Negative Influence of femoral nerve block on quadriceps strength recovery following total knee replacement: A prospective randomized trial.

BACKGROUND:Postoperative pain is a major concern after total knee replacement (TKR) and can be relieved using different methods, including femoral nerve block (FNB). Quadriceps strength recovery (QSR) is the most sensitive objective indicator of functional recovery after TKR. The goal of this study was to compare the QSR following TKR between three approaches to analgesia. HYPOTHESIS:FNB delays QSR at short- and mid-term follow-up. METHODS:In this prospective randomized trial, with single-blind assessment involving 135 patients admitted for TKR in an academic center, the three following groups included were: (A) Continuous FNB 48h+PCA, (B) Single-shot FNB+PCA and (C) PCA alone. No intra-articular local anesthesia was carried out for all patients. Groups were comparable for demographic and surgical data. FNB was carried out and controlled (electric stimulation) by an expert anesthesiologist prior to the surgery. Follow-up was standardized in all groups using blinded assessors. Quadriceps strength was measured using a certified dynamometer at 6 weeks, 6 months and 12 months. Multivariate analysis (Kruskal-Wallis, Mann-Whitney) was used for the main outcome. RESULTS:A total of 135 patients were included. Two patients in group B were excluded due to a direct fall in the first postoperative week with extensor mechanism rupture and peri-prosthetic femoral fracture. QSR was significantly decreased in patients with FNB at all times (mean±SD): 6 weeks (A: 51.3±23.3%; B: 62.2±21.9%;C: 77.4±19.5%; p<0.01), 6 months (A: 65.4±22.9%; B: 82.1±24.2%;C: 95.7±20.7%; p<0.01) and 12 months (A: 87.8±17.6%; B: 97.8±26.9%;C: 104.8±25.2%; p=0.02). No significant difference between continuous or single-shot FNB was observed. CONCLUSION:FNB has a negative influence on QSR at short- and mid-term follow-up. FNB should not yet be recommended for analgesia after TKR. LEVEL EVIDENCE:I High-quality randomized controlled trial with statistically significant difference.