12. Surface Markings of the Upper Extremity

The position of the radial artery in the forearm is represented by a line from the lateral margin of the Biceps tendon in the center of the anticubital fossa to the medial side of the front of the styloid process of the radius when the limb is in the position of supination. The situation of the distal portion of the artery is indicated by continuing this line around the radial side of the wrist to the proximal end of the first intermetacarpal space. 6 On account of the curved direction of the ulnar artery, two lines are required to indicate its course; one is drawn from the front of the medial epicondyle to the radial side of the pisiform bone; the lower two-thirds of this line represents two-thirds of the artery; the upper third is represented by a second line from the center of the hollow in front of the elbow-joint to the junction of the upper and middle thirds of the first line. 7 The superficial volar arch (Fig. 1237) can be indicated by a line starting from the radial side of the pisiform bone and curving distalward and lateralward as far as the base of the thumb, with its convexity toward the fingers. The summit of the arch is usually on a level with the ulnar border of the outstretched thumb. The deep volar arch is practically transverse, and is situated about 1 cm. nearer to the carpus. 8

FIG. 1237– Palm of left hand, showing position of skin creases and bones, and surface markings for the volar arches. (See enlarged image) Nerves (Figs. 1235, 1236).—In the arm the line of the median nerve is practically the same as that for the brachial artery; at the bend of the elbow the nerve is medial to the artery. The course of the nerve in the forearm is marked by a line starting from a point just medial to the center of one joining the epicondyles, and extending to the lateral margin of the tendon of Palmaris longus at the wrist. 9 The ulnar nerve follows the line of the brachial artery in the upper half of the arm, but at the middle of the arm it diverges and descends to the back of the medial epicondyle. In the forearm it is represented by a line from the front of the medial epicondyle to the radial side of the pisiform bone. 10

The course of the radial nerve can be indicated by a line from just below the posterior axillary fold, to the lateral side of the humerus at the junction of its middle and lower thirds; thence it passes vertically downward on the front of the arm to the level of the lateral epicondyle. The course of the superficial radial nerve is represented by a continuation of this line downward to the junction of the middle and lower thirds of the radial artery; it then crosses the radius and runs distalward to the dorsum of the base of the first metacarpal bone. 11 The axillary nerve crosses the humerus about 2 cm. above the center of a line joining the tip of the acromion to the lower edge of the deltoid tuberosity. 12

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