Narrowing the blockade field: development of an optimal postoperative analgesia regimen for total knee arthroplasty.

Abstract

Total knee arthroplasty (TKA) is associated with significant postoperative pain. Pain management for TKA is complex, and even with administration of multiple nerve blocks, highquality postoperative analgesia cannot always be achieved. Multiple regional approaches, including femoral nerve block (FNB), fascia iliaca block, conventional or three-in-one (i.e., inguinal paravascular) lumbar plexus block, and adductor canal block (ACB) (with or without periarticular infiltration), have been attempted to minimize knee pain following the procedure with variable success. Historically, FNB has been the most commonly performed regional technique. Although FNB provides substantial coverage of the operative area, it may spare areas innervated by other inferior branches of the lumbar plexus, including the lateral femoral cutaneous and obturator nerves, resulting in inadequate analgesia. Since branches of the sciatic nerve also innervate the knee, various studies have examined whether supplementing FNB with sciatic nerve block (SNB) provides superior analgesia following TKA. In this issue, Abdallah et al. discuss their meta-analysis of several recent randomized-controlled trials, which they performed in an attempt to address the effectiveness of a combined FNB and SNB approach. The authors show that, although individual studies provide mixed results, overall trends suggest that combining SNB and FNB can reduce opioid consumption and alleviate knee pain postoperatively compared with FNB alone. As Gaston Labat, the father of modern regional anesthesia, stated in his classic textbook, ‘‘Anatomy is the foundation upon which the entire concept of regional anesthesia is built.’’ Thus, a comprehensive understanding of anatomy is critical in order to select the appropriate block for the procedure and to provide effective analgesia. Branches from the lumbar (femoral and obturator nerves) and sacral (tibial and common peroneal nerves) plexuses provide innervation to the knee joint, and the saphenous nerve, a branch of the posterior division of the femoral nerve, provides some sensory supply to the medial aspect of the knee. The involvement of multiple nerves highlights the complexity of providing quality analgesia following knee surgery. In theory, a combination of lumbar plexus block and proximal SNB would provide the most effective analgesia; however, this approach would be complicated technically and would likely result in extensive motor block of the entire lower extremity. Although FNB is generally considered the gold standard for TKA analgesia, it has declined in popularity in favour of approaches that block a narrower region proximal to the knee. Indeed, one reason FNB has gradually fallen out of favour is its propensity for prolonged motor blockade. This attribute can cause quadriceps weakness and a delay in patient mobilization and rehabilitation, which raises concerns about delayed discharge from the hospital. Since proximal SNBs (which were the only approaches included in the Abdallah et al. meta-analysis) target the sciatic nerve before its bifurcation, both the tibial and common peroneal nerves are anesthetized, increasing the potential for sensory and motor blockade. Nevertheless, Abdallah et al. found that the addition of SNB did not significantly delay functional recovery or discharge from hospital. This finding suggests that the FNB alone can be responsible for the motor impairment that precludes early mobilization and that its effects eclipse any effects of the SNB that would impede early mobilization. B. C. H. Tsui, MD (&) Department of Anesthesiology and Pain Medicine, University of Alberta, 2-150 Clinical Sciences Building, Edmonton, AB T6G 2G3, Canada e-mail: btsui@ualberta.ca