Abstract:Objective To explore the differences in the incidence and pain intensity of rebound pain after nerve block with different concentrations of ropivacaine in patients with ankle fractures, in order to provide a basis for optimizing perioperative analgesia protocols. Methods A total of 88 patients who underwent elective open reduction and internal fixation for ankle fractures under general anesthesia at Nanjing First Hospital from January to December 2023 were prospectively selected and randomly divided into two groups using a random number table: the high-concentration group (n=44) and the low-concentration group (n=44). Before anesthesia induction, patients in both groups received a single ultrasound-guided adductor canal block combined with a popliteal sciatic nerve block. The low-concentration group received 40 mL of 0.125% ropivacaine, while the high-concentration group received 40 mL of 0.375% ropivacaine. All patients received perioperative multimodal analgesia. The incidence, intensity, and duration of rebound pain within 48 hours postoperatively were recorded for both groups. Resting Numeric Rating Scale (NRS) scores were recorded at 6 h, 12 h, 24 h, and 48 h postoperatively. Lovett muscle strength grading of the lower leg was recorded at 24 h and 48 h postoperatively. The time to first patient-controlled intravenous analgesia (PCIA) press, as well as the number of effective PCIA presses and rescue analgesic administrations within 48 hours postoperatively were recorded. Adverse reactions were also documented. Results There was no statistically significant difference in the duration of rebound pain between the two groups (P>0.05). The incidence of rebound pain within 48 hours postoperatively was lower in the low-concentration group than in the high-concentration group[13.6% (6/44) vs 40.9% (18/44), χ2=8.250, P=0.004]. The NRS score at 12 hours postoperatively was significantly lower in the high-concentration group compared to the low- concentration group[1 (1, 2) vs 2 (1, 3), Z=2.157, P=0.031], while the NRS score at 24 hours postoperatively was significantly higher in the high-concentration group[4 (3, 5) vs 3 (2, 4), Z=2.132, P=0.033]. The time to first PCIA press postoperatively was significantly earlier in the low-concentration group than that in the high-concentration group (P<0.05). The number of effective PCIA presses and rescue analgesic administrations within 48 hours postoperatively were significantly lower in the low-concentration group compared to the high-concentration group (P<0.05). Lower leg muscle strength at 24 hours postoperatively was higher in the low-concentration group than that in the high-concentration group (P<0.05), but no significant difference was observed at 48 hours postoperatively (P>0.05). Conclusion The use of low-concentration ropivacaine for nerve block is associated with a lower incidence and milder intensity of rebound pain. Adductor canal block combined with sciatic nerve block using low-concentration ropivacaine is more suitable for perioperative multimodal analgesia in patients with ankle fractures.