The evolution of neuromonitoring in lateral lumbar interbody fusion: From detection to prevention

Intraoperative neuromonitoring has played a critical role in the development and adoption of lateral lumbar interbody fusion (LLIF), yet traditional monitoring modalities have demonstrated important limitations in their ability to accurately evaluate lumbar plexus function during transpsoas access. Triggered electromyography, posterior tibial nerve somatosensory evoked potentials, and transcranial motor evoked potentials improved intraoperative safety but provided limited sensitivity, specificity, and procedural resolution for detecting clinically meaningful femoral nerve injury. As a result, surgeons frequently relied on indirect surrogate markers, including retractor duration, to estimate neurologic risk. Recent advances in neuromonitoring have shifted the field toward more anatomically relevant assessments of the neural structures at risk during LLIF. Saphenous somatosensory evoked potentials and transabdominal muscle action potentials (TMAP) provide direct evaluation of the sensory and motor components of the femoral nerve and have demonstrated improved ability to detect neurologic stress during transpsoas surgery. Integration of TMAP within an event-based monitoring framework has enabled correlation of neuromonitoring changes with discrete procedural steps, demonstrating that neurologic stress most commonly occurs from mechanical insult rather than as a function of retractor duration alone. These advances have facilitated a transition from passive detection of neurologic compromise toward active neuromonitoring-guided technique refinement. Identification of high-risk procedural steps has informed modifications in transpsoas docking strategy and has been associated with reductions in both intraoperative neuromonitoring perturbations and postoperative neurologic deficits. The evolution of neuromonitoring in LLIF therefore represents a paradigm shift from injury detection toward real-time decision-making, surgical optimization, and ultimately prevention of neurologic injury.