Ultrasound-guided flexor sheath block as a valid alternative to blind techniques for finger pain treatment: the horseshoe sign.

Background: The flexor sheath digital block allows effective analgesia and anesthesia for finger pain control. To date, only blind techniques are described in the literature in patients with finger fractures, supposedly due to the superficial position of the structures used as landmarks. We describe an ultrasound-guided technique with a definite endpoint to achieve this block.