Periarticular injection and continuous femoral nerve block versus continuous femoral nerve block alone on postoperative opioid consumption and pain control following total knee arthroplasty: Randomized controlled trial

Abstract

Continuous femoral nerve block (CFNB) has been used to prevent the breakthrough pain after total knee arthroplasty (TKA). Multimodal drug injection (PMDI) has also been shown to decrease opioid consumption and pain. We investigated whether the use of PMDI further improves analgesic and rehabilitation outcomes when used in conjunction with CFNB. This is a prospective randomized controlled study of 44 patients undergoing primary TKA. The treatment group (n=23) received a PMDI of combined ropivacaine, epinephrine, ketorolac and morphine, and the controlled group (n=21) received saline at wound closure. Total opioid consumption, pain scores, knee range of motion (ROM) outcomes, length of stay, and patient satisfaction were measured and compared. The total consumption of morphine is similar between the two groups (52.6±40.6 vs. 41.5±32.9, p=0.325). The mean morphine consumption of the treatment group was significantly lower than the control at 4h after surgery (4.2±5.5 vs. 11.3±8.1, p=0.002) but comparable on POD1, POD2, and POD3. The mean pain scores were significantly higher in the treatment group than the control group at POD2 (at rest: 47.3±29.1 vs. 23.8±20.6, p=0.004; after PT: 57.7±25.4 vs. 35.2±26.8, p=0.007) and POD3 (at rest: 30.9±30.3 vs. 14.8±20.9, p=0.045; after PT: 50.2±30.6 vs. 29.0±32.1, p=0.035), and not significantly different at 4h after surgery or at POD1. Mean maximal knee flexion ROM in degrees during active and active assisted mobilization showed no significant difference between the control and the treatment groups on POD2 and POD3. The mean length of stay of the treatment group is significantly longer than the control group (5.1±2.1 vs. 3.8±1.6, p=0.032). At discharge, no significant difference exists between the two groups for mean patient satisfaction. The addition of PMDI led to a decrease in opioid consumption in the immediate postoperative period but with no significant difference in the total consumption within the first three days postoperatively. This finding provides an opportunity for appropriate preoperative treatment and education for both patients and caregivers.