Adam G. Cota
Gregory D. Dikos

Most intertrochanteric fractures occur in patients older than 65 years of age as the result of low-energy falls. The vast majority of these fractures are treated surgically to decrease complications associated with prolonged immobility such as respiratory infection, venous thromboembolism, decubiti, and generalized deconditioning. Appropriate implant selection, adequate fracture reduction, and proper implant placement are critical to reduce postoperative complications. These surgeon-controlled factors can be optimized with quality preoperative and intraoperative imaging, along with a thorough understanding of the radiographic anatomy of the proximal femur.

Applied Anatomy

The hip joint capsule inserts at the intertrochanteric line anteriorly and the base of the femoral neck posteriorly. The intertrochanteric region of the proximal femur is extracapsular and has a robust blood supply. Therefore, intertrochanteric fractures have much better healing potential than do intracapsular femoral neck fractures.
The proximal femur is the insertion site for a number of opposing muscle groups. Forces exerted by these muscles result in shortening, varus angulation, and external rotation typical of intertrochanteric fracture. These forces must be understood to obtain acceptable fracture reduction.
The gluteus medius inserts on the tip of the greater trochanter and abducts the head and neck fracture fragment. The adductor muscle group inserts on the medial proximal femoral shaft. These two opposing muscle forces result in the typical varus alignment of the fracture.
The gluteus medius internally rotates the head and neck fracture fragment. In contrast, the forces generated by the gluteus maximus and gluteus minimus externally rotate the proximal femoral shaft. Depending on the fracture anatomy, the short external rotators remain attached to and act on either the head and neck fragment or the femoral shaft fragment.
The rectus femoris and hamstrings cross the intertrochanteric zone of injury and result in axial shortening of the fracture.
The iliopsoas flexes, adducts, and externally rotates the fracture fragment in continuity with the lesser trochanter. With comminution of the posteromedial cortex, forces on the head and neck fragment generated by the abductors will be unopposed by the iliopsoas.

Radiographic Anatomy

AP Hip Radiograph

The femoral neck is anteverted 10 to 15 degrees relative to the femoral condyles.
A true AP image of the hip is taken with the lower extremity internally rotated 10 to 15 degrees to account for femoral anteversion.
The neck-shaft angle is the angle between the long axis of the femur and the axis of the femoral neck. A normal neck-shaft angle is 120 to 135 degrees. A neck-shaft angle >135 degrees indicates valgus alignment, while a neck-shaft angle <120 degrees indicates varus alignment (Fig. 18-1).

Gardner1e-ch018-image001 — Figure 18-1 The normal neck-shaft angle is 120 to 135 degrees. The typical deformity of an intertrochanteric fracture is varus or a neck-shaft angle <120 degrees.

Lateral Hip Radiograph

A lateral image is obtained with the affected hip internally rotated 15 degrees. The x-ray beam is oriented parallel to the table and angled 45 degrees cephalad relative to the long axis of the patient’s body to orient the x-ray beam perpendicular to the axis of the femoral neck (Fig. 18-2).
When viewed on the lateral image, the femoral neck lies anterior to the axis of the femur.
The greater trochanter is a posterior structure. When viewed on a lateral image, the greater trochanter overhangs the femoral shaft posteriorly.

Gardner1e-ch018-image002 — Figure 18-2 The femoral neck is anterior to the axis of the femur, and the greater trochanter overhangs the femur posteriorly.

Preoperative Imaging

AP Pelvis Radiograph

The AP radiograph is used to assess the fracture pattern, comminution, coronal plane alignment, and bone quality.
Stable intertrochanteric fractures are those with intact lateral and posteromedial cortices. Once reduced, stable fracture patterns are able to share compressive forces with internal fixation devices (Fig. 18-3).
Unstable intertrochanteric fractures involve the lateral cortex or have posteromedial comminution and are unable to share physiologic loads with internal fixation devices. The unstable patterns are reverse obliquity fractures, transtrochanteric fractures, fractures with posteromedial comminution, fractures with lateral wall involvement, and fractures with subtrochanteric extension.¹ Identification of these fracture patterns is imperative for appropriate implant selection (Fig. 18-4A–D).
On the AP pelvis radiograph, the patient’s normal neck-shaft angle should be measured from the contralateral, uninjured hip. This normal neck-shaft angle is used intraoperatively to assess the reduction of the fracture.
Coronal plane alignment can also be assessed using the tip of the greater trochanter as a radiographic landmark (Fig. 18-5). The tip of the greater trochanter should be coplanar with center of the femoral head. Varus alignment will cause the tip of the trochanter to be cephalad to the center of the femoral head. Valgus alignment will result in the tip of the trochanter being caudal to the center of the head.¹

Gardner1e-ch018-image003 — Figure 18-3 Stable intertrochanteric fracture pattern.

Gardner1e-ch018-image004a — Figure 18-4 Examples of unstable intertrochanteric fracture patterns. A: Reverse obliquity fracture. B: Transtrochanteric fracture. C: Subtrochanteric extension. D: Posteromedial comminution.

Gardner1e-ch018-image004b — Figure 18-4 Examples of unstable intertrochanteric fracture patterns. A: Reverse obliquity fracture. B: Transtrochanteric fracture. C: Subtrochanteric extension. D: Posteromedial comminution.

Gardner1e-ch018-image005 — Figure 18-5 The tip of the greater trochanter should be coplanar with the center of the femoral head.

Cross-Table Lateral Radiographs

The cross-table lateral radiograph is used to visualize posterior comminution, anterior cortical overlap, and sagittal plane alignment (Fig. 18-6).

Gardner1e-ch018-image006 — Figure 18-6 The lateral radiograph of the hip reveals sagittal plane displacement and alignment.

Femur Radiographs

When planning for a long cephalomedullary implant, full-length femur radiographs are indicated to evaluate for shaft deformities and previous implants that may preclude the use of the intended fracture implant.
Anterior femoral bow and canal diameter should be assessed to ensure appropriate implant selection.

Traction Radiographs

A traction AP radiograph of the injured hip is performed with gentle traction and internal rotation of the affected lower extremity.
When there is significant shortening through the fracture, traction radiographs are helpful in defining the fracture pattern.

CT Imaging

Although not routinely indicated, CT imaging can be used to evaluate complex, multifragmentary patterns to assist with implant selection and reduction strategy.