Comparison of lumbar plexus block using the short axis in-plane method at the plane of the transverse process and at the articular process: a randomized controlled trial

BACKGROUND Although the safety and effectiveness of the short-axis in-plane method has been confirmed for lumbar plexus block, the operation is difficult and has a high rate of epidural spread at the plane of the articular process. Therefore, we developed a new in-plane technique, called the beach chair method, which displays images from the transverse process. We compared the operative difficulty and incidence of epidural spread of the beach chair method with those of the control method (at the plane of the articular process) in this randomized controlled clinical trial. METHODS Sixty patients, aged 18 to 75 years, scheduled for unilateral arthroscopic knee surgery were randomized to receive double-guided lumbar plexus block by the beach chair method (n = 30) or the control method (n = 30) with 30 ml 0.5% ropivacaine hydrochloride; all patients received a sciatic nerve block with 10 ml 1% lidocaine hydrochloride and 10 ml 0.5% ropivacaine hydrochloride. RESULTS The incidence of epidural spread after lumbar plexus block was significantly lower in the beach chair group than that in the control group [1 case (3.3%) vs. 9 (30.0%), P = 0.006]. Moreover, the imaging time (34.2 ± 16.7 s vs. 48.9 ± 16.8 s, P = 0.001), needling time (85.0 ± 45.3 s vs. 131.4 ± 88.2 s, P = 0.013) and number of needle punctures (2.7 ± 1.3 vs. 4.5 ± 2.1, P = 0.000) were significantly lower in the beach chair group than those in the control group; the ultrasound visibility score of the beach chair group was better than that of the control group. There were no significant differences in the remaining indicators. CONCLUSIONS The beach chair method was easier and was associated with a lower incidence of epidural spread than the control method. Therefore, the beach chair method (at the plane of the transverse process) provides another promising option for lumbar plexus block for the non-obese population. TRIAL REGISTRATION Chinese Clinical Trial Registry (ChiCTR), Registration number:ChiCTR-INR-15007505, registered on November 06, 2015.