This section is from the book "Applied Anatomy: The Construction Of The Human Body", by Gwilym G. Davis. Also available from Amazon: Applied anatomy: The construction of the human body.
The head and neck of the radius are rarely fractured. When broken, the line of fracture through the head is usually longitudinal and a portion of the head is chipped off. The fragment is liable to become displaced, and either creates inflammation and suppuration or becomes fixed and greatly interferes with motion. For these reasons the fractured head has been frequently excised. A similar displacement may occur when the neck of the radius is fractured.
In this latter injury an anterior angular deformity is said to have been produced by the action of the biceps pulling the lower fragment, to which it is attached, forwards.
The classical specimen in the Mutter Museum of the College of Physicians of Philadelphia is usually instanced as an example of this action. The possibility of its occurrence suggests the treatment of the injury with the elbow flexed to relax the biceps muscle.
Traumatic epiphyseal separations are possible, but so rare as to be seldom detected. Supracondylar fractures in children, though not infrequently described as separations of the epiphysis are probably more often true bony fractures.
The lower end of the humerus ossifies by four centres. Three of them, those for the lateral (external) condyle, capitellum and outer portion of the trochlea, and inner portion of the trochlea, appear at the twelfth, third, and twelfth years and fuse and unite with the shaft at about the sixteenth year. The fourth, for the internal condyle, appears at the fifth and unites about the seventeenth or eighteenth year. The epiphyseal line runs close to the edge of the articular surface and is below the level of a transverse line joining the upper edges of the two condyles (Fig. 315). A true epiphyseal separation would thus be intra-articular and would involve comparatively only a thin shell of the articular surface. As already stated most of the cases regarded as epiphyseal separations are probably true supracondylar fractures.
Most of the olecranon process is a direct outgrowth from the shaft of the ulna. At about the tenth year a thin shell forms at its extremity which unites at the sixteenth year. Therefore fractures which pass through the bottom of the greater sigmoid cavity are not separations of the epiphysis but true fractures.