Staged screw removal in external plate fixation for distal tibial fractures: a finite element study on adaptive biomechanics

High-energy distal tibial fractures present treatment challenges due to poor soft tissue coverage and risk of delayed union. External locking plates offer stability while preserving biology, yet the optimal strategy to dynamically modulate fixation rigidity in accordance with healing progression remains unclear. We constructed finite element models of a comminuted distal tibial fracture incorporating callus at four healing stages (0, 1, 3, and 6 months). Seven screw configurations and the effect of an intact fibula were evaluated under 800 N axial load. Outcome measures included fracture site displacement, stress shielding rate, and stresses in callus and implant. In early healing (0–1 month), displacement exceeded 1 mm even with 3- or 4-screw constructs, and plate stress approached 2900 MPa, underscoring the need for protected weight-bearing. By 3 months, all configurations maintained sub‑millimeter displacement. Reducing screws from a 4-screw to a 2-screw configuration at this stage significantly lowered the stress shielding rate from 76.3% to 71.8% and increased callus stress by approximately 14%, without compromising stability. An intact fibula consistently reduced displacement and implant stress by 50–80%. This study provides biomechanical support for an “adaptive fixation” strategy: initial rigid fixation with protected weight-bearing, followed by staged screw removal after callus maturation (around 3 months) to reduce stress shielding and enhance mechanobiological stimulation. The presence of an intact fibula substantially improves construct stability and should be considered in clinical management.