Abstract
Introduction
Previous studies utilizing electromyography (EMG) have reported that the incidence of thigh complications during transpsoas lateral lumbar interbody fusion (LLIF) ranged from 0.7 to 75%. The reliability of EMG has been questioned because of false-positives, false-negatives, and electrical interference from common operating-room equipment. Mechanomyography is a new neuromonitoring technique that functions by measuring the mechanical activity in muscles, or “twitch,” noninvasively using surface-mounted accelerometers on the skin following nerve stimulation and muscle contraction. MMG may provide an alternative to EMG for neuromonitoring. In this study, we evaluated the incidence of thigh complications during transpsoas LLIF utilizing MMG to monitor the lumbar plexus.
Materials and Methods
A retrospective review of prospectively collected data of four different surgeons at four separate institutions was performed. A total of 85 consecutive patients, with 175 instrumented levels, were included who underwent transpsoas LLIF surgery (L1–L5) during a 1-year period. Immediate postoperative and routine follow-up clinical examinations at 3, 6, and 12 months were obtained.
Results
The rate of all ipsilateral thigh symptoms (pain, numbness, and weakness) was 21.2% (18/85). Eight patients (9.4%) had iliopsoas or quadriceps weakness (3/5 motor strength). Overall, 10 patients (11.8%) had anterior thigh pain and/or numbness. Most patients with postoperative thigh symptoms (16/18) had 3 or 4 level procedures performed for adult degenerative scoliosis (ADS) and included the L45 level. All thigh symptoms resolved within 3 months.
Conclusion
MMG is a safe and effective alternative to EMG for nerve mapping during transpsoas LLIF surgery and overcomes deficiencies related to the high rates of false-positives and false-negatives inherent to EMG. In addition, unlike EMG, MMG is not affected by electrical artifact seen with common operating-room equipment such as the bovie electrocautery and bair hugger body warmer. With the use of MMG, the rate of ipsilateral thigh symptoms was 21.2%, which is consistent with currently reported rates for transpsoas LLIF procedures utilizing EMG. In our study, most thigh symptoms occurred in patients with multilevel LLIF procedures performed and direct trauma to the psoas may have contributed to our results and the actual rate of nerve-related thigh symptoms might be lower. All symptomatic patients had L45 included in their construct. MMG is a safe alternative to EMG to monitor the lumbar plexus when performing transpsoas LLIF.