Investigating Contact Models in Clavicle Fixation Plates: A Finite Element Study of Their Impact on Biomechanical Performance.

Clavicle fractures are among the most common orthopedic injuries and frequently require plate fixation to restore anatomical alignment and mechanical stability. The biomechanical performance of fixation constructs is strongly influenced by the contact interactions between the plate, bone, and screws. This study investigated the effect of four contact formulations (bonded, no-separation, frictionless, and frictional) on the structural stiffness, stress distribution, and interfragmentary strain of clavicle fixation plates using finite element analysis. A three-dimensional (3D) clavicle model reconstructed from computed tomography (CT) data was subjected to 200 N inferior bending, 200 N axial compression, and 4 N·m torsional loading. The bonded model exhibited the highest structural stiffness under all loading conditions (+66% bending, +60% compression, and +38% torsion relative to the intact model), but also generated high stress concentrations, reaching 620.3 MPa under bending. The frictional and frictionless models produced lower stiffness values (+64% bending, +16% compression, and +28% torsion), while the no-separation model demonstrated intermediate stiffness. Peak plate stress varied considerably among contact formulations, with the no-separation model producing the highest value under bending (655.3 MPa). Interfragmentary strain was lowest in the bonded model (<2%), whereas frictional and frictionless models generated higher strain levels (2-10%), corresponding to mechanical conditions associated with secondary healing. The no-separation model exhibited intermediate strain values. These findings demonstrate that contact conditions strongly influence the biomechanical behavior of clavicle fixation constructs. Incorporating physiologically realistic contact models may improve finite element predictions and support the optimization of fixation strategies and implant design.