Peri-articular local infiltration analgesia versus femoral nerve block for postoperative pain control following anterior cruciate ligament reconstruction: Prospective, comparative, non-inferiority study

Abstract

Introduction: Femoral nerve block (FNB) is considered as a major advance in anterior cruciate ligament (ACL) reconstruction as it reduces the need for parenteral opioids. However, the incidence of transient or even permanent neurological deficits due to the FNB is estimated at 1.94% after knee surgery. The primary objective of this study was to compare local infiltration analgesia (LIA) to FNB during ACL reconstruction procedures. The study hypothesis was that LIA was not less effective than FNB on early postoperative pain.

Patients and methods: A retrospective analysis of data collected prospectively in the FAST cohort included a series of continuous patients who underwent primary repair for isolated ACL with a hamstring graft in 2013-2014. Changes in our anesthesia practices over time allowed us to form three successive groups: Group 1 - FNB, Group 2 - FNB+LIA, Group 3 - LIA only. Ultrasound-guided FNB was done pre-operatively. The LIA was done at the end of the procedure by the surgeon with systematic infiltration of all skin incisions and the hamstring donor site; no intra-articular injections were performed. The primary endpoint was the average early postoperative pain (Days 0-3) described by the patient on a visual analogue scale (0-10). Sample size calculation pointed to 36 subjects being needed per group for a non-inferiority study.

Results: The study involved 126 patients: G1=42, G2=38, G3=46. The patients were comparable at enrolment. The average early postoperative pain levels were 3.1±2.4, 2.8±2.0 and 2.5±2.2, respectively (P=0.66). A trend toward higher intake of tramadol was noted in the LIA group on D0 to D3, with a significant trend test on Day 1 (P=0.03) and Day 2 (P=0.02).

Conclusion: After reconstruction of isolated ACL tears with a hamstring graft, FNB is not more effective than LIA on patients' early postoperative pain. Patients who received a FNB consumed significantly less opioid-like analgesics.

Level of evidence: III - Prospective, comparative, non-randomized study.

Keywords: ACL reconstruction; Early postoperative analgesic treatment; Femoral block; Local infiltration analgesia.