Subtrochanteric Femur Fractures

Etiology

Subtrochanteric fractures present in a bimodal distribution. Young patients are generally involved in high-energy mechanisms such as motor vehicle collisions. Elderly patients generally present after low-energy mechanisms such as ground-level falls.[3] Additionally, older patients who are taking bisphosphonates may sustain a pathologic or atypical subtrochanteric fracture due to cortical weakness.

Epidemiology

Subtrochanteric fractures account for approximately 7% to 34% of femur fractures. They are sustained equally between males and females. Studies have shown that 7% of patients with atypical subtrochanteric femur fractures were exposed to the bisphosphonate alendronate. The reported one-year mortality of elderly patients with subtrochanteric femur fractures is 25%.

Pathophysiology

The subtrochanteric region is defined as within 5 centimeters distal to the lesser trochanter. Subtrochanteric fractures often are associated with intertrochanteric fractures.

The strong gluteal and thigh muscles create a classic deformity. The proximal fragment is held in abduction, flexion, and external rotation. The gluteus medius and minimus attach at the greater trochanter and provide an abduction force. The short external rotators also attach along the greater trochanter and intertrochanteric crest and provide an external rotation force. The iliopsoas attaches at the lesser trochanter and provides a flexion force. The distal fragment is held shortened and in adduction due to the pull of the adductors on the medial femoral condyle.

Immense load-bearing forces are exerted through the peri-trochanteric region. The medial cortex is subjected to compressive forces, while the lateral cortex is subjected to tensile forces.

The proximal femur obtains its blood supply from primary nutrient vessels and periosteal vessels. The nutrient artery enters at the linea aspera in the proximal third of the femur. It is important not to expose or strip the proximal linea aspera for this reason. The femoral head obtains its blood supply from the medial femoral circumflex artery, and it is important to be cognizant of its proximity to the piriformis fossa. Though an injury to the medial femoral circumflex artery is not commonly reported during piriformis entry nailing in adults, it is a known, devastating complication in skeletally immature patients.[4]

History and Physical

It is important to assess the etiology of the fracture in low-energy-mechanism, elderly patients. A thorough history is paramount. In the case of the elderly patient, a fragility fracture is most common. However, if a patient is on chronic bisphosphonates for bone health, they may have an atypical fracture characterized by cortical thickening at the fracture site. A history of antecedent thigh pain also may be noted in these cases.

The proximal fragment, which is held in flexion, may threaten the skin anteriorly. It is always important to assess for an open fracture. A thorough neurovascular exam with particular attention to assessment of vascular status is important.

Evaluation

Imaging

Orthogonal radiographs of the entire femur should be obtained. It is also important to obtain orthogonal radiographs of the hip and knee joints. There may be an associated femoral shaft or distal femur fracture. If there is an intertrochanteric extension of the fracture, it is important to assess the integrity of the potential start site if intramedullary nailing is selected for fixation. A traction view or CT scan may be helpful for fragment assessment. Additionally, an anteroposterior (AP) traction view can help determine whether closed reduction may be feasible or if open reduction techniques are needed.

Classifications

AO/OTA

• 32-A3.1 Simple (A) Transverse (3), Subtrochanteric fracture (0.1)
• 32-B3.1 Wedge (B) Fragmented (3), Subtrochanteric fracture (0.1)
• 32-C1.1 Complex (C) Spiral (1), Subtrochanteric fracture (0.1)

Russel-Taylor

• Type I: No extension into piriformis fossa
• Type II: Extension into greater trochanter with the involvement of piriformis fossa

Treatment / Management

Open Fractures

Treat open fractures with the expeditious administration of appropriate antibiotics. Perform a bedside irrigation and debridement upon patient arrival and, ideally, an operative debridement within 2 hours if the patient is stable.

End-of-Bed Skeletal Traction

Consider traction on a case-by-case basis. Traction is generally not required in elderly patients with low-energy mechanisms. However, traction is helpful in younger patients as the strong muscular attachments cause shortening and the flexed proximal fragment may threaten skin anteriorly.[5][6][7]

After assessment of the knee joint radiographically, a distal femoral or proximal tibial traction pin may be placed. End-of-bed traction of 12 pounds (5 kg) is generally used and may be adjusted based on the patient’s weight. Skeletal traction greater than 20 pounds (9 kg) is not recommended.

Cephalomedullary Nailing

Cephalomedullary nailing is the mainstay in treatment of subtrochanteric femur fractures due to decreased blood loss, reduced operative time, superior biomechanical strength, fewer complications, and expedited time to weight bearing.[8][9] It is important to assess the integrity of the trochanteric or piriformis start site prior to committing to nailing. The patient may be placed in the lateral or supine position. Proponents of the lateral position cite its advantage in allowing reduction in the sagittal plane and more facile access to a piriformis start site. Proponents of supine positioning cite more accurate rotational control and access to other extremities that may require concurrent intervention in the multiply injured patient. Additionally, supine positioning allows for the use of a traction table to assist with reduction. It is important to make individualized decisions in these cases.(A1)

Trochanteric and piriformis fossa start site nails are widely available. Studies have shown no difference in outcomes between these two nails.[10] However, the piriformis fossa is in anatomic alignment with the medullary canal and may prevent valgus malreduction of the proximal fragment that may be caused due to the design of trochanteric start nails.(B2)

Cephalomedullary nailing achieves relative stability and secondary bone healing. It is important to note that the fracture must be reduced prior to reaming and placement of the intramedullary device. In subtrochanteric fractures, this often requires percutaneous reduction techniques. Many adjunctive reduction aids can be used, such as reduction clamps, collinear clamps, Schanz pins used as joysticks, a ball spiked pusher, a femoral distractor, or a bone hook. A balance must be maintained between achieving secondary bone healing, preserving the proximal femur’s blood supply, and obtaining a satisfactory reduction with these techniques, which are placed at the fracture site and can potentially disturb some of the fracture biology.

Postoperative weight-bearing status should be determined on a case-by-case basis and is dependent on the quality of fixation. Multiple studies suggest that utilizing longer intramedullary devices reduces motion at the fracture site.[11]

Submuscular Fixed-angle Plating

Though cephalomedullary nailing is preferred, submuscular plating is indicated in certain instances when the patient or fracture is not suitable for a cephalomedullary nail. Such an instance might include an extension of the fracture into the greater trochanter or piriformis fossa, preventing a safe, adequate start site for a nail. In this case, a direct lateral approach to the femur is utilized to apply a laterally based plate. The vastus lateralis may be split or elevated to expose the femur. A direct reduction is then obtained, and a plate is placed along the lateral femur. Various plate designs can be chosen including a blade plate, a dynamic condylar plate, or a proximal femoral locking plate. A blade plate converts tensile force along the lateral cortex into a compressive force on the medial cortex, thus essentially serving as a tension band construct. This construct requires an intact medial cortex without comminution to avoid plate failure. Patients are generally made non-weight-bearing following plating of subtrochanteric femur fractures.

Differential Diagnosis

• Hip Fracture

• Knee Fracture Management

• Pelvic Fracture

• Peripheral Vascular Injury Management

Complications

The most common complication after fixation is a varus and procurvatum malunion or nonunion due to the characteristic deformity at the fracture site. This complication can be decreased by achieving an adequate reduction and stable fixation at the time of initial intervention. As with all fracture nonunions, it is important to rule out potential systemic contributors to the nonunion such as vitamin and mineral deficiencies, and infection. Once systemic contributors are ruled out or addressed, revision can then be carried out with a focus on correcting the deformity.