Objective To evaluate the effects of ultrasound-guided infiltration between the popliteal artery and capsule of the knee (iPACK) combined with adductor canal block (ACB) on postoperative pain and secretion of pain mediators following total knee arthroplasty (TKA).

Methods A total of 90 patients undergoing TKA were selected and divided into a control group and an observation group according to a random number table method, with 45 patients in each group. Patients in the control group received ultrasound-guided ACB combined with low-dose intravenous patient-controlled analgesia (IV PCA), and patients in the observation group received iPACK combined with ACB. The baseline data, pain levels at different postoperative time points, and secretion of pain mediators of patients were analyzed in the two groups. Walking distance at 12 hours and 48 hours, time to first ambulation, and knee range of motion were also assessed at 12 hours and 48 hours postoperatively. Additionally, postoperative complications and satisfaction with analgesic treatment were compared between the two groups.

Results At 6 hours and 48 hours postoperatively, there was no statistically significant difference in VAS scores of patients between the two groups in both resting and active states (P ＞ 0.05); At 12 hours and 24 hours postoperatively, the VAS scores in the observation group were lower than those in the control group in both resting and active states (P ＜ 0.05 to P ＜ 0.01). Within-group comparison showed that VAS scores in the two groups at 12, 24, 48 hours postoperatively were higher than those at 6 hours postoperatively (P ＜ 0.05). There were no statistically significant differences in the levels of neuropeptide Y (NPY), substance P (SP), and bradykinin (BK) of patients between the two groups before surgery and at 6 hours postoperatively (P ＞ 0.05); At 12, 24, 48 hours postoperatively, the levels of NPY, SP and BK in the observation group were significantly lower than those in the control group (P ＜ 0.01). There were no statistically significant differences in the walking distances at 24 hours and 48 hours after surgery, and time to first ambulation of patients between the two groups (P ＞ 0.05); The knee range of motion at 24 hours and 48 hours after surgery was significantly higher in the observation group than in the control group (P ＜ 0.01). The complication rate in the observation group and control group was 6.67% and 13.33%, respectively, and there was no statistically significant difference in the complication rate between the two groups (P ＞ 0.05). The overall satisfaction rate with analgesia treatment in the observation group was 97.78%, which was higher than that in the control group (84.44%) (P ＜ 0.05).

Conclusions Ultrasound-guided iPACK combined with ACB can significantly enhance the postoperative analgesic effect of knee arthroplasty, with a short onset time, excellent analgesic effect, and no impact on lower limb muscle strength. It exhibits good safety and high patient satisfaction, making it an ideal analgesic method after TKA.