A systematic approach to ultrasonography of the forearm was developed by the
authors to identify the nerve(s) innervating the injured region of the hand. The
radial nerve was identified using a 2-step procedure. First, the probe was
placed over the radial artery at the wrist so that the artery was seen in
cross-section. Second, the probe was moved proximally to the midforearm, keeping
the radial artery in the middle of the screen. The radial nerve was visualized
adjacent to the radial side of the radial artery. The ulnar nerve was identified
using the same 2-step procedure, starting at the distal ulnar artery. The ulnar
nerve was visualized adjacent to the ulnar side of the ulnar artery. The median
nerve does not have an associated median artery, except in rare anatomic
variants. Therefore, in the first step, the probe was centered over the volar
wrist, between the ulnar and radial arteries, and moved proximally. The median
nerve was visualized in the midforearm among the flexor digitorum muscle bundles
(Figure).
(71K)
Figure. Ulnar, median, and radial nerves (arrow) and arteries (arrowheads) in
the forearm.
The skin was prepared with povidone-iodine. Under real-time ultrasonographic
guidance, the sonographer or an assisting physician, using a 25-gauge needle,
injected 2 to 3 mL of a mixture of 1% lidocaine and 0.25% bupivacaine lateral
and medial to the identified nerve.
(Ann Emerg Med 2007;48(5):558)