Mechanical Effects of a Design Opening in a Three-Dimensional-Printed Mallet Finger Orthosis: A Finite-Element Study

Background: Mallet finger is commonly managed by immobilizing the distal interphalangeal (DIP) joint in extension.Three-dimensional (3D) printing enables customized orthoses, but geometric features introduced for access, ventilation, or comfort may alter device mechanics.This study used finite-element (FE) analysis to quantify the mechanical effect of a longitudinal vent in a 3D-printed mallet finger orthosis.Methods: Two orthosis geometries, one with a 26.2 mm × 7.6 mm longitudinal vent and one without the vent, were evaluated under axial compression and anatomical DIP loading.Peak effective stress was compared under axial compression, while maximum principal stress (MPS) and lateral displacement were evaluated under DIP loading.Mesh sensitivity was assessed using MPS sampled at a consistent DIP joint location across progressively refined meshes.Results: Under axial compression, peak effective stress decreased from 4.409 MPa in the orthosis with the vent to 3.409 MPa in the orthosis without the vent, representing a 22.7% reduction.Under anatomical DIP loading, MPS decreased from 0.2554 to 0.1331 MPa, representing a 47.9% reduction, while the maximum displayed lateral displacement decreased from 1.957 × 10⁻³ to 6.518 × 10⁻⁴ mm, representing a 66.7% reduction.Conclusion: Under the evaluated conditions, the longitudinal vent increased stress concentration and deformation in the 3D-printed mallet splint.However, the stresses remained well below the measured material strength.Vent design should balance structural performance with the clinical benefits of ventilation.Future clinical studies are needed before further design recommendations can be made.