Introduction Total knee arthroplasty is associated with significant postoperative pain. Continuous adductor canal blocks via an inserted adductor canal catheter are effective analgesia interventions with the advantage of decreasing quadriceps weakness and the potential of extending the analgesic effect. The classical adductor canal catheter insertion technique may have a high likelihood of catheter dislodgement out of the canal. The interfascial plane between the sartorius muscle and femoral artery (ISAFE) approach has the potential of decreasing the adductor canal catheter migration. The purpose of this study was to evaluate the incidence of catheter dislodgment to outside the adductor canal, for ISAFE and classical approaches. We hypothesized that ISAFE approach would result in a lower dislodgment rate.

Methods Ninety-seven patients for unilateral total knee arthroplasty were included and randomized to either ISAFE intervention group or conventional group. The primary outcome was the incidence of adductor canal catheter dislodged to outside the adductor canal, on ultrasound evaluation, 24 hours after the surgery. Secondary outcomes were pain scores, opioid consumption and continuous adductor canal block related complications for the first 48 hours after surgery.

Results The catheters placed using ISAFE approach had a lower rate of dislodgement in comparison to the control group (18.6% vs 44.9%, respectively, p=0.01), at 24 hours after surgery; and lower pain scores for rest, on the first two postoperative days.

Conclusions ISAFE group had a significantly lower rate of dislodgement at 24 hours. The continuous adductor canal block analgesic benefit for knee arthroplasty depends on the position of the tip of the catheter inside the adductor canal.