Biomechanical Assessment of Pilot Hole Undersizing on the Viscoelastic Behavior of Trabecular Bone A Finite Element Study

Screw stability in bone fixation is a critical concern in orthopedic surgery, significantly influenced by factors such as screw design, bone quality, and
quantity, and the surgical techniques employed. One such technique, the undersizing of the pilot hole, plays a pivotal role in enhancing screw stability by increasing the mechanical interlock between the screw and bone. This technique, which involves drilling a pilot hole smaller than the screw’s core diameter, can augment insertional torque, thereby potentially improving the initial fixation strength. However, the increased friction and resistance that result from undersizing also elevate the prestresses within the bone and screw, presenting a delicate balance between achieving stability and risking bone damage, particularly in osteoporotic conditions. Moreover, the viscoelastic behavior of trabecular bone, characterized by its time-dependent mechanical properties, adds another layer of complexity to screw stability. The bone’s ability to deform or relax under
sustained load can influence both immediate and long-term fixation outcomes, with prestresses induced during screw insertion, further affecting stability. Therefore, while undersizing the pilot hole can enhance the mechanical interlock and initial stability, careful consideration must be taken during surgery to avoid potential complications such as microcracks or fractures. Surgeons must adapt their techniques to balance the benefits
of increased stability against the risks associated with heightened prestresses, ensuring optimal surgical outcomes. This study aims to utilize finite element analysis (FEA) to evaluate how pilot hole under-sizing influences the bone-screw system's stiffness while accounting for trabecular bone's viscoelastic properties.