Cementless implants achieve long-term fixation and consequent clinical stability primarily via biologic means - bony ingrowth into a porous-coated intramedullary implant surface. The adequacy of this biologic fixation depends upon numerous factors, including the initial or short term fixation of the implant with respect to the bone. Initial fixation refers to the post-operative limitation of relative motion between the implant surface and the adjacent bone. A press-fit, or interference fit, must be achieved in order to create initial fixation which is essential to the success of the procedure. Theoretically, biological and press-fit fixation is enhanced with increases to stem-bone contact area. Although reaming increases contact area by creating a more regular (circular) surface area, the actual size and shape of the intramedually canal is not accurately known by orthopedic surgeons who use radiographs for preoperative planning. A device that will provide real-time size and shape information of the femoral intramedullary canal during a prosthesis press-fit operation has been designed. The device measures canal size and shape and will provide the operator with the percentage of stem-bone contact area and cortical thickness vs. reamer size. Material selection and mechanistic operation of the device will be presented.