PreOp Planning for Arthrodesis

- Debridement:
 - all foreign material must be removed from the knee;
      - retained frags of cement can act as nidus for residual infection;
 - infected granulation tissue & scar tissue should be excised to provide healthy vascularized soft tissue surrounding the knee.
 - number of debridements needed before wound closure depends on surgeon's ability to remove all infected material and on whether or not 
      bone-grafting is to be performed.
 - at least two separate debridement procedures should be performed after implant removal, and there should be at least one negative culture,
      before bone-grafting is done;
 - removal of components & primary arthrodesis should be reserved for cases in which reimplantation is not considered possible & there
      is minimal arthritic involvement of adjacent joints.
 - intravenous antibiotics for 6 weeks after complete removal of an Infected Total Knee prosthesis;
- Knee Flexion:
 - optimum position for knee arthrodesis is slight flexion;
 - w/ minimum bone loss:
     - 10-20 deg of flexion allows foot to clear ground during swing phase of gait w/o circumduction of hip;
     - there should be slight valgus and 10 deg of external rotation;
 - w/ marked bone loss:
       - in instances of marked bone loss, position closer to full extension maintains as much length as possible.
       - in no instance should knee be placed in > 20 degrees of flexion;
- Bone Apposition:
 - most important factor for success of arthrodesis is bone apposition;
 - there must be vascular cancellous bone apposition.
 - resection of 1-2 mm of bone from distal aspect of femur & proximal aspect of tibia exposes vascular bone;
 - whenever possible, the interdigitation of bone ends should be done to improve stability and bone apposition.
 - large, hinged implants & implants w/ intramedullary stems necessitate sacrifice of more bone, and less bone is left for apposition than
      is left with resurfacing designs;
 - similarly, the knee with multiple revisions has less chance of a successful result than does a knee treated with primary operation.
- Bone Grafting:
 - is performed at time of arthrodesis for cases w/ extensive bone loss;
 - in presence of bone loss, cancellous bone-grafting, by incr surface available for bone apposition, can improve the chances of success;
 - bone graft should be placed about periphery of arthrodesis site to allow revascularization from surrounding soft tissues;
     - intramedullary circulation of the bone is usually compromised by prior implant and cement

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

Last updated by Data Trace Staff on Thursday, September 1, 2011 12:23 pm