Superior trunk block matched the interscalene block but spared motor function

Design

Prospective, randomised, participant- and assessor-blinded, active-controlled trial

Population

68 adults undergoing elective arthroscopic shoulder surgery

Primary outcome

Postoperative pain (visual analogue scale) at rest and activity to 24 hours

Effect

No significant pain difference; superior trunk block preserved more motor function (P = 0.007)

The interscalene brachial plexus block is the usual regional technique for shoulder arthroscopy but commonly causes phrenic nerve paresis and dense arm weakness. This randomised trial compared it with a superior trunk block in 68 patients, using the same liposomal bupivacaine admixture in both.

Pain scores were comparable: there was no significant difference in resting or activity visual analogue scores at any timepoint to 24 hours. The difference was in motor function — the superior trunk group preserved more upper-limb movement on the modified Bromage scale (P = 0.007) — while early shoulder function at 24 hours was identical (median UCLA score 30 in both). No block-related complications occurred in either group.

For a service running enhanced-recovery pathways, this supports the superior trunk block as a motor-sparing alternative that keeps the analgesia. It is a single-centre trial of 68 patients, so confirmation in larger cohorts is still needed before it becomes the default.

• Randomised trial, 68 patients, shoulder arthroscopy; interscalene vs superior trunk block, same liposomal bupivacaine mix.
• No significant difference in rest or activity pain scores at any point to 24 hours.
• Superior trunk block preserved more upper-limb motor function (modified Bromage, P = 0.007).
• Early shoulder function at 24 hours was identical (median UCLA score 30 in both).
• No block-related complications in either group.

Why it matters

It offers a way to keep shoulder-surgery analgesia while avoiding the dense arm weakness and phrenic paresis that make the interscalene block limiting.

Don't overread it

This was a single-centre trial of 68 patients; it shows comparable analgesia with better motor-sparing, not a broader outcome advantage.

The statistics, in plain English

Equivalent pain scores with a significant motor-function advantage means the benefit is in what the block avoids, not better analgesia; with only 68 patients at one centre, the estimate needs replication.

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