Design of wear tester for hip prostheses

Total hip arthroplasty is a surgical procedure used to correct joint function in degenerative disorders of the hip joint. In the hip prostheses, clinical successes and developing technology together with the life of hip prostheses vary between 15 and 20 years. Depending on the increasing average life expectancy, total hip prostheses require longer usage times. According to these demands, hip prostheses which can be used during 30 to 40 years are needed. The life expectancy of hip prosthesis varies depending on the patient's personal characteristics with prosthetic materials and design. The concrete models of the studies, taking into account these factors for the increase in life span and the development of prosthesis, are subjected to pre-clinical testing at the stage of reaching the patient. For pre-clinical testing, hip simulators are used instead of animal subjects. The aim of this study is to design and manufacture the hip simulator according to the standards in order to determine the wear-life relationships of the manufactured and used hip prostheses. In the test device designed to have four degrees of freedom, spring systems were used to provide muscle and ligament effect in the hip joint simulation. After the production of parts designed with machining lathes, the assembly process was performed and three engines were programmed to move in harmony with each other. The first tests were carried out in one million cycles with a view to a wear value of 250,000 cycles. When the values obtained in the ISO 14242 standard were compared, a deviation of 1.18% was observed. The reason for this was the loss of efficiency in the engine performance characteristics. In addition, in the microscope images and mass loss values of the samples tested, the number of cycles increased and the wear rate and surface defects increased.