Many Intraoperative Monitoring Modalities Have Been Developed To Limit Injury During Extreme Lateral Interbody Fusion (XLIF/MIS XLIF): Does That Mean XLIF/MIS XLIF Are Unsafe?

BACKGROUND: Extreme lateral interbody fusions (XLIF) and Minimally Invasive (MIS) XLIF pose significant risks of neural injury to the; lumbar plexus, ilioinguinal, iliohypogastric, genitofemoral, lateral femoral cutaneous, and subcostal nerves. To limit these injuries, many intraoperative neural monitoring (IONM) modalities have been proposed. METHODS: Multiple studies document various frequencies of neural injuries occurring during MIS XLIF/XLIF: plexus injuries (13.28%); sensory deficits (0-75%; permanent 62.5%); motor deficits (0.7-33.6%; most typically iliopsoas weakness (14.3%-31%)), and anterior thigh/groin pain (12.5-25%.-34%). To avoid/limit these injuries, multiple IONM techniques have been proposed. These include; using finger electrodes during operative dissection, employing motor evoked potentials (MEP), eliminating (no) muscle relaxants (NMR), and using “triggered” EMGs. RESULTS: In one study, finger electrodes for XLIF at L4-L5 level for degenerative spondylolisthesis reduced transient postoperative neurological symptoms from 7 [38%] of 18 cases (e.g. without IONM) to 5 [14%] of 36 cases (with IONM). Two series showed that motor evoked potential monitoring (MEP) for XLIF reduced postoperative motor deficits; they, therefore, recommended their routine use for XLIF. Another study demonstrated that eliminating muscle relaxants during XLIF markedly reduced postoperative neurological deficits/thigh pain by allowing for better continuous EMG monitoring (e.g. NMR no muscle relaxants). Finally, a “triggered” EMG study” reduced postoperative motor neuropraxia, largely by limiting retraction time. CONCLUSION: Multiple studies have offered different IONM techniques to avert neurological injuries following MIS XLIF/XLIF. Does this mean that these procedures (e.g. XLIF/MIS XLIF) are unsafe?