Contamination of the medullary canal following pin-tract infection

We developed an ovine model of an external-fixator pin-tract infection. Wit h use of a novel method of tissue sampling, infection of the medullary cana l was confirmed in all (10 of 10) external-fixator pins that were contamina ted with Staphylococcus aureus after they were inserted. In addition, all ( five of five) adjacent, uncontaminated pins became infected. We demonstrate d that pin-tract infection can be difficult to diagnose clinically, despite gross infection of the tract, and that bacteria can spread within the medu lla, Three of the infected pins (20%) did not appear clinically infected, w ere not loose, and were normal on radiographs after 1 week. Staphylococcus aureus was isolated from the medulla around all 15 pin tracts, and nine oth er organisms were isolated from the tracts. Despite the presence of infecti on, the majority of the pins remained well fixed in the bone after 2 weeks.