Stability diagnosis of orthopedic implants based on resonance frequency analysis with fiber transmission of nanosecond laser pulse and acceleration sensor

Stability of orthopedic implant such as pedicle screw and acetabular cup is essential to prevent bone union failure. The subsequent complication is cause further surgery because of its aberration and looseness. A quantitative diagnosis approach which can be adaptable in surgery was developed resonance frequency analysis scheme based on laser induced vibration. As a principle of the diagnosis, a laser pulse irradiated onto the orthopedic implants to induce vibration, then the induced vibration was measured by acceleration sensor or laser Doppler vibrometer. The measured signal was analysed by fast Fourier transform method. In the case of the evaluation for acetabular cup which was set by press-fit, one of the peak frequencies of the induced vibration were increased with increasing an index of the stability defined by pull-down force as mechanical evaluation. The diagnosis scheme was considered for adaptation to surgery situation including usage for another implants and flexible handling. Optical multimode fiber and pedicle screw were used for validation. The stability diagnosis system was proposed as quantitative evaluation scheme adaptable in the surgery situation.