[Clinical characters of culture-negative prosthetic joint infection]

To explore the clinical characters and histopathologic differences between patients with culture-positive and culture-negative prosthetic joint infection (PJI).

Between January 2012 and July 2013, 66 PJI patients in accord with diagnostic criteria were enrolled. According to the results of preoperative aspiration and intraoperative cultures, the patients were divided into culture-negative group (CN group, n = 21) and culture-positive group (CP group, n = 45). There was no significant difference in gender, age, height, weight, and body mass index between 2 groups (P > 0.05). Preoperative C reactive protein (CRP), erythrocyte sedimentation rate (ESR), and prosthesis survival time were compared between 2 groups. Intraoperative frozen sections and paraffin sections were both performed to identify infections, and histological typing was performed according to Morawietz's methods.

The preoperative CRP was (1.29 +/- 1.84) mg/dL in CN group and (5.08 +/- 9.57) mg/dL in CP group, showing significant difference (t = 2.094, P = 0.038). The preoperative ESR was (22.86 +/- 28.42) mm/1 h in CN group and (36.74 +/- 31.26) mm/1 h in CP group, showing significant difference (t = 7.761, P = 0.000). The median survival time of prosthesis was 72 months (range, 8-504 months) in CN group and 25 months (range, 15 days-300 months) in CP group, showing significant difference (U = 2.231, P = 0.026). Morawietz's histological typing results showed that 2 cases were rated as type I, 7 cases as type II, and 12 cases as type III in CN group; 6 cases were rated as type I, 25 cases as type II, 13 cases as type III, and 1 case as type IV in CP group. The positive culture rate was 68.18% (45/66), and pathogenic bacteria was dominated by Staphylococcus, accounting for 68.89%.

The patients with culture-negative PJI have slow onset and mild inflammatory response, so comprehensive diagnosis should be made based on pathological detection, laboratory examination, and intraoperative cultures.