CHAPTER 21 Elbow blocks
Sonoanatomy
The examination begins with the patient supine, the arm abducted, the forearm supinated, and the wrist halfway between pronation and supination (Fig. 21.5). A systematic survey should be performed from superficial to deep and medial to lateral. A high frequency ultrasound transducer is used. With a transverse orientation, the median nerve is found medial to the brachial artery at the elbow as a hyperechoic structure (Fig. 21.6). This is on the medial side of the antecubital fossa. The radial nerve, after winding around the humerus, descends in the intermuscular septum between the brachialis and brachoradialis initially, and then the extensor carpi radialis. The radial nerve is easily seen with ultrasound, as the deep and superficial branches between the brachioradialis and brachialis muscles at the elbow. This nerve appears as a hyperechoic oval structure on the radial side of the antecubital fossa. The two key structures to identify include the hypoechoic brachioradialis and brachialis muscles. The radial nerve lies in the fascial thickening between these (Fig. 21.7). The ulnar nerve is seen posterior to the medial epicondyle at the elbow level in the condylar groove (Fig. 21.8).

Figure 21.6 Sonosatomy relevant to median nerve block at the elbow. MN: median nerve; BA: brachial artery; B: bone.