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

Calancie, Blair; Donohue, Miriam L; Harris, Colin; Canute, Gregory W.; Singla, Amit; Wilcoxen, Kaitlin G; Moquin, Ross R.

doi:10.3171/2014.2.spine13648

Cited by 22 publications

(24 citation statements)

References 71 publications

(80 reference statements)

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“…Figure 2 shows a case in which we believe this happened, illustrating small evoked responses in hand and foot (AbH) muscles to strong (20-mA) stimulation through the balltipped probe of the initial left T-4 pedicle track. As discussed in the companion manuscript, 9 such high thresholds to probe stimulation were not a cause for concern. After implanting a screw along that pedicle track, the threshold to screw stimulation (12 mA; response to 18mA shown in Fig.…”

Section: Resultsmentioning

confidence: 86%

“…9 In the present article we report the effect that providing feedback of monitoring results to the surgical team had on the incidence of screw placements with significant encroachment on the spinal canal.…”

Section: Resultsmentioning

confidence: 99%

“…2B) was found to be much lower than what we had just seen testing the pedicle track with the balltipped probe (20 mA). Figure 2 from the companion manuscript 9 shows just how rare it is for a screw threshold to be less than that of its pedicle track. We asked the surgeon to remove the screw and recheck the pedicle track with probe stimulation, and lower-limb EMG activity was now evoked at a threshold of only 5.1 mA when stimulating at the pedicle's midpoint (response to 8 mA stimulation shown in Fig.…”

Section: Resultsmentioning

confidence: 99%

“…9 From study onset, the results of all intraoperative testing were withheld from the surgical team; that is, the team was blinded to test results. Beginning with the third patient tested, we added a provision to provide feedback to the surgical team-to break the blind-but only if testing indicated a high probability that the stimulating probe was in physical contact with, or in close proximity to, the dura mater of the spinal cord; a screw placed under these circumstances could cause either immediate or delayed injury to the spinal cord, so this risk needed to be avoided.…”

Section: Methodsmentioning

confidence: 99%

“…First, as described in the companion manuscript, 9 testing both pulse trains and single pulses helped us determine whether EMG activity from leg muscles was being evoked by direct stimulation of lower motor neuron axons, or if instead the response was being mediated by upper motor neuron axons (that is, being stimulated within the spinal cord) that were then, through temporal summation, transsynaptically recruiting lower motor neurons to discharge. Second, single-pulse stimulation helped us identify the rare patient with a hyperexcitable spinal cord, alerting us to modify our alarm criteria for predicting an inappropriate (that is, medially biased) pedicle track.…”

Section: Methodsmentioning

confidence: 99%

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

Calancie¹,

Donohue

Moquin³

2014

SPI

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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.

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Section: Resultsmentioning

confidence: 86%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

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