PSEUDOFRACTURES may be described as transverse zones of rarefaction varying in width from less than a millimeter to more than a centimeter, affecting various portions of the skeletal system and usually symmetrically distributed. They are mistaken frequently for true fractures and, since they are generally an indication of certain weaknesses or dysfunction of the skeletal system, it is important that their true character be identified. Several authors have concluded that certain of these lesions constitute a new disease entity, while others have reported them under a great variety of names, such as pseudofractures (36), spontaneous fractures (61), Looser's zones (23), Umbauzonen (48), Umbaufrakturen (63), multiple spontaneous idiopathic symmetrical fractures (56), osteoporosis melolytica (47), march fractures (19), and insufficiency fractures (33). Because of the obvious confusion regarding the significance of the condition and the relationship of the different forms which it assumes, this study was undertaken in an attempt to ascertain the relation of the lesions to one another and to determine whether or not there is any justification for considering them a new disease entity. Roentgenographically these skeletal defects show three different forms. (1) Those associated with certain malacic diseases may appear as small, subperiosteal notches in the cortex when viewed tangentially, or as small, irregularly circular, punched-out zones of decalcification when viewed en face (Figs. 1 and 2). This type of defect slowly progresses across part or all of the bone as a band of decalcification, finally appearing as if the lime salts had been erased in that area without disturbing the continuity of the bone (Figs. 3 and 4). The margins of these zones are usually straight and lie at right angles to the long axis of the bone. They may. however, be irregular, diagonal, or Z-shaped. The ends of the bony fragments adjacent to the band of pseudofracture may show a narrow zone of increased density. A periosteal reaction is sometimes observed in the region of the defect, and in curved bones may be apparent only on the concave side. (2) Those lesions not associated with malacic disease may be revealed as cracks or fissures extending through the cortex on one side, most often on the convex surface in pathologically curved bones (Figs. 5 and 6). (3) The third type of lesion appears as a fusiform callus formation and periosteal reaction only (Fig. 7). No crack or zone of decalcification is apparent roentgenographically. The condition involves flat bones as well as long bones and may be widespread throughout the skeletal system (Fig. 8). In advanced cases it has a tendency to affect paired bones in a more or less symmetrical manner, although single lesions may be found. The defects differ from actual fractures in several respects. They appear to develop spontaneously without gross trauma, but gross trauma may convert them into true fractures (Figs. 3b and 6b).
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Camp et al. (1941) studied this question.