Humerus

Key Features & Anatomical Relations

The humerus (humeral bone) is the single bone found in the arm and is the largest bone in the upper limb. It is classified as a long bone and includes the following bony features:

- parts: head, anatomical neck, greater and lesser tubercles, body, and condyle;

- surfaces: anterolateral, anteromedial and posterior surfaces, and anterior, medial and lateral borders;

- landmarks: capitulum, trochlea, intertubercular sulcus, deltoid tuberosity, and olecranon and coronoid fossae.

More information regarding these and other bony features can be found in the Parts, Surfaces and Landmarks tabs for this bone.

The humerus is located:

- distal to the pectoral girdle;

- proximal to the radius and ulna.

It articulates with the:

- scapula at the glenohumeral (shoulder) joint;

- ulna at the humeroulnar joint, contributing to the formation of the elbow joint;

- radius at the humeroradial joint, also contributing to the formation of the elbow joint.

Ossification

Ossification of the humerus occurs at eight ossification centers, these are found in the:

- body, which appears in utero at the eighth week;

- head, which appears before birth or within the first six months after birth;

- greater tubercle, which appears within the first to second years;

- lesser tubercle, which appears within the fifth year;

- capitulum, which appears within the first year;

- trochlea, which appears within the ninth to tenth years;

- medial epicondyle, which appears within the fourth to sixth years;

- lateral epicondyle, which appears during the twelfth year.

The ossification centers for the head, greater tubercle, and lesser tubercle have all united by the sixth year. This united structure fuses with the body during adolescence.

The ossification centers for the capitulum, trochlea, and lateral epicondyle have all united by middle adolescence. This united structure fuses with the body during the fourteenth to sixteenth years, while the ossification center for the medial epicondyle fuses with the body during the twentieth year (Standring, 2016).

Variations

The intertubercular sulcus is often deeper, and more pronounced in males than females. In some individuals:

- a supracondylar process may occasionally be present on the distal portion of the anteromedial surface of the humerus and is formed by ossification of the variably present ligament of Struthers;

- a supratrochlear foramen may occasionally be present immediately superior to the capitulum and trochlea (Tubbs, Shoja and Loukas, 2016).

Surface Anatomy

The following bony features of the humerus are relevant to surface anatomy:

- the head may be felt during deep palpation of the axillary fossa;

- the greater tubercle may be deeply palpated through the deltoid muscle along the area inferior to the acromion;

- the lesser tubercle may be deeply palpating through the deltoid muscle along the area inferior to the coracoid process;

- both the medial and lateral epicondyles are subcutaneous and therefore easily palpable.

List of Clinical Correlates

- Fracture of humerus

- Dislocation of glenohumeral joint

- Dislocation of elbow joint

References

Standring, S. (2016) Gray's Anatomy: The Anatomical Basis of Clinical Practice. Gray's Anatomy Series 41st edn.: Elsevier Limited.

Tubbs, R. S., Shoja, M. M. and Loukas, M. (2016) Bergman's Comprehensive Encyclopedia of Human Anatomic Variation. Wiley.