Is Local Infiltration Analgesia the Preferred Analgesic Approach for Total Knee Arthroplasty?: Commentary on an article by Caroline Pic, MD, et al.: "No Benefit of Adductor Canal Block Compared with Anterior Local Infiltration Analgesia in Primary Total Knee Arthroplasty. A Single-Blinded Randomized Controlled Clinical Trial".

Abstract

Commentary Dr. Pic and colleagues are to be congratulated for performing a well-conducted randomized controlled trial. They address the important question of whether an adductor canal block (ACB) is better than local infiltration analgesia (LIA) for total knee arthroplasty, as judged by intravenous morphine usage in the first 48 hours. All 98 patients in this study received comprehensive multimodal analgesia: spinal anesthesia; posterior pericapsular infiltration with ropivacaine; oral acetaminophen, ketoprofen, and nefopam; and patient-controlled analgesia using intravenous morphine. The study failed to show a benefit from performing the nerve block. Because the ACB was not better, and because LIA seems to the authors to be safe and easier to perform, they conclude that LIA may be the technique of choice for pain relief after knee arthroplasty. Nevertheless, there are some caveats to consider when evaluating the study by Pic et al. First, it was a superiority trial, so strictly speaking one can only conclude that ACB was not shown to be superior to LIA. It was not designed as an equivalence trial, which would potentially have allowed investigators to claim that the 2 therapies “are the same.” Second, the authors have the reasonable belief that LIA is safe and easy to perform, but the study did not directly address either safety or ease of performance, and the study was too small to prove safety. However, many experienced anesthesiologists would likely also claim that ACB is safe and easy to perform. Now let us consider the paper’s conclusion; should we stop using peripheral nerve blocks for knee arthroplasty? The short answer is that the literature is still in conflict. Pic et al. emphasize this uncertainty by citing 3 meta-analyses comparing ACB to LIA that reach different conclusions on this very topic. One determined that ACB reduced opioid consumption more than LIA, with no differences in pain scores, strength, or ambulation1. Another found that LIA reduced both pain scores and opioid consumption more than ACB2. The paper by Pic et al. describes an excellent trial, but a single study may not be sufficient to clarify the literature. To take a Bayesian point of view, it is likely that an experienced orthopaedist will have an opinion as to whether LIA is better or worse than ACB for these patients. Although a good study should “move the needle” a bit, a single one may not be enough to cause the physician to abandon one practice for another. It is important to consider the details of a study and judge to what extent the study results can be generalized to one’s own practice. Local factors to consider include patient characteristics, local expertise, the overall analgesic plan, and use of additional nerve blocks. As the meta-analyses indicate, there is too much heterogeneity in the available studies to reach a clear conclusion. For example, the study by Pic et al. elegantly uses the same injectate for both LIA and ACB, plain 0.2% ropivacaine. However, is that the best choice for each injection? Many surgeons prefer complex mixtures for LIA, and anesthesiologists frequently use adjuvants for ACB and other nerve blocks. It is likely that a study that used perineural adjuvants such as dexamethasone in the ACB would show a longer duration of analgesia in the nerve block group. Alternatively, perhaps a study using a different formulation for the LIA would show that LIA gives better results than ACB. Perhaps the best way forward for now is to use both LIA and ACB. The combination of long-duration, motor-sparing nerve blocks with LIA is common practice at some institutions, and results in lower pain scores than LIA alone3. Sawhney et al. showed that the combination of LIA and ACB reduced pain with ambulation on the day after surgery more than either therapy alone4. Thus, although the study by Pic et al. is an important contribution, how to best provide motor-sparing analgesia for total knee arthroplasty remains an active field of research.