Innovative splinting solutions: Additive manufacturing of acrylonitrile butadiene styrene-based mallet finger orthoses

Mallet finger is a common deformity of the distal interphalangeal joint resulting from extensor tendon injury, frequently observed in athletes and individuals exposed to high-impact fingertip trauma. To address limitations in conventional splinting methods, this study introduces two ergonomic mallet finger splint designs fabricated using acrylonitrile butadiene styrene via fused deposition modeling 3D printing. These designs—a modular two-piece splint with Velcro fastening and a single-piece cylindrical splint—incorporate strategically placed ventilation holes to enhance airflow, reduce perspiration, and improve patient comfort during prolonged wear. Microstructural evaluation using scanning electron microscopy revealed characteristic inter-bead voids and interlayer bonding typical of fused deposition modeling-printed acrylonitrile butadiene styrene, while post-aging samples exhibited signs of embrittlement and microcrack formation. These morphological changes were correlated with mechanical performance, where tensile strength (30.73 MPa), modulus of elasticity (1.59 GPa), and other key properties showed only marginal reductions (2–4.7%) after thermal aging at 60 °C for seven weeks, confirming the material's structural stability. The integration of microstructural insights with mechanical data validates acrylonitrile butadiene styrene as a durable, biocompatible, and thermally stable material for orthopedic applications, offering a practical and customizable alternative to traditional mallet finger treatments.