Distal femoral replacement can provide for rapid recovery and good outcomes in older patients with periprosthetic fractures marked by significant comminution and osteopenia.
The non-revision indications for distal femoral replacement include femoral nonunion and acute distal femoral fracture in selected elderly patients with a high probability of survival. Distal femoral replacement is indicated as a revision procedure in patients with severe comminuted periprosthetic fractures who have associated implant failure, antiquated implants or osteopenic bone, and is indicated for catastrophic revision scenarios such as cases of severe lysis, ligamentous instability or extensor mechanism dysfunction, and for patients who require a salvage option.
Distal femoral replacement
Our experience from 1998 to 2005, included 39 distal femoral replacements performed in 37 patients with an average follow up of 46 months. The patients had an average age of 76 years and 75% were women. The indication for distal femoral replacement was periprosthetic fracture in 33% of patients; infected knee that came to a second stage of reimplantation in 26% and aseptic loosening in 13%. Our average bone loss was about 7 cm.
When performing distal femoral replacement, preoperative planning is crucial to the success of the operative intervention. Planning commences with radiographic evaluation of both the involved and contralateral extremity. Radiographs of the contralateral extremity should include the entire extremity as well as AP and lateral views with magnification markers of the distal femur. These radiographs will be helpful in determining length of the extremity being reconstructed as well as size of the components to be used. Since most of the systems are modular, preliminary planning for the length of the distal femoral replacement and the diameter of the stem to be utilized can be performed.
As per all revisions, the patient should be evaluated preoperatively for any possibility of an infectious process. In addition, the patient’s medical status should be optimized. Nutritional status should be evaluated and addressed, and the patient’s preoperative hemoglobin and hematocrit should be determined. It is appropriate to treat the patient preoperatively with erythropoietin if indicated.
Figure 1. The exposed distal femur is skeletonized. If an implant is present, it is removed along with any bone fragments until viable bone is encountered.
Figure 2. The femoral canal is reamed sequentially to accept the appropriate diameter stem.
Images: Joint Implant Surgeons, Inc.
On the day of the operative intervention, the patient should be seen and evaluated for anesthesia. I prefer spinal anesthetic with intravenous sedation. Since these procedures require extensive surgical dissection, perioperative tranexamic acid is used.
The patient is positioned in the supine position as per standard protocol for total knee arthroplasty. It is advisable to prep and drape both lower extremities as is done for bilateral total knee arthroplasty. This will allow for an intraoperative assessment of leg length reconstruction. The extremity should be exsanguinated, and a tourniquet, which has been placed extremely high on the thigh, should be elevated. The incision should be long and generous so as to avoid any tension on the wound. A standard medial parapatellar arthrotomy is preferred, which is extended as far proximally as necessary to expose the distal femur. The distal femur is skeletonized as described by the femoral peel approach (Figure 1). The implant and bone fragments are removed until viable bone is encountered. Prior to removal, a measurement of the length should be obtained to assist in determination of the length of the distal femoral replacement.
Figure 3. With trial implants placed in
appropriate rotation and alignment,
patellofemoral tracking is assessed to
determine that it is satisfactory.
Attention is now turned to the tibia, which is prepared in the standard fashion. Rotation of the tibia is determined by standard techniques, usually lining up the tibia with the middle-third of the tibial tubercle. Attention is now turned to the distal femur. The canal is reamed to accept the appropriate diameter (Figure 2). The length of the stem should be approximately 150 mm. I prefer cemented fixation. The trial is now assembled and placed within the femoral canal and articulated with the tibial component.
What follows next is the most critical part of the operative intervention and relies heavily on what I call “ocular navigation.” First, leg length must be determined. This can be determined by assessing leg length with the contralateral limb, and also by evaluating the joint line with respect to the patellofemoral articulation. Next, rotation must be determined. With the knee in flexion, the femoral component should be slightly externally rotated by approximately 3°. The component is placed in this position and then the knee is brought to extension, and the overall alignment and rotation of the component are noted with respect to the tibiofemoral articulation and finely tuned. Next, patellofemoral tracking is assessed to determine that it is satisfactory (Figure 3). When all of these are in order, a mark should be placed on the femur so as to identify the final position of the definitive implant. The femoral and tibia canals should be lavaged and irrigated. Appropriate cement restrictors placed and the components should be carefully cemented in place paying strict attention to the rotation of the femur and the tibia as determined during the trialing (Figure 4). Once the cement is set, the final components can be articulated with the appropriate bushings, axle, yoke, bearing, locking screws, etc. (Figure 5). I suggest releasing the tourniquet in a pulsatile fashion. Once the anesthesiologist identifies the timing of the release of the tourniquet, the oxygen saturation and blood pressure of the patient are noted. If there is significant change in either, the tourniquet is quickly re-inflated. This process is repeated until there is no change in either oxygen saturation or blood pressure. Generally, two or three pulsations of the tourniquet release may be required.
Figure 4. The final components should be carefully cemented into place paying strict attention to the rotation of the femur, as shown here, and the tibia as determined during the trialing.
Meticulous closure is then accomplished over a drain, and the extremity is placed in a bulky Robert Jones dressing in full extension. The drain is pulled on the postoperative day 2 and range of motion is started at that time. Since the components are cemented, weight-bearing can be as tolerated and physiotherapy commences per routine.
Figure 5. Once the cement is set, the final components can be articulated with the appropriate bushings, axle, yoke, bearing and locking screws.
In this series, there were two patient deaths within 3 months of surgery. These patients had a significant number of comorbidities. There were four revisions or reoperations; three for recurrent infection and one periprosthetic fracture. Our average Knee Society function score was 35 and the clinical score was 87. Our survivorship at 4 years for any reoperation was 87%. Other researchers have reported 95% survivorship at up to 8 years using rotating hinge distal femoral replacements for non-tumor cases.
Distal femoral replacements function well in the elderly arthroplasty patient. These replacements are a viable option and alternative for periprosthetic fractures, and allow rapid mobilization with minimal morbidity.
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For more information:
Adolph V. Lombardi Jr., MD, FACS, can be reached at Joint Implant Surgeons, 7277 Smith’s Mill Rd., Suite 200, New Albany, Ohio 43054; email: email@example.com
Lombardi receives royalties from, is on the speakers’ bureau for, is a paid consultant of and receives research/institutional support from Biomet Inc.; is a paid consultant of and receives research/institutional support from Pacira; receives royalties from Innomed Inc. and receives research support from Stryker and Kinamed.