Individualizing biomechanical shoulder models using scaling, morphing and fittings

It is increasingly apparent the necessity of subject specific biomechanical models that are aimed at clinical applications, in particular in the design and analysis of orthopedic implants, preoperative planning and interpretation of post operative outcomes. Currently, imaging techniques like MRI and CTs can potentially provide a source for complete individualized models; however, the constraints of clinical reality preclude the creation of full complex models of a region of interest. This gap can be bridged by creating idealized generic musculoskeletal models that can be morphed into patient specific models using limited CT and morphometric data obtained pre-operatively. The transformation from the generic model to a specific one is achieved by a volumetric morphing technique using non uniform scaling, translations, rotations and shear matrices combined with the optimum fitting, in a least squares sense, of spheres, cylinders, ellipsoids, circles, ellipses, planes and general curves, around bony and muscle structures.