Exciting Performance of Plasma Fibrinogen in Periprosthetic Joint Infection Diagnosis.

OBJECTIVE: To test the significance of serum C-reactive protein (CRP), the erythrocyte sedimentation rate (ESR), the platelet count/mean platelet volume ratio (PC/MPV), plasma fibrinogen, and D-Dimer in periprosthetic joint infection (PJI) diagnosis. METHODS: We retrospectively analyzed the clinical data of 149 patients diagnosed from July 2016 to December 2019 with primary osteoarthritis (OA group, average age 63.18 years [range, 53-82 years] 18 males, 46 females), PJI (PJI group, average age 63.74 years [range, 52-81 years], 16 males, 31 females), and aseptic loosening (aseptic group, average age 63.18 years [range, 53-80 years], 12 male, 26 female) in our department. Demographic data and the sensitivity and specificity of preoperative CRP, ESR, PC/MPV, fibrinogen, and D-Dimer in PJI diagnosis were compared. RESULTS: There were no significant differences when the demographic data of the three groups were compared. The expression level of CRP (50.67 ± 58.98 mg/L), ESR (50.55 ± 25.81 mm/h), PC/MPV (35.79 ± 18.00), and fibrinogen (4.85 ± 1.33 µg/mL) in the PJI group were higher than in the OA group (CRP: 4.09 ± 9.68 mg/L; ESR:13.44 ± 9.32 mm/1 h; PC/MPV: 24.97 ± 7.58; fibrinogen: 3.09 ± 0.55 µg/mL) and the aseptic group (CRP: 7.01 ± 11.83 mg/L; ESR: 22.47 ± 17.53 mm/1 h; PC/MPV: 25.18 ± 11.48; fibrinogen: 3.39 ± 0.80 µg/mL), respectively. The expression level of plasma D-dimer (1.60 ± 1.29 mg/L) in the PJI group was higher than in the OA group (0.49 ± 0.42 mg/L) but similar to that in the aseptic group (1.21 ± 1.35 mg/L). Receiver operating characteristic (ROC) curve analysis demonstrated that the areas under the ROC curve (AUC) for CRP, ESR, PC/MPV, fibrinogen, and D-dimer were 0.892 (95% confidence interval, 0.829-0.954), 0.888 (0.829-0.947), 0.686 (0.589-0.784), 0.873 (0.803-0.943), and 0.835 (0.772-0.899), respectively. When PC/MPV > 31.70, fibrinogen >4.01 µg/mL, and D-dimer >1.17 mg/L were set as the threshold values for the diagnosis of PJI, the sensitivity of PC/MPV in PJI diagnosis was lower than that of ESR and plasma fibrinogen. In contrast, there was no significant difference when comparing the specificity of CRP, ESR, PC/MPV, fibrinogen, and D-dimer in PJI diagnosis. CONCLUSION: Plasma fibrinogen is a good new auxiliary diagnostic marker for PJI.

Diagnostic Value of MRI Lamellated Hyperintense Synovitis in Periprosthetic Infection of Hip.

OBJECTIVE: To investigate the correlation between magnetic resonance imaging (MRI) lamellated hyperintense synovitis and periprosthetic infection of hip arthroplasty and estimate its value in the diagnosis of infection after hip replacement. METHODS: A retrospective analysis of 50 patients who underwent MRI from January 2016 to June 2019 after hip replacement was performed. The MRI scanning was performed with a 1.5T clinical imaging unit using SEMAC protocols. A total of 25 patients (cohort 1) showed infected total hip arthroplasty, and 25 patients had non-infected arthroplasty as controls (cohort 2). Two musculoskeletal radiologists, blinded to the clinical diagnosis, reviewed all the images for the presence of lamellated hyperintense synovitis independently. The cases were rereviewed by each reader after 2 weeks. The sensitivity, specificity, positive predictive value, and negative predictive value were calculated using the first reads. The Kappa statistic was used to assess inter-observer and intra-observer reliability. RESULTS: The incidence of lamellated hyperintense synovitis was 76%-88% in the experimental group and 8%-16% in the control group. The sensitivity of lamellated hyperintense synovitis for infection was 0.80-0.88 (95% confidence interval [CI]:0.59 - 0.97), the specificity was 0.84~0.92 (95% CI: 0.64 -0.99), the positive predictive value 0.83-0.92 (95% CI: 0.67 - 0.98), the negative predictive value 0.81 - 0.88 (95% CI: 0.65 - 0.96). The agreement between two readers was substantial (Kappa = 0.76, 95% CI: 0.58 - 0.94, P < 0.05). There were moderate inter-observer agreements for both readers, reader 1 (Kappa = 0.48, 95%CI: 0.23 - 0.72, P < 0.05) and reader 2 (Kappa = 0.44，95% CI: 0.19 - 0.69, P < 0.05). CONCLUSION: In this cohort, the presence of lamellated hyperintense synovitis in the MRI of hip arthroplasty showed high sensitivity and specificity for infection. This sign had substantial intra-observer reliability and moderate inter-observer reliability in the classification of the synovial pattern.