Guided ultrasonic wave monitoring for osseointegration assessment of an intraosseous transcutaneous amputation prosthesis

This study investigated the feasibility of guided ultrasonic wave monitoring of bone attachment to uncemented orthopaedic implants during the rehabilitation process (osseointegration), which is crucial for implant stability and long-term survival. Experiments were conducted using a simplified three-layer synthetic bone model of an intraosseous transcutaneous amputation prosthesis (ITAP) implant, used for femoral amputee patients, where epoxy curing simulated the bone ingrowth process associated with increasing bone-implant interface layer stiffness, representing the early stages of osseointegration. Longitudinal guided wave signals were excited and recorded at the distal end of the percutaneous part of the stainless-steel implant. Finite element analysis (FEA) was validated from the experiments and employed to investigate the sensitivity and wave mode selection. FEA simulations showed frequency shifts and group velocity changes of the guided wave modes with increased osseointegration, matching theoretical predictions. Evaluation of the reflected wave pulse in the time domain for both experimental monitoring and FEA simulations showed a significant increase in arrival time (10%) and amplitude drop (>50%). The results showed that the longitudinal guided waves are sensitive to stiffness changes during the bone healing process and provide insights for the development of in-vivo osseointegration monitoring during patient rehabilitation.