Design and Finite Element Evaluation of a Customized 3D-Printed Wrist-to-Finger Orthosis Targeting Carpal Tunnel Pressure Reduction

Carpal tunnel syndrome (CTS) is a common condition caused by increased carpal tunnel pressure and compression of the median nerve. Wrist–hand orthosis is widely used as a nonsurgical treatment to maintain the wrist in a near-neutral position and reduce pressure within the carpal tunnel. However, conventional orthosis often suffers from poor comfort, inadequate ventilation, localized pressure, and low patient compliance. This study aimed to design and evaluate a customized, multi-material 3D-printed wrist-to-finger orthosis that incorporated individual finger supports, perforated regions, and a volar clearance zone intended to avoid direct shell contact over the carpal tunnel region. A customized proof-of-concept orthosis was designed using a dual-material structure consisting of a rigid polylactic acid (PLA) outer shell and a flexible thermoplastic polyurethane (TPU) inner liner. The TPU liner was incorporated at skin contact regions to improve comfort, while the PLA shell provided structural support. Perforated lattice patterns were integrated to enhance ventilation and reduce weight, and a dedicated clearance zone was created on the volar side of the wrist to minimize direct pressure on the carpal tunnel area. Finite element analysis (FEA) was conducted under three loading conditions to evaluate stress distribution and deformation. The design refinement reduced the calculated mass from 258.27 to 205.36 g, corresponding to a 20.5% reduction. The maximum sampled von Mises stresses on the final PLA shell were 1.04 MPa on the upper surface and 0.99 MPa on the lower surface. Flexural testing demonstrated that the orthosis possessed adequate stiffness and maintained structural integrity under applied loads. The developed customized proof-of-concept orthosis demonstrates the feasibility of combining multi-material fused filament fabrication (FFF), personalized design, and FEA to produce a lightweight, breathable, comfortable, and mechanically reliable device for CTS management. The incorporation of a TPU liner and a carpal tunnel clearance zone has the potential to improve user comfort while maintaining the mechanical support required for effective treatment.