3. Basic IOM principles in orthopedic spine surgery

Abstract

Intraoperative Neurophysiological Monitoring (IOM) during orthopedic spinal surgery has evolved, through numerous publications in the world literature; and has progressed to the point where the multimodal monitoring technique has become the gold standard for avoiding post-operative complications. The methods used include free-running electromyography (FREMG), triggered electromyography (TGEMG), somatosensory evoked potentials (SSEP) and trans-cranial motor evoked potentials (TCMEP). The basic issues in the application of these methods will be presented on a day-to-day basis in the operating room. We have had daily, practical experience in IOM of spinal orthopedic surgeries for over 21 years and this experience, has taught us some practical tips that make a difference, when making decisions in the operating theater. The continuing development and perfection of methods in orthopedic spinal surgery has not decreased the likelihood of intraoperative damage to the spinal cord and peripheral nerves. The risk ranges from faulty patient positioning; the modern practice of pedicle instrumentation where increased density of bilateral screws per level is the rule; to the recently developed and feared lateral trans-psoas approach. The purpose of this presentation is to help avoid pitfalls in obtaining adequate signals for analysis, deciding what the most important information is, and correlating this with the surgical timing in different orthopedic spinal surgeries. Finally, I will briefly discuss how to proceed in the presence of alarm parameters, and how to identify a false negative or a false positive result.