الفهرس | Only 14 pages are availabe for public view |
Abstract Avascular necrosis (AVN) of the femoral head is an increasingly common cause of musculoskeletal disability, and it poses a major diagnostic and therapeutic challenge. Although patients are initially asymptomatic, avascular necrosis of the femoral head usually progresses to joint destruction, requiring total hip replacement (THR), usually before the fifth decade. In fact, 50% of patients with avascular necrosis experience severe joint destruction as a result of deterioration and undergo a major surgical procedure for treatment within 3 years of diagnosis. Femoral head collapse usually occurs within 2 years after development of hip pain. The lack of level 1 evidence in the literature makes it difficult to identify optimal treatment protocols to manage patients with pre-collapse avascular necrosis of the femoral head, and early intervention prior to collapse is critical to successful outcomes in joint preserving procedures. There have been a variety of traumatic and a traumatic factors that have been identified as risk factors for osteonecrosis, but the etiology and pathogenesis still remains unclear. Summary & Conclusions 104 Current osteonecrosis diagnosis is dependent upon plain anteroposterior and frog-leg lateral radiographs of the hip, followed by magnetic resonance imaging (MRI). Generally, the first radiographic changes seen by radiograph will be cystic and sclerotic changes in the femoral head. Although the diagnosis may be made by radiograph, plain radiographs are generally insufficient for early diagnosis, therefore MRI is considered the most accurate benchmark. MRI detects chemical changes in the bone marrow and provides the doctor with a picture of affected area and bone rebuilding process. In addition MRI may show diseased areas that are not yet causing any symptoms. High soft tissue contrast, the ability to image in multiple planes, the ability to manipulate tissue contrast, and high sensitivity to marrow based pathologic condition gives MRI significant advantage over other imaging techniques. The final outcome of the treatment for follow-up was directly related to the size and the topography of the lesion. The importance of the lesion size for outcome prediction was recognized and several methods were proposed for lesion size assessment. Summary & Conclusions 105 Methods based on radiographs provide a rough assessment of the lesion size. Several methods were based on MR imaging but performing only 2D assessment, i.e. they estimate the area of the lesion in the central slice, or the arc of involvement of the weightbearing area. Some methods have been proposed for the evaluation of the actual volume of the lesion. Many studies associated the location of the necrotic lesion to the risk of collapse; lesions that extend to the superolateral area of the head are characterized by high risk of collapse. Hips that fail usually have wide lesions extending beyond the lip of the acetabulum. Femoral heads with lesions mainly located on the medial area of the head retain a lateral supportive pillar of intact bone that may act as a stress shield for the affected segment and protects it from excessive loads. The absence of this pillar in hips with wide lesions (extending in the supero-lateral segment of the head) makes those hips susceptible to early collapse. The loss of the spherical contour of the articular surface is a key point at all classification systems, once has occurred the role of prophylactic surgery is limited. MRI should be done for its high specificity and sensitivity for early disease, according to the findings the disease is classified under the above mentioned criteria, the patient is going to benefit from a prophylactic surgery if the size of the lesion is less than 30% of the femoral head this is Summary & Conclusions 106 best measured using 3D MRI reconstruction from T1W coronal images using special software and 3D finite element analysis these two methods are reproducible and time saving also the location of the lesion should be located medially and the necrotic lesion should show signal characteristic that fall under Mitchel classification A or B and surrounded with little or no edema, although these last two criteria are supportive for the decision making and not crucial as the size and location of the lesion |