Periplexus Versus Intraplexus Interscalene Block for Shoulder Arthroscopy
For arthroscopic rotator cuff repair under regional anesthesia alone, needle-tip philosophy still divides rooms: deposit local inside the fascial sheath (intraplexus) or just outside it (periplexus). A September 19, 2026 open-access randomized trial in BMC Anesthesiology compared the two for surgeon-rated surgical conditions. Both worked well—and the study was not powered to settle a small gap.
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. Median score was 5.0 in both groups (P=0.676). A perfect score of 5 occurred in about 89.7% of intraplexus versus 86.1% of periplexus cases (risk difference −3.5%, 95% CI −19.8% to 14.3%). No patient converted to general anesthesia. Secondary outcomes did not differ significantly. The authors note a ceiling effect and a wide confidence interval— and they do not claim non-inferiority.
What this changes—and what it doesn’t
My takeaway 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 peri- versus intraplexus based on what I can see clearly and how I want to manage risk around the plexus—not on an assumed large efficacy cliff between the two. A trial this size with near-perfect scores in both arms cannot rule out modest differences; the wide CI is the story as much as the point estimate.
Technique still does not erase anatomy. Phrenic involvement, vessel proximity, and unintended neuraxial spread remain interscalene realities whether the tip sits just outside or just inside the sheath. Regional-only shoulder lists also live or die on block onset, surgical communication, and a ready backup plan—none of which this comparison rearranges.
Clinical takeaways
- 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 both; no GA conversion).
- The study does not establish non-inferiority; ceiling effects and a wide CI leave room for small differences.
- Choose needle-tip position for visualization and safety comfort more than for a presumed large efficacy gap when blocks are well performed.
- Underpowered designs for tiny deltas are common in regional anesthesia—read “no significant difference” as “not proven different,” not “proven identical.”
- Watch block-specific risks (including phrenic effects) regardless of peri- versus intraplexus preference.
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.