Distal femoral fractures comprise approximately 3%–6% of all femoral fractures.1 The associated mechanism of injury can be of high or low energy; high-energy mechanisms such as motor vehicle accidents are more common in the younger population as compared with low-energy mechanisms such as fall from stand in the elderly and osteoporotic patients.2 Distal femoral fractures are often complex, intraarticular, and comminuted, irrespective of etiology and thus make achieving and maintaining an adequate reduction challenging. Special care must be taken to avoid disrupting the soft tissue envelope to reduce the risk of nonunion.3 The AO/OTA system is most universally used for fracture classification.4 Fracture patterns include type A (extraarticular), type B (partial articular/unicondylar), and type C (complete articular/bicondylar). Further classification into subtypes 1, 2, and 3 indicates the progressively increasing degree of comminution.
Patients with a suspected distal femoral fracture often present after trauma with pain in the knee or thigh, the inability to bear weight on the affected extremity, and associated swelling and/or deformity. Initial evaluation should involve a careful assessment of the skin to check for the possibility of an open fracture or soft tissue injury that might compromise the surgical approach. A complete assessment of the neurovascular status of the affected lower extremity should be performed. Initial imaging includes plain radiographs of the knee and femur. For suspected type B or C fractures, Computed Tomography (CT) may be obtained for further characterization of the articular surface and the degree of comminution. CT is extremely useful in diagnosing the presence of a “Hoffa” fragment, a coronal plane fracture, most commonly involving the lateral femoral condyle.5 Temporizing measures typically involve immobilization with a long-leg splint or knee immobilizer. In cases of extreme deformity, a closed reduction may be required.
Surgical reduction and fixation of displaced, intra- articular fractures of the distal femur is generally indicated.6 Nonsurgical management is reserved for nonambulatory patients or patients too frail to tolerate a surgical procedure. The goal of clinical management of distal femoral fractures is the anatomic reduction of the articular surface and restoration of limb length, rotation, and alignment. A stabile fixation construct is important to allow early knee range of motion to optimize functional recovery. Preservation of the soft tissue attachments to bone fragments is critical in reducing the risk of nonunion. Although restoring alignment in both the coronal and sagittal planes is important in restoring normal knee range of motion and kinematics, the coronal plane has been shown to be most significant with regard to overall outcome. Patients with fractures that heal with greater than 15 degrees of valgus or any degree of varus have been reported to develop posttraumatic arthritis.7
Nonsurgical management involves protected weight or non-weight bearing in an unlocked, hinged knee brace to maintain the range of motion. Indications for nonsurgical management include distal femoral fractures that are nondisplaced and stable, as well as patients with medical conditions who preclude surgical treatment. Evidence of radiographic union of the fracture is required before the gradual return to weight bearing. Complications of nonsurgical management include those that are associated with decreased mobility, including decubitus ulcers, thromboembolic disease, and loss of knee function.
Surgical fixation has consistently demonstrated superior outcomes as compared with nonsurgical treatment with respect to improvement in alignment, bony union, knee range of motion, and functional outcome.8
Methods of surgical fixation include external fixation, fixed-angle blade plates, dynamic condylar screws (DCS), locking plates, and intramedullary nails; the characteristics of the fracture in addition to the overall medical condition of the patient generally determine the type of fixation.
External fixation is typically employed as a temporizing measure for the unstable polytrauma patient and for those with compromised overlying soft tissue. Alternatively, external fixation may be a definitive treatment for patients with severely comminuted or open fractures with concomitant medical conditions incompatible with additional surgery.
The fixed-angle blade plate is a 95-degree angled plate that provides stable fixation by controlling alignment in 3 planes. It is a very technically demanding procedure as it is a single piece, and requires restoration of alignment in all 3 planes for optimal function.
The DCS was introduced as an alternative to the fixed-angle plate, with a screw replacing the blade plate. This device requires restoration of alignment in 2 rather than the 3 planes. A significant advantage is that it is 2 separate pieces, which allows for less dissection of soft tissue before placement.
Precontoured anatomic locking plates, such as the Less Invasive Stabilization System, afford the added versatility of multiple distal screw hole options combined with the ability to lock or compress. Insertion is obtained with a less invasive, submuscular plating technique, which results in decreased soft tissue disruption. Alignment guides allow for the percutaneous placement of proximal screws. After reduction, the plate is affixed to the lateral aspect of the femur. The plate maintains alignment of the closed reduction and allows for relative stability and secondary healing.9 The plate design is anatomically shaped, based on femoral CT data and trials to maximize best fit for the most femora. Screw angle options were optimized to allow condylar fixation without penetrating the intercondylar notch or patellofemoral joint.
Fixation with an intramedullary nail is often used for extraarticular fractures and simple or minimally comminuted intraarticular fractures. This implant allows for fracture fixation with minimal disruption of the soft tissues and endosteal arterial supply. Biomechanical studies performed by Zlowodski et al show similar axial strength between intramedullary nailing and side-plate fixation constructs.10,11 Complications may arise from malalignment of the fracture because of insufficient fracture reduction, a poor starting point, or eccentric reaming.
SURGICAL MANAGEMENT OF PERIPROSTHETIC DISTAL FEMORAL FRACTURES
The incidence of periprosthetic fracture of the distal femur is approximately 0.6%–1.6% for patients with primary total knee arthroplasty and revision total knee arthroplasty, respectively;12 however, it is expected to increase significantly in the next years to decades. The location of the femoral component often complicates treatment and makes obtaining adequate screw purchase in the distal fragment more challenging.
In the setting of a periprosthetic distal femoral fracture, the variety of screw angle options in the anatomic locking plate allows for multiple fixed-angle points of fixation around the arthroplasty implants13 and has therefore been the preferred method.
“SHORT” VERSUS “LONG” PLATING FOR PERIPROSTHETIC DISTAL FEMUR FRACTURES WITH IPSILATERAL TOTAL HIP ARTHROPLASTY
There is controversy whether to span the plate over the distal aspect of the femoral stem of a total hip arthroplasty (THA) to avoid stress riser. Many argue that using a long plate will protect the bone from a fracture between the implants. Currently, there is no clinical evidence to support either surgical treatment plan. With a long plate, proximal fixation most often requires cable fixation because of diaphyseal fit of the femoral stem. A short plate avoids additional soft tissue dissection around the proximal femur, which might be beneficial in a patient with poor host biology and soft tissue envelope. Deciding whether or not to overlap the femoral prosthesis depends on the clinical judgment of the treating surgeon. Patient and soft tissue factors, the location of the fracture, and the amount of intact bone between the fracture and the femoral component all need to be taken into account.
Initiation of immediate postoperative knee range of motion is essential to prevent stiffness and loss of function. This is achieved with early physical therapy and lower extremity strengthening. A hinged knee brace may be used to protect against varus and valgus stresses across the fracture if there is concern for the quality of fracture fixation. Toe-touch or nonweight-bearing precautions should be maintained for 6–12 weeks after surgery or until evidence of radiographic fracture healing.
There are few comparative clinical studies in recent literature regarding optimal fixation of distal femoral fractures. Outcomes using a minimally invasive percutaneous approach with precontoured lateral locked plates are biomechanically similar or superior to standard open approaches with alternative fixation devices without the morbidity associated with extensive soft tissue dissection. Lower infection and nonunion rates compared with the standard open technique have been demonstrated.13 Additionally, lateral locking plates have been shown to be an effective method for surgical fixation when used for the treatment of periprosthetic proximal and distal femoral fractures, those with a high-energy mechanism of injury, and those that are mechanically unstable.14 However, nonunion occur also with the lateral locked plating. A recent study found that risk factors for nonunion inpatients with lateral locked plating systems for distal femoral fractures include obesity, occurrence of an infection, use of stainless steel, and open fractures.3
In comparison with the fixed-angle blade plate and DCS, the lateral locking plate demonstrates stiffness and fatigue ratings that fall between these 2 implants.10 Biomechanical studies have demonstrated that axial load strength of lateral locked plates is superior to the condylar blade plate and retrograde intramedullary nail, and torsional strength that is sufficient, but inferior to these designs.10 The advantage of the lateral locking plate is its specific development for minimally invasive insertion with use of an insertion jig that allows for easy screw targeting.10,11,14 Time to union, knee range of motion, and total complications were equivalent in a comparison of the lateral locking plate and the minimally invasive DCS construct, whereas the lateral locking plate demonstrated a lower rate of early implant failure.15
Management of distal femoral fractures is challenging, as they are often complex, intra-articular, and comminuted in nature. Periprosthetic fractures add an additional level of complexity as they limit screw placement and often occur in the setting of poor bone quality. Innovations in surgical methods, such as percutaneous plating, allow for fixation of multiple fracture types using minimally invasive approaches. By minimizing soft tissue and endosteal arterial disruption in addition to biomechanical advantages imparted through achieving multiple points of fixation, percutaneous plates promote early mobilization and knee range of motion, allowing for optimal functional recovery and bone healing. Distal femur fractures in a patient with an ipsilateral total hip replacement present a rare but likely increasing problem. Further research is required to identify mechanically favorable constructs to assure a good clinical outcome.
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