[Effects of different concentrations of ropivacaine in femoral nerve block on early motor function following total knee arthroplasty].

Objective: To compare the effects of different concentrations of ropivacaine femoral nerve block on postoperative pain and early exercise fllowing total knee arthroplasty(TKA).

Methods: A total of 90 patients who underwent primary TKA between September 2022 and February 2023 were consecutively enrolled in this study. The cohort consisted of 34 males and 56 females, with a mean age of (66.66±7.03) years old. According to different concentrations of ropivacaine, patients were divided into 0.1% group, 0.2% group and 0.4% group, with 30 patients in each group. The age, gender, body mass index(BMI), American Society of Aneshesiologists(ASA) grade, operation time, anesthesia time, tourniquet using time, Post Anesthesia care unit(PACU) stay duration, ambulation time, first reaching to Bromage 0 grade time, visual analogue scale(VAS), hospitalization period and postoperative adverse reactions were compared among the three groups.

Results: All 90 patients were followed up for an average of (31.56±5.62) days, and no postoperative adverse reactions occurred. There were no significant differences among the three groups in terms of age, gender, BMI, ASA classification, operation time, anesthesia time, tourniquet application time, PACU stay duration, and hospitalization period (>0.05). Significant differences were observed in VAS scores at 1, 2, 4, 6, and 12 hours post-operation among the three groups (<0.05). Additionally, significant variations were noted in ambulation time and the first reaching to Bromage level 0 time among the three groups (<0.05). In terms of postoperative pain, the VAS of the 0.1% group at 1, 2, 4, 6, and 12 hours after surgery(1.93±0.52), (2.57±0.77), (3.10±0.71), (3.10±0.71), (3.07±0.45) points were higher than those of the 0.4% group (1.57±0.50), (2.10±0.55), (2.23±0.57), (2.47±0.73), (2.50±0.57) points, and the differences were statistically significant (<0.05);the VAS of the 0.1% group at 4, 6, and 12 hours after surgery were higher than those of the 0.2% group (2.43±0.57), (2.53±0.57), (2.63±0.56) points, and the differences were statistically significant (<0.05);there was no statistically significant difference in VAS between the 0.2% group and the 0.4% group (>0.05). In terms of early postoperative mobility, the time to ambulation time (8.30±2.76) h and the time to achieve the first Bromage grade 0 (6.13±2.18) h were significantly prolonged in the 0.4% group compared to both the 0.1% group (6.93±1.76) h, (4.17±1.18) h and the 0.2% group (6.53±1.59) h, (4.87±1.53) h. No statistically significant differences were observed between the 0.1% and 0.2% groups (>0.05).

Conclusion: 0.2% ropivacaine femoral nerve block can effectively reduce postoperative pain after TKA and can perform early exercise earlier.