Periplexus Versus Intraplexus Interscalene Block for Shoulder Arthroscopy
For arthroscopic rotator cuff repair under regional anesthesia alone, needle-tip philosophy still divides operating rooms. Should local anesthetic be deposited inside the fascial sheath (intraplexus) or just outside it (periplexus)? A September 19, 2026 open-access randomized trial in BMC Anesthesiology compared the two approaches for surgeon-rated surgical conditions. Both worked well, although the study was not powered to settle a small difference.
In and colleagues randomized adults having arthroscopic rotator cuff repair with planned regional-only anesthesia (no planned general anesthetic) to intraplexus (n=32) or periplexus (n=36) interscalene brachial plexus block. After two exclusions, roughly 30 versus 36 patients entered the final analysis. The primary outcome was surgeon-rated surgical condition on a 5-point ordinal scale. The median score was 5.0 in both groups (P=0.676). A perfect score of 5 occurred in about 89.7% of intraplexus and 86.1% of periplexus cases (risk difference −3.5%, 95% CI −19.8% to 14.3%). No patient converted to general anesthesia, and secondary outcomes did not differ significantly. The authors acknowledge a ceiling effect and a wide confidence interval, and they do not claim non-inferiority.
What the trial does and does not settle
My conclusion is practical rather than doctrinal. When the block is solid, either needle-tip strategy can deliver excellent operating conditions for this surgery. I would choose a periplexus or intraplexus approach based on what I can see clearly and how I want to manage risk around the plexus, rather than on an assumed large difference in efficacy between the two. A trial of this size, with near-perfect scores in both arms, cannot rule out modest differences, and the wide confidence interval is as informative as the point estimate.
Technique does not erase anatomy. Phrenic involvement, vessel proximity, and unintended neuraxial spread remain realities of interscalene block whether the tip sits just outside or just inside the sheath. Regional-only shoulder lists also depend on block onset, communication with the surgeon, and a ready backup plan, and this comparison changes none of those requirements.
Implications for practice
In this RCT of regional-only arthroscopic rotator cuff repair, surgeon-rated conditions were excellent and similar with intraplexus and periplexus interscalene injection (median 5.0 in both groups, with no conversion to general anesthesia). The study does not establish non-inferiority, because ceiling effects and a wide confidence interval leave room for small differences. When blocks are well performed, I would base needle-tip position on visualization and safety comfort more than on a presumed large efficacy gap.
Underpowered designs for very small differences are common in regional anesthesia, and in such studies “no significant difference” should be read as “not proven different” rather than “proven identical.” Block-specific risks, including phrenic effects, deserve the same vigilance regardless of one’s preference for a periplexus or intraplexus approach.
Source
- In CB, Lee S, Sung TY, et al. Periplexus versus intraplexus injection for interscalene brachial plexus block during arthroscopic rotator cuff repair: a randomized controlled trial. BMC Anesthesiology. Published September 19, 2026. Article (doi: 10.1186/s12871-026-04258-0)
This post is clinician commentary for educational discussion. It is not medical advice for any reader’s personal care. Anesthesia and perioperative decisions should be made with the treating clinician based on the individual patient’s circumstances.