Remodeling of the femoral shaft after Charnley total hip replacement

Changes in the femoral shaft after Charnley total hip replacement (THR) were studied from the viewpoint of bone remodeling and the pathogenesis was discussed. The study was conducted on 104 hips followed up for 5 to 12 years after THR. The width of bone, medulla and cortex was measured at the tip level of the stem on each radiograph taken within one month after surgery and at the last examination. The changes were classified into 6 types according to the mode of increase or decrease of the whole bone width, medulla and cortex. They were also divided into 4 groups in terms of pathogenesis: (1) physiological change due to the aging process, (2) osteoporosis (59 hips belonging to Group 1 and 2), (3) abnormal distribution of stress (18 hips), and (4) no change (27 hips). Most common was the type in which the cortex is diminished by endosteal resorption and the clear zone is visible because the medullary cavity is enlarged. These changes can be explained by the aging process and osteoporosis.