THA after acetabular fracture fixation: Is frozen section necessary?

Background: Infection is uncommon after THA performed for failed acetabular fracture repair, despite a high reported incidence of culture-positive fixation implants. The use of frozen section analysis at the time of THA after acetabular fracture fixation surgery is unknown. Questions/purposes: We asked whether frozen section analysis predicted occult infection after THA performed after acetabular fracture repair. Methods: We retrospectively reviewed the charts of 43 of 49 patients with prior acetabular fracture fixation who had intraoperative frozen section and culture data from a conversion THA between 2002 and 2010. The average age of patients at fracture was 53 years; conversion was performed after an average of 553 days (median, 369 days; range, 51-2951 days). Five patients had an infection after acetabular fracture surgery (three deep, two superficial). At conversion we obtained an average of three frozen section specimens per patient; 10 specimens in eight patients contained greater than 10 polymorphonuclear cells/high-power field. The minimum followup was 51 days (median, 256 days; range, 51-2085 days). Results: Five patients had positive intraoperative cultures, three of whom had a positive frozen section. All patients who had prior deep infection developed positive intraoperative cultures. The sensitivity, specificity, positive predictive value, and negative predictive value of frozen section analysis were 0.60, 0.87, 0.38, and 0.94, respectively. Conclusion: Infection complicating THA after acetabular fracture repair is uncommon. A history of deep infection complicating the acetabular fracture surgery was the strongest predictor of infection. Frozen section analysis has a high specificity and negative predictive value. Level of Evidence: Level III, diagnostic study. See Guidelines for Authors for a complete description of levels of evidence.