Introduction: Inadequate control of postoperative pain after total knee arthroplasty (TKA) has been associated with a poor functional recovery. This study investigated whether the addition of a single injection femoral nerve block (FNB) to continuous epidural analgesia (EA) provides improved pain control, lowered side effects, and a further acceleration in achievement of rehabilitation goals.

Material and methods: Eighty patients undergoing TKA and receiving EA with 18 ml of 0.5% marcaine were randomized whether to receive or not a single dose of FNB. A nerve stimulator and 30 ml of 0.375% marcaine with 5 μg/ml of epinephrine were used to perform FNB prior to surgery. Post-operative continuous EA was self-administered by the patient adding bolus (up to 4bolus/hour) to the basal infusion rate of 2 ml/hour of 0.175% marcaine. Standardized post-operative rehabilitation protocol were followed for both groups. Therapists and clinicians were blinded to treatment group. Overall narcotic consumption, bolus dosing, and side effects were recorded. Outcomes measurements included postoperative strength and sensation, range of motion and progression, pain score (VAS), achievements of functional milestones and length of stay.

Results: Femoral nerve block group had significantly lower pain scores and lower epidural consumption in comparison to the group without block (p< 0.01). Range-of-motion was significantly greater through post-operative day three in the FNB group (p< 0.04). There was a consistent trend toward improved achievements in rehabilitation milestones after FNB. Decreased quadriceps strength was noted in 33% of the FNB patients on post-operative day one compared to 10% of the patients with isolated EA.

Discussion: We found significant improvements both in terms of analgesia and in functional parameters adding a FNB to continuous EA following TKA. Combination of the two techniques has a sound basis for preventing severe post-operative pain after TKA.