In cementless Total Hip Arthroplasty (THA), achieving high primary implant fixation is crucial for the long-term survivorship of the femoral stem. While orthopedic surgeons traditionally assess fixation based on their subjective judgement, novel vibration-analysis fixation-monitoring techniques show promising potential in providing the surgeon with objective and quantifiable fixation measurements. This study presents a dynamic response measurement protocol for implant endpoint insertion and evaluates this protocol in the presence of artificial soft tissue. After the artificial femur was prepared in accordance with the THA protocol, the implant was inserted and progressively hammered into the cavity. The Pearson Correlation Coefficient (PCC) and Frequency Response Assurance Criterion (FRAC) corresponding to each insertion hammer hit were derived from the Frequency Response Functions (FRF) corresponding to each insertion step. The protocol was repeated with the artificial femur submerged in artificial soft tissue to imitate the influence of anatomical soft tissue. The FRAC appeared overall more sensitive than the PCC. In the presence of the artificial soft tissue the technique yielded higher PCC and FRAC values earlier in the insertion process. The measurements with artificial soft tissue produced FRFs with fewer peaks, lower resonance frequencies, and overall higher damping factors. The soft tissue appears to limit the fixation-change detection capabilities of the system and a promising potential remedy to this limitation is suggested.

The clinical implementation of currently used devices for intraoperative fixation monitoring of femoral implants via vibration-based methods in cementless total hip arthroplasty is challenging, due to practical and regulatory issues. Motivated by the effectiveness of electromagnetic excitation in similar dental applications, this study investigates the use of electromagnetic excitation for femoral implant stability monitoring during cementless total hip arthroplasty. The results obtained from electromagnetic excitation were largely consistent with reference results obtained through impact excitation, with a Pearson Correlation Coefficient of 0.79 in the 0.1-8 kHz frequency band. Moreover, the peak frequencies obtained via the two methods yielded a relative difference of 0.20 ± 0.22 %. Next, the excitation device was successfully utilized in conjunction with a laser vibrometer to monitor the stability of the femoral implant during an in vitro insertion, proving the feasibility of contactless implant stability monitoring. These results indicate the promising potential of this contactless method for clinical implementation.