Femur, proximal—introduction

Introduction

Fractures of the proximal femur occur predominantly in the elderly population with osteoporosis. Most of these fractures are caused by low-energy injuries. In younger individuals, these fractures are less common and are usually the result of high-energy injuries.

The treatment of proximal femoral fractures is usually surgical and various fixation devices have been commonly used, including the dynamic hip screw (DHS), the dynamic condylar screw (DCS), angled blade plates or condylar plates, and different types of proximal intramedullary nails. There are new types of locking plates available, such as the DHS blade and DHS side plate with combination hole, and the proximal femur locking compression plate (PF-LCP).

The choice of procedure depends on several factors, including:

Condition of the soft tissue
Fracture configuration
Medullary canal size
Associated injuries
Patient‘s condition
Timing of the intervention
Experience of the surgical team
Facilities available

Incidence

31-A extraarticular fractures of the trochanteric area are common in the elderly and may extend distally into the femoral shaft, or they can occur in combination with an additional segmental fracture distally.

31-B extraarticular intracapsular femoral neck fractures may be associated with ipsilateral femoral shaft fractures. This is a common fracture in the elderly but the population is generally slightly younger than those sustaining intertrochanteric fractures.

31-C fractures are intracapsular, involving the articular surface of the femoral head. These uncommon injuries are rarely associated with fracture extension into the femoral shaft but may be associated with hip dislocation.

Current methods of treatment

Proximal femoral fractures with distal extensions or segmental fractures, if surgical stabilization is indicated, should be managed whenever possible with a single implant system, such as the angled blade plate (condylar), the DHS or DCS with a long side plate, a proximal femur locking plate (PF-LCP), or an intramedullary nail with locking options to the femoral neck (eg, unreamed femoral nail, proximal femoral nail, trochanteric femoral nail). In case of femoral neck fractures with ipsilateral shaft that cannot be fixed with a single implant, two different implant systems may have to be considered, such as three cancellous bone screws or a DHS with a two-hole side plate to fix a femoral neck fracture, and a long, broad plate (dynamic compression plate (DCP), limited contact dynamic compression plate (LC-DCP), or locking compression plate (LCP)) or a distal femoral nail to fix the distal segmental fracture in the shaft.

Indications and contraindications for MIPO

The role of MIPO in the management of proximal femoral fractures is rather limited but suitable indications include complex fractures, such as:

Ipsilateral neck and shaft fractures
Trochanteric fractures with extensions distally into the shaft involving the nail entry point
Subtrochanteric fractures

Complex fractures in the subtrochanteric region of the femur have a significant risk of nonunion and implant failure following conventional open plating techniques. By limiting the extent of medial and lateral dissection, MIPO reduces the incidence of nonunion and hence the need for primary or secondary bone grafting and accompanying morbidity.

To facilitate indirect reduction, the fractures should be relatively recent. Otherwise, soft-tissue contractures will make it difficult to obtain a satisfactory reduction.

Surgical anatomy

The important neurovascular structures lie along the medial aspect of the proximal femur and are usually not at risk because in general, fractures of the proximal femur are approached from the lateral aspect during surgical fixation.

The proximal femur varies in size and shape, in ways that can be summarized as follows: the head is 40–60 mm in diameter making up 2/3 of a sphere; the femoral neck is about 5 cm in length; the neck shaft angle is 130° ± 7° with an anteversion of 10–17°.

In displaced trochanteric and subtrochanteric fractures, the proximal fragment tends to be abducted, flexed, and externally rotated due to the attachments of the gluteus medius, minimus, iliopsoas, and the short external rotators, respectively ( Fig 16.1-1 ). Malreduction will result unless the action of these muscles is neutralized or counteracted.

The greater trochanter has a posterior flare which is not a part of the femoral neck and this must be considered when planning the entry point for the fixed angle device. In the case of 95°-angled implants, the entry point in the greater trochanter is in the anterior third of its lateral bulge 2 cm proximal to the vastus ridge. A more posterior entry point will result in perforation of the posterior cortex of the femoral neck. When using 135°-angled implants, the entry point should be directly in the middle of the lateral cortex, 2.5 cm distal to the vastus ridge at the level of the lesser trochanter which is situated posteromedially. This reduces the risk of perforation of the anterior cortex of the femoral neck ( Fig 16.1-2 ).

In intertrochanteric or subtrochanteric fractures with intact lesser trochanter the proximal femur will deform in flexion, abduction, and external rotation.

Deforming forces caused by pulling of the muscles.

a 95°-angled implants must be inserted in the anterior third of the lateral aspect of the greater trochanter; 135°-angled implants must be inserted in the middle or posterior third of the lateral cortex in the lateral view. b Proximal femur with an insertion point of the guide wire for a 95° implant 2 cm above the vastus ridge, and the entry point for a 135° implant 2.5 cm distal to the vastus ridge.

Aims of fracture reduction

In femoral neck fractures the aim of fracture reduction is to achieve a stable configuration before fixation to reduce the complications of nonunion and avascular necrosis, as well as the risk of implant failure.

Garden‘s alignment index for displaced femoral neck fractures refers to the angle of the compression trabeculae on the AP x-ray view relative to the longitudinal axis of the femoral shaft, and the angle of the compression trabeculae on the lateral view relative to the femoral shaft. On the AP view, this angle should be 160°, while on the lateral view, it should be 180°. Acceptable reduction lies within the range of 155–180° on both views ( Fig 16.1-3 ). Acceptable reduction minimizes nonunion and avascular necrosis. When Garden‘s alignment index is less than 155° in AP or more than 180° in lateral, the incidence of avascular necrosis increases from 7.3% to 53.8%. Valgus reduction of more than 20° also results in an increased rate of avascular necrosis. Failure to achieve a satisfactory alignment index by closed methods may be an indication for open reduction of the femoral neck fracture.

In cases of femoral neck fractures where there is posterior comminution, anatomical reduction may result in loss of the posterior buttressing effect, with subsequent loss of reduction and nonunion ( Fig 16.1-4a ). In such cases, valgus-impacted reduction and fixation with three parallel cancellous bone screws will increase the stability of the reduction ( Fig 16.1-4b, Fig 16.1-5 ).

In the case of trochanteric fractures, 60% are unstable due to loss of the medial buttress. In these unstable fractures, the aim of reduction is to have sufficient bone contact so that up to 75% of the load can be taken up by the bone, and only 25% will be taken up by the implant. Depending on the number of displaced fragments, closed reduction of the proximal femur to its anatomical shape is usually possible.