The fracture pattern has a tendency to be more vertically oriented and biomechanically more unstable. This occurs from an axially loaded, high-energy force onto an abducted hip. In young adults with better bone quality, higher-energy mechanisms of injury usually cause a basicervical or more distal neck fracture. A transverse fracture pattern with impaction at the fracture site is common. Elderly patients with poor bone quality or a low-energy injury usually sustain an intertrochanteric hip fracture or a subcapital femoral neck fracture. The fracture pattern seen in young adults is different than that of elderly patients. Radiographic evaluation should include anteroposterior (AP) and lateral plain radiographs of the entire femur, as well as an AP radiograph of the pelvis. 9– 12 Variables that have been hypothesized as contributing to femoral head osteonecrosis include vascular damage from the initial femoral neck fracture, 4, 12-15 the quality of reduction or fixation of the fracture (restoring flow to the distorted arteries), 4, 16-20 elevated intracapsular pressure (tamponade from blood), 12, 21-26 and the position of the implants. Terminal branches supplying the femoral head are intracapsular thus disruption or distortion of these terminal branches likely plays a significant role in the development of osteonecrosis. 8 The lateral epiphyseal artery complex originates from the MFCA and courses along the posterosuperior aspect of the femoral neck before supplying the femoral head. 5– 8 The largest contributor to the femoral head, especially the superolateral aspect of the femoral head, is the MFCA. Femoral head blood supply comes from three main sources: the medial femoral circumflex artery (MFCA), the lateral femoral circumflex artery (LFCA), and the obturator artery.
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