The Effect of Single-Injection Femoral Nerve Block Versus Continuous Femoral Nerve Block After Total Knee Arthroplasty on Hospital Length of Stay and Long-Term Functional Recovery Within an Established Clinical Pathway

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Abstract
Total knee arthroplasty (TKA) may result in severe pain, and single-injection femoral nerve blocks (SFNB) have been demonstrated to have a limited duration of analgesia. Continuous femoral nerve blocks (CFNB) can prolong the analgesic duration of SFNB. We prospectively randomized 36 patients undergoing TKA to CFNB versus SFNB and evaluated the effect on hospital length of stay (LOS) as the primary outcome within a standardized clinical pathway. Secondary outcomes included visual analog scale (VAS) pain scores, opioid consumption, and long-term functional recovery at 12 wk. Mean VAS resting scores were significantly lower among patients who received CFNB versus SFNB: first day (1.7 vs 3.3 [P = 0.002]) and second day (0.9 vs 3.2 [P < 0.0001]) after surgery. Mean maximal VAS scores during physical therapy were significantly lower among patients who received CFNB versus SFNB: first day (4.7 vs 6.3 [P = 0.01]) and second day (3.9 vs 6.1 [P = 0.0005]) after surgery. Mean oxycodone consumption was significantly lower among patients who received CFNB versus SFNB: 15 mg versus 40 mg (P = < 0.0001) on the first day after surgery; 20 mg versus 43 mg (P = 0.0004) on the second day after surgery. There was no difference in hospital LOS (3.8 vs 3.9 days) or long-term functional recovery (117° versus 113° knee flexion at 12 wk) between the two groups. The lack of effect provided by increased duration of analgesia (from CFNB) after TKA may now have minimal impact on hospital LOS and long-term functional recovery in the contemporary healthcare environment within the United States.