Effect of Pericapsular Nerve Group Block with Different Concentrations and Volumes of Ropivacaine on Functional...

The pericapsular nerve group (PENG) block provides satisfactory postoperative analgesia without hampering motor function for total hip arthroplasty (THA); however, unexpected motor block has been observed clinically. It is unknown whether this motor block is related to the dose of ropivacaine. We aimed to conduct a prospective randomized trial to test whether reducing the volume or concentration of ropivacaine was better for less motor block after PENG block.

Ninety-nine patients with fracture or femoral head necrosis scheduled for THA were randomly allocated to receive 20 mL 0.5% ropivacaine (Group A), 20 mL 0.25% ropivacaine (Group B), and 10 mL 0.5% ropivacaine (Group C). The primary outcome was the incidence of postoperative quadriceps motor block at 6 hours. Secondary outcomes were the incidence of postoperative quadriceps motor block at 0, 12, 24 and 48 hours; pain scores on the numeric rating scale (NRS) at all postoperative time points (0, 6, 12, 24, and 48 hours); the time to first walk; the incidence of rescue analgesia; side effects such as dizziness, ache, nausea, and vomiting; and patient satisfaction.

Compared with Group A, Group C resulted in a lower incidence of quadriceps motor block at 0 hours, 6 hours and 12 hours postoperatively (P < 0.05), while Group B only resulted in a lower incidence of motor block at 12 hours postoperatively (P < 0.05). No intergroup differences were found in terms of postoperative pain scores, the incidence of rescue analgesia, adverse events or patient satisfaction (P > 0.05).

A higher incidence of motor blockade was observed when 20 mL of 0.5% ropivacaine was administered, which was mainly caused by the excessive volume. Therefore, we recommend performing PENG block with 10 mL 0.5% ropivacaine.