Histological assessment of the presence or absence of infection in fracture non-union.

Abstract

Infection is a major cause of non-unions. Infection is not always evident clinically, nor on bacteriological analysis. If it is untreated, non-union treatment may fail. To establish whether histological analysis is of value as an adjunct to microbiology in establishing the diagnosis of infection. Sixty patients who had both bacteriological and histological analysis of their non-unions were studied. Infection was indicated by an acute inflammatory response. In 45 of the 60 fractures, microbiological and clinical diagnoses were in agreement; in this subset the histology results were compared to the established diagnoses. The histological diagnosis for the 45 fractures in the group with a definite diagnosis gave four false negatives but no false positives. This represents a sensitivity of 87.1%, (95% CI, 70-96%) and a 100% specificity (95% CI, 77-100%). The overall accuracy was 91.1%. (95% CI, 79-98%) The predictive value of a positive test was 100% and of a negative test was 77.8%. In 25% of the series a definite diagnosis could not be made with purely clinical and microbiological information; with the additional histological information it was possible to determine the infection status of the non-union. Histology is of particular use when the microbiology is negative or equivocal.