Sequential Lidocaine and Liposomal Bupivacaine for Popliteal Sciatic Nerve Block in Foot and Ankle Surgery: A Randomized Controlled Trial

In foot and ankle surgery, prolonged analgesia after popliteal sciatic nerve block (PSNB) may be accompanied by delayed motor recovery. The effects of sequential lidocaine and liposomal bupivacaine (LB), particularly on early motor function, remain uncertain.

Eighty adults undergoing foot and ankle surgery were randomized to preoperative 1.5% lidocaine (20 mL) followed by postoperative 0.665% LB (20 mL), or preoperative 0.5% ropivacaine (20 mL). Participants and outcome assessors were blinded; block providers were not. For the coprimary comparisons, resting pain was assessed at 24 hours using a 0-10 visual analog scale and motor function at 3 hours using the modified Bromage score.

In complete-case analyses, 37 lidocaine-LB and 38 ropivacaine recipients were included. Median (IQR) 24-hour resting pain was 0 (0-2) versus 1 (0-3) (difference, -1; 95% CI, -3 to 0; P<0.001); the difference was below the prespecified 1.5-point threshold for clinical importance. The 3-hour motor score was 1 (1-1) versus 0 (0-0) (difference, 1; 95% CI, 1 to 1; P<0.001), meeting the study-defined 1-point threshold. Exploratory comparisons favored lidocaine-LB for later pain, 24-hour rescue analgesia and recovery quality, and postoperative nausea and vomiting. One suspected local anesthetic systemic toxicity event-mild tinnitus 15 minutes after preoperative lidocaine-was recorded; no specific treatment was given.

Compared with single-injection ropivacaine, sequential lidocaine-LB was associated with better early motor scores and statistically lower 24-hour resting pain. The pain difference did not meet the prespecified threshold for clinical importance. Functional benefit and comparative safety remain unestablished. Larger multicenter trials should assess mobility and safety, together with the cost and feasibility of the additional block.