Femoral Nerve Block in Anterior Cruciate Ligament Surgery: A Prospective Randomized Trial

Abstract

Early painless rehabilitation is essential after anterior cruciate ligament surgery (ACL). Postoperative main management with femoral nerve block (FNB) is a frequently used method, but it is still unknown how to administer this procedure in order to achieve faster and better analgesia. Purpose: To compare effectiveness of pain management after single shot FNB vs. continuous infusion FNB during the first 48 hours after ACL surgery. Materials and Methods: Forty-three patients older than 18 years, ASA I-II, underwent ACL reconstruction with autograft. Patients are prospectively randomized into two separate groups: Group 1 (G1) received single shot FNB with bupivacaine diluted in 10mL saline solution. Group 2 (G2) received continuous infusion FNB with bupivacaine and epinephrine (1:300.000) for 48 hours. Pain was assessed at rest and with controlled passive motion of the knee. Thigh hypoesthesia and need for additional analgesia were evaluated at 6, 12, 24 and 48 hours. Statistical analysis was performed with Fisher´s exact test (%) and Mann-Whitney´s test (VAS). Statistical significance was considered with P value <0.05. Results: FNB was successful in all patients, and thigh hypoesthesia was present in 100% of G2 vs. 17% in G1 at 24 hours, declining to 74% vs. 0% at 48 hours, respectively. Postoperative pain scores were low and did not differ between both groups. Additional analgesia was required in 33% of patients in G1 vs. 0% in G2. Neither side effects nor complications were related to both methods of FNB. Conclusion: FNB is a safe and successful method for controlling pain after ACL reconstruction, allowing early rehabilitation in both methods of local anesthesic administration. No differences in pain control were found after 48 hours, but continuous infusion FNB descreses need for additional anesthesia at 24 hours of surgery.