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Laboratory Evaluation of Infected / Septic THR

- See Laboratory work up for Infected Total Knee:

- Culture Specimen:
    - in the report by Levine BR and Evans BG, the authors studied 3 different intraoperative culture techniques and their
           diagnostic value in determining clinical infection in patients after a total joint replacement;
           - 24 patients (34 cases) met the selection criteria and were evaluated using intraoperatively collected tissue samples, swab 
                   samples, and fluid samples injected into standard blood culture vials.
           - they found that the use of fluid aspirate from intraoperative wounds immediately injected into blood culture vials is a highly
                   specific, sensitive, and accurate diagnostic culture technique (100%, 92%, and 94%, respectively);
           - superiority of vial cultures is enhanced when organisms grown from the liquid media only are discounted as contaminants;
           - references:
                   - Use of Blood Culture Vial Specimens in Intraoperative Detection of Infection 
                   - Comparison of bacterial results from conventional cultures of the periprosthetic membrane and the synovial or pseudocapsule during hip revision arthroplasty.

- Blood Work:
    - WBC:
            - has uniformly been found to be of little value in the evaluation of the painful THR in the absence of fulminant sepsis;
            - WBC is generally normal, but ESR is usually elevated;
    - ESR
            - useful in the dx of infection when there is no other reason for ESR elevation (RA or other types of inflammatory arthritis);
    - C-reactive protein: (may be more sensitive than ESR);
            - 10 mg per liter is used as the threshold for infection;  
            - should return to normal values in 2-3 weeks;
    - IL-6
    - referenes:
            - Inflammatory Blood Laboratory Levels as Markers of Prosthetic Joint Infection. A Systematic Review and Meta-Analysis
            - Combining C-reactive Protein and Interleukin-6 May Be Useful to Detect Periprosthetic Hip Infection
            - Adverse local tissue reactions in metal-on-polyethylene total hip arthroplasty due to trunnion corrosion. The risk of misdiagnosis


- Hip Joint Aspiration / Culture: (see: technique of hip aspiration)
    - includes preoperative and intraoperative cultures;
    - in difficult cases, consider obtaining multiple cultures;
    - preoperative aspiration:
          - mainly indicated when history, ESR, CRP are equivocol for infection;
          - 1/3 of cases, there are no clinical features to suggest infection, and diagnosis is made only on the basis of intraop cultures;
          - arthrogram can be performed following hip aspirate inorder to evaluate for loosening;
          - be sure that lidocaine does not enter the joint (bacterostatic);
          - multiple cultures should be taken if possible;
     - culture specimen:
          - in the report by Levine BR and Evans BG, the authors studied 3 different intraoperative culture techniques and their diagnostic
                  value in determining clinical infection in patients after a total joint replacement;
                  - 24 patients (34 cases) met the selection criteria and were evaluated using intraoperatively collected tissue samples, swab
                          samples, and fluid samples injected into standard blood culture vials.
           - they found that the use of fluid aspirate from intraoperative wounds immediately injected into blood culture vials is a highly
                  specific, sensitive, and accurate diagnostic culture technique (100%, 92%, and 94%, respectively);
           - superiority of vial cultures is enhanced when organisms grown from the liquid media only are discounted as contaminants;
           - ref: Use of Blood Culture Vial Specimens in Intraoperative Detection of Infection

- false negative results:
          - sensitivity is generally greater than 90 %, if patients have not recieved antibiotics in the previous 2-3 weeks;
          - it is not uncommon for a joint aspirate to exhibit no growth, even in face of sepsis, particularly from an organism of low
                  virulence or if antibiotics have be given;
          - Tunney MM ,et al (1999), authors note that some patients undergoing revision THA for perceived aseptic loosening,
                  - may actually have low grade infection present on the biofilm surface of implant, which may not appear on standard cultures;
                  - w/ ultrasonication, bacteria were retrieved from 26 / 120 implants, where as, bacteria were cultured from only 5 patients
                           using routine cultures;
                  - authors also noted that in 18/26 of patients (cultures obtained from ultrasonification), there were significant
                          inflammatory cells present;
                          - of these 26 patients w/ positive cultures, infection was suspected in only 6;
                  - propionibacterium acnes was cultured in 12 samples (and cultured in another 4 samples along with another organism);
                  - conclusion: infection with low virulence organisms with propionibacterium and staph epi often cause delayed infections
                          with a long interval between inoculation of bacteria and the onset of symptoms (which may explain why these implants
                          are classified as aseptically loose);
          - 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;
                  - references:
                          - Improved detection of infection in hip replacements. A currently underestimated problem
                          - Diagnosis of infected total knee: findings of a multicenter database.
                          - Prior Use of Antimicrobial Therapy is a Risk Factor for Culture-negative Prosthetic Joint Infection
                          - A 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.

- false positive:
          - may be as high as 13% in THR patients, but is generally less than 5% (ie specificity is about 96%);
          - as pointed out by Lachiewicz et al 1996, false positives can be reduced if cultures which only grow in liquid medium are
                  considered contaminants (unless there is growth of an anaerobic strain of bacteria);
          - references:
                  - The value of aspiration of the hip joint before revision total hip arthroplasty
                  - Failed total hip replacement: assessment by plain radiographs, arthrograms, and aspiration of the hip joint.
    - bacteriology:
            - staph aureus and staph epidermidis are the most commonly found organisms;
            - anaerobic infections
            - above two bacterial species along with pseudomonas are slime producers (glycocalyx) which makes them particularly resistant
                  to treatment w/ antibiotics;
                  - gram negative organisms which do not produce a glycocalyx may not be as virulent as previously thought;
            - consider need for Ziehl Nielsen stains, mycobacterial cultures, and fungal cultures;
            - references:
                  - Methicillin-resistant Staphylococcus epidermidis in infection of hip arthroplasties.
                  - Deep infection of cemented total hip arthroplasties caused by coagulase negative staphylococci
                  - Diagnosing Periprosthetic Infection: False-positive Intraoperative Gram Stains
                  - Adverse local tissue reactions in metal-on-polyethylene total hip arthroplasty due to trunnion corrosion. The risk of misdiagnosis

Gram Stain:
    -
Should Gram Stains Have a Role in Diagnosing Hip Arthroplasty Infections? 
 
   - Diagnosing Periprosthetic Infection: False-positive Intraoperative Gram Stains


- Frozen Section Histology



Pathobiology of infection in prosthetic devices.

Improved detection of infection in hip replacements. A currently underestimated problem.  

The value of hip aspiration versus tissue biopsy in diagnosing infection before exchange hip arthroplasty surgery.

Accuracy of joint aspiration for the preoperative diagnosis of infection in total hip arthroplasty.

Perioperative Testing for Joint Infection in Patients Undergoing Revision Total Hip Arthroplasty

Analysis of Synovial Fluid in Culture-negative Samples of Suspicious Periprosthetic Infections

Serum and Synovial Fluid Analysis for Diagnosing Chronic Periprosthetic Infection in Patients with Inflammatory Arthritis

A comprehensive microbiological evaluation of fifty-four patients undergoing revision surgery due to prosthetic joint loosening.