Review article: Factors influencing the outcome of internal fixation of intracapsular femoral neck fractures in young adults

Femoral neck fractures in the elderly population are common as a result of a simple fall. In 2007, about 70,000 people over 60 years of age suffered hip fractures, and the number rises 2% a year1. However, these injuries are relatively uncommon in physiologically young adults and accounts for only 3% of the total hip fracture population2, most commonly resulting from high energy trauma. The management of femoral neck fractures in the two populations differ; for an elderly patient, the intention of surgical treatment is to restore mobility and to prevent complications associated with being immobile, and there is less priority given to preserving the femoral head. Surgical treatment is often achieved with the use of hemiarthroplasty or total hip replacement unless the fracture is undisplaced, in which case internal fixation with a cannulated hip screw system may be used in attempt to restore the femoral head.

In young adults, the treatment goals are to restore the femoral head, prevent nonunion and avascular necrosis (AVN) of the femoral head. In order to achieve the above, optimum surgical treatment involves anatomic reduction and stable internal fixation with multiple screws3. The use of arthroplasty is avoided, given the patient's age and higher level of activity.

However, the incidences of nonunion and AVN following surgery for femoral neck fracture remains high. The reported rate of AVN and nonunion after a femoral neck fracture in young patients ranges from 10 to 30%4 and 10 to 20%5,6 respectively. This complication may lead to collapse of the femoral head and subsequent osteoarthritis.

One of the main causes for internal fixation failure is inadequate reduction. The incidences of nonunion and AVN in inadequately reduced fractures are significantly higher than in adequately reduced ones. Banks et al has shown that incidences of nonunion and AVN is as high as 69.5% and 58% respectively in a poorly reduced fractures compared with 18% and 29% seen in adequately reduced fractures7. Non-surgical management of an undisplaced fracture is associated with higher complication rates and there is an increased risk of subsequent displacement6.

Apart from achieving anatomical reduction and stable internal fixation, there are other factors that are thought to influence the outcome following surgery, such as fracture displacement and pattern, timing of surgery, role of capsulotomy, method of reduction (open or closed) and type of fixation. These remain controversial due to lack of evidence available in the published literature.

This article aims to review the current literature addressing the different variables which are thought to influence the outcome of young adults undergoing internal fixation for intracapsular fracture of proximal femur. The following variables will be discussed:

  1. Fracture pattern
  2. Time to surgery
  3. Role of capsulotomy
  4. Methods of fixation

1. Fracture Pattern
An elderly patient with a proximal femoral fracture from a simple fall tends to sustain an intertrochanteric hip fracture or a subcapital neck fracture. It is more common to see a transverse fracture pattern with impaction at the fracture site. However, due to better bone quality and higher energy injury mechanism, intracapsular femoral neck fracture seen in young adults more commonly result in basicervical fracture which is more vertically oriented, making it more biomechanically unstable8.

The two most commonly used radiological classifications of intracapsular femoral neck fracture are Garden and Pauwels classifications. The Garden classification is frequently used to describe femoral neck fractures in the elderly patients9. Number of studies have shown that intra- and inter-observer variations when using this classification is only useful in diving the fracture into those that are undisplaced (grade I and II) and displaced (grade III and IV). The Pauwels classification is based on the angle of the fracture line to the horizontal and has been suggested to be more descriptive of femoral neck fractures in young adults. The more vertical fracture will have greater shearing stress across the surface of the fracture. The Pauwels system divides intracapsular femoral neck fractures into 3 types; type I is when fracture line is less than 30

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