Determination of The Hip Stem Loosening Using Vibration Method

Abstract

Aseptic loosening is a common problem in total hip replacement surgery. Routine radiological imaging techniques are used for postoperative diagnosis. The alternative technique is required to develop because of the low success rate in current diagnostic techniques. The purpose of this study is to develop the new method to diagnose the aseptic loosening of the stem using vibration technique. Two different experimental setups were established in this study, vibrational and cyclic loading tests. In the vibrational test, the bone-prosthetic models were vibrated from the distal femur at a certain frequency and then the vibration data were taken via accelerometer from the trochanter region of the femur. The vibration data were converted to the frequency domain for evaluations. The stability of the femur-prosthesis system was determined by evaluating the fundamental frequency change and harmonics generated at the FFT analysis. In the cyclic loading test, the femur-prosthesis system was forced to fatigue at a maximum amplitude of 1700 N and 1 Hz frequency. After every 5000 cycles in the test, the femoral prosthesis system was connected to the vibrational test and the loosening of the system was considered. After 115000 cycles, the harmonic frequencies were observed and the amplitude value of the fundamental frequency was decreased. The experiments were stopped when the stem was pulled out easily from the femur. As the degree of the loosening increased, the number of the harmonics increased and the fundamental frequency values decreased. In conclusion, the vibration method can be used as an alternative technique to determine the degree of the hip stem loosening.