Osseointegration evaluation can be quantified by mechanical non-destructive acoustic modal analysis in an in-vivo study

Successful osseointegration of orthopedic implants relies on achieving mechanical stability of screw fixation. Various techniques have been utilizing to assess screw stability; however, some of these methods are destructive or time-consuming. Non-destructive techniques, such as modal analysis, have gained interest in evaluating screw stability. This study aimed to assess the primary and secondary stability of screws in an in-vivo animal experiment by comparing conventional methods with two modal methods, namely Periotest® and acoustic modal analysis (AMA). To achieve this goal, eight rabbits were implanted with cylindrical threaded screws. The screw fixation stability was evaluated using four different test methods. Initially, the peak insertion torque (PIT) was measured for each bone screw during the implantation process. Additionally, AMA and Periotest® were employed to assess the natural frequency (NF) and Periotest® value (PTV) of the bone-screw structure, respectively. Finally, a destructive pull-out test was conducted to determine the peak pull-out force (PPF). The average primary stability values were measured 5.15 N.cm for PIT, 2507±59 Hz for NF, 21.85±4.1 for PTV, and 94.45±12 for PPF. In contrast, the secondary stability showed varying results with an average increase of 39% for NF, 101% for PTV, and 194% for PPF. The research also compared the non-destructive AMA with the destructive pullout test, considered the gold standard for stability evaluation of bone screws. The study found that AMA exhibited a linear relationship with the pullout test, making it an accurate method for assessing orthopedic and spinal screw applications.