The incidence of periprosthetic supracondylar fractures of the femur after total knee arthroplasty (TKA) ranges from 0.6% to 2.5%.1 Treatment of periprosthetic fractures is often complicated by advanced patient age and osteoporosis, which frequently accompanies these fractures. Management of a periprosthetic fracture depends on the relation between the fracture site and the prosthesis, displacement of the prosthesis, integrity of the fixation of the prosthesis, extent of the bone loss caused by fracture comminution or preexisting osteolysis, general health of the patient, and surgeon expertise.2,3 The aim is to achieve fracture union around a stable, well-aligned arthroplasty with preserved or restored bone stock and therefore to return the patient to previous level of function. Although nonoperative treatments have been shown to be successful,4,5 in the great majority of cases surgical treatment is advised for these fractures.6-10 In cases in which bone stock is adequate for fixation rather than replacement of the distal femur, 2 modalities are commonly used: retrograde intramedullary nailing and locking plates. Each has its drawbacks and advantages.11,12
Although external fixation has been used in the treatment of distal femoral fractures,13 it is seldom considered in the treatment of periprosthetic fractures. Several authors have described cases that used external fixators, occasionally spanning the knee. The specific types of external fixators discussed in the literature have included ring fixators,14-17 hybrid fixators,18 and uniplanar nonspanning fixators14,19 (Table). Use of a simple anterior spanning external fixator in treating a periprosthetic femoral fracture has received little attention in the literature.
The patient provided written informed consent for print and electronic publication of this case report.
Case Report
A 54-year-old woman with previous total hip arthroplasty (THA) and ipsilateral TKA tripped on a carpet and sustained a comminuted fracture of the distal femur just above the TKA prosthesis (Figure 1). She was a Jehovah’s Witness and thus refused all blood products. She had an extensive history of osteoporosis, morbid obesity (5 feet tall, 250 pounds; body mass index, 49), diabetes, and rheumatoid arthritis. Evaluation by the internal medicine service revealed severe coronary artery disease on a stress thallium test and anemia with hematocrit of 24%. Given the patient’s medical comorbidities and religious status, and the location of the comminuted distal femur fracture, several treatment options were considered. First was nonoperative treatment with a cast or cast-brace (hinged cast). Because of her body habitus, however, we thought she would very likely experience skin complications, inadequate immobilization of the bone, and significant discomfort. Ultimately, use of a spanning external fixator was chosen as the safest course, given the significant medical risks accompanying a more extensive surgical reconstruction. With the spanning external fixator, the main risks were the inability to fully control fracture alignment and the potential introduction of infection into the functional THA. We thought that, by limiting the amount of time in the fixator and managing the pin site aggressively, we could minimize the risk for infection in this setting.
The procedure was performed with the patient under general anesthesia. During surgery, a lateral image of the femur was used to identify the distal end of the THA prosthesis. A level was marked 2 to 3 cm distal to the tip of this prosthesis, and another about 1 cm above the fracture (noted to be above the most proximal extent of the knee joint). These planned pin-entry sites were prepared from an anterior approach with incisions (using a No. 11 blade) of about 1 cm each. Blunt dissection was carried down to the femur. Each planned pin site was predrilled with a 3.5-mm drill; then, a 5-mm Shanz pin was placed. This process was repeated immediately distal to the tibial component and at the junction of the mid and distal thirds of the tibia (Figure 2). The preliminary external fixator frame was then applied. Once the reduction was satisfactory in the anteroposterior and lateral planes, the fixator clamps were tightened. A second row of bars was then incorporated.
Six weeks after surgery, radiographs showed early callus formation. Removing the external fixator and examining the knee under anesthesia confirmed there was no significant motion through the fracture site. A cast-brace (fiberglass thigh segment, fiberglass lower leg cast with hinged knee segment) was then applied. We remained concerned about skin complications but were encouraged by the early healing achieved with the fixator. The patient was started on a physical therapy program of gait training with a walker and toe-touch weight-bearing on the injured extremity. She also started a limited lower-extremity strengthening program. Three months after surgery, she was tolerating weight-bearing on the injured extremity with no pain. At 6 months, knee radiographs showed fracture consolidation with active range of motion of 10° to 120° and no pain (Figures 3A, 3B). Distal sensation, motor function, and vascular examination were normal. Two years after surgery, radiographs of the right knee showed minor malalignment in the coronal and sagittal planes (Figures 4A, 4B) and complete consolidation of the fracture.
