Two continuous femoral nerve block strategies after TKA

The purposes of this study were to compare the pain score, systemic opioid consumption, and range of motion (ROM) between the group where the use of continuous femoral nerve block (CFNB) was discontinued on postoperative day 3 (POD 3) and the group where it was discontinued on POD 7 within an established clinical pathway for postoperative recovery after total knee arthroplasty (TKA) and to assess the treatment-related side effects and complications, as well as the functional status of these two groups of patients at 2 years after surgery.

This prospective, randomized, double-blinded trial compared the analgesic efficacy and the functional outcomes between group A (n = 30) where continuous femoral nerve block was performed until POD 3 (discontinued prior to the initiation of range of motion (ROM) exercises) and group B (n = 33), where the continuous femoral nerve block was performed until POD 7 (discontinued during the ROM exercise) after TKA.

The resting pain scores of group B were lower than those of group A but there was no significant difference between the two groups (n.s., P = 0.387). However, the peak pain scores during ROM exercise, beginning on POD3 through to POD14, were significantly lower in group B than in group A (P = 0.001). The cumulative morphine IV-PCA requirements through the POD 2 were similar in the two groups (n.s., P = 0.811). However, the cumulative oral oxycodone consumption during hospitalization was significantly lower in group B than in group A, P < 0.0001. Group B showed significantly greater satisfaction with their method of analgesia than group A (P = 0.001). Group A scored 2.0 (2.0–3.0), whereas group B scored 1.0 (1.0–2.0). At 2 years, there was no significant difference in the functional outcomes (the knee flexion and extension angle, the Knee Society Score, and WOMAC pain, stiffness, and function scale).

The study group who received 7-day continuous femoral nerve block after TKA showed superior analgesia and higher patient satisfaction during the hospital stay than those given 3-day continuous femoral nerve block. Despite the additional time, effort and cost to place and manage continuous femoral nerve catheters, the 7-day continuous femoral nerve block can be recommended as an effective and safe regional component of a multimodal analgesia strategy after TKA.

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