Total hip replacement is a representative treatment for avascular necrosis of the femoral head. However, the stress shielding caused by the replacement induces dissociation of the artificial hip joint and various complications. Many studies have tried to explore the stress shielding but, most studies have been conducted at macro level and not at micro level. Thus, this study aimed to quantitatively analyze the structural behavior of the proximal femur according to total hip replacement at the micro level to explore the stress shielding. For this purpose, this study selected the artificial hip joint of the single wedge type and implanted the joint into a proximal femur that has a high resolution of 50 μm. Then the structural behavior of the implanted femur was analyzed by comparing that of the intact femur under three daily activity loads. As a result, the high possibility was confirmed that the stress shielding will occur in both cortical and cancellous bones under the one-legged stance movements. Additionally, it was discovered that the cancellous bone had a considerably lesser chance of adducting at an angle similar to the neck shaft angle of an artificial hip joint.

In this paper, we design and fabricate a wearable walking-assist robot using a tendon-driven method. Most wearable walking-assist robots are designed using the method of the attaching of the motors to the hip, knee, and ankle joints. The robot needs the capacities of the motors attached to the hip and knee joints to equal the weights of the motors attached to the knee and ankle joints and the motor attached to the ankle, respectively. To solve these problems, we design and fabricate the wearable walking-assist robot using a tendon-driven method that rotates the joints by attaching the motors of the hip, knee, and ankle joints to the waist joint, and pulling it with a line. The gait patterns of a normal person are photographed and analyzed, thereby providing the ankle position (x, y) during the walking that is then calculated using the forward kinematic equation, while each joint angle is calculated using the inverse kinematic equation. As a result of the characteristic experiment of the wearable walking-assist robot, the resultant walking aspect is similar to that of the normal person.

In this paper, we designed and fabricated a hip joint torque sensor that can measure the torque applied to the hip joint of a walking assistant robot that can be used by a leg patient. To do this, we modeled the structure of the hip joint torque sensor so that it can be connected to the thigh link and the body of the walking assist robot. We calculated the rated torque of the hip joint torque sensor using computer simulation and determined the size of the torque sensor using a finite element program. The hip joint torque sensor was made by constructing a Wheatstone bridge and attaching a strain gauge. The characteristic test of the fabricated torque sensor was performed using a calibration device, and the reproducibility error and the nonlinearity error of the torque sensor were both less than 0.04%. Therefore, it is proposed that the developed hip joint torque sensor can be attached to the thigh link of the wearable walking assist robot, and the torque sensor can accurately measure the torque applied to the hip joint.