The effect of visualized saphenous nerve block through minimally invasive far medial-subvastus approach on the analgesia after total knee arthroplasty

Abstract

Objective: To report a method of visualized saphenous nerve block (VSNB) through minimally invasive far medial-subvastus approach distal to the adductor canal in total knee arthroplasty (TKA), and investigate the effect of VSNB in this way on postoperative pain relief. Methods: A total of 100 patients with knee osteoarthritis were prospectively included from June 2018 to October 2019, 29 males and 71 females, aged 50-87(70±8) years. All patients undergoing TKA through minimally invasive far medial-subvastus approach were randomized to visualized saphenous nerve block combined with periarticular infiltration analgesia group (Group VSNB+PIA) or only periarticular infiltration analgesia group (Group PIA),50 cases in each group. The visual analogue scale (VAS) was used to evaluate the pain degree of patients. Furthermore, the scores of VAS in resting and active state at 4, 8, 12, 24, 48, 72 hours after operation and the proportion of patients receiving parecoxib within 72 hours after operation were compared between the two groups. Results: There was statistically significant difference between the two groups in terms of VAS scores in resting state after surgery(F=15.295,P<0.05).The postoperative VAS scores of Group VSNB+PIA at 4, 8, 12, 24 hours at resting state were 1.3±0.8, 1.4±0.7, 1.7±0.8, 3.1±0.8 respectively, which were all significantly lower than those of Group PIA (1.6±0.9, 1.8±0.8, 2.3±0.9, 3.6±0.8) (P<0.05). The overall difference in terms of VAS scores at active state after surgery was statistically significant between the two groups(F=18.532, P<0.05). The postoperative VAS scores of Group VSNB+PIA at 4, 8, 12, 24 hours at active state were 2.0±0.8, 2.2±0.7, 2.7±0.6, 3.7±0.7 respectively, which were all significantly lower than those of Group PIA (2.3±0.8, 2.7±0.7, 3.3±0.8, 4.4±0.7)(P<0.05). Fourteen percent of patients (7/50) in VSNB+PIA group accepted parecoxib within 72 hours after surgery, which was significantly lower than that in PIA group (34%, 17/50) (P<0.05). Conclusions: It is easy to expose the saphenous nerve beyond the adductor canal through minimally invasive far medial-subvastus approach. The Combination therapy of VSNB+PIA is more effective than the simple per-articular infiltration analgesia in providing pain relief after total knee arthroplasty.