Hip Fracture

Patients who sustain an undisplaced subcapital hip fracture (a fracture occurring beneath the femoral head at the head neck junction; it is an intracapsular fracture of the hip) have a lower risk of avascular necrosis and nonunion, and the fracture is therefore best managed by in situ fixation of the fracture. This consists primarily of partially threaded screws that can grip the cancellous bone of the femoral head and are placed in a parallel position along the axis of the femoral neck to allow compression of the fracture site. This compression will enhance stability and progression to union. Three or four pins are generally utilized (see Figure 1).

The displaced subcapital hip fracture continues to be somewhat of an enigma and challenge, and there is no specific ideal treatment program. In general, in elderly people, high rates of avascular necrosis and nonunion mean that no attempt is made to salvage the hip. Agreement exists that a prosthetic replacement will be utilized, Figure 2. Displaced subcapital hip fracture treated with unipolar prosthesis (Austin Moore: Howmedica). (X-ray provided by P. Rockwood.) but the specific type of prosthesis has been controversial. The traditional method uses an uncemented unipolar prosthesis. This consists of a single-size femoral stem that is placed into the femoral canal with the diameter of the head size of the ball varying according to patient size (see Figure 2). This is a cost-effective, straightforward management of these fractures. However, questions about this device concern its ability to achieve fixation and its potential for long-term acetabular erosion. Both conditions may lead to pain and require revision surgery. More recent evidence suggests that a cemented unipolar replacement maybe superior in outcome to the uncemented type, although acetabular erosion remains a potential problem.

Bipolar hip replacement consists of a femoral stem, similar to that used in total hip replacement, which allows matching of size to the femoral canal (usually with cement techniques) to fix it to the proximal femur. The bipolar component allows a floating acetabulum or second head to fit on top of the standard total hip head, and this allows, in theory, for motion to occur at the smaller head to the larger head (the standard total hip femoral head articulates with the longer acetabular head), as well as the larger head to the acetabulum. One theoretical advantage of the bipolar design has been that it can be converted relatively easily to a total hip replacement—the bipolar larger head can be removed and a cup placed into the acetabulum without replacing the femoral component. The significant disadvantage, compared to unipolar replacement, has been that it is substantially more expensive.

Total hip arthroplasty has also been utilized in the management of displaced subcapital hip fractures. However, long-term outcomes are poor compared to total hip arthroplasty for osteoarthritis of the hip. There are numerous variables for this, including that patients tend to be more frail, the bone stock is less, and patients tend to have a higher dislocation rate. Overall, it has higher morbidity and mortality rates than the same procedure for osteoarthritis.