Biomechanical studies on hip prosthesis stem

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The condition inside the bone inserted with a hip prosthesis stem was grasped by utilizing an echo characteristic from a boudary surface via ultrasonic waves, and the mensurement method for detecting a slight loosenig after the total hip replacement was investigated. Also, contact stress distribution between socket and condyle was clarified dynamically by the finite element method. The following results are shown below.(1) The ultrasonic wave was emitted toward the femur with a hip prosthesis stem, which was immersed in a water tank, and the distances from a normal probe to the boudary surfaces of the femur and the hip prosthesis stem were measured. consequently, the thicknesses of the femur and bone marrow regions are obtained precisely.(2) The ultrasonic wave was emitted toward the femur covered with flesh by inserting a hip prosthesis stem via a normal probe attached to the flesh. From the echo waveform from the boundary surfaces, the thicknesses of the femur, bone marrow and flesh regions are obtained precisely.(3) In the experiment of (1) and (2), the moving distance of the hip prosthesis stem inside the femur can be measured with 0.1mm accuracy.(4) The section of the upper side of the normal human femur can be measured approximately using the simple measurement device via the ultrasonic wave.(5) The thickness of femur agrees approximately with that of the X-ray CT.(6) The ultrasonic method can measure the thicknesses of the bone and the bone marrow within the femur on the patient inserted with the hip prosthesis stem.(7) The strain conditions occurring to strain gauges bonded to a pig femur are clarified.(8) The contact stress distribution between socket and condyle is clarified dynamically by the finite eliment method.