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.
Clinical Features.—The symptoms simulate those of dislocation rather than of fracture. Thus, unnatural mobility at an epiphysial junction may closely resemble movement at the adjacent joint, especially when the epiphysis is an intra-capsular one. The relationship of the bony points, however, serves to indicate the nature of the lesion. The degree of deformity is often slight, because the transverse direction of the lesion, the breadth of the separated surfaces, and the firmness of the periosteal attachment along the epiphysial line often prevent displacement. In many cases a distinct, rounded, smooth, and regular ridge, caused by the projection of the diaphysis, can be felt. The peculiar “muffled” nature of the crepitus is one of the most characteristic signs. The older the patient, and the further ossification has progressed, the more does the crepitus resemble that of fracture.
Of the subsidiary signs, loss of power in the limb is one of the most constant; indeed, in young children it is sometimes the first, and may be the only, sign that attracts attention. Pain and tenderness along the epiphysial line are valuable signs, particularly when the lesion is due to indirect or muscular violence and there is no bruising of soft parts. Localised swelling, accompanied by ecchymosis, is often marked; and the adjacent joint may be distended with fluid.
As distinguishing this injury from a dislocation, it may be noted that in epiphysial separation there is no snap felt when the deformity is reduced, the tendency to re-displacement is greater, and the amount of relief given by reduction less than in dislocation. The use of the Röntgen rays at once establishes the diagnosis.
Prognosis and Results.—In the majority of cases union takes place satisfactorily by the formation of callus in the spongy tissue of the diaphysis and on the deep surface of the periosteum. In spite of the favourable nature of the prognosis in general, however, the friends of the patient should be warned that a completely satisfactory result cannot always be relied upon.
Deformity, with stiffness and locking at the adjacent joint, especially at the elbow, may result from imperfect reduction, or from exuberant callus. Arrest of growth of the bone in length is a rare sequel, and when it occurs, it is due, not to premature union of the epiphysis with the shaft, but to diminished action at the ossifying junction.
When the growth of one of the bones of the leg or forearm is arrested after separation of its epiphysis while the other bone continues to grow, the foot or hand is deviated towards the side of the shorter one.
Partial separations may be overlooked at the time of the accident and cause trouble later from bending of the bone, as in one variety of coxa vara. The epiphysis at the lower end of the femur may be displaced into the ham and press on the popliteal vessels.
Treatment.—The general principles which govern the treatment of fractures apply equally to epiphysial separations, the essential being the accurate replacement of the epiphysis.
In compound separations of epiphysis, the end of the diaphysis may be pushed through the skin. The entrance of sepsis may prove an obstacle to any operative measure that would otherwise be indicated.