CORTICAL POROSIS UNDER PLATES - REACTION TO UNLOADING OR TO NECROSIS

Cortical porosis under plates used for the fixation of fractures is often attributed to the interference of the plates with cortical perfusion, resulting in necrosis, which in turn induces remodeling. To our knowledge, no histomorphometric studies have been published that demonstrate the correlation between cortical necrosis and porosis. The objective of this study was to test the hypothesis that cortical necrosis is related to changes associated with porosis. Standard and railed plates mere applied to intact femora in ten dogs. Histomorphometric studies done at eight and twenty-four weeks after insertion of the plate failed to show a significant positive correlation between necrosis and porosis irrespective of the type of plate used. Porosis was always greater in the inner cortical sector, where no increased necrosis was noted, than in the outer cortical sector, where necrosis was present. CLINICAL RELEVANCE: Osteopenia under plates is a well accepted occurrence that causes weakening of bone. Reduction in the plate-bone contact area has been recommended to reduce necrosis-induced porosis. Two important findings contradict this recommendation: the absence of a positive correlation between necrosis and porosis and the absence of a difference in necrosis and porosis when plates with different bone-contact areas, were used. Railed plates did not reduce the occurrence of necrosis or porosis.