(Adapted and redrawn from Russell TA, Taylor JC. Subtrochanteric fractures of the femur. In: Browner BD, Jupiter JB, Levine AM editors. Skeletal trauma. 2nd ed. Philadelphia: Saunders; 1992. p. 1836; drawing by Hella Thun.)

In the early days of the Arbeitsgemeinschaft für Osteosynthesefragen (AO), these fractures were all treated using widely open reduction with substantial detachment of soft tissue and plate osteosynthesis. The 95-degree condylar plate was the most successful device for this approach. However, the biologic consequences of soft tissue damage induced substantial numbers of postoperative infections, nonunions, and consecutive implant failures. Steady improvements in intramedullary implant design and the surgical implementation of the relative stability paradigm brought about an important change in treatment strategies in patients with subtrochanteric fractures. The major advantage of the use of intramedullary devices is that the patients can be mobilized much faster because they are able to resume almost full weight bearing after the surgical procedure. Despite these advances in intramedullary device use, two current demographic trends are increasing the demand for the use of plates in osteosynthesis of subtrochanteric fractures:

1. The percentage of obese patients is increasing steadily. Because the implantation of medullary devices is substantially jeopardized by impaired closed reduction or limited length of alignment jigs, the use of plates may be indicated in obese patients. Although it is clear that the biomechanical disadvantages of plates may be even more evident in obesity, plate fixation may be the only remaining option if a patient’s body mass renders nail insertion impossible.

2. In patients with heavily comminuted trochanter fractures and in the growing population of old and very old patients with subtrochanteric fractures, nail insertion may not be possible. The reason is that drilling devices or the implant itself will detach the comminuted fragments to a degree that will not permit even a reduced weight-bearing construction.¹

This chapter emphasizes the treatment of subtrochanteric fractures with plate systems, both fixed and sliding.

Classifications and Stability

Lundy ² described subtrochanteric fractures as injuries of the proximal femur from the fossa piriformis to the isthmus. In older publications, the fracture was considered to occur more distally, between the lesser trochanter and 5 cm distal to it.^3,⁴ The AO concentrated on an even smaller area, between the lesser trochanter and 3 cm distal to it.⁵

Biomechanically, the lateral cortical bone is subjected to high tensile forces, and the medial cortex is subjected to extremely high compressive forces.⁶ Hence, when developing potential therapeutic strategies, investigators must take into account that internal fixation techniques require substantial mechanical strength to support the significant forces exerted on the femur.

Certain elements contribute substantially to the stability of the subtrochanteric zone. These factors can easily be assessed by asking the following questions:

1. What is the status of the posteromedial cortical bone zone? A fracture with a substantial comminution zone or no bony contact is considered unstable.

2. What is the direction of the major fracture line? Generally, the fracture line is oriented in the anteroposterior radiograph from the greater trochanter laterally down to the medial lesser trochanter. These types of fractures are considered more stable. In contrast, when the major fracture line is oriented from a lateral lower starting point up to a medial crossing through the cortical bone (a “reversed” fracture), the fracture is considered unstable.

3. How many major fragments are present? The more fragments the fracture has, the more unstable it is. Hence, comminution is a major unfavorable prognostic factor in subtrochanteric fractures.

4. What is the status of the lateral cortical bone? If it has many fragments, the lateral bone will not be able to withstand tension forces, and the placement of plates will be contraindicated.

Several classifications for subtrochanteric fractures have been proposed.^3,⁷ Most classifications distinguish between stable and unstable fracture types. Hence, the number of bone fragments and direction of fracture lines is the classifier for grouping injuries.

AO Classification

Within the AO classification system, Mueller ⁸ proposed the designation 31 for the proximal femur and A3 for the extra-articular trochanteric region. According to this nomenclature, 31A3.1 represents the reversed fracture, which is considered unstable. The designation 31A3.2 represents a subtrochanteric fracture with a transverse fracture line visible on the anteroposterior radiograph, and 31A3.3 is a multiply fragmented comminuted subtrochanteric fracture with a separate fragment of the lesser trochanter (Fig. 14-2).

Figure 14-2 AO fracture classification system.

Russell-Taylor Classification

In the international literature, the Russell-Taylor classification is more widely used than the AO classification.⁹ This classification system is principally based on two issues: stability and fracture extension. Fractures without extension of the anteroposterior fracture line into the piriformis fossa are designated type I; the others are considered type II. In both types, fractures without comminution of the lesser trochanter are designated A, and those with comminution zone are B (Fig. 14-3).