#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_.
[Illustration: FIG. 8.--Partial Separation of Epiphysis, with Fracture running into Diaphysis.]
[Illustration: FIG. 9.--Complete Separation of Epiphysis.]
[Illustration: FIG. 10.--Partial Separation with Fracture of Epiphysis.]
[Illustration: 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.
_Morbid Anatomy._--In a true separation the epiphysial cartilage remains attached to the epiphysis. As a rule the epiphysis is not completely separated from the diaphysis, the common lesion being a separation along part of the epiphysial line, with a fracture running into the diaphysis (Fig. 8). It is not uncommon for more than one epiphysis to be separated by the same accident--for example, the lower end of the femur and the upper ends of the tibia and fibula. Epiphysial separations, like fractures, may be _simple_ or _compound_. Incomplete separations are liable to be overlooked at the time of the accident, but there is reason to believe that they may form the starting-point of disease. Strain of the epiphysial junction--the _juxta-epiphysial strain_ of Ollier--is a common injury in young children.