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Knee Fusion using External Fixation

- See: Ilizarov Technique

- Discussion:
    - advantages:
          - allows arthrodesis in presence of active infection;
          - external fixation is adjustable;
          - allows access to the soft tissues;
          - leaves no longstanding foreign body;
          - requires little additional soft-tissue dissection;
    - disadvantages:
          - non-rigid fixation;
          - potential cause of neurovascular injury;
          - requires second procedure for removal of fixator;
    - outcomes:
          - in the report by Manzotti et al, the authors followed 6 patients (4 women, 2 men) treated between 1992 and 1998;
          - average age was 56.6 years (range, 23-70 years) and the mean number of previous surgical procedures was seven (range, 4-10 procedures);
          - average followup was 34 months;
          - 5 patients who had completed treatment;
          - all had obtained a stable knee arthrodesis after a mean external fixation time of 6.8 months without additional surgical procedures or bracing;
          - the authors recommended arthrodesis for patients with extensive bone loss, significant limb shortening or axial deformity or both,
                  active infection, or previous failed arthrodesis.
          - ref: Knee Arthrodesis After Infected Total Knee Arthroplasty Using the Ilizarov Method

- Technique:
    - implant removal;
    - preparation of the osseous bed;
        - preparation of the bone ends should expose vascular bone, provide bone apposition, correct limb alignment, and preserve as much 
                bone stock as possible;
        - when bone cuts are being performed, extramedullary TKR cutting jigs can be used to achieve alignment and bone apposition;
        - bone resection should be limited to one to two mm of bone from the femur and tibia;
        - proximal part of tibia is be cut 1st to provide cut that is 90 deg to coronal plane and has the desired degree of posterior slope in the 
                sagittal plane;
        - limb is aligned in 0 to 5 degrees of valgus, and the distal part of femur is cut parallel to the cut tibial surface;
        - bone ends should be vascular, stable, apposed, & in correct flexion and valgus;

      - application of the external fixator;
          - most external fixators are weak in anteroposterior bending;
                - addition of an anterior frame with half-pins improves fixation;
                - for knee arthrodesis, a biplanar Ex Fix w/ sagittal pins and a ventral frame to control anteroposterior bending forces provides 
                        improved fixation;
      - femoral pins:
          - 3 centrally threaded 5 mm transfixing pins are placed in distal part of the femur from medial to lateral, w/femoral vessels being 
          - two anterior half-pins are placed in distal part of femur & two are placed in the proximal part of the tibia and connected to the 
          - increased stability is achieved by placing the anterior pins as far as possible from the arthrodesis site;
      - bone-grafting;
            - bone graft is placed about the periphery of the arthrodesis site to allow revascularization from the surrounding soft tissues;
            - posterior bone graft should be placed before the external fixator is tightened;

- Post Op:
    - external fixation is maintained until clinical union of arthrodesis site has been achieved, usually at ten to twelve weeks;
    - after external fixator has been removed, a cylinder cast is used for four to twelve weeks or until radiographic union is present

- Example using Ilizarov:

Failed total knee arthroplasty treated by arthrodesis of the knee using the Ace-Fischer apparatus.

Single plane and biplane external fixators for knee arthrodesis.