1070 Muscle Mechanomyography (MMG) for Peripheral Nerve Monitoring During Lateral Lumbar Fusion: The New Kid on the Block?

Abstract

INTRODUCTION: The lateral transpsoas approach has become a valuable minimally invasive option in lumbar spine surgery to achieve fusion, decompression, and deformity correction. However, femoral nerve injury during psoas retraction remains a significant concern, especially in the lower spinal levels. A newer alternative to electromyography (EMG), muscle mechanomyography (MMG) measures muscle fiber oscillation during contraction, providing a more specific and quantifiable response with a high signal to noise ratio. These characteristics make MMG an attractive option for intraoperative neuromonitoring (ION) in minimally invasive spine surgery. METHODS: Patients who underwent LLIF between 2018-2021 with MMG ION were included and compared to a historical cohot of patients who underwent LLIF from 2016-2021 with EMG ION. The femoral nerve palsy rate defined by ipsilateral thigh numbness, hip flexor, or quadricep weakness immediately post operatively were collected for both groups. Patients were re-evaluated at 3 month and 1 year follow up intervals. RESULTS: The rate of ipsilateral thigh numbness, hip flexor, and quadricep weakness at hospital discharge were 14.6% (6/41), 9.8% (4/41), and 7.3% (3/41) respectively for the MMG group, comparable to 14.8% (9/61), 23% (14/61), and 14.8% (9/61) observed in the EMG control group. Improvement in thigh numbness and leg weakness was observed for both groups at 3 month and 1 year follow up. No patients with leg weakness had less than antigravity strength. There were no statistically significant difference amongst patient demographics for both cohorts. CONCLUSIONS: In conclusion, MMG appears to be clinically equivalent to EMG as an intraoperative modality for femoral nerve monitoring in LLIF procedures. Further research is needed to evaluate the additional clinical advantages proposed by mechanomyography, such as low signal interference and quantifiable nerve localization.