This cadaver study measured brachial plexus strain across 17 shoulder positions during simulated lateral decubitus arthroscopy. Strain gauges were placed on the upper trunk, lateral cord, median nerve, and radial nerve in five cadavers. The goal was to find positions that keep arthroscopic visibility while minimizing traction strain on the nerves.
When you set up a lateral decubitus shoulder arthroscopy with arm traction, remember that the position giving the best view is not the safest for the plexus. The classic 30° flexion / 70° abduction gives excellent visibility of all three regions but the highest nerve strain in this study.
The practical rule: opening the arm up with more flexion or abduction unloads the plexus, so favor positions like 45° flexion / 90° abduction and drop traction weight when you can. Because strain scales inversely with nerve cross-sectional area, small and thin patients are at higher risk for the same weight, so be conservative with traction loads in them.
This is the mechanical basis for the transient paresthesias reported in traction-based shoulder arthroscopy, and it explains why positioning discipline matters even for a routine scope.
This cadaver study measured brachial plexus strain across 17 shoulder positions during simulated lateral decubitus arthroscopy. Strain gauges were placed on the upper trunk, lateral cord, median nerve, and radial nerve in five cadavers. The goal was to find positions that keep arthroscopic visibility while minimizing traction strain on the nerves.
When you set up a lateral decubitus shoulder arthroscopy with arm traction, remember that the position giving the best view is not the safest for the plexus. The classic 30° flexion / 70° abduction gives excellent visibility of all three regions but the highest nerve strain in this study.
The practical rule: opening the arm up with more flexion or abduction unloads the plexus, so favor positions like 45° flexion / 90° abduction and drop traction weight when you can. Because strain scales inversely with nerve cross-sectional area, small and thin patients are at higher risk for the same weight, so be conservative with traction loads in them.
This is the mechanical basis for the transient paresthesias reported in traction-based shoulder arthroscopy, and it explains why positioning discipline matters even for a routine scope.