Key points

Introduction

Subtrochanteric fractures involve the segment of the proximal femur from the lesser trochanter to the isthmus. The major fracture involves a zone between the inferior border of the lesser trochanter and the junction of the proximal and middle one-third of the femur (approximately a 5-cm segment) ( Fig. 1 ). Fractures in this area may extend proximally into the trochanteric area or neck and distally into the shaft. Reverse trochanteric or transverse trochanteric fractures, although involving the proximal trochanteric area, present many of the same challenges as subtrochanteric fractures. There is no single method of treatment that can be applied to all patterns of subtrochanteric fractures and, therefore, they are challenging for even an experienced surgeon. Due to historically high failure rates and the complex nature of these fractures, numerous studies have been performed to improve implant designs and outcomes of treatment. Despite new technology and implants, malunion, nonunion, and implant failure can occur with some frequency.

Typical fracture involving subtrochanteric region extending into lesser trochanter seen with high-energy trauma.

Epidemiology

Subtrochanteric fractures account for approximately 25% of all hip fractures and have a bimodal age and gender distribution. They are seen in either young men as a result of high-energy injuries (often highly comminuted and significantly displaced) or in elderly osteoporotic women as a result of low-energy falls (typically long spiral fractures) ( Fig. 2 ). The high-energy cases often have concomitant injuries involving thoracoabdominal and head injuries in 10% to 30% of patients and associated noncontiguous long bone, spine, and pelvic injuries in up to 50% of patients. Mortality rates as high as 21% have also been described. These fractures may also occur as a result of a stress riser in the lateral cortex of the proximal femur secondary to placing cannulated screws too distally during treatment of femoral neck fractures or drilling too inferiorly when performing core decompression or bone grafting for avascular necrosis of the hip. Other causes include gunshot wounds and the more recently described “atypical” proximal femur fracture as a result of prolonged bisphosphonate therapy ( Fig. 3 ).

( A , B ) Typical long spiral fracture seen in elderly patients (in this case a 93/M [93 year old male]).

“Atypical” femur fracture. Note transverse lateral cortical fracture with associated hypertrophy and failure in tension.

Introduction

Subtrochanteric fractures involve the segment of the proximal femur from the lesser trochanter to the isthmus. The major fracture involves a zone between the inferior border of the lesser trochanter and the junction of the proximal and middle one-third of the femur (approximately a 5-cm segment) ( Fig. 1 ). Fractures in this area may extend proximally into the trochanteric area or neck and distally into the shaft. Reverse trochanteric or transverse trochanteric fractures, although involving the proximal trochanteric area, present many of the same challenges as subtrochanteric fractures. There is no single method of treatment that can be applied to all patterns of subtrochanteric fractures and, therefore, they are challenging for even an experienced surgeon. Due to historically high failure rates and the complex nature of these fractures, numerous studies have been performed to improve implant designs and outcomes of treatment. Despite new technology and implants, malunion, nonunion, and implant failure can occur with some frequency.

Typical fracture involving subtrochanteric region extending into lesser trochanter seen with high-energy trauma.

Epidemiology

Subtrochanteric fractures account for approximately 25% of all hip fractures and have a bimodal age and gender distribution. They are seen in either young men as a result of high-energy injuries (often highly comminuted and significantly displaced) or in elderly osteoporotic women as a result of low-energy falls (typically long spiral fractures) ( Fig. 2 ). The high-energy cases often have concomitant injuries involving thoracoabdominal and head injuries in 10% to 30% of patients and associated noncontiguous long bone, spine, and pelvic injuries in up to 50% of patients. Mortality rates as high as 21% have also been described. These fractures may also occur as a result of a stress riser in the lateral cortex of the proximal femur secondary to placing cannulated screws too distally during treatment of femoral neck fractures or drilling too inferiorly when performing core decompression or bone grafting for avascular necrosis of the hip. Other causes include gunshot wounds and the more recently described “atypical” proximal femur fracture as a result of prolonged bisphosphonate therapy ( Fig. 3 ).

( A , B ) Typical long spiral fracture seen in elderly patients (in this case a 93/M [93 year old male]).

“Atypical” femur fracture. Note transverse lateral cortical fracture with associated hypertrophy and failure in tension.

Unique anatomy and biomechanics

The subtrochanteric region below the lesser trochanter is subjected to the greatest stress in the human body, with forces exceeding 1200 psi in a 90 kg individual. Because of the numerous deforming forces in the subtrochanteric region and the unique bony anatomy, reduction of these fractures remains difficult. The subtrochanteric region consists of primarily cortical bone, and the healing of this region is significantly slower than the well-vascularized metaphyseal bone of the intertrochanteric zone. The fracture line is too proximal to be adequately controlled with implants that function well for the femoral shaft and too distal and often in a reverse direction to be adequately controlled with implants used solely for intertrochanteric fractures (ie, sliding hip screw). In cases of significant posteromedial comminution, the forces are dramatically increased on the implant and thus result in greater chance of fixation failure, nonunion, and revision surgery.

The typical fracture deformity is flexion, abduction, and external rotation of the proximal fragment ( Fig. 4 ). The abductors and short external rotators attached to the greater trochanter and the iliopsoas muscles attached to the lesser trochanter exert their forces on the proximal fragment, creating this described deformity. The adductor muscles act on the distal fragment to create varus and shortening at the fracture site. During fracture reduction, these deforming forces must be primarily neutralized and the reduction needs to be maintained during fixation for best results. It is usually unrewarding to allow the fixation device itself to achieve fracture reduction, unlike intramedullary nailing of mid-diaphyseal fractures.

Note flexion of proximal fragment with external rotation since greater trochanter becomes more visible.

Latest-generation intramedullary devices have been designed for trochanteric entry and femoral head and neck fixation proximally. The adult femoral shaft has an asymmetric anterior bow with an average radius of curvature between 109 and 120 cm (increasing with age). The average proximal neck-shaft angle is 129° in men and 133° in woman with some variability. The femoral neck and head are anteverted approximately 13° and offset anteriorly relative to the central axis of the femoral shaft. Care must be taken with use of a trochanteric entry intramedullary nail to avoid a varus deformity in the frontal plane due to the eccentric entry point and the canal fit that the nail obtains just distal to the fractured zone.

Classification

The Russell-Taylor classification is the most commonly used classification despite the variety of classification systems described for these fractures. It can help guide management of these fractures and choice of implants. Type I fractures spare the piriformis fossa and are amenable to intramedullary implants with a standard entry site. Type II involve the piriformis fossa and these fractures require extramedullary implants or intramedullary nails with a trochanteric entry site. Each fracture type is subclassified into types A and B. Type A fractures do not involve the lesser trochanter and are amenable to standard lesser trochanteric locking bolts. Type B fractures involve the lesser trochanter, and reconstruction or cephalomedullary nails allow for proximal fixation into the femoral head and neck. Fractures that lie within 2 cortical diameters of the lesser trochanter are considered high subtrochanteric fractures, and these tend to exhibit the classic deformities and challenges associated with subtrochanteric fractures (described previously). Fractures distal to this level are considered to be low subtrochanteric fractures and behave more similarly to femoral shaft fractures. Low subtrochanteric fractures typically do not exhibit the deformities associated with classic subtrochanteric fractures.

Historical evolution of fixation devices

The development of implants for subtrochanteric fractures has always been driven by the challenging nature of these fractures and associated failures or limitations with historical implants. Nonoperative treatment with skeletal traction was associated with unacceptable results and significant varus, rotational, and shortening deformities in up to 50% of cases. It was not until the triflanged nail plate devices (Jewett nail plate, McLaughlin nail, Smith-Petersen nail, and Thornton plate) were developed that internal fixation became a popular modality for these fractures. The need for obtaining secure proximal fixation in the femoral head in cases of subtrochanteric fractures led to development of devices, such as the Küntscher Y nail and the Williams Y nail. These devices were associated with their own failures and limitations and failed to gain general acceptance.

Zickel introduced a nail in 1964 specifically for subtrochanteric fractures as a way to address these concerns. First used clinically in 1966, the Zickel nail was the original precursor to the cephalomedullary implants of today and gained popularity through the 1980s for subtrochanteric and pathologic proximal femoral fractures in North America. It also began to suffer from complications, however, related to its design, method of insertion, and instrumentation, resulting in loss of fracture reduction and implant failure.

Although successful use of sliding hip screw devices has been reported in the treatment of subtrochanteric fractures (either in distal fractures or, in cases of proximal fractures, with the trochanteric stabilization plate), they are generally not recommended. The Medoff sliding plate, which allows compression along 2 axes, also continues to be used in certain countries in Europe with some success but its use has not gained popularity in the United States.

The 95° dynamic condylar screw and the angled blade plate were developed (Association for Osteosynthesis/Association for the Study of Internal Fixation) as an alternative to the early implants and remained the mainstay of achieving more successful outcomes while advanced nails designs were also being developed. The angled blade plate, although technically demanding, has remained an excellent device for surgeons comfortable with this implant, especially when used with tissue-sparing techniques ( Fig. 5 ).

( A ) Lag screw fixation of spiral fracture with blade plate used in neutralization fashion. ( B ) Note straight blade plate without matching anterior bow and need to position longer plates slightly more posterior.

As surgeons moved from direct to indirect reductions in extra-articular fractures, intramedullary nails became the focus. To overcome the limitation of standard nails in case of piriformis fracture extension, Wiss and Brien described the use of the standard centromedullary nails in a side-reversed fashion to allow oblique screws to be directed into the femoral head and neck using a freehand technique. The development of the reconstruction nail allowed interlocking screws to be precisely targeted into the femoral head and neck, allowing for secure proximal fixation, thus extending the use of intramedullary nails in type B fractures and revolutionizing the treatment of subtrochanteric fractures. Although initially introduced for use in intertrochanteric fractures, the cephalomedullary nails were soon adapted for use in subtrochanteric fractures. Cephalomedullary nails designed for trochanteric entry have become the mainstay of contemporary subtrochanteric fracture management owing to superior results and low reoperation rates ( Table 1 ).

The newly developed locked proximal femoral plate has gained little popularity although it also can be used successfully in the treatment of subtrochanteric fractures ( Fig. 6 ). It can be technically less demanding to insert than the traditional angled blade plate because of its extra degree of freedom and its ability to compress the proximal fragment to the plate with cortical screws (which can be exchanged for locking screws as final fixation). Careful and meticulous insertion is critical, however, to assure appropriate fracture compression and reduction and to avoid implant failure. Newer designs have been found to equivalent to angled blade plates in terms of their indications and but clinical results continue to lag behind those of the angled blade plate.

( A ) Lag screw fixation with locking proximal femoral plate used in neutralization mode. ( B ) Newer plates have matching anterior bow.

In general, intramedullary implants with proximal cephalomedullary screws or blades reside closer to the weight-bearing axis and hence are subjected to a lower bending moment in comparison to laterally placed extramedullary implants, such as the angled blade plate and the dynamic condylar screw. Intramedullary implants also allow for minimally invasive implantation, which helps in minimizing devascularization and blood loss. The cephalomedullary nails, therefore, have been used with increasing frequency, although many experienced surgeons may continue to prefer the stability achieved with use of the angled blade plate.