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.

Original Text by Clifford R. Wheeless, III, MD.

Last updated by Data Trace Staff on Thursday, May 10, 2012 11:57 am