This study evaluates the thermal stability, mechanical performance, and geometric accuracy of polylactic acid (PLA) manufactured using fused deposition modeling (FDM) in the context of orthosis design. PLA is widely used in medical 3D printing due to its accessibility, biocompatibility, and ease of processing; however, its anisotropy, surface roughness, and low softening temperature impose functional constraints in orthotic applications. A hand orthosis model was produced in both vertical and horizontal print orientations, assessed for dimensional accuracy, subjected to three-point bending tests including cyclic loading, and monitored using thermal imaging during printing. Findings indicate that vertical orientation provides superior surface quality and higher bending stiffness, while geometric deviations remained within clinically acceptable limits. Thermal imaging showed stable printing conditions, and mechanical testing demonstrated that PLA withstands forces exceeding those typically generated by spastic or contractured muscles. The results suggest that PLA is suitable for short-term or pediatric orthoses, though limitations such as brittleness and thermal sensitivity should be considered. Future work should explore alternative lattice geometries, connection methods, and comparisons with higher-performance polymers.