220. An analysis of intraoperative neurophysiological monitoring events during single position minimally invasive spine surgery

Abstract

<h3>BACKGROUND CONTEXT</h3> The single position minimally invasive (MIS) lateral approach allows access to the anterior and posterior columns with the patient positioned in the lateral decubitus position. The purpose of this approach was to mitigate complications associated with open procedures while achieving circumferential fusion. More recently, an alternative prone-lateral technique has been developed streamlining surgical access with potential advantages. The purpose of this study was to identify differences in intraoperative neurophysiological monitoring (IOM) event rates between single position lateral decubitus and prone-lateral patients during MIS spine surgery. <h3>PURPOSE</h3> To determine if lateral decubitus positioning will correlate with the occurrence of neurophysiological monitoring events during MIS spine surgery. <h3>STUDY DESIGN/SETTING</h3> Retrospective cohort. <h3>PATIENT SAMPLE</h3> A total of 524 MIS patients were included. <h3>OUTCOME MEASURES</h3> Intraoperative neurophysiological monitoring, lateral decubitus, prone lateral. <h3>METHODS</h3> MIS spine surgery patients with available surgical positioning and IOM data were included if they were in a single position. Patients were stratified into 2 groups based on operative positioning: lateral decubitus (Lat) and prone lateral (PL). IOM was performed using somatosensory evoked potentials (SSEPs) and electromyography (EMG) techniques. An abnormal event was defined as any confirmed loss of signal during the operative period in the anatomical distribution of the surgery. Means comparison tests and multivariable logistic regression analysis assessed differences between patient groups. <h3>RESULTS</h3> Of 524 patients eligible, 226 (43.1%) had available positioning and IOM data. Of these, 88 met inclusion criteria (52 Lat and 36 PL). The majority were male (49, 55.7%), mean age of 49.2 yrs and 2.0 levels fused and 18 (20.5%) undergoing an osteotomy. In total, 19 (21.6%) patients had an abnormal IOM event. There was a significant difference in abnormal IOM event rates for patients who were in Lat (31%) and PL (8%) positioning, p=0.012. Multivariable analysis adjusting for surgical invasiveness showed that PL patients were 76.8% less likely to experience an abnormal IOM event than Lat patients (OR .232 [CI .060-.905], p=.035). Of the Lat patients with an abnormal IOM, 6.3% had postoperative sensory loss in the saphenous nerve. <h3>CONCLUSIONS</h3> Lateral decubitus positioning appears to be independently associated with abnormal intraoperative neurophysiological monitoring events when compared to prone lateral positioning during MIS. This has the potential to help with risk stratification in the future when determining patients undergoing a single position procedure. <h3>FDA DEVICE/DRUG STATUS</h3> This abstract does not discuss or include any applicable devices or drugs.