الفهرس 
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Abstract
Femoral neck fractures are intracapsular fractures that occur in the proximal femur in the area beginning distal to articular surface of the femoral head and ending just proximal to the intertrochantric region. These fractures are uncommon in young patients with normal bone & in older patient of races in which osteoprosis is uncommon. These fractures are classified according to: 1) patient characters such as age, associated diseases & time of diagnosis2) Fracture characters such as anatomic location of fracture, direction of fracture angle & displacement of fragments. Management of patients with femoral neck fractures depends on several factors such as age & cooperation of the patient & the fracture itself (displaced or non-displaced). In young patients with femoral neck fractures, rapid reduction and stable internal fixation is the best management because a healed fracture with a living head is always better than a replacement and can be achieved with a procedure that is less invasive than arthroplasty. In the elderly patients, the expected life span and prefracture activity level must be considered before choice of the line of management. Unipolar hemiarthroplasty is appropriate for inactive patients with decreased demands but bipolar prosthesis is most appropriately used in patients who are community ambulators and whose likelihood of success with internal fixation is low provided that they have a normal acetabulum.
Total hip replacement is recommended in femoral neck fractures if there is preexisting arthrosis, rheumatoid arthritis, Paget’s disease or neoplasms that involve both sides of the joint.
In management of femoral neck fractures, long-term studies of unipolar hemiarthroplasty demonstrated it’s associated with acetabular erosion and protrusion and high revision rate especially in active patients and community ambulators.
In spite of that, unipolar prostheses still have a place in the management of displaced femoral neck fractures particularly in very old age or in frail demented patients or in patients who are not expected to be ambulant because they are less costly if compared with bipolar prosthesis.
Some studies reported that bipolar endoprosthesis provides no advantages in the treatment of displaced femoral neck fractures in elderly patients regarding quality of life and functional outcome.
Several long-term studies of bipolar prosthesis in management of femoral neck fractures demonstrated decreased rate of acetabular erosion and protrusion and improved functional outcomes.
The principle behind the reduction of the incidence of acetabular erosion associated with bipolar prosthesis lies in the fact that the interprosthetic movement reduces the shear forces on the outer metal-bone articulation by continually altering the position of load bearing to different parts of the acetabulum.
from the previous studies we conclude that the bipolar prosthesis is the most suitable for patients having displaced femoral neck fractures who are active community ambulators and whose likelihood of success with internal fixation is low because this device reduces the acetabular erosion and improves functional outcomes.
Still the relative amount of motion between the inner head and the polyethylene bearing and between the outer surface and the acetabular cartilage has been a topic of some debate, in arthritic group; motion occurred principally through the inner bearing while in the fracture group; it occurred principally between the outer shell and the normal articular cartilage.
Some authors reported that inner bearing motion decreased with time then becomes absent and the bipolar prosthesis behaves as unipolar one. Others reported that, motion is maintained at both bearing surfaces although there is greater motion at the outer bearing cartilage interface ( in normal acetabulum ).
It was found that the greater motion at the inner bearing correlated with better clinical results. Therefore the amount of motion at the two interfaces appears dependent on a number of variables and still a topic of debate.