Ensuring bone-to-bone contact reduces interfragmentary strain in forearm shaft plating: A finite element study.

Abstract

Forearm diaphyseal fixation requires a mechanical environment appropriate for healing, but effects of residual gaps and cortical contact patterns remain unclear. This study used finite element analysis to quantify how gap size and contact pattern affect fracture-site strain and plate stress and to inform fixation strategy. Computed tomography scans from uninjured contralateral forearms of five adults with forearm diaphyseal fractures were used to create subject-specific models of the central 4/6 radius fixed with a small-fragment Ti-6Al-7Nb low-contact locking compression plate. We modeled simple transverse fractures with 0-2.0 mm gaps, partial-contact constructs with opposite-cortex contact or plate-side contact, and a comminuted configuration with two intermediate fragments. Coulomb friction (μ = 0.1) was used. A dorsal load up to 40 N was applied under cantilever conditions. Outcomes were plate equivalent stress, cortical-edge equivalent stress, and minimum principal strain within the gap. Full cortical contact minimized plate stress and maintained cortical load sharing. Residual gaps increased plate stress and altered cortical load transfer; small gaps generated the largest compressive interfragmentary strain. Opposite-cortex contact reduced plate stress and interfragmentary strain compared with plate-side contact. In comminution, intermediate fragments redistributed load and reduced average strain at the main fracture. Bone-to-bone contact and gap minimization improve the initial mechanical environment in simple fracture configurations. When only partial apposition is possible, opposite-cortex contact is mechanically preferable to plate-side contact. In comminution, bridge constructs may promote load sharing favorable to secondary healing.