[1] We do not employ the term “diastasis,” which has been used in different senses by different writers.

In young subjects before the bones are fully developed the epiphyses may be separated from the diaphyses. The use of the X-rays has added greatly to our knowledge of these lesions.

It is useful to remember that in the upper extremity the epiphyses in the regions of the shoulder and wrist, and, in the lower extremity, those in the region of the knee, are the latest to unite; and that it is in these situations that growth in length of the bone goes on longest and most actively (twenty to twenty-one years). Injuries of these epiphyses, therefore, are most liable to interfere with the growth of the limb.

An epiphysis is nourished from the articular arteries and through the vessels of the periosteum.

Pathological Separation of Epiphyses.—There are certain pathological conditions, such as rickets, scurvy, congenital syphilis, tubercle, suppurative conditions, and tumour growths, which render separation of the epiphyses liable to occur from injuries altogether insufficient to produce such lesions under normal conditions.

Traumatic Separations.[2]—Speaking generally, it may be said that injuries which in an adult would be liable to produce dislocation, are in a young person more apt to cause separation of an epiphysis. Indirect violence, especially when exerted in such a way as to combine traction with torsion,—for example, when the foot is caught in the spokes of a carriage wheel,—is the commonest cause of epiphysial separation. Direct violence is a much less frequent cause. Muscular action occasionally produces separation of the epiphyses—for example, the anterior superior iliac spine, the small trochanter of the femur, or the upper end of the fibula.

[2] We desire here to acknowledge our indebtedness to Mr. John Poland's work on Traumatic Separation of the Epiphyses.

Fig. 8.—Partial Separation of Epiphysis, with Fracture running into Diaphysis. Fig. 9.—Complete Separation of Epiphysis.
Fig. 10.—Partial Separation with Fracture of Epiphysis. Fig. 11.—Complete Separation with Fracture of Epiphysis.

The majority of separations take place between the eleventh and the eighteenth years, chiefly because during this period the injuries liable to produce such lesions are most common. They do not occur after twenty-five, because by that time all the epiphyses have united. In females this form of injury is rare, and almost invariably occurs before puberty.

The following are the most common seats of separation in the order of their frequency: (1) the lower end of the femur; (2) the lower end of the radius; (3) the upper end of the humerus; (4) the lower end of the humerus; (5) the lower end of the tibia; and (6) the upper end of the tibia.