Biomedical Implant Design

The number of joint replacing surgeries is increasing worldwide. Massive metal implants are commonly used. These may cause stress shielding, a condition where the bone in contact with the implant disappears (osteopenia), causing costly and painful resurgeries. We utilize complex shaped biocompatible metallic biomaterials such as Ti grade 5 as well as biodegradable high-performance metals such as Mg and its alloys for the creation of implant structures with designed porosity. This way, we tune stiffness reducing the development of osteopenia. However, designed porosity is yet but one factor for the success of an implant. Fast recovery and proper functionality is determined by bone cells attachment and integration into the implants’ structure. AM renders rough surfaces that favor osseointegration, where already differentiated bone cells (osteoblasts) find sites to attach. Undifferentiated precursor cell (Bone Marrow derived Stromal Cells- BMSCs) differentiation into osteoblasts also determines bone healing. Surface sites are not only anchor points but provide incentives for cells to differentiate. We aim to build implants that trigger the self-healing capacity of the human body. By geometric design, we tune the global stiffness to the one of human bone, tailoring properties to the specific site of interest. The surface topography of the porous structure shall govern cell fate through a combination of geometrical (nano- (cell anchor points), micro (surface roughness) and macrosopic (engineered topology) features) and chemical cues. From a tissue engineering perspective, this requires knowledge on topology induced osteogenesis, the conformal control over surface features on complex 3D geometries, the construction of surfaces enhancing cell differentiation into osteoblasts and prototypes equipped with such surfaces for future in vivo tests. Mechanical, chemical and biological consideration will lead to future implants allowing shorter recovery times, sustainable outcomes and implants that function throughout the designed lifetime omitting painful resurgeries and associated costs.

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