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Staged Revision for Infected Total Knee Joint

- see 2 stage hip spacer

- Discussion:
    - staged revision w/ antibiotic spacer: (see antibiotics in cement and local antibiotic delivery for septic joints)
    - debridement of components is followed by 6 weeks of  IV antibiotics;
          - it is essential that all foreign material including cement be removed;
    - 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;
          - ref: A comprehensive microbiological evaluation of fifty-four patients undergoing revision surgery due to prosthetic joint loosening.
    - antibiotic spacers is inserted to maintain soft tissue length across the joint;
          - 2-3 packs of cement are required, each containing at least 1-2 gm mg of vancomycin (upto 8 gm) and 2.4 gm of tobramycin;
    - waiting longer than 6-12 weeks for reinsertion of components, may cause excessive knee stiffness;
    - technical considerations:
          - use the polyethylene component to help determine the appropriate thickness and cross sectional area of the spacer;
          - shape a thin anterior cement flange which helps to prevent the patella from adhering to the anterior aspect of the femur;
          - if this flange is made too thick, then it may be difficult to close the skin w/o tension;
          - 1st generation spacer consisted of a cemented femoral endoskeleton which articulated with a ATB cemented acetabulum
                    (cement on cement articulation);
          - 2nd generation spacer also contains an antibiotic laden endoskeleton, but includes a polyethylene component which is
                  embedded in an ATB laden cement bed;
                  - this polyethylene component should be constrained (to prevent dislocation);
          - Antiobiotic Properties in Cement:
                  - StageOne™ Knee Cement Spacer Molds
                  - references: Successful treatment of total hip and knee infection with articulating antibiotic components: a modified treatment method.

                  - Characteristics of Individual Antibiotics: 
                          - note that lincomycin, tetracycline, and rifampin should not be added to methylmethacrylate;
                          - antibiotics must be added to the cement in a powered form (which may or may not be available from the pharmacy); 
                           - gentamicin and tobramycin properties in cement
                           - vancomycin properties in cement
          - articulating spacer:
                  - foil is applied to femoral surface (along with sterile lubricant) which keeps cement from adhering to the osseous surface;
                  - cement is applied to the distal femoral surface and is shaped similar to that of femoral component (approx 10 mm thick);
                         - use the tibial polyethylene spacer component to help shape the cement (molding technique);
                  - tibial component is fashioned using a similar technique with thickness appropriate to maintain optimal soft tissue tension;
                  - when cement hardens, the foil is removed, and the spacers are reapplied;
                  - ref: Articulating versus static spacers in revision total knee arthroplasty for sepsis. The Ranawat Award.

- outcomes:
    - in the study by Segawa, et al. (1999), of 29 knees that were managed with a delayed-exchange arthroplasty,
          28 (97 %) had erradication of the infection and 90% had good knee function;
          - these authors generally perform their exchange arthroplasty at 8 weeks postop (2 weeks after discontinuation of IV antibiotics);
    - in the report by Fehring TK, et al. (2000), the authors report on their experience with an articulating knee spacer;
          - they note that static spacer blocks make exposure at reimplantation difficult secondary to quadriceps shortening;
          - in an attempt to avoid this complication, the authors molded a temporary implant made of antibiotic cement;
          - 25 patients were treated with static nonarticulating spacers
                 - knee arthroplasties in three of these patients became reinfected (12%)
                 - 15 of the 25 patients with static spacers had unexpected bone loss between stages.
                 - range of motion at final followup averaged 98° in the patients who received static spacers
          - since 1996, 30 patients were been treated with tobramycin-laden articulating spacers;
                 - one of these patients became reinfected (7%);
                 - no appreciable bone loss could be measured in the patients who received articulating spacers;
                 - range of motion was 105° in the patients who received articulating spacers;
          - Infection After Total Knee Arthroplasty. A Retrospective Study of the Treatment of Eighty-one Infections
          - Articulating versus static spacers in revision total knee arthroplasty for sepsis. The Ranawat Award.

- When to Re-Implant ?
          - Mont MA (2000): authors sought to determine whether aspiration of affected joint and culture of specimen, performed before
                 reimplantation and after discontinuation of antibiotic therapy, would to identify who might have a recurrent infection;
          - 69 patients who were treated for a culture-proven deep infection at the site of a total knee arthroplasty;
                 - group I consisted of 35 patients who were treated with removal of prosthetic components and irrigation and debridement of
                         joint, followed by six weeks of antibiotic therapy and reimplantation of a prosthesis;
                         - of the thirty-five patients in Group I, 5 (14 %) had recurrence of infection;
                         - 1 of the patients was managed with a successful second-stage revision, three were managed with arthrodesis
                                 of the knee, and one continued dwith chronic antibiotic suppressive treatment;
                 - group II was composed of 34 patients who were treated with removal of the components and irrigation and debridement of 
                         joint, six weeks of antibiotic therapy, and then repeat culture four weeks after the antibiotic course had ended;
                         - if the culture was negative, the patient was managed with a second-stage reimplantation of a prosthesis;
                         - if the culture was positive, the protocol was repeated, beginning with irrigation and debridement;
                         - of the 34 patients in Group II, 3 (9 %) had a positive culture after the course of antibiotics;
                         - 1 other patient (3 percent) in Group II, who had a negative culture, had a recurrent infection and was eventually
                                  managed with arthrodesis of the knee;
                 - pre-revision cultures, grown after discontinuation of antibiotic treatment and before reimplantation of components, helped
                         to identify the patients with infection at the site of a total knee arthroplasty in whom the infection might recur;
        - References:
                 - Evaluation of preoperative cultures before second-stage reimplantation of a total knee prosthesis complicated by infection. A comparison-group study.
                 - 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?

- Duration of Antibiotics:
  - Is there a role for extended antibiotic therapy in a two-stage revision of the infected knee arthroplasty?

- Complications:
    - 20 % of patients have a recurrence of infection following this treatment;
    - MRSA has a high failure rate;
    - references:
           - Two-stage Exchange Arthroplasty for Infected Total Knee Arthroplasty: Predictors of Failure
           - The Fate of Spacers in the Treatment of Periprosthetic Joint Infection

Patient outcome with reinfection following reimplantation for the infected total knee arthroplasty.

Two-stage reimplantation for the salvage of total knee arthroplasty complicated by infection. Further follow-up and refinement of indications.

Two-stage reimplantation in infected total knee arthroplasty.

Infection After Total Knee Arthroplasty. A Retrospective Study of the Treatment of Eighty-one Infections.  

Comparison of a static with a mobile spacer in total knee infection.

Patient Satisfaction and Functional Status After Treatment of Infection at the Site of a Total Knee Arthroplasty with Use of the PROSTALAC Articulating Spacer.

Patient outcome with reinfection following reimplantation for the infected total knee arthroplasty.

Results after Late Polymicrobial, Gram-negative, and Methicillin-resistant Infections in Knee Arthroplasty

Assessing the Gold Standard: A Review of 253 Two-Stage Revisions for Infected TKA