An intraoperative neurophysiological monitoring method for testing functional integrity of the low extremity peripheral nerves during hip surgery

Abstract The objective of this study was to establish multimodal methodologies to monitor functional integrity of sciatic and femoral nerves during hip surgeries. One hundred patients underwent hip surgery using intraoperative neurophysiological monitoring (ION) of sciatic and femoral nerves have been evaluated retrospectively. Multimodal ION methods included posterior tibial nerve somatosensory-evoked potentials; bilateral lower limb motor-evoked potentials (MEPs), free-running electromyography and electroencephalography to measure the depth of anesthesia. We also applied a new neurophysiologic technique for intraoperative use: anterior root muscle response (ARMR) recorded bilaterally in the following lower limb muscles: quadriceps muscle innervated by femoral nerve; tibialis anterior and extensor digitorum communis brevis innervated by peroneal branch of sciatic nerve; and triceps surae and abductor hallucis innervated by posterior tibial branch of sciatic nerve. Baselines were successfully recorded in all patients for all tested techniques except for two of them where ARMR was not recordable most likely due to patients’ obesity. Detection of significant changes occurred in 39% of patients in one or more parameters of the different methods. In 34% of patients, changes were reversible, after appropriate surgical maneuvers, with no postoperative neurologic deficit, while in 5% of patients, the changes were irreversible correlating with a postoperative neurological deficit. In conclusion, multimodal ION techniques allow the identification of the moment of injury and the surgical maneuver that may damage nerves or roots before an irreversible injury occurs and/or avoid permanent postoperative neurological deficits. ARMR monitoring could emerge as a new intraoperative monitoring technique to assess the functional integrity of lumbosacral roots, plexus, and nerves. This new technique has the potential to give more specific information about the functional integrity of motor part of peripheral nerves than MEPs.