Intraoperative electromyographic monitoring to optimize safe lumbar pedicle screw placement – a retrospective analysis

Abstract

BackgroundThe foremost concern of a surgeon during pedicle screw fixation is safety. Assistive modalities, especially intraoperative electromyographic monitoring (EMG) can function as an essential tool to recognize screw malposition that compromise neural integrity, so that the screws can be repositioned immediately rather than later. We intend to study the efficacy of intraoperative EMG monitoring to detect potential pedicle breach and evaluate whether reoperation rates were significantly reduced.MethodsRetrospectively, patients who underwent posterior stabilization with pedicle screws for various pathologies were analysed and those with screws among L1-S1 levels were shortlisted. They were divided into two groups. Group 1 included patients in whom trigger EMG (t-EMG) was used to confirm appropriate screw placement and Group 2 included those in whom it was not used. Responses to t-EMG and corresponding stimulation thresholds were recorded for Group 1 patients. The sensitivity and specificity of the test was calculated. Reoperation rates due to postoperative neurologic compromise caused by malpositioned screws were compared between both the groups.ResultsA total of 518 patients had 3112 pedicle screws between L1-S1 levels. Among Group 1 [n = 296; Screws = 1856], 145 screws (7.8%) showed a positive response for t-EMG at stimulation thresholds ranging between 2.6 to 19.8 mA. The sensitivity and specificity of t-EMG to diagnose potential pedicle breach was found to be 93.33% and 92.88% respectively. Only one patient among Group 1 required reoperation. However, among Group 2 [n = 222; screws = 1256], six patients required reoperation. This indicated a significant decrease in the number of malpositioned screws that caused neurological compromise [p = 0.02], leading to subsequent decrease in reoperation rates [p = 0.04] among Group 1 patients.ConclusionsTrigger EMG is well efficient in detecting potential pedicle screw breaches that might endanger neural integrity. In combination with palpatory and radiographic assessment, it will certainly aid safe and secure pedicle screw placement. It can also efficiently reduce reoperation rates due to neurologic compromise provoked by a malpositioned screw.

Incidence of pedicle breach following open and minimally invasive spinal instrumentation: A postoperative CT analysis of 513 pedicle screws applied under fluoroscopic guidance

“…With the advent of neuromonitoring, intra-operative assessment of potential pedicle breaches that can compromise neurological integrity has improved [ 10 , 40 , 41 ]. In combination with fluoroscopy, neuromonitoring has become a valuable tool to identify such breaches [ 42 ].…”

“…Although it has become a common procedure, and in-spite of spine surgeons being proficient with the technique, malpositioning of pedicle screws can still occur [ 8 , 9 ]. Such malpositioning not only compromises the stability of the construct but also endangers neural integrity [ 10 ]. Various authors have reported different rates of pedicle breach ranging between 1.7% to 35% during open pedicle screw placement and 2.6% to 12.3% during minimally invasive pedicle screw placement [ 11 – 14 ].…”

Transabdominal Motor Action Potential Monitoring of Pedicle Screw Placement During Minimally Invasive Spinal Procedures: A Case Study

“…One such study, which was conducted in the abdominal and leg muscles of sheep, showed that EMG could be effectively used to indicate the pedicle screw position [2]. EMG has been utilized as a technique to facilitate accurate pedicle screw placement for both the thoracic and lumbar spine [2,4], and its ability to detect breaches in the pedicle cortex is advantageous to imaging techniques during minimally invasive procedures [14]. However, lateral pedicle breaches are difficult to identify using EMG alone [14].…”

“…The current study suggests a novel method to improve neuromonitoring during pedicle screw placement using the transabdominal motor action potential (TaMAP) technique. This neurophysiological tool can assess the functional integrity of individual nerve roots in real-time and may help surgeons recognize impending neural injuries that cannot be detected by traditionally used techniques such as electromyography (EMG) [4]. Back pain is one of the most common conditions worldwide, suggested to affect 80% of adults during their lifetime; thus, safely monitoring screw placement for treating back pathologies is of crucial importance [5].…”

Neuromonitoring in Cervical Spine Surgery: When Is a Signal Drop Clinically Significant?

“…IONM during spinal surgery utilizes three different modalities, namely, somatosensory evoked potential (SSEP), motor evoked potential (MEP), and electromyography (EMG) [10][11][12]. In view of the devastating consequences of a neurological injury, many surgeons advocate the routine use of IONM to detect possible intraoperative insult; hence immediate remedial measures can be taken [13].…”