Objective: Continuous femoral nerve block (CFNB) for knee arthroplasty can provide adequate postoperative pain relief, however it also can cause muscle weakness and delay ambulation. The present study attempted to determine the optimal CFNB regimen for pain control, without compromising postoperative physical therapy (PT).

Material and Method: The medical records of 214 patients who had undergone knee replacement with three different CFNB regimens were reviewed. Group 1: bolus with 0.5% ropivacaine or bupivacaine, followed by 0.2% or 0.25% bupivacaine infusion; Group 2: bolus with 0.5% ropivacaine or bupivacaine, followed by 0.125% bupivacaine infusion; Group 3: bolus with 1.5% mepivacaine, followed by 0.125% bupivacaine infusion. The primary outcome assessed was the ability to participate in PT on postoperative day (POD) 2, and was compared between groups. Additionally, the association of demographic variables, pain score, opioid consumption, and anesthetic data with impairment of PT participation was investigated.

Results: The incidence of impaired PT was 8% in group 1, 0% in group 2, and 7.8% in group 3. There were no differences in pain scores between the three groups, but group 3 had higher opioid consumption and shorter time to first analgesic, as well as higher average pain score on POD1. Impaired PT performance on POD2 was associated with regimens 1 and 3, older age, higher ASA class and general anesthesia, and associated with longer hospital stay.

Conclusion: A more aggressive femoral nerve block regimen may result in motor weakness, but a less aggressive regime may lead to inadequate pain control. A mid-level regimen improved PT performance without compromising pain control.

Keywords: Femoral nerve block, Local anesthetics, Knee arthroplasty, Posteroperative pain, Motor weakness, Physical therapy