Optimizing bone screw insertion: The impact of pre-drilling diameter, bone quality, and spindle speed on mechanical stability and thermal dynamics in synthetic models

In orthopedic surgery, proper bone screw fixation is paramount to ensure patient recovery. However, complications like screw loosening, bone fracture, or poor fixation can arise from inappropriate insertion protocols. This study aims to determine the optimal pre-drilling diameter for secure screw fixation while minimizing thermal damage and mechanical failure in orthopedic procedures. Through comprehensive experimentation on synthetic bone coupons simulating normal and osteoporotic bones, we investigated the influence of pre-drilling diameter, bone density, and insertion velocity on bone screw fixation. A study measured temperature at the insertion site, insertion torque, and pull-out strength. Our study found that the pre-drilling diameter is pivotally important to the thermal dynamics and mechanical stability of screw insertion. Smaller diameters in synthetic bone coupons generate higher temperatures due to increased friction and diminished heat dissipation, exacerbated by higher spindle speeds. Bone screw insertion torque displays a predictable three-phase behavior, reaching peak levels at cortical engagement and reducing in cancellous bone. Additionally, smaller hole diameters necessitate increased torque during insertion. Pull-out tests demonstrated that screws placed in smaller pre-drilled holes bear more robust fixation. However, smaller diameters also resulted in potential synthetic bone surface damage during extraction. This study emphasizes the critical nature of optimizing pre-drilling diameter to achieve a successful balance between secure screw fixation and low insertion torque. Accommodating the variable bone qualities and operational conditions are essential to minimize the risk of thermal damage and mechanical failure. Future clinical guidelines derived from these findings could lead to enhanced patient outcomes after orthopedic procedures requiring bone screws.