Flexor Digitorum Tendon Sheath and First Annular (A1) Pulley

This is a supplement to page 45-46 of The Resident’s Manual of Ultrasound-Guided Procedures.

If you see the fluid quickly outline the tendon sheath, that’s a success.

Like others, this injection should not create a large bubble! That means you’re not within the sheath.

There was a lot to talk about on this page and I couldn’t fit any more information in the book.

The A1 pulley is usually seen slightly proximal to the MCP joint but in practice, it’s whichever pulley you find closest to the MCP joint.

The A2 pulley is more distal, close to the middle of the proximal phalanx, and it’s a bit wider.

Ideally, you should palpate the location of the nodule, where it catches, and/or where the pain is and plop the transducer right on top of that! If you get the medicine in the tendon sheath, it will treat most of the pulleys in the area.

This is a cool video. You can actually see the initial push of the injectate enter the space between the superficialis and profundus tendons of flexor digitorum (this one is of the 3rd digit).