Seronegative infections in hip and knee arthroplasty

The Fate of Revision Total Knee Arthroplasty With Preoperative Abnormalities in Either Sedimentation Rate or C-Reactive Protein

BACKGROUND

Erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) are important markers in the evaluation and treatment of painful total knee arthroplasty (TKA). Elevation of both markers usually occurs with infected TKAs while a normal ESR and CRP usually point to aseptic causes for failure. The purpose of this study is to compare (1) rate of revision, (2) infection, and (3) reason for reoperation in a group of patients undergoing revision TKA with a single abnormality in either ESR or CRP in an otherwise negative conventional infection work-up compared to patients with normal preoperative ESR and CRP.

METHODS

We retrospectively reviewed 791 consecutive revision TKAs performed at our institution between years 2004 and 2011. Following exclusion for infection, periprosthetic fracture, prior revision TKA, positive cultures, incomplete records, and patients with less than 24-month follow-up, a total of 228 aseptic revisions (89 knees with 1 abnormal serologic marker) were available for final analysis. No patients met the current established criteria for infection. All knees underwent revision TKA using antibiotic-impregnated cement. The 2 groups were compared in terms of overall survivorship, infection rate, and rate and causes of subsequent aseptic revision.

RESULTS

The average follow-up was 60 months (24-110). There were no significant differences between the 2 groups in terms of age, sex, American Society of Anesthesiologists class, and Charlson comorbidity index. A preoperative abnormality of either ESR or CRP significantly increased the risk for reoperation for all reasons (odds ratio [OR], 3.2; P = .0028), infection (OR, 4.0; P = .034), and revision for aseptic loosening (OR, 3.69; P = .044). There were no differences in reoperations for any other reason. The average time to revision in the study group was 28.3 months compared to 40.0 months in the control group (P = .213).

CONCLUSION

A single abnormality in either the ESR or CRP increased the likelihood of both infection and reoperation following revision TKA. Conventional methods and criteria for infection detection may not be sufficiently sensitive or specific in these cases. Further work-up with additional modalities may help increase the confidence of aseptic failure before revision TKA.

Two-stage revision arthroplasty for periprosthetic joint infections: What is the value of cultures and white cell count in synovial fluid and CRP in serum before second stage reimplantation?

INTRODUCTION

Besides CRP in serum, white cell counts and cultures of synovial fluid are routinely used to detect periprosthetic joint infections. But the sensitivities of these parameters do vary from 12 to 100 %. In two stage revision arthroplasty before the second stage surgeons have to decide if reimplantation is justified. Therefore, we investigated the value of cultures and white cell count from the synovial fluid with a polymethyl methacrylate spacer in place and CRP in serum before reimplantation to detect persistent infection in a standardized setting.

METHODS

115 patients with a two-stage revision hip or knee arthroplasty were included in this study. All patients had an antibiotic loaded polymethylmethacrylate spacer. Retrospectively synovial cultures, white blood count in synovial fluid and CRP in serum were assessed before reimplantation.

RESULTS

The sensitivity of the synovial cultures was 5 % (95 % CI 0.13-24.87), with a specificity of 99 % (95 % CI 94.27-99.97). For white blood count in synovial fluid the sensitivity was 31.3 %, specificity was 39.1 %. Sensitivity for CRP in serum was 42.10 %, specificity was 84.21 %.

CONCLUSION

Cultures from synovial fluid and white blood count in synovial fluid and CRP seem to be uncertain parameters to exclude persistent infection. We do not recommend joint aspiration before reimplantation anymore. Further research is necessary to find other markers to confirm or exclude persistent infection.

Diagnosis of Periprosthetic Infection: Novel Developments

The diagnosis of periprosthetic joint infection (PJI) has been performed by obtaining a history and physical examination, blood tests, and analysis of the synovial fluid and tissue samples. The measurement of serum biomarkers are routinely used to diagnose PJI. These markers may be elevated in other inflammatory conditions, necessitating the need for more specific biomarkers to diagnose PJI. Serum biomarkers may be more specific to PJI. Synovial CRP, α-defensin, human β-defensin-2 and -3, leukocyte esterase, and cathelicidin LL-37 biomarkers hold promise for the diagnosis of PJI.