Design and biomechanical evaluation of a patient-specific 3D-printed wrist splint for carpal tunnel syndrome: a finite element analysis study

INTRODUCTION: Conventional wrist splints for carpal tunnel syndrome (CTS) may have limited anatomical fit and ventilation. This study developed and mechanically evaluated an anatomy-matched, 3D-printed wrist splint using stress-guided Voronoi lattice optimisation. MATERIALS AND METHODS: Wrist and forearm geometry from one healthy adult volunteer was acquired by structured-light scanning (0.2 mm point distance). A 3.0 mm shell was optimised by preserving longitudinal and transverse load-bearing features and removing material from low-strain regions. A coupled splint-soft-tissue finite element analysis (FEA) model with frictional contact (μ = 0.4) simulated a static 50 N wrist-flexion load. Global displacement predictions were assessed by mechanical bench testing of the printed polylactic acid (PLA) splint. A non-porous 3.0 mm solid shell derived from the same anatomy served as the design comparator. RESULTS: Under the simulated load, maximum von Mises stress was 18.4 MPa against a PLA yield strength of 60 MPa, with a minimum safety factor of 3.26. Predicted distal displacement was 2.15 mm, compared with 2.32 mm in bench testing (7.33% relative error). Compared with the solid-shell control, the optimised design reduced mass by 45.93% and achieved a 45.2% open surface area while retaining adequate static load-bearing capacity. CONCLUSIONS: This single-volunteer proof-of-concept study supports the feasibility of a lightweight, anatomy-matched splint with mechanically validated global displacement under static loading. Effects on ventilation, skin comfort, and CTS symptoms require physiological and clinical evaluation.