An infection that becomes established in bone is difficult to treat, since bone is relatively avascular. The result is an osteomyelitis. If this process occurs over years, the bone becomes markedly remodelled. At the site of involvement, there is a cental area of pale necrotic "sequestrum" that is surrounded by irregular remodelled "involucrum" that produces marked distortion. The weakened bone is prone to fracture. In this case, the irregular involucrum is seen above in the upper femur. In the view below, the sequestrum is seen around the metallic prosthesis used to stabilize a femur at the hip.