Practice Essentials
During the past 50 years, the treatment of subtrochanteric fractures has evolved in conjunction with improved understanding of both fracture biology and biomechanics. Previously, nonsurgical treatment of these fractures was associated not only with significant shortening and malrotation but also with the morbidity and mortality of prolonged immobilization. Early surgical repair techniques had unacceptably high complication rates; however, the benefits of restoring the anatomy and encouraging early mobilization are recognized and have led to significant research and improvement in implants. Currently, subtrochanteric fractures remain technically challenging, even to experienced fracture surgeons. [1, 2, 3]
The difficulty of treating these fractures stems in part from the fact that this injury pattern is anatomically distinct from other proximal femoral peritrochanteric fractures and in part from the difficult features of femoral shaft fractures. As a result, they must be treated with specially designed implants that can withstand significant muscular forces for prolonged periods of healing. These strong muscle forces deform the fracture fragments and make reduction difficult. In addition, comminution is common in this region, and implants must withstand significant early loading.
Today, treatment of these fractures in adults is almost exclusively surgical. With the improvements in surgical techniques and implants, most of the treatment goals can typically be achieved by surgical means. In selected patients with grossly contaminated fractures and in patients who are medically unstable for surgical intervention, treatment with skeletal traction can be considered. In skeletally immature patients, traction followed by cast bracing is an accepted treatment option.
Not surprisingly, subtrochanteric fracture has significantly higher rates of malunion and nonunion than other femoral fractures do. Still, with an improved understanding of this fracture and the specific treatment options, successful results can be obtained. [1, 2]
Anatomy
The subtrochanteric region of the femur, arbitrarily designated as the region between the lesser trochanter and a point 5 cm distal, consists primarily of cortical bone. The femoral head and neck are anteverted approximately 13º with respect to the plane of the femoral shaft. The piriformis fossa lies at the base of the neck and is oriented in line with the femoral shaft. The lesser trochanter is posteromedial, and it is the point of insertion for the psoas and iliacus tendons. The femoral shaft has both an anterior and a lateral bow.
The major muscles that surround the hip create significant forces that contribute to fracture deformity. The gluteus medius and minimus tendons attach to the greater trochanter and abduct the proximal fragment. The psoas and iliacus attach to the lesser trochanter and flex the proximal fragment. The adductors pull the distal fragment medially.
All of these muscles are well vascularized, and this can lead to significant hemorrhage at the time of injury or during surgical approaches. To approach the proximal lateral femur, the vastus lateralis must be split or elevated off the intermuscular septum close to the large perforating branches of the profunda femoris. Division of these vessels can lead to copious bleeding, making surgical exposure difficult. With open surgical procedures, meticulous handling of these vessels and soft tissue is of paramount importance because the blood supply is critical to fracture healing.
Pathophysiology
The subtrochanteric region of the femur heals predominantly through a primary cortical healing; consequently, a subtrochanteric fracture is quite slow to consolidate. [4] In addition, this region is exposed to high stresses during activities of daily living. Axial loading forces through the hip joint create a large moment arm, with significant lateral tensile stresses and medial compressive loads.
The calcar is a portion of bone along the posteromedial femur, just below the lesser trochanter, that extends proximally into the posteroinferior femur. Significant compressive forces have been described in this region, which contribute to the dense cortical bone of the subtrochanteric femur. A man who weighs 200 lb can generate forces in excess of 1200 lb per square inch (psi). [5]
In addition to the bending forces, muscle forces at the hip also create torsional effects that lead to significant rotational shear forces. During normal activities of daily living, up to six times the body weight is transmitted across the subtrochanteric region of the femur. [6]
Etiology
In elderly patients, minor slips or falls that lead to direct lateral hip trauma are the most frequent mechanism of injury. [7, 8] This age group is also susceptible to metastatic disease that can lead to pathologic fractures. In younger patients, the mechanism of injury is almost always high-energy trauma, either from direct lateral trauma (eg, motor vehicle accident [MVA]) or from axial loading (eg, a fall from height).
Gunshot wounds cause approximately 10% of high-energy subtrochanteric femur fractures. Iatrogenic fractures may also occur secondary to stress risers following previous surgery on the proximal femur. [9, 10]
Epidemiology
Subtrochanteric fractures account for approximately 10-30% of all hip fractures, and they affect persons of all ages. Most frequently, these fractures are seen in two patient populations—namely, older osteopenic patients who have sustained a low-energy fall [8, 11] and younger patients who have been involved in high-energy trauma.
A more recently identified patient population consists of individuals who experience subtrochanteric fractures after bisphosphonate use. [12] These so-called atypical fractures have a transverse or short oblique pattern with cortical thickening and a medial cortical "beak."
Prognosis
Data regarding the outcomes of patients with subtrochanteric femur fractures are relatively sparse. [13] In young patients, these injuries are common among those with multiple traumatic injuries; thus, outcomes are likely to be poorer than those in patients with isolated femur fractures. Associated fractures and soft-tissue injuries to the knee can complicate rehabilitation efforts. In older patients, subtrochanteric fractures can be grouped with other proximal femur fractures with relatively high morbidity and mortality.
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Injury radiograph of high-energy intertrochanteric fracture with reverse obliquity.
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Subtrochanteric fracture repaired with cephalomedullary nail.
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The Seinsheimer classification of subtrochanteric femur fractures.
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The Arbeitsgemeinschaft für osteosynthesefragen–Association for the Study of Internal Fixation (AO-ASIF) classification of subtrochanteric femur fractures.
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The Russell-Taylor classification of subtrochanteric femur fractures.
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Reverse obliquity subtrochanteric femur fracture malreduced with a short cephalomedullary nail
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Subtrochanteric femur fracture reduction revised and stabilized with a blade plate. Patient went on to heal and return to full function without pain.
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Subtrochanteric femur fracture repaired with cephalomedullary device
