What is the concordance rate of preoperative synovial fluid aspiration and intraoperative biopsy in detecting periprosthetic joint infection of the shoulder?

Commercial Synovial Antigen Testing is Inferior to Traditional Culture for the Diagnosis of Periprosthetic Joint Infection in Patients Undergoing Revision Total Knee Arthroplasty

BACKGROUND

Despite its limitations, a culture remains the "gold standard" for pathogen identification in patients who have periprosthetic joint infection (PJI). Recently, a synovial fluid antigen test has been introduced by a commercial entity. The purpose of this multicenter study was to determine the accuracy of the antigen test in the diagnosis of PJI.

METHODS

This retrospective study identified 613 patients undergoing revision total knee arthroplasty who had undergone preoperative synovial fluid analysis. A PJI was defined using the 2018 International Consensus Meeting (ICM) criteria. Patients who had an extended period (> 180 days) from aspiration to revision procedure (n = 62), those presenting within 90 days of their index arthroplasty procedure (n = 17), and patients who had an inconclusive ICM score (n = 8) were excluded. Using receiver operator characteristic curve analyses, we examined the utility of the microbial identification (MID) antigen test and any positive culture (either preoperative or intraoperative) in the diagnosis of PJI.

RESULTS

A total of 526 patients were included. Of these, 125 (23.8%) were ICM positive and 401 (76.2%) were ICM negative. Culture demonstrated an area under the curve (AUC) of 0.864, sensitivity of 75.2%, and specificity of 97.5%. On the other hand, the MID test exhibited an AUC of 0.802, sensitivity of 61.6%, and specificity of 98.8%. The AUC of culture was significantly higher than that of the MID test (P = .037). The MID test was positive in 41.9% of culture-negative PJI cases. We also observed a high rate of discordance (29.7%) when both culture and the MID test were positive in the ICM-positive group.

CONCLUSIONS

Synovial fluid antigen testing does not provide additional clinical benefit when compared to traditional cultures for the diagnosis of PJI. The antigen test had low sensitivity in the diagnosis of PJI and a relatively high rate of discordance with culture.

LEVEL OF EVIDENCE

Level III.

How Reliable Is the Absolute Synovial Polymorphonuclear Neutrophil Cell Count in Diagnosing Periprosthetic Joint Infection?

BACKGROUND

Diagnosing periprosthetic joint infection (PJI) is a daunting task for even the most experienced orthopedic surgeons, as there is currently no test available that can provide absolute accuracy. Utilizing an established synovial indicator for detecting PJI without incurring additional costs or resources would be the optimal solution for predicting the presence of infection. Therefore, we hypothesized that synovial absolute neutrophil count (ANC) would improve the diagnostic accuracy of chronic knee and hip PJI.

METHODS

The study included 260 patients (134 men and 126 women, mean age of 70 years [range, 26 to 89]) who underwent aspiration during preoperative workup. Of these, 109 patients (41.9%) were diagnosed with chronic PJI (50 knees, 59 hips), and 151 patients (58.1%) were diagnosed as aseptic (94 knees, 57 hips). Data obtained from all patients included age, sex, procedure type (total hip or total knee arthroplasty), operation side, synovial white blood cell count (cells/μL), synovial polymorphonuclear cells percentage, and synovial α-defensin immunoassay value at the admission were retrieved from the electronic medical record.

RESULTS

The calculated optimal threshold for synovial ANC of 1,415.5 cells/μL was associated with an area under the receiver operating characteristic curve (AUC) of 0.930 for chronic knee PJI diagnosis. The calculated optimal threshold for synovial ANC of 2,247 cells/μL was associated with an AUC of 0.905 for chronic hip PJI diagnosis.

CONCLUSIONS

This study has conclusively shown that the synovial ANC serves as a valuable marker in the complicated diagnosis of PJI. This highly effective and efficient approach should be utilized for obtaining further information through standard tests, thereby ruling out the possibility of PJI.

LEVEL OF EVIDENCE

III.

What Is the Most Reliable Concordance Rate of Preoperative Synovial Fluid Aspiration and Intraoperative Biopsy to Detect Periprosthetic Joint Infection in Knee, Hip and Shoulder Arthroplasty?

The accuracy of preoperative synovial fluid microbe detection in periprosthetic joint infection (PJI) is widely reported. However, the reliability of this diagnostic modality amongst the different joints is not yet described. We aimed to compare the concordance rate between preoperative synovial fluid and intraoperative tissue cultures in shoulder, knee and hip PJIs. A total of 150 patients who met the 2018 International Consensus Meeting criteria for shoulder, hip and knee PJI were retrospectively reviewed. This cohort was divided into three groups based on the involved joint (should, hip or knee), with 50 patients in each group. Cultures were collected and held for culture for 14 days. The overall concordance rate was 56.7%. Concordance rates between preoperative and intraoperative cultures were 60%, 56% and 54% for the knee, shoulder and hip joints, respectively. The analysis of high- or low-virulence and difficult- or not-difficult-to-treat germs did not reveal any significant differences between preoperative and intraoperative cultures in any of the groups. However, even considering the higher concordance in knee PJI, the overall discordance between preoperative and intraoperative cultures should prompt surgeons not to rely solely on preoperative synovial fluid culture data in determining appropriate treatment and antibiotics.

Successful eradication rate following one-stage septic knee and hip exchange in selected pre-operative culture-negative periprosthetic joint infections

PURPOSE

The main requirement for performing the one-stage septic exchange is the pre-operative identification of the pathogen and its susceptibility. The purpose of this study is to evaluate the success rate with special focus on reinfection in a cohort of patients who underwent one-stage septic knee or hip revision for pre-operative culture-negative PJI.

METHODS

We retrospectively analyzed 640 patients treated by one-stage revision for chronic knee or hip PJI between January 1, 2016, and December 31, 2018. Only cases with pre-operative culture-negative PJI, with culture-negative synovial aspirations and one negative open biopsy, were analyzed. We evaluated the septic and aseptic complication and the rate of complication-free survival defined as the time from the date of first operation and the date of complication events.

RESULTS

A total of 22 patients fulfilled the inclusion and were enrolled. The mean age of the group was 73.2 ± 9.8 years, with a median ASA score of 3 (range 3-4). After mean follow-up of 3.6 ± 2.6 years, 86.4% (19 out of 22) of patients reported no complications. Two patients (9.1%) after one-stage hip required revision arthroplasty due to septic failure, while one patient (4.5%) with one-stage knee had revision for femoral component aseptic loosening.

CONCLUSION

Our analysis suggests that the absence of pre-operative pathogen detection may not be contraindication to the one-stage revision in selected patients. The one-stage exchange might be considered in patients with pre-operative negative cultures in presence of ASA > 3 and multiple comorbidities that are not able to tolerate multiple surgeries.