Total Femur Arthroplasty

Total femur arthroplasty is an uncommon limb salvage procedure that is performed following multiple failed total hip or total knee arthroplasties or for orthopaedic oncology. It is an alternative to amputation that can allow patients to remain ambulatory.

Indications and Contraindications

Indications

Failed total hip or knee arthroplasty with insufficient bone stock for reimplantation of prosthesis
Complex periprostetic fracture not amendable to other treatment
Failed internal fixation of complex per prosthetic fracture
Limb-salvage procedure in tumor surgery

Contraindications

Nonfunctional quadriceps mechanism
Inadequate tibial host bone for fixation

Anatomy

Thorough knowledge of the applicable anatomy involving the pelvis, hip, thigh, knee, and tibia
Significant neurovascular structures at risk
- Superior gluteal artery
- Femoral artery
- Femoral nerve
- Femoral vein
- Sciatic nerve
- Peroneal nerve
- Popliteal artery
- Popliteal vein.
Identification and protection of neurovascular structures at risk, with careful placement of retractors

Preoperative Assessment

The patient who presents for consideration of a total femoral arthroplasty has most likely undergone multiple hip or knee arthroplasty revisions and previous surgeries or injuries and now has insufficient bone to support implantation of revision arthroplasty prosthesis. Alternatively, total femur replacement can be used for limb salvage procedures in oncology patients.

Workup

Identify the cause of implant failure, such as trauma, loosening, or infection.
Obtain standard infection screening serum blood tests -- white blood cell count with differential, erythrocyte sedimentation rate, and C - reactive protein -- and consider aspiration of any prosthetic joints involved if infection is a potential concern.
Examine the soft tissues of the lower extremity to ensure adequate soft tissue coverage of the prosthesis.
Evaluate motor strength about the hip and knee, compare leg lengths, and assess distal neurovascular status.
Document any history of hip instability.

Acetabulum

In patients who have had a prior total hip arthroplasty, retention of the existing acetabular component is appropriate if the implant is stable and in good position and the intraoperative stability with the total femoral component is acceptable.
Ideally, a large-diameter femoral head is implanted to promote stability; use of a constrained acetabular liner may be necessary.
Revision of an existing acetabular component to an implant which accepts a constrained liner may be required in some patients.

Tibia

A hinged articulation is required for a total femoral implant.
In a patient with a prior non-hinged total knee arthroplasty, the existing tibial component will require revision to permit the hinged articulation.

Imaging

Standard and lateral views of the pelvis, hip, femur, and knee are the foundation of evaluating current implants and remaining bone.
Computed tomography from the hemipelvis to the proximal tibia should be obtained if adequacy of bone stock in the acetabular and tibial regions cannot be determined on plain radiographs.
Full-length films or computed tomographic studies will assist with leg lengths and alignment. If significant deformity is present the contralateral limb can serve as a guide for the appropriate target length of the total femoral reconstruction.

Preoperative Preparation

Explain the complexity of the total femoral replacement to the patient, including alternative treatments and the risks involved, such as the need for revision of their total femur.
Patients should understand that this procedure will not return them to normal status and that they may require an assistive device, such as a walker or cane, for the remainder of their lives.
Prior to surgery, perform a preoperative evaluation to medically optimize the patient for surgery.

Approach

A direct lateral approach can be used to expose the entire femur and proximal tibia, utilizing a lateral parapatellar approach at the knee and the posterior approach at the hip.
A dual incision approach may be used, with a medial parapatellar approach at the knee and choice of extendable approach at the hip.
We prefer to utilize the extended posterior approach to the hip, which transitions smoothly into a lateral approach to the femur and lateral parapatellar approach.

Positioning

The patient is positioned on the table in a semilateral decubitus position.
A beanbag provides excellent stabilization.

Technique

Begin the skin incision proximal to the greater trochanter and cross at the junction of the anterior two third and posterior one third of the greater trochanter down the lateral aspect of the femur, until the incision curves slightly anteriorly at the knee to the lateral parapatellar approach. Split the tensor fascia lata and IT band in line with the incision.

Release the short external rotators in the standard fashion, and elevate the vastus lateralis from the intramuscular septum down the length of the femur. Ligate the perforating vessels.

Enter the knee joint through the lateral parapatellar fascia in line with the elevated vastus lateralis. The lateral, anterior, and posterior aspects of the femur can readily be released in this fashion.

Using a malleable retractor to protect surrounding neurovascular structures, make an osteotomy at the mid level of the femur with a sagittal saw. This will mobilize the proximal and distal segments, allowing for release of the medial side of the femur. The collateral and cruciate ligaments of the knee may be resected to remove the distal femur.

Remove the proximal femur and peel the abductors from the greater trochanter with bovie cauterization. We utilize a modular set, allowing for construction and customization of the length and offset intraoperatively. The removed bone may be measured to obtain the initial trial length of the total femur.

Prepare the tibia with the stemmed hinge prosthesis of choice. The patella may be resurfaced or revised as necessary.

If the acetabular cartilage is not significantly worn, we recommend use of bipolar heads. The larger bipolar head will provide increased hip stability.

Perform a trial of the femur using one of two methods of in situ assembly: 1) Place the tibia trial first, then link the femur to the tibia and reduce the hip; or 2) place the tibia and femoral prostheses separately and link the hinge knee at the end. Assessment of the trial components involves hip stability, knee range of motion, leg length, patellar tracking, and overall soft tissue tension.

After thoroughly irrigate the incision, assemble the components. Cement the tibia in place, and then link the femoral prosthesis and reduce it at the hip. We place deep drains.

Reattach the vastus lateralis, abductors, and external rotators to the prosthesis.

Repair the tensor with interrupted absorbable suture and then close the subcutaneous tissues and skin.

Pearls and Pitfalls

Pearls

Preoperative evaluation for occult sepsis
Preoperative determination of target leg length
Preoperative determination of acetabular component and need for constraint

Pitfalls

Avoidance of tension on the peroneal nerve to minimize risk of postoperative palsy
Careful intra-operative assessment of patellar tracking to ensure patella stability
Significant elevation of the level of the knee joint

Postoperative Care

Postoperative rehabilitation for total femur arthroplasty can last 6 to 8 weeks longer than a primary total hip or total knee arthroplasty. While full independence can be achieved, an appropriately tailored program is vital. For example:

Active hip abduction may not be permitted for several weeks due to reattachment of the abductor muscles to the implant.
Partial weight-bearing may be necessary if bone allograft was used during reconstruction of the pelvis or femur.
Knee flexion may not be allowed if reattachment of the extensor mechanism to a tibial prosthesis is necessary.

Patients may continue to need assistive devices such as a cane or walker for ambulation after full recovery.

Outcome

The outcome after total femur arthroplasty is influenced by certain patient factors, such as age, muscle strength, overall patient functional capacity, as well as the occurrence of a postoperative complication. In a case series of total femur replacement for tumor resection of primary and metastatic disease, patients had a mean Musculoskeletal Tumor Society (MSTS) functional score of 66%-72%.^1-4 In a study of 100 total femur arthroplasties performed for non-oncologic procedures, MSTS functional evaluation scores for the hip improved from 1.25 to 3.29 points, and knee scores improved from 2.09 to 3.29 points.⁵

Complications

Complications after this procedure are not infrequent due to the complexity of the surgery, with infection and hip instability the most common complications.^5-7 Patients should understand the risk of these complications and the expected functional compromise before undergoing total femur arthroplasty.

Hendersen et. al described five modes of failure for tumor endoprosthesis:⁸

Type 1: Soft-tissue failures
Type 2: Aseptic loosening
Type 3: Structural failure
Type 4: Infection
Type 5: Tumor progression

Additionally, one study reported patella impingement on tibial polyethylene in 11 of 63 patients due patella baja and failure to restore the joint line.⁹

References

Kalra S, Abudu A, Murata H, et al. Total femur replacement: primary procedure for treatment of malignant tumours of the femur. Eur J Surg Oncol.2010;36(4):378-383.
Natarajan MV, Balasubramanian N, Jayasankar V, et al. Endoprosthetic reconstruction using total femoral custom mega prosthesis in malignant bone tumours. Int Orthop.2009;33(5):1359-1363.
Ruggieri P, Bosco G, Pala E, et al. Local recurrence, survival and function after total femur resection and megaprosthetic reconstruction for bone sarcomas. Clin Orthop Relat Res.2010;468(11):2860-2866.
Ahmed AR. Total femur replacement. Arch Orthop Trauma Surg.2010;130(2):171-176.
Friesecke C, Plutat J, Block A. Revision arthroplasty with use of a total femur prosthesis. J Bone Joint Surg Am.2005;87(12):2693-2701.
Ward WG, Dorey F, Eckardt JJ. Total femoral endoprosthetic reconstruction. Clin Orthop Relat Res.1995(316):195-206.
Lombardi AV, Jr., Berend KR. The shattered femur: radical solution options. J Arthroplasty.2006;21(4 Suppl 1):107-111.
Henderson ER, Groundland JS, Pala E, et al. Failure mode classification for tumor endoprostheses: retrospective review of five institutions and a literature review. J Bone Joint Surg Am.2011;93(5):418-429.
Schwab JH, Agarwal P, Boland PJ, et al. Patellar complications following distal femoral replacement after bone tumor resection. J Bone Joint Surg Am.2006;88(10):2225-2230.