Exposure of radial nerve in middle and distal thirds of arm. A, Skin incision begins at posterior margin of deltoid muscle and extends distally in midline and laterally and anteriorly. It ends at interval between brachioradialis and brachialis. B, Posterior skin flap has been dissected and retracted; deep fascia is incised in line with skin incision. Dotted lineindicates incision in triceps muscle between long and lateral heads. C, Radial nerve and accompanying vascular bundle have been exposed by retraction of these two heads of triceps muscle. Radial nerve has been dissected to point at which it passes beneath lateral head of triceps muscle. D, Arm is externally rotated a few degrees. Interval between proximal end of brachioradialis and brachialis is to be dissected, exposing radial nerve along anterolateral aspect of humerus. E, Dotted lineindicates incision through which lateral head of triceps is mobilized from underlying bone, facilitating exposure of radial nerve deep to it. F, Exposure. SEE TECHNIQUE 77.10.