Intraoperative neuromonitoring of anterior root muscle response during hip surgery under spinal anesthesia

The aim of this study was to evaluate the anterior root muscle (ARM) response monitorability during total hip arthroplasty (THA) under spinal anesthesia. A total of 20 adults (64.6 ± 13.87 years old) were monitored using ARM response and free-run electromyography during THA. To elicit the ARM response from muscles, percutaneous stimulation of the lumbosacral roots was performed by self-adhesive electrodes placed over the skin of the projection of the first and third lumbar interspinous space (anode) and over the abdominal skin of the umbilicus (cathode). Latency and amplitude values of the ARM response were recorded from both sides (non-operated and operated) and from five muscles as follows: rectus femoris (RF), vastus lateralis (VL), biceps femoris long-head (BF), Tibialis Anterior (TA) and gastrocnemius. The most recorded ARM response in a muscle was the TA (n = 38); the least recorded AMR response in a muscle was the BF (n = 33). The mean stimulus intensities for the non-operated and the operated sides were 462.5 ± 112.8 V and 520.0 ± 172.3 V (p = 0.834), respectively. The mean latencies and amplitude values of the ARM response from muscles were as follows: 8.8 ± 1.4 ms; 98.8 ± 114.5 µV for RF; 9.8 ± 2.1 ms; 119.1 ± 122.23 µV for VL; 9.5 ± 1.6 ms; 39.6 ± 30.3 µV for BF; 15.1 ± 1.9 ms; 146.6 ± 150.9 µV for TA; 15.6 ± 2.4 ms; 81.0 ± 99.9 µV for Gastrocnemius. The present study demonstrates that the ARM response could easily and safely be obtained during THA under spinal anesthesia. This non-invasive technique may have a potential to detect early neurological deficit in patients who need complex hip surgery under spinal anesthesia.