The Healing of Experimental Fractures by Compression Osteosynthesis: II.Morphometric and Chemical Analysis

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Abstract
The effects of rigid plate fixation on the structure and chemical composition of bones during healing of experimental fractures were studied by morphometric and chemical analysis at intervals of 3-24 wk after attachment of 6 hole AO [atypical osteosynthesis] plates to osteotomized rabbit tibiae. After fracture union gradual porotic transformation was observed from 9 wk onwards, with rapid excavation and breakdown of the cortical wall. After 24 wk the degree of porosity increased from 9.0 .+-. 4.8% to 37.5 .+-. 10.2% (P < 0.001). This osteoporosis was accompanied by formation of new subperiosteal bone. The changes in the tubular bone led to a progressive increase in overall diameter and in the area occupied by the medullary cavity throughout the experiment. In the osteotomy area the content of hexosamines and the ratio of hexosamines to hydroxyproline were increased at 3 wk, indicating formation of connective tissue in the fracture area. Later no chemical signs of callus formation were detected. Despite the slight increase in the hydroxyproline content reflecting the formation of new bone subperiosteally, the chemical composition of the unresorbed cortical bone remained unchanged.