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Screws That Hold: Stability Analysis of Distal Tibial Fractures Using FEA and a Novel Fixation Index

Authors :

Amirhossein Karami¹ Mohadese Rajaeirad² Mohamed Elfekky³ Nima Jamshidi⁴

1- گروه مهندسی پزشکی، دانشکده مهندسی، دانشگاه اصفهان 2- گروه مهندسی پزشکی، دانشکده مهندسی، دانشگاه اصفهان 3- Tarabichi joint care 4- دانشگاه اصفهان

Keywords :

distal tibia fracture،Finite element analysis،biomechanics،screw fixation،fixation stability index

Abstract :

The biomechanical stability of fracture fixation plays a critical role in postoperative recovery and long-term functional outcomes. This finite element (FE) study compared three screw-based fixation methods for distal tibial fractures, following the AO Surgery Reference guidelines. Patient-specific tibial anatomy was reconstructed from routine clinical CT scans using Mimics software, and fracture models were created to represent a standard extra-articular distal tibial fracture. Each fixation configuration was assessed under physiologically relevant loading conditions. Von Mises stress distributions were calculated for both the intact tibial segment and the fracture fragment, as well as for the fixation screws. In addition, strain and displacement values were determined for each configuration. To provide a single comparative measure, a novel Fixation Stability Index (FSI) was introduced, defined as the product of mean bone stress and strain divided by the maximum fragment displacement. Results showed that medial malleolar split intra-articular fracture yielded the highest FSI (3.77), indicating superior stability, while transverse simple extraarticular fracture had the lowest (1.0). Peak screw stresses were lowest in lateral tibial split intra-articular fracture (61.8 MPa), suggesting reduced implant fatigue risk. Maximum fragment displacement ranged from 0.39 mm to 10.7 mm, and strain distributions were consistent with observed stress patterns. These findings suggest that the FSI provides an effective and quantitative approach for comparing fixation strategies in FEbased orthopedic biomechanics. Incorporating such parameters into preoperative planning may improve fixation choice and enhance patient-specific outcomes.