External fixator pin tract infection model in the caprine (goat) tibia: a randomized, prospective, blinded study

Six goats had 2 Schanz pins inserted in each tibia. Twenty-four pins were inoculated with saline or Staphylococcus aureus. Three investigators, blinded to the inoculum, evaluated 23 pins at 14 days. Clinical pin tract infections developed in all inoculated pins and in 5/12 uninoculated pins, Quantitative cultures demonstrated that infections were produced in 10/11 inoculated and in 0/12 uninoculated pins. Prediction of culture status by clinical criterion (P<.01, Fisher Exact Test) had 100% sensitivity and a 58% specificity. The prediction of infection in inoculated sites by culture criterion (P<.001, Fisher Exact Test) had a 91% sensitivity and 100% specificity. A reproducible long bone pin tract infection model was developed that produced clinically and microbiologically evident pin tract infections.