[Endoprosthesis and bone reaction]

Prosthetic implants cause a reaction on the part of the surrounding bone. Bone reaction can be interpreted as a dynamic response of the internal bone architecture to stress and strain. On the other hand, instability at the bone-implant interface or biological reactions to wear particles may lead to bone resorption. Standard X-ray examination has remained the most important tool for evaluation of the bone-implant relationship. Knowledge of the radiological features of bone remodelling and bone reaction is therefore a prerequisite for the orthopaedic surgeon. Based on eight case reports after prosthetic replacement of the hip, important radiological signs of bone reaction are presented. If possible a biomechanical or biological explanation is attempted. The information drawn from these cases, as well as from the current literature, suggests that after prosthetic joint replacement routine X-ray follow-up is required, even in asymptomatic patients, and that progressive osteolysis requires early operative revision, even if there are no acute clinical problems.