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ht is less distorted than that of the parts lying outside the perpendicular. The light and the plate remaining constant, the amount of distortion varies directly with the distance between the object and the plate. To ensure accuracy in the diagnosis of fracture by the X-rays, it is necessary to take two views of the limb--one in the sagittal and the other in the coronal plane. By the use of the fluorescent screen, the best positions from which to obtain a clear impression of the fracture may be determined before the radiograms are taken. Stereoscopic radiograms may be of special value in demonstrating the details of a fracture that is otherwise doubtful. Imperfect technique and faulty interpretation of the pictures obtained lead to certain fallacies. In young subjects, for example, epiphysial lines may be mistaken for fractures, or the ossifying centres of epiphyses for separated fragments of bone. The os trigonum tarsi has been mistaken for a fracture of the talus. In the vicinity of joints the bones may be crossed by pale bands, due to the rays traversing the cavity of the joint. In this way fracture of the olecranon or of the clavicle may be simulated. The neck of the femur may appear to be fractured if a foreshortened view is taken. It is possible, on the other hand, to overlook a fracture--for example, if there is no displacement, or if the line of fracture is crossed by the shadow of an adjacent bone. In deeply placed bones such as those about the hip, or in bones related to dense, solid viscera--for example, ribs, sternum, or dorsal vertebrae--it is sometimes difficult to obtain conclusive evidence of fracture in a radiogram. It is to be borne in mind also, and especially from the medico-legal point of view, that, as early callus does not cast a deep shadow in a radiogram, the appearance of fracture may persist after union has taken place. The earliest shadow of callus appears in from fourteen to twenty-one days, and can hardly be relied upon till the fourth or sixth week. The disturbed perspective produced by divergence of the rays may cause the fragments of a fracture to appear displaced, although in reality they are in good position. If the limb and the plate are not parallel, the bones may appear to be distorted, and errors in diagnosis may in this way arise. In this relation it should be mentioned that perfect apposition of the fragments and anatomically accurate restoration of the outline of the bo
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