Discussion
postoperative pain, nausea, NVM, pain
RECRUITMENT
The most important finding of this study was that distal FTB and proximal ACB preserve quadriceps muscle strength better than FNB at 6 h postoperatively. However, there were no significant differences between the three blocks in functional outcomes and patients who received a FNB showed better pain control.The quadriceps strength loss of the FNB-G1 was significantly higher at 6 h postoperatively, but there were no differences between the three groups at 24 or 48 h. Moreover, this initial difference in strength preservation did not translate to worse clinical outcomes. No significant differences were found in functional test outcomes at any time point nor LOS. Most of the authors have also reported worse quadriceps strength preservation with the use of FNB [The ACB has been proposed as an emerging effective analgesic technique in TKA [Our inferior analgesic outcomes with the use of the ACB may be explained by the absence of a consistent technique among the literature to perform this block. Initially, surface anatomical landmarks were used to locate the ACB injection point, but that was shown to be inaccurate as it usually leaded to the femoral triangle [Clinical differences due to multiple ACB locations could be partially explained by the nerve of the vastus medialis (NVM). This branch of the femoral nerve importantly contributes to the innervation of the anteromedial knee joint [In our study, we did not use perioperative corticosteroids nor LIA. Both of them could be useful tools to enhance pain control in a multimodal analgesia setting. It has been reported that intravenous dexamethasone reduces postoperative pain, opioid consumption and nausea [Our study is subjected to several limitations. First, an interim analysis detected significant differences in analgesic outcomes between the three groups and recruitment was stopped. Therefore, the minimum sample size was not reached. The interim analysis was not planned in advance; however, it was carried out due to an apparent highly heterogeneity in pain control among patients. Second, there was an uneven distribution of participants between the three groups. It could have been better controlled by using a block randomization design. However, the study groups were comparable in terms of baseline demographic data (we consider that the higher median age in G1 was statistically significant but clinically not relevant). Third, the study did not contain a control group without PNB (the local analgesic effect could be provided by LIA). On the other hand, it is a double-blinded RCT, which may allow to provide the highest level of evidence. Another strength of our work is that all the PNB were performed by an experienced anesthesiologist, using strict injection point location through anatomic and US landmarks. Furthermore, to homogenize the three groups, we used a 30 mL volume for all the PNB and an iPACK block was added to all participants.