This paper presents a parametric modeling framework for the design and additive manufacturing (AM) of personalized fixation plates based on the Method of Anatomical Features (MAF). The study focuses on the proximal humerus cloverleaf plate-a complex, multi-branch construct for fracture stabilization-and demonstrates its adaptation to a low-cost polymer prototype fabricated by fused-deposition modeling (FDM). The proposed method defines a hierarchical feature structure in which key geometric parameters-curvature, plate thickness, branch orientation, and screw-hole pattern-are derived from anatomical descriptors obtained directly from patient-specific data. The MAF framework ensures consistent anatomical alignment and scalability of the design across individual morphologies. The workflow further demonstrates cross-anatomical reusability through a tibial adaptation case, showing that identical parametric logic can be transferred to other long bones by redefining landmark sets. The resulting approach enables efficient design iteration, manufacturability evaluation, and physical validation through AM prototypes.