FIGURE 1.14. Distal humerus, inferior surface, showing

articular surface and contours of trochlea and capitulum.

radial sulcus. The anterior portion of the distal third provides the origin area for the brachialis muscle (see above

under shaft of the humerus). The posterior portion of the

distal third and medial border of the medial and distal

thirds of the shaft provide the wide origin area of the medial

head of the triceps. The distal third of the medial border is

raised into a ridge, the medial supracondylar ridge. This

ridge becomes more prominent distally. The medial supracondylar ridge provides an anterior lip for a portion of the

origin of the brachialis muscle. The ridge also provides a

posterior lip for a portion of the medial head of the triceps

brachii. The medial intermuscular septum attaches in an

intermediate portion of the medial supracondylar ridge.

The lateral border of the humerus extends from the dorsal part of the greater tuberosity to the lateral epicondyle.

The lateral border separates the anterolateral surface of the

humerus from the posterior surface. The proximal half of

the lateral border is rounded and indistinctly marked, serving for the attachment of part of the insertion of the teres

minor, and the origin of the lateral head of the triceps

brachii. The sulcus or groove for the radial nerve (see above)

crosses the central portion of the lateral border of the

humerus. The distal part of the lateral border forms a

rough, prominent margin, the lateral supracondylar ridge.

The lateral supracondylar ridge provides the attachment

area for several structures. Superiorly, there is an anterior lip

for the origin of the brachioradialis muscle. Distal to this

area, the lateral supracondylar ridge provides an area for the

origin for the extensor carpi radialis longus. Distally, there

is a posterior lip for a portion of the origin of the medial

head of the triceps brachii. The intermediate portion of the

lateral supracondylar ridge provides the attachment site for

the lateral intermuscular septum.