INFECTION AFTER INTRAMEDULLARY NAILING - AN EXPERIMENTAL INVESTIGATION ON RABBITS

The purpose of this study was to investigate three relevant aspects of intramedullary nailing in terms of their effect on the occurrence of local infection. In an infection model on the rabbit tibia, the follow ing were compared: a hollow and a solid nail (Experiment I), a reamed with an unreamed technique (Experiment II), and a steel with a titaniu m nail (Experiment III). In order to minimize the number of animals re quired, a grouped sequential procedure combined with an ''up and down' ' dosage technique was applied. Microbiological evaluation was both qu alitative and quantitative. The results in Experiment I (n=44) indicat ed an infection rate for the hollow nail (59%) almost double that of t he solid nail (27%) (P less than or equal to 0.05). Experiment II (n=4 4) produced an infection rate of 50% for the unreamed technique compar ed to 64% for the reamed technique, a difference which, on the basis o f the number of bacteria present, was also statistically significant ( P less than or equal to 0.05). In Experiment III (n=44) an infection r ate of 82% was recorded for the steel nail compared to 59% for the tit anium nail (P less than or equal to 0.05). The results of the three ex periments are only partially comparable with each other because of the grouped sequential procedure and the different inocula used. Nonethel ess it would seem that the dead space inherent in the design of the ho llow nail represents a considerable risk with regard to the occurrence of local infection. Reaming the medullary cavity with the attendant r eduction in local vascularity and necrosis and the lesser biocompatibi lity of steel compared to titanium may be additional risk factors whic h should not be overlooked.