Transformation of the external form of ribs overlying empyema cavities occurs so constantly that the nature of the transformation and its pathogenesis seemed worthy of investigation. An extensive search of the literature failed to provide information dealing with the subject, with the exception of descriptions of the gross deformities of ribs (Hedblom1).
These ribs, as every surgeon engaged in thoracic surgery has frequently observed, have lost their normal contour and have become relatively round, triangular or rectangular and somewhat larger in cross-sectional dimensions. As illustrated in figure 2 A, these changes have resulted from the deposition of subperiosteal new bone on the inferior borders and internal surfaces of the ribs. The greatest deposits are laid down along the angles of the ribs and taper off with the pleural reflections at both extremities, where they become quite normal in appearance. Since adjacent ribs frequently are in contact or overlap, synostoses