CORTICAL POROSIS UNDER PLATES - REACTION TO UNLOADING OR TO NECROSIS

Cortical porosis under plates used for the fixation of fractures is of ten attributed to the interference of the plates with cortical perfusi on, resulting in necrosis, which in turn induces remodeling. To our kn owledge, no histomorphometric studies have been published that demonst rate the correlation between cortical necrosis and porosis. The object ive of this study was to test the hypothesis that cortical necrosis is related to changes associated with porosis. Standard and railed plate s mere applied to intact femora in ten dogs. Histomorphometric studies done at eight and twenty-four weeks after insertion of the plate fail ed to show a significant positive correlation between necrosis and por osis irrespective of the type of plate used. Porosis was always greate r in the inner cortical sector, where no increased necrosis was noted, than in the outer cortical sector, where necrosis was present. CLINIC AL RELEVANCE: Osteopenia under plates is a well accepted occurrence th at 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 co rrelation 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 o r porosis.