Background and Aims The femoral triangle block (FTB) and adductor canal block (ACB) have become standard analgesia for total knee arthroplasty (TKA). We compared the anatomical difference and postoperative recovery between two blocks.
Methods We randomly assigned 118 patients to the FTB or ACB group. Patients were given 10 mL of 0.25% levobupivacaine as FTB or ACB. FTB was defined as at the mid-thigh, and ACB at the apex of the femoral triangle. The primary outcome was to achieve the discharge criteria (pain control with oral analgesics, knee flexion >90°, and ambulatory rehabilitation). ACB would be noninferior to FTB if the 95% confidence interval of the two groups’ differences were closer to zero than -9 hours (margin). We compared the local anesthetic spread, straight leg raise (SLR), and other outcomes.
Results The time to achieve discharge criteria was 56.3±17.3 hours in the ACB group and 56.2±18.4 hours in the FTB group, a difference of 0.1 hours (95% CI: -6.4–6.6 hours, p=0.97), establishing noninferiority. At one hour postoperatively, 48 of 60 patients in ACB and 40 of 58 patients in FTB were capable of SLR (Odds ratio:0.59, p=0.29), a non-significant difference. The distance between the two points was 5.1 (4.9–5.4) cm, and the spread of local anesthetics was 6.9 cm cephalad, 5.1 cm caudad. There were no differences in pain scores or other outcomes.
Conclusions ACB was non-inferior to FTB in time to achieve discharge criteria. We must warn of the potential quadriceps weakness after local anesthetic injection because of the high cephalad spread.