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Revision Total Knee Arthroplasty

- PreOperative Considerations and Implant Selection:
    - work up of the painful TKR:

- Hip and Knee Infiltration Technique
    - Local Analgesia Infiltration Techniques – Hip and Knee Arthroplasty

Exposure for Revision Arthroplasty:
     - surgical approach for primary TKR 
     - intraoperative gram stain, frozen section, and culture
            - The Routine Use of Atypical Cultures in Presumed Aseptic Revisions Is Unnecessary
     - 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;
            - consider adding tissue culture (or at least saline) to the tissue sample inorder to improve true positive results;
            - references:
                      - A microbiological evaluation of 54 patients undergoing revision surgery due to prosthetic joint loosening.
                      - The fate of the unexpected positive intraoperative cultures after revision total knee arthroplasty
                      - The Chitranjan Ranawat Award: Should prophylactic antibiotics be withheld before revision surgery to obtain appropriate cultures?
                      - Use of broth cultures peri-operatively to optimise the microbiological diagnosis of musculoskeletal implant infections.

- Component Removal:
    - prior to component removal, take the knee thru a ROM and evaluate patellar tracking and evaluate knee stability in extension,
           mid-flexion, and full flexion;
           - it is important to consider patellar tracking, since this will affect final rotation of the femoral component;
           - if their is optimal patellar tracking, then the surgeon should accept the orientation of the pre-existing femoral bone cuts;
    - know the status of pre-existing flexion and extension gaps before the components are removed, since this will have a
           bearing on anterior-posterior translation of the femoral medullary stem (and component);

- Tibial Preparation

- Femoral Preparation: 
        - The results of revision knee arthroplasty with and without retention of secure cemented femoral components.

- Restoration of the Joint Line:
        - position of the implants relative to the joint line: joint line is approximately 1 cm proximal to the fibular head, or 2 cm distal to 
                medial epicondyle;
    - references:
          - Joint line position restoration during revision total knee replacement
          - Influence of prosthetic joint line position on knee kinematics and patellar position
          - Joint line elevation in revision TKA leads to increased patellofemoral contact forces

- Revision of the patellar component

 - Cement Considerations:
    - before cement is mixed, clearly note areas of minor bone defects (between trial components and bone), and plan to add additional
              cement to these areas;
    - before the cement is mixed, ensure that all components are laid out on the table;
    - cementing technique:
          - apply cement to only condylar surfaces if press-fit stems are being used;
          - cement is applied to cut medullary surfaces, but in most cases cement is not placed into the medullary canal;
                - if stems are being cemented, consider use of a cement plug and an injection gun;
    - addition of antibiotics to cement
                - in some patients, consideration the addition of antibiotics to cement:
                      - indicated if there are additional risk factors for infection;
                      - generally, either 600mg tobramycin or 500mg vancomycin is added per 40g bag of cement;
    - ref: Stem fixation in revision total knee arthroplasty: a comparative analysis.

- Complications:
    - infection:
           - may occur in 4% of patients (which is roughly 10 time higher than should occur in primary knees);
    - early failure:
           - component survivorship is roughly 80 % at 8 years;
           - good to excellent results occur 50-80% of the time with complications occurring 15-30%;
           - wound comlications should be handled aggressively with skin graft, gastrocnemius flap or free flap;

- Postoperative Rehabilitation:
    - quadriceps snip can be rehabilitated routinely
    - quadriceps turndown or tubercle osteotomy requires no ROM for 2 weeks and no active extension for 2-6 weeks