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Infected Total Knee Joint

- See: TKR menu, work up of the painful knee, and prevention of infection and infected THR;

- Diagnosis:
    - early dx of an infected prosthesis requires a high index of suspicion.
    - infection may cause only knee pain, persistent effusion, or early painless loosening, or more obvious signs, including inflammation,
             drainage, and sepsis;
    - classification: (ref: Treatment based on the type of infected TKA improves infection control.)
             - type I (early postoperative) 
                     - Failure of Irrigation and Débridement for Early Postoperative Periprosthetic Infection 
             - type II (late chronic)
                     - standard of care: two-stage revision arthroplasty
                     - removal of the prosthesis and cement and debridement; 
                     - placement of an antibiotic-impregnated cement spacer and IV antibiotics; 
                     - delayed second-stage revision arthroplasty;
             - type III (acute hematogenous) - such as from dental procedures
                     - [Arthroscopic treatment of hematogenous infected total knee arthroplasty: 5 cases]
                     - Late hematogenous infections after total knee arthroplasty: experience with 3013 consecutive total knees.
             - type IV (positive intraoperative cultures with clinically unapparent infection) 
                     - Prosthetic joint infection diagnosed postoperatively by intraoperative culture.
    - risk factors for infection: 
    - incidence:
             - in the report by Peersman G, et al, 6489 TKR were done in 6120 patients between 1993 and 1999;
                     - of these knee replacements, 116 knees became infected and 113 were available for followup;
                     - 97 of these knees (86%) had deep periprosthetic infections and the remaining 16 knees had superficial wound infections;
                     - 1/3 of deep infections occurred within the first 3 months after surgery and the remaining 2/3 occurred after 3 months;
                     - overall early deep infection rate for patients undergoing a primary TKR was 0.39%, whereas rate for patients undergoing
                               a revision TKR was 0.97%;
                     - predominant infectious organisms were gram-positive (staph aureus, staph epidermidis, and strept group B);
                     - 20% percent of the knees that were infected clinically had no organisms that could be identified
                     - patients had been treated empirically at another institution w/ antibiotics before a culture of joint was obtained; 
                     - ref: Infection in total knee replacement: a retrospective review of 6489 total knee replacements.

- Laboratory Studies and Aspiration  (see bacterial menu); 

- Radiographs:

    - periosteal new bone formation & subchondral bone resorption are highly suggestive of infection;
    - infectious process usually begins at the bone cement interface;

- Bone Scans:
    - may indicate loosening after 6-12 months, but can not distinguish between septic and aseptic loosening;
          - may indicate loosening after 6-12 months, but can not distinguish between septic and aseptic loosening;
          - Radionuclide bone scintigraphy in the detection of significant complications after total knee joint replacement
    - indium scans may increase specificity;
          - differential technetium-99 and indium-111 bone scans are 82% accurate in diagnosing infection (though these studies are is
                      rarely necessary);
          - a negative bone scintigram is reassuring and makes loosening or infection unlikely;
    - references:
          - Infected knee prosthesis: diagnosis with In-111 leukocyte, Tc-99m sulfur colloid, and Tc-99m MDP imaging.
          - Three-phase bone scan and indium white blood cell scintigraphy following porous coated hip arthroplasty: a prospective study of the prosthetic tip
          - The predictive value of indium-111 leukocyte scans in the diagnosis of infected total hip, knee, or resection arthroplasties.

- Treatment Options

    - antibiotic treatment based on organism:   (see: vancomycin in calcium sulfate vs local antibiotic delivery for septic joints)
    - debridement and retention of prosthesis 
          - indicated for acute infections in which the diagnosis is made within weeks of surgery; 
    - one-stage revision:
          - has had limited use with low virulence organisms; 
          - references:
                  - Primary exchange revision arthroplasty for infected total knee replacement: a long-term study.
                  - High Rate of Infection Control with One-stage Revision of Septic Knee Prostheses Excluding MRSA and MRSE 
                  - High Infection Control Rate and Function After Routine One-stage Exchange for Chronically Infected TKA
                  - Is Single-stage Revision According to a Strict Protocol Effective in Treatment of Chronic Knee Arthroplasty Infections?  
          - delayed diagnosis of infection - following revision for "aseptic loosening";
                  - this applies to patients who undergo revision for what is considered to be aseptic loosening who subsequently develop
                          positive cultures several days postop;
                  - note potential fasle positive result:
                          - cultures which are noted to be positive only on culture broth (not culture medium) may falsely indicate infection (lab
                          - true positive culture should demonstrate at least two or more cultures from different sites of the wound;
                  - Segawa H, et al (1999), treatment was successful for 5 infections that were diagnosed on basis of positive intraop cultures; 
                          - IV antibiotics were continued for 6 weeks;
                          - single debridement might not have been adequate in this situation (noting that other authors have reported a higher
                                  success rate with multiple debridements - especially w/ infections that present later than 2 weeks);
                         - reference: 
                                   - Infection After Total Knee Arthroplasty. A Retrospective Study of the Treatment of Eighty-one Infections  

    - two staged revision w/ antibiotic spacer: (see antibiotics in cement and see local antibiotic delivery for septic joints)
         - Confirming Sterility of an Autoclaved Infected Femoral Component for Use in an Articulated Antibiotic Knee Spacer: A Pilot

    - antibiotic suppression:
         - success rate of 20-30%;
         - antibiotic treatment will not eliminate chronic deep infection about prosthesis;
         - antibiotic management can be used as suppressive treatment for established infection.
         - antibiotic suppression can be used if the following are met:
                 - prosthesis removal is not feasible (pt not candidate for anesthesia) 
                 - microorganism is of low virulence & susceptible to antibiotics;
                 - patient can tolerate antibiotic w/o serious toxicity;
                 - prosthesis is not loose; 
         - references:
                 - Conservative treatment of staphylococcal prosthetic joint infections in elderly patients
                 - Long-term suppression of infection in total joint arthroplasty.
                 - Prolonged suppressive antibiotic therapy for infected orthopedic prostheses
                 - Chronic Suppression of Periprosthetic Joint Infections with Oral Antibiotics Increases Infection-Free Survivorship

    - knee arthrodesis:
         - may be indicated for TKR infected w/ especially virulent organisms (Pseudomonas, MRSA) or for cases in which there has been
                 loss of the extensor mechanism;
         - references: Intramedullary fixation for arthrodesis of the knee after infected total knee arthroplasty.
    - resection arthroplasty:
         - resection arthroplasty is good option in debilitated, minimally ambulatory patient with extensive bone loss and infection w/
                 highly virulent bacterium.
         - references:
                 - Excision arthroplasty for infected constrained total knee replacements.
                 - Resection arthroplasty as a salvage procedure for a knee with infection after a total arthroplasty.
                 - Resection arthroplasty: an alternative to arthrodesis for salvage of the infected knee total knee arthroplasty
    - above knee amputation:
         - reference: Amputation after failed total knee arthroplasty.

- Salvage Procedures:
   - references:
          - Gastrocnemius muscle flap coverage of exposed or infected knee prostheses.

Alternatives to Reimplantation for Salvage of the Total Knee Arthroplasty Complicated by Infection.

Salvage of infected total knee arthroplasty.

Long-term results of various treatment options for infected total knee arthroplasty.

Total knee arthroplasty in diabetes mellitus.

The management of infected total knee replacements.

Treatment of infected total knee arthroplasty.

Old sepsis prior to total knee arthroplasty.

Deep sepsis following total knee arthroplasty. Ten-year experience at the University of California at Los Angeles Medical Center.

Long-term outcome of 42 knees with chronic infection after total knee arthroplasty.

The Insall Award Paper: Infection in Total Knee Replacement: A Retrospective Review of 6489 total knee replacements

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