Femoral neck fractures are intracapsular fracutres 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 diagnosis, (2) 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 nondisplaced). 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. Total hip replacement is recommened 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 its association with acetabular erosion and protrusion and high revision rate especially in active patients and community ambulators. 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 priniciple behind the reduction of the incidence of a cetabular erosion associated with the bipolar prosthesis lies in the fact that the interprosthetic movement reduces the shear forces on the outer metal-bone articulation by continually altering the postion of load bearing to different parts of the acetabulum.