The effect of single-injection femoral nerve block on rehabilitation and length of hospital stay after total knee replacement

Background and Objectives: Continuous-infusion femoral nerve block (FNB) improves analgesia and rehabilitation after total knee replacement. In this study, we investigated the efficacy of single-injection FNB to achieve similar results. Methods: A total of 30 patients were prospectively and randomly assigned to receive 40-mL injections of either 0.25% bupivacaine (group B) or saline (group S) after total knee replacement. Blinded observers evaluated the patients for postoperative pain, morphine consumption, ambulating distances, and maximal knee flexion; pain was scored on the visual analog scale (VAS). Results: Compared with group S patients, group B patients had significantly lower VAS pain scores (P <. 01 in the postoperative anesthesia care unit, P <.05 on the day after surgery); group B patients also showed significantly lower total morphine use (P <.05) and a lower incidence of morphine-related side effects. Significantly more group B than group S patients could ambulate on the day after surgery (93% v 46%, P <.05), and mean ambulatory distance was significantly better for group B than group S patients at discharge (166 37 v 117 +/- 24 feet, P <.01). Knee flexion was significantly better for group B than group S patients on the second day after surgery (70degrees v 60degrees, P <.01), but the between-group difference was no longer statistically significant at discharge. Mean length of acute hospitalization was significantly shorter for group B (3 days; range, 3 to 5 days) than group S patients (4 days; range, 3 to 6 days, P <.05). Conclusions: Single-injection FNB provided effective analgesia, facilitated early ambulation, and reduced the length of acute hospitalization in patients undergoing total knee replacement.