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 VAS difference; superior trunk block more motor-sparing (higher modified Bromage, p=0.007)

The interscalene block is the default for shoulder-arthroscopy analgesia, but it commonly causes phrenic nerve paresis and a dense, near-complete motor block of the arm. The superior trunk block is an anatomically targeted alternative meant to keep analgesia while sparing distal motor function. This randomised trial gave 68 patients an identical liposomal bupivacaine admixture via either block.

Pain scores at rest and on movement did not differ between the techniques at any time point to 24 hours, so analgesia was comparable. But the superior trunk block preserved significantly more upper-limb motor function on the modified Bromage scale, while early shoulder function at 24 hours was the same.

For a unit using enhanced-recovery pathways, this supports the superior trunk block as a motor-sparing option that does not trade away pain control — useful where early mobility matters or where phrenic-sparing is desirable. It is a single, small trial, so confirm it fits your technique and case mix before switching a default.

• Rest and activity pain scores did not differ between superior trunk and interscalene blocks through 24 hours.
• The superior trunk block preserved significantly more upper-limb motor function (higher modified Bromage scores, p=0.007).
• Early shoulder function at 24 hours was comparable (identical median UCLA score of 30).
• Consider the superior trunk block where motor-sparing or phrenic-sparing matters, confirming it suits your technique first.

Why it matters

It offers a way to keep shoulder analgesia without the dense motor and phrenic blockade that limits the interscalene approach.

Don't overread it

Single-centre, 68 patients — it supports the superior trunk block as an option, not as a proven superior default.

The statistics, in plain English

That the pain scores did not separate means the two blocks worked equally for analgesia; the motor difference on the Bromage scale is where they diverged. With 68 patients this shows the motor-sparing effect but cannot rule out small analgesic differences.

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