A 66-year-old woman underwent a primary total knee arthroplasty for advanced osteoarthritis of her right knee. Four years after the index arthroplasty, she sustained a closed, displaced, comminuted, supracondylar periprosthetic femur fracture after a mechanical fall. This was treated with a retrograde intramedullary nail ( Fig. 30.1 ). Two years later, the patient had persistent distal thigh pain associated with weight bearing, which was relieved with rest. Radiographic evaluation demonstrated a nonunion of the fracture with varus malalignment. She subsequently underwent removal of the intramedullary nail and open reduction and internal fixation with a periarticular locking plate and application of autogenous iliac bone crest to the site of nonunion ( Fig. 30.2 ). Eight months after this operation, the patient had persistent pain, radiographic and computed tomographic evidence of a persistent nonunion. She underwent additional autogenous bone grafting and supplemental plate fixation to the medial aspect of the distal femur. The nonunion persisted, eventually leading to failure of the medial plate (screw fracture) ( Fig. 30.3 ). Given her symptoms of a persistently painful nonunion, she underwent resection of the nonunion and distal femoral replacement ( Fig. 30.4 ).
Algorithm
The algorithm shows the treatments for distal femoral supracondylar periprosthetic femur fractures ( A ), periprosthetic patella fractures ( B ), and periprosthetic tibia fractures ( C ). ( APC, Allograft prosthetic composite; IMN, intramedullary nail; ORIF, open reduction and internal fixation.)
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Chapter Synopsis
This chapter describes the indications, surgical technique, complications, and outcomes for periprosthetic fractures of the femur and tibia around a total knee arthroplasty (TKA). Nonoperative, operative, and revision techniques are discussed.
Key Points, Pearls, and Pitfalls
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Goals of treatment associated with a good outcome in supracondylar periprosthetic femur fractures include range of motion greater than 90 degrees, fracture shortening less than 2 cm, flexion/extension malalignment less than 10 degrees, and varus/valgus malalignment less than 5 degrees.
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Consider preparing the well leg and including it in the operative field, so that it may be elevated during lateral imaging of the operative femur.
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Use of a sterile tourniquet allows inclusion of the proximal thigh in the operative field.
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Use of a bump placed under the distal metadiaphyseal region of the femur may help prevent hyperextension of the supracondylar fracture and aid in reduction.
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A posterior-stabilized (PS) TKA presents a greater challenge, because there is frequently less distal femoral bone in which to gain purchase. Additionally, the presence of a PS femoral component may prevent insertion of a retrograde intramedullary nail.
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Polymethylmethacrylate or allograft can be used to augment fixation in severely comminuted or osteoporotic bone.
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Surgical intervention for periprosthetic patella fractures has a high associated complication rate and should be reserved for removal of loose components or repair of a disrupted extensor mechanism.
Introduction
Periprosthetic fractures around total knee arthroplasty (TKA) components are increasing in incidence, because more knee replacements are performed each year and many more patients are advancing in age with a TKA already in place. The incidence of a supracondylar periprosthetic fracture occurring adjacent to a primary TKA is between 0.3% to 5.5%. Fractures around the tibial or patellar components have an incidence of 0.3% to 0.5% and 0.1% to 2.5%, respectively. Risk factors identified with periprosthetic fractures include rheumatoid arthritis, chronic steroid therapy, osteolysis, stress shielding, osteopenic bone, frequent falls, older age, female gender, neurologic disorders, use of constrained implants, revision surgery, and technique-specific factors (e.g., anterior femoral cortical notching; overaggressive sawblade resection; use of canal-fitting, press-fit, or stemmed components).
Fractures around TKA components can occur intraoperatively or postoperatively. Postoperative periprosthetic fractures tend to occur more commonly on the femoral side, at or near the anterior flange of the implant. Fractures on the tibial side are more often associated with implant loosening. In the face of well-fixed implants and sufficient adjacent bone stock, open reduction and internal fixation (ORIF) is regarded as the treatment of choice. Fractures associated with component loosening are best treated with revision arthroplasty. Osteopenia and osteoporosis contribute to both the etiology of these injuries and the challenge of their treatment. Postoperative periprosthetic fractures tend to occur more commonly on the femoral side, at or near the anterior flange of the implant.
Indications and Contraindications
Nonoperative management may be considered in patients with unacceptable risks of anesthesia, or nondisplaced fractures (i.e., femur type I ; patellar type I ; tibia type IA, IIA, III, or IVA ). Complications relating to recumbency, including pneumonia, venous thromboembolism, and decubitus ulcers, should be monitored for very closely. Nonoperative management tends to result in decreased range of motion (ROM) of the affected joint, in spite of intensive rehabilitation after mobilization is initiated.
Operative management is indicated for displaced, open, or unstable fractures and for fractures associated with loose components. Management objectives include fracture healing, pain-free function, restoration and maintenance of knee ROM, and correct limb alignment, length, and rotation. Goals of treatment associated with a good outcome include fracture healing, ROM greater than 90 degrees, fracture shortening less than 2 cm, flexion/extension malalignment less than 10 degrees, and varus/valgus malalignment less than 5 degrees.
Preoperative Considerations
Preoperative radiographs in two planes should be obtained to evaluate fracture location, proximity to the implant, and quality of remaining bone ( Fig. 30.5 ). Full-length radiographs of the fractured bone should be obtained to evaluate for potential implants or abnormal bony morphology, which may affect surgical reconstruction or technique used. The prior operative report should be obtained to provide detailed information on the implanted components. This information can be used to determine whether the components are modular, what level of constraint was used, and the relative sizes of the implants. Compatibility and modularity issues may necessitate complete revision arthroplasty. A detailed history should be obtained to investigate for symptoms occurring before the injury that may be associated with loose components or infection. If an infectious process is suspected, an erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) level should be obtained. Review of prior films should be undertaken, whenever possible, to evaluate for preinjury component–limb alignment and to assess for any signs of progressive aseptic loosening. The physical examination should focus on the quality and integrity of the skin and soft tissues, the neurovascular status of the limb, and the presence of previous surgical incisions.
Equipment
The following equipment is required:
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Radiolucent operative table
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C-arm or portable x-ray machine
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Sterile tourniquet
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Fracture reduction instruments (e.g., collinear reduction clamp, reduction forceps and clamps)
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Femoral distractor
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Cerclage cables and wires
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Devices for ORIF (e.g., intramedullary nails [IMNs], periarticular locking plates, 95-degree fixed-angle plates, condylar buttress plates, distal condylar screws and side plates)
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Revision TKA equipment (e.g., stemmed components, metallic augments, allograft)
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Metal-cutting, high-speed drill or bur
Surgical Technique
Set-up
The patients should be positioned in the supine position on a radiolucent table. A bump may be placed under the ipsilateral buttock to aid in internal rotation of the limb. Both lower extremities should be prepared and brought into the operative field. This allows the surgical team to move the contralateral leg out of the way during lateral imaging. A sterile tourniquet should be used to ensure access to the proximal thigh if needed.
Surgical Approaches
Femur
Surgical exposure of the distal femur can be achieved through a posterolateral approach. The distal aspect of the incision should be centered over the lateral femoral epicondyle. The incision can be extended proximally along the posterior aspect of the femur, in an attempt to leave as large a skin bridge as possible with the anterior TKA incision. The superficial dissection carries through the subcutaneous fat, and the iliotibial band is incised in line with its fibers and the skin incision. Identification of the vastus lateralis and anterior reflection of the muscle off of the intermuscular septum provides direct visualization of the periosteum; the extent of the dissection is related to the fracture, the components in place, and the surgeon’s comfort level with percutaneous fixation techniques. Any perforating vessels that may cross the field should be coagulated or ligated. Dissection at this stage of the procedure should be slow and deliberate, because transection of the perforating vessels can cause significant blood loss.
Surgical exposure of the medial aspect of the distal femur is achieved through an anteromedial approach. A longitudinal incision is made over the interval between the vastus medialis and the rectus femoris. Distally, the extensor mechanism should be incised in a medial parapatellar fashion. This should be extended rostrally, as needed. Proximally, the vastus intermedius will be exposed. The vastus intermedius is incised in line with its fibers and elevated to expose the femoral shaft. Care should be taken during dissection around the distal medial one-third of the thigh, because the femoral vessels traverse through the adductor hiatus.
Tibia
Access to the proximal tibia can be obtained through an anterior exposure achieved by extending the prior incision distally or through a separate medial or lateral approach (depending on the fracture location). Caution should be exerted with the use of a separate medial or lateral incision, because there is a potential for necrosis of the skin bridge. Additionally, surgical incisions should be directed medial or lateral to the tibial tubercle and not directly over this bony landmark.
Treatment Options
Femur
Type I
Nondisplaced fractures of the distal femur with an intact prosthesis can be treated nonoperatively or operatively. Casting with restricted weight bearing for 6 weeks and close radiographic follow-up is recommended if nonoperative intervention is pursued. Operative intervention with ORIF allows for earlier mobilization and ROM. Fracture stabilization can be achieved with a retrograde IMN or with plate and screw fixation. We recommend periarticular submuscular plate and screw fixation via a percutaneous approach ( Fig. 30.6 ).
Type II
Treatment of the displaced supracondylar periprosthetic femur fracture with a stable implant can be approached several ways. Factors to consider include fracture pattern, comminution, amount of bone attached to the femoral component distally, design of the femoral component (cruciate retaining or cruciate sacrificing), quality of the host bone (e.g., osteopenic, osteoporotic), and temporal occurrence to the index procedure. Fractures that occur intraoperatively during primary TKA can often be treated with the use of a stemmed femoral component that bypasses the fracture site. Supplemental stabilization with a cerclage cable or wire, plate and screws, or lag screws may be considered ( Fig. 30.7 ).
