A Design Method for Orthopedic Plates Based on Surface Features

Matching of orthopedic plates and bony surfaces does not have a high certainty of success because bone anatomy differs among individuals. Considering that surfaces of both orthopedic plates and bones manifest themselves as freeform surfaces and are especially suitable for surface feature-based design, a novel surface feature-based method for designing orthopedic plates is put forward, with detailed steps as follows. First, the bone surface feature (BSF) is established through feature representation of an average bone surface model, obtained based on the investigated samples. Second, the abutted surface of an orthopedic plate is established directly based on the BSF surface to increase matching between the plate and bony surface. The abutted surface feature (ASF) is then established through feature representation of the abutted surface. Third, the hierarchical mapping relationship between BSF and ASF is setup based on the framework of “three-level parameters and two-grade mappings.” The result is that semantic parameters defined on BSF and ASF are separated as an operation interface to make it convenient to edit orthopedic plates according to bone sizes. Finally, the orthopedic plate is generated by thickening the abutted surface, which is generated based on parameters defined on BSF. Taking radius as an example, a group of volar plates suitable for distal radius with different sizes are generated, showing that the proposed method is valid and feasible. Meanwhile, biomechanical stresses of designed volar plates are analyzed with finite element analysis, and the result shows that designed volar plates have good structural strength.