportunity to adjust the trajectory that the screw would ultimately take within the pedicle. The final screw position relative to the pedicle's medial wall for all sites in which feedback was withheld from the surgical team was compared with the screw position for those sites in which either form of feedback (“break the blind” or “planned”) was provided to and acted upon by the surgical team. Results Of the 820 pedicle tracks tested among the 71 surgical cases included in this study, a total of 684 were operated upon without any form of feedback. Planned feedback was provided for an additional 107 pedicle tracks, of which 15 triggered an intraoperative alarm (evoked electromyogram response in leg muscles to stimulus intensity ≤ 10 mA) leading to a warning to the surgical team of a medially biased pedicle track. Finally, the blind was broken 29 times, in each case when testing revealed a particularly low threshold (≤ 4 mA) for evoked responses in leg muscles when stimulating along the pedicle track with the ball-tipped probe. As detailed in the companion paper to this one, there were 32 screws with threads lying at least 2 mm medial to the pedicle wall. In all 32 instances (100%), either these screws were in the “no feedback” category (n = 29) or they were in a feedback category but the surgeon elected to not revise the pedicle-track trajectory. Two patients returned to the operating room for revision of screw placements because the screws were encroaching upon the central canal; the pedicle tracks for these screws had been in the “no feedback” category. Conclusions This is the first blinded and randomized study to prove that implementing a novel neuromonitoring strategy during placement of thoracic pedicle screws can significantly reduce the incidence of clinically relevant thoracic pedicle screw medial malpositioning.

Accuracy of robot-assisted pedicle screw insertion in adolescent idiopathic scoliosis: is triggered electromyographic pedicle screw stimulation necessary?

“…Neurologic complications of spine deformity surgery in pediatric patients are rare, but potentially devastating (1)(2)(3). Numerous strategies have been developed and implemented to help reduce the incidence of these complications by ensuring adequate pedicle screw placement and providing early recognition of changes in neurophysiology (4)(5)(6)(7)(8). Neuromonitoring has become the standard of care with regard to monitoring for changes in neurophysiology, with numerous modalities by which to monitor the sensory and motor pathways of the nervous system (1,4,7,9).…”

Neuromonitoring with pulse-train stimulation for implantation of thoracic pedicle screws: a blinded and randomized clinical study. Part 1. Methods and alarm criteria

“…That is, knowing which fibers mediated this response did not change any actions we took when thresholds were particularly low and suggestive of a medial defect (these actions are detailed in the companion report 7 ). Where single-pulse stimulation was helpful for us was in the interpretation of findings from the rare patients (2 of 75) in whom responses from leg muscles were evoked by stimulation of spine levels rostral to T-11 with single-pulse inputs.…”

“…In the second paper we describe the role that feedback of our test results to the surgical team played in helping to prevent medial malpositioning of thoracic pedicle screws. 7 A preliminary report of this study has been published.…”

“…This decision might also be better informed after considering the role that feedback of our intraoperative testing played in the avoidance of significant medial screw malpositionings; these data are contained in the companion report. 7 …”

The Indian Basket Trick: a case of delayed paraplegia with complete recovery, caused by misplaced thoracic pedicle screw

“…Routine MEP after insertion of each pedicle screw in the thoracic spine, as well as triggered EMG stimulation of each pedicle screw to rule out breaching once all screws have been inserted, could improve safety in challenging cases (Calancie et al 2014a , b ). As in the present case, according to several clinical studies (Danesh-Clough et al 2001 ; Raynor et al 2002 ; Reidy et al 2001 ; Rodriguez-Olaverri et al 2008 ; Shi et al 2003 ), current intraoperative neurophysiological monitoring techniques do not always accurately reveal the presence of thoracic pedicle screws within the spinal canal.…”