The distal femoral replacement prosthesis is indicated when there is either insufficient bone stock or poor bone quality.
The tibial component requires revision to be compatible with the new distal femoral replacement.
2. Preoperative planning
Templating is performed to determine the appropriate length of the distal femoral bone resection.
The minimum length of the distal femoral replacement prosthesis is generally in the range of 60-70 mm in most implant systems.
Additional intercalary segments are available to meet the reconstructive requirements.
The minimum length of the stem for the distal femoral replacement prosthesis is typically 100-125 mm.
3. Patient preparation
The patient is placed in the supine position. A radiolucent table may facilitate intraoperative fluoroscopy if required.
4. Surgical approach
This procedure requires an adequate visualization of the knee joint. The most commonly used is a midline skin incision followed by a medial parapatellar arthrotomy. A proximal and distal extension may be necessary to achieve sufficient visualization and soft tissue releases.
Removal of femoral component
Dissection is carried out around the distal femur using the electric cautery. The collateral ligaments and the posterior joint capsule are detached from the distal femur. Care must be undertaken to avoid injury to the neurovascular structures, and to the extensor mechanism of the knee.
The femoral component is removed with the distal femur fracture fragments.
Additional bone resection may be necessary according to preoperative planning.
Preparation of the femur
The femoral resection level can be evened with a planer to optimize contact with the new prosthesis.
The femoral canal is prepared with reamers of increasing size. The depth of the reaming is determined by the length of the selected stem.
The diameter of the stem is determined by the reamer diameter which achieves cortical contact with the diaphyseal bone. One should allow for at least 2 mm of cement mantle around the stem if cement fixation is selected.