Incidence of postoperative neurological deficit with the use of an intraoperative neuromonitoring protocol for lateral lumbar interbody fusion

OBJECTIVE Intraoperative neuromonitoring (IONM) has become commonplace in assessing neurological integrity during lateral approaches to lumbar interbody fusion surgeries. Neuromonitoring is designed to aid surgeons in identifying the potential for intraoperative nerve injury and reducing associated postoperative complications. However, standardized protocols for neuromonitoring have not been provided, and outcomes are not well described. The purpose of this study was to provide a standardized protocol for IONM, and to describe clinical outcomes in a cohort of individuals who underwent lateral lumbar interbody fusion (LLIF) surgery. METHODS A retrospective review of 169 consecutive patients who underwent LLIF surgery at a single institution from October 2014 to October 2016 was performed. Patient characteristics, intraoperative details, clinical outcomes, and postoperative deficits (PODs) were compared between patients who did and did not trigger IONM alerts, and between patients who did and did not demonstrate a POD. A protocol for IONM decision-making was generated based on these observations. RESULTS Most patients (91.7%) underwent surgery for a degenerative spine condition. Twenty-three patients (13.6%) triggered neuromonitoring alerts, and 16 patients (9.5%) demonstrated a POD. Leg pain, back pain, and disability improved significantly (p < 0.045), and 2 patients had both motor and sensory deficits at the 12- week postoperative time point. Patients with a POD demonstrated greater operating room time (p = 0.034) and a greater number of interbody fusion levels (p = 0.015) but were less likely to have triggered a neuromonitoring alert (p = 0.04). There was no association between retractor time and POD (p = 0.98). When an IONM protocol was followed, individuals who experienced a POD were less likely to trigger an alert than those who did not experience a POD (p = 0.04). CONCLUSIONS This study provides a protocol algorithm for IONM alert responses in patients undergoing LLIF surgery. PODs are most associated with multilevel fusion, and patients with alerts had a low rate of persistent deficit. Future research is needed to validate these findings using a more rigorous comparative study design.