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Laboratory Findings for Infected Total Knee Replacement:

- See Laboratory Finding in Infected THR

    - WBC 
    - ERS
    - IL-6
    - C-reactive protein 
          - references:
                    - Mark B. Coventry Award: Synovial C-reactive Protein: A Prospective Evaluation of a Molecular Marker for Periprosthetic Knee Joint Infection 
                    - C reactive protein and skin temperature post total knee replacement.
                    - Use of Erythrocyte Sedimentation Rate and C-Reactive Protein Level to Diagnose Infection Before Revision Total Knee Arthroplasty. A Prospective Evaluation
                    - A Simple, Cost-Effective Screening Protocol to Rule Out Periprosthetic Infection
                    - Inflammatory Blood Laboratory Levels as Markers of Prosthetic Joint Infection: a Systematic Review and Meta-Analysis

    - aspiration: gram stain, cell count & culture:
            - most accurate method of dx, and is required prior to all revisions; 
            - synovial fluid analysis:
                    - white cell count greater than 2,000/mm may indicate sepsis, when the majority of cells are PMNs; 
                    - diff dx: gout and pseudogout synovitis w/p arthroplasty;   
                           - references:
                                    - Synovial fluid leukocyte count and differential for the diagnosis of prosthetic knee infection. 
                                    - Preoperative testing for sepsis before revision total knee arthroplasty.
                                    - Determining “True” Leukocytosis in Bloody Joint Aspiration
                                    - Cell Count and Differential of Aspirated Fluid in the Diagnosis of Infection at the Site of Total Knee Arthroplasty
                                    - Letter: Cell Count and Differential of Aspirated Fluid in the Diagnosis of Infection at the Site of Total Knee Arthroplasty
                                    - Analysis of Synovial Fluid in Culture-negative Samples of Suspicious Periprosthetic Infections
                                    - Acute crystal-induced arthritis following arthroplasty
                                    - Gout-induced arthropathy after total knee arthroplasty: a report of two cases
                                    - [Gouty arthritis in a total knee prosthesis]
                                    - Synovial fluid white cell and differential count in the diagnosis or exclusion of prosthetic joint infection
                                    - The natural progression of synovial fluid white blood-cell counts and the percentage of polymorphonuclear cells after primary total knee arthroplasty: a multicenter study.

             - gram stain: (see bacterial menu); 
                    - some authors recommend not getting intraoperative gram stains.
                    - be aware that the quality of the gram stain result depends to a degree on the quality of the technician performing the test; 
                    - the sensitivity of intraoperative gram stain is only 27%;
                    - gram negative bacilli:gram negative cocci:, gram positive bacilli:, gram positive cocci 
                    - ref:
                            - Gram stain detection of infection during revision arthroplasty
                            - The role of intraoperative Gram stain in revision total joint arthroplasty.
                            - The role of intraoperative gram stain in the diagnosis of infection during revision total hip arthroplasty.
                            - Diagnosing Periprosthetic Infection: False-positive Intraoperative Gram Stains
            - cultures: (see bacterial menu); 
                    - false positive results:
                            - cultures which show growth in broth only are generally not considered positive (probable lab error);
                            - when cultures are taken at time of revision, surgeon should be suspicious if only one sample (out of many) grows a pathogen (generally
                                    2 positive culture samples are required to indicate a definite infection);
                                    - some surgeons require that a sample yield 5 colonies per plate in order to indicate infection; 
                    - false-negatives / culture negative infections: (see biofilm formation)
                            - 25% false neg result w/ aspiration rate means that positive cultures often will be isolated only after components are removed & tissue is cultured; 
                            - there is some evidence that false negatives may mainly include staph epidermidis;
                            - need for tissue biopsy cultures from the component membrane interface
                                      - remember that in the case of biofilm, there may be minimal infection in joint fluid and capsule, and the main area of
                                               infection will be over the component /bone-membrane interface;
                            - culture negative references:
                                    - Periprosthetic joint infection with negative culture results: clinical characteristics and treatment outcome.
                                    - Culture-Negative Prosthetic Joint Infection
                                    - Analysis of Synovial Fluid in Culture-negative Samples of Suspicious Periprosthetic Infections
                                    - Prior Use of Antimicrobial Therapy is a Risk Factor for Culture-negative Prosthetic Joint Infection
                            - references:
                                    - Improved detection of infection in hip replacements. A currently underestimated problem
                                    - Diagnosis of infected total knee: findings of a multicenter database.
                                    - A comprehensive microbiological evaluation of fifty-four patients undergoing revision surgery due to prosthetic joint loosening.
                                    - Diagnosis of periprosthetic infection following total hip arthroplasty--evaluation of the diagnostic values of pre- and intraoperative parameters and the associated strategy to preoperatively select patients with a high probability of joint infection.
                                    - Molecular Identification of Bacteria from Aseptically Loose Implants
                                    - INFECTED TOTAL KNEE: no pathogen, no treatment? 
                                    - Is that joint infected? Diagnosing the difficult post-arthroplasty infection

                    - broth only cultures:
                           - cultures which show growth in broth only are generally not considered positive (probable lab error); 
                            - Performance Characteristics of Broth-only Cultures After Revision Total Joint Arthroplasty

                    - references:
                            - Improved aero-anaerobe recovery from infected prosthetic joint samples taken from 72 patients and collected intraop in Rosenow's broth.
                            - The value of pre-operative aspiration in the diagnosis of an infected prosthetic knee: a retrospective study and review of literature.
                            - Aspiration of the knee joint before revision arthroplasty.
                            - [The value of preoperative knee aspiration and arthroscopic biopsy in revision total knee arthroplasty]
                            - Prospective analysis of preoperative and intraoperative investigations for the diagnosis of infection at the sites of 202 total hip arthroplasties.
                            - The Coventry Award. The value of preoperative aspiration before total knee revision.
                            - Biofilm Theory Can Guide the Treatment of Device-Related Orthopaedic Infections 
                            - Is Aseptic Loosening Truly Aseptic? 
                            - Role of knee aspiration after resection of the infected total knee arthroplasty.
                            - Is "aseptic" loosening of the prosthetic cup after total hip replacement due to nonculturable bacterial pathogens in patients with low-grade infection?  
                            - Sonication of removed hip and knee prostheses for diagnosis of infection.
                            - Prior Use of Antimicrobial Therapy is a Risk Factor for Culture-negative Prosthetic Joint Infection 

    - intra-operative frozen section: 
           - peri-implant membrane: high concentration of neutrophils is essentially diagnostic of ongoing infection;

     - references for nasal swabbing:
                  - Use of Intranasal Mupirocin to prevent methicillin-resistant Staphylococcus aureus infection in intensive care units
                  - The role of MRSA screening in joint-replacement surgery
                  - Methicillin-resistant Staphylococcus aureus on orthopaedic wards: incidence, spread, mortality, cost and control
                  - Preoperative use of mupirocin for the prevention of healthcare-associated Staphylococcus aureus infections: a cost-effectiveness analysis.
                  - Controlling the usage of intranasal mupirocin does impact the rate of Staphylococcus aureus deep sternal wound infections in cardiac surgery patients.

Sonication of Removed Hip and Knee Prostheses for Diagnosis of Infection
Direct Demonstration of Viable Staphylococcus aureus Biofilms in an Infected Total Joint Arthroplasty. A case report.  
Is There a Role for Tissue Biopsy in the Diagnosis of Periprosthetic Infection? 
Protein profiling for periprosthetic joint infection
Diagnosis of Periprosthetic Joint Infection: The Utility of a Simple Yet Unappreciated Enzyme
The Routine Use of Atypical Cultures in Presumed Aseptic Revisions Is Unnecessary