Aims. This study aimed to investigate the role of quantitative histological analysis in the diagnosis of fracture-related infection (FRI). Patients and Methods. The clinical features, microbiology culture results, and histological analysis in 156 surgically treated nonunions were used to stratify the likelihood of associated infection. There were 64 confirmed infected nonunions (one or more confirmatory criteria: pus, sinus, and bacterial growth in two or more samples), 66 aseptic nonunions (no confirmatory criteria), and 26 possibly infected nonunions (pathogen identified from a single specimen and no confirmatory criteria). The histological inflammatory response was assessed by average neutrophil polymorph (NPs) counts per high-power field (HPF) and compared with the established diagnosis. Results. Assuming a cut-off of over five neutrophils per high-power field to diagnose septic nonunion, there was 80% sensitivity and 100% specificity (accuracy 90%). Using a cut-off of no neutrophils seen in any high-power field to diagnose aseptic nonunion, there was a sensitivity of 85% and a specificity of 98% (accuracy 92%). Conclusion. Histology can be used in a bimodal fashion as a diagnostic test for FRI. The presence of more than five NPs/HPF had a positive predictive value for infected nonunion of 100%, while the complete absence of any NPs is almost always indicative of an aseptic nonunion (positive predictive value of 98%). Cite this article: Bone Joint J 2018;100-B:966–72

Aim. The aim was to investigate the value of quantitative histological analysis in the diagnosis of fracture-related infection (FRI). Patients and Methods. The clinical features, microbiology culture results and histological analysis in 156 surgically treated non-unions were used to stratify the likelihood of associated infection. There were 64 confirmed infected non-unions (≥1 confirmatory criteria; pus, sinus and bacterial growth in ≥2 samples), 66 aseptic non-unions (no confirmatory criteria) and 26 possibly infected (pathogen identified from a single specimen and no confirmatory criteria). The histological inflammatory response was assessed by average neutrophil polymorphs (NPs) counts per high power field (HPF) and compared to the established diagnosis. Results. Assuming a cut-off of >5NPs/HPF for positive histological diagnosis, there was 80% sensitivity and 100% specificity (accuracy 90%). Using a cut-off of any NPs/HPF (>0) for negative histological diagnosis there was a sensitivity of 98% and a specificity of 85% (accuracy 92%). Conclusion. Histology can be used in a bimodal fashion as a diagnostic test for FRI. The presence of >5 NPs/HPF has a positive predictive value of 100%, while the complete absence of any NPs is almost always indicative of an aseptic non-union (negative predictive value: 98%)

Objectives. The risk of infection after type III° open fractures is high (10–50%). Preemptive antibiotic therapy may prevent posttraumatic infection and improve the outcome. Recommendations about the type and duration of antibiotic vary among the institutions and it remains unclear whether gram-negative bacilli or anaerobs need to be covered. In Europe, the most commonly recommended antibiotic is amoxicillin/clavulanic acid. We retrospectively analyzed microbiology, characteristics and outcome of patients with open type III° fractures treated at our institution. Methods. Between 01/2005 and 12/2009 we retrospectively included all type III grade open fractures of the leg at our institution classified after Gustilo (JBJS Am 1976) into type IIIA (adequate soft-tissue coverage of bone with extensive soft-tissue laceration or flaps), IIIB (extensive soft-tissue loss with periosteal stripping and bone exposure), and IIIC (requiring arterial injury repair). Demographic characteristics, clinical presentation, microbiology, surgical and antibiotic treatment and patient outcome were recorded using a standardized case-report form. Results. 30 cases of patients with type III° open fractures were included (25 males, mean age was 40.5 years, range 17–67 years). 27 fractures (90%) were located on the lower leg and 3 (10%) on the upper leg. 24 cases (80%) were high-energy and almost half of the patients (n=16, 53%) had a polytrauma. Microbiology at initial surgery was available for 19 cases (63%), of which 10 grew at least one organism (including 8 amoxicillin/clavulanic acid-resistant gram-negative bacilli [GNB], 7 amoxicillin/clavulanic acid-resistant Bacillus cereus), 11 were culture-negative. Preemptive antibiotics were given in all cases (100%) for an average duration of 8.5 days (range 1–53 days), the most common antibiotic was amoxicillin/clavulanic acid in 60 % (n=18). 11 cases just received preemptive antibiotic treatment, in 19 of 30 cases the antibiotic therapy was changed and prolonged. Microbiology at revision surgery was available for 25 cases and 22 grew at least one pathogen (including 32 amoxicillin/clavulanic acid-resistant gram-negative bacilli and 10 amoxicillin/clavulanic acid-resistant Bacillus cereus), 3 were culture-negative. Conclusions. At initial surgery, most common isolated organisms were coagulase-negative staphylococci (43%), Bacillus cereus (23%), and gram-negative bacilli (27%), and others (7%) of which 48% were resistant to amoxicillin/clavulanic acid. At revision surgery, isolated organisms were gram-negative bacilli (64%), Bacillus cereus (20%), and others (16%) of which 88% were resistant to amoxicillin/clavulanic acid. The spectrum of amoxicillin/clavulanic does not cover the most common isolated organisms