Landmarks Medical and Surgical

by Luther Holden; James Shuter

137. Landmarks of elbow.—It is of great importance to be familiar with the relative positions of the various bony prominences about the elbow. We can always feel the internal and external condyles. The internal is the more prominent of the two, and a trifle higher.

Olecranon.—We can always feel the olecranon. This is somewhat nearer to the inner than to the outer condyle. Between the olecranon and the internal condyle is a deep depression in which lies the ulnar nerve (vulgarly called the ‘funny bone’).

On the outer side of the olecranon, just below the external condyle, is a pit in the skin, constant even in fat persons (when the elbow is extended). This pit is considered one of the beauties of the elbow in a graceful arm; it is seen in a child as a pretty little dimple. To the surgeon it is most interesting, as in this valley behind the supinator longus and the radial extensors of the wrist he can distinctly feel the head of the radius rolling in pronation and supination of the forearm. It is, therefore, one of the most important landmarks of the elbow, since it enables us to say whether the head of the radius is in its right place, and whether it rotates with the shaft.

Can the tubercle of the radius be felt? Yes, but only on the back of the forearm in extreme pronation. Its projection is then distinctly perceptible just below the head of the bone.

Relations of olecranon and condyles.—To examine the relative positions of the olecranon and condyles in the different motions of the elbow joint, place the thumb on one condyle, the tip of the middle finger on the other, and the tip of the forefinger on the olecranon. In extension, the highest point of the olecranon is never above the line of the condyles; indeed, it is just in this line. With the elbow at right angles the point of the olecranon is vertically below the line of the condyles. In extreme flexion the point of the olecranon lies in front of the line of the condyles.

All these relative positions would be altered in a dislocation of the ulna, but not (necessarily) in a fracture of the lower end of the humerus.

Sometimes, though rarely, we meet with a hook-like projection of bone above the internal condyle. It is called a ‘supra-condyloid’ process; it can be felt through the skin, with its concavity downwards, and is a rudiment of the bony canal which, in many mammalia, transmits the median nerve and ulnar artery. A third origin of the pronator teres is always attached to it; this origin covers the brachial artery.[10]

Bursæ.—The subcutaneous bursa over the olecranon, if distended, would be as large as a walnut. A second bursa sometimes exists a little lower down upon the ulna. There is also a small subcutaneous bursa over each of the condyles.

The vertical extent of the elbow joint is limited, above by a line drawn from one condyle to the other; below, by a line corresponding to the lowest part of the head of the radius.

138. Interosseous arteries.—About one inch below the head of the radius, the ulnar artery gives off the common interosseous; and this divides, about half an inch lower, into the anterior and posterior interosseous. Thus, in amputating the forearm, say two inches below the head of the radius, four arteries at least would require ligature.