Impact-Based Analysis Method (IBAM) to evaluate the primary stability of the pedicle screw: A proof of concept

The long-term success of spinal instrumentation depends on the initial stability of pedicle screws (PS), yet current intraoperative assessments rely on surgeon subjectivity. This study introduces a quantitative, non-invasive approach—the Impact-Based Analysis Method (IBAM)—to support intraoperative decision-making. The IBAM measures screw stability using low-amplitude impacts delivered with an instrumented hammer on the surgical screwdriver after screw insertion. An IBAM indicator, defined as the average time difference between the two earliest local maxima in the force signal, was analyzed under varying stability conditions in artificial bone samples. Experimental factors included bone density (ρ), insertion depth (D), and pilot hole diameter (ϕ). The IBAM indicator was compared with the PS pull-out force for each configuration. Although the main effects showed opposite trends for the pull-out force and the IBAM indicator, their relative magnitudes were similar (ρ∼35%, D∼25%, ϕ∼15%). The relationship between the pull-out force and the IBAM indicator followed a power-law model (adjusted R² = 0.85) with a negative exponent. As screw stability increased, the pull-out force rose while the IBAM indicator decreased, demonstrating complementary sensitivity to bone-implant interface changes. While results are promising, the simplified experimental design limited the ability to fully capture bone-implant interaction complexity. Future studies should aim to validate IBAM in vivo to confirm its clinical applicability.