9. Biomechanics of Pathology

Martha Mainstream’s twin sister Matilda also had pain in her groin and in the thigh, but this had been a problem for only a couple of months. The discomfort was so persistent at night that she had great difficulty turning over in bed. Matilda had no cats to feed; she simply fell in her kitchen &or more accurately, her leg collapsed, causing her to fall. When she arrived at the hospital, the orthopaedic resident took a careful medical history before examining her and learned that she had had a mastectomy five years earlier but otherwise had had no serious medical problems. Unfortunately, the roentgenogram of the femur showed a large lucent lesion with a pathologic fracture that was most likely a metastatic focus related to her mastectomy. Many complex biochemical and biological activities are associated with such a fracture, but some are straightforward biomechanical ones, and the question arises, “How does replacement of bone by tumor weaken the bone?”