Femur

the long tubular bone of the upper part of the leg, which articulates with the hip at the acetabulum. The lower end of the femur, the tibia and patella form the knee joint. Also, see femur.

2. Pathology

Some portions of the femur, such as the femoral head and femoral neck, may be involved in specific ways in some musculoskeletal disorders; these structures are discussed in more detail under the respective entryword. Partial absence and shortening of the proximal end of the femur leads to a spectrum of conditions known as proximal femoral focal deficiency.

The distal end of the femur has rounded projections termed condyles. The femoral condyles may undergo spontaneous osteonecrosis, characterized by collapse of the weight-bearing surface. The most typical location of osteochondritis dissecans is the condylar surfaces of the femur, particularly the medial condyle and nonweightbearing surfaces. Routine radiography can reveal osteochondral lesions, but purely chondral lesions require other imaging methods, such as arthrography, CT arthrography, MR imaging or arthoscopy.

In Gauchers disease, bone modelling deformities leading to expansion of the contour of the long tubular bones are most frequent in the lower ends of both femoral shafts. When the bone has a straightened or convex margin, the appearance is termed an Erlenmeyer flask deformity; this is often associated with epiphyseal osteonecrosis.

Fractures of the femur are common. Stress fractures often involve the shaft of neck of the femur and may occur in numerous activities, such as long-distance running, ballet dancing and marching. Fractures of the proximal end are particularly frequent in elderly persons with osteoporosis, especially women. Pathologic fractures are seen in persons with skeletal metastases, Paget's disease and other disorders. Acetabular fractures also occur and may be displaced or nondisplaced. Varus angulation typifies fractures of the middle segment of the femoral shaft. Dislocations of the femoral head may occur with or without fracture.

Legg Calv Perthes disease represents an osteochondrosis involving the head of the femur. Vascular insufficiency to the femoral head is suspected to be the cause, although trauma with compression of the femoral head by the adjacent acetabular roof has also been suggested as a causative mechanism. Likewise, the role of synovitis and raised intra-articular pressure in the pathogenesis of Legg Calv Perthes disease has been emphasized. The Catterall classification system categorizes the grades of involvement of the femur in Legg Calv Perthes disease. The categories in this system, which help predict prognosis, are based on site of epiphyseal involvement and on the presence or absence of a sequestrum, the cresent sign, bone collapse and metaphyseal abnormalities.

DR