Periplexus versus intraplexus injection for interscalene brachial plexus block during arthroscopic rotator cuff repair: a randomized controlled trial

The optimal needle-tip position for ultrasound-guided interscalene block remains debated. This study compared surgical conditions after intraplexus and periplexus injection during arthroscopic rotator cuff repair. In this prospective, randomized, assessor-blinded, controlled study, patients undergoing elective arthroscopic rotator cuff repair under regional anesthesia without planned general anesthesia were allocated to receive ultrasound-guided interscalene block using either intraplexus or periplexus injection. The primary outcome was surgical condition, independently rated by the blinded surgeon on a prespecified 5-point ordinal scale; the primary analysis compared the ordinal score distribution between groups. Secondary outcomes included arthroscopic irrigation pressure, sensory and motor block onset, supplemental medication, postoperative pain, patient satisfaction, adverse events, and site-specific pain responses. A post hoc exploratory analysis estimated the risk difference and confidence interval for the proportion of patients with a final surgical condition score of 5. All 68 randomized patients received the assigned block: 32 were allocated to intraplexus injection and 36 to periplexus injection. Two intraplexus participants were excluded after intervention because key intraoperative assessments were not captured owing to an operational data-collection failure, leaving 30 and 36 patients, respectively, in the final dataset. Primary-outcome data were available for 29 and 36 patients, respectively. Median surgical-condition scores were 5.0 [5.0–5.0] in both groups (Mann-Whitney U test, P = 0.676). A score of 5 was recorded in 26 of 29 patients (89.7%) in the intraplexus group and 31 of 36 patients (86.1%) in the periplexus group. The risk difference for periplexus versus intraplexus injection was − 3.5% points, with a Newcombe 95% confidence interval of -19.8 to 14.3% points. No participant required conversion to general anesthesia. No statistically significant between-group differences were detected for the reported secondary and exploratory outcomes. No statistically significant between-group difference in the observed surgical-condition ratings was detected. However, the marked ceiling effect and wide confidence interval limit inference, and the post hoc comparison with a non-prespecified − 30% point threshold does not establish non-inferiority. Clinical Research Information Service, KCT0004638, registered 22 January 2020.