## 1 Introduction  
Devices used to promote bone fusion and stabilization, which come into direct contact with the human body environment, must meet a range of requirements adapted to their intended use and the individual needs of the patient [1]. The materials from which they are manufactured must be characterized by an appropriate set of mechanical properties and corrosion resistance in the tissue environment, which affects biocompatibility. Direct contact between the body and the device takes place through the surface of the device. This makes the surface structure of the device an important factor in determining its suitability for practical use. Among its characteristics, wettability, topography, and chemical composition are mainly considered. These parameters affect the application of the device, in particular its integration into bone [2, 3, 4, 5, 6, 7]. Most often, titanium alloys are used for the manufacture of personalized implants, which are characterized by lightness, thanks to their low density (4.3-4.5 g/cm\({}^{3}\)). The high strength, combined with the lightness, guarantees the durability of the device with the right geometry and weight. The reduced modulus of elasticity of, for example, Ti6 Al4V alloy ensures a good mechanical match to the properties of the bone, which supports its regeneration processes. Thanks to its very high corrosion resistance in the tissue environment, the material has very good biocompatibility. It is very important in view of its long residency in the body, which ensures appropriate stabilization and later recovery [8; 9]. The development of design and manufacturing processes contributes to modern solutions in fracture stabilization and allows the creation of advanced implants, such as joint endoprostheses or dental implants, for example. These are most often manufactured using traditional methods [10; 11]. Obtaining personalized implants by traditional methods is difficult, so they are being replaced by implants manufactured by additive methods. Examples of such technologies include selective melting of metal powders Selective Laser Melting (SLM) [12], Direct Metal Laser Sintering (DMLS), or laser beam melting (LBM). Powders of titanium alloys (e.g., Ti6 Al4V ELI) are most used as the feedstock for DMLS or LBM printing [13; 14]. With the help of CAD (Computer-Aided Design) and medical imaging methods such as CT (Computed Tomography) or MRI (Magnetic Resonance Imaging), it is possible to design an implant individually tailored to the patient's needs. Ti6 Al4V ELI titanium alloy, due to its lower content of interstitial impurities, e.g., oxygen or nitrogen, is characterized by increased ductility and reduced alloy embrittlement compared to Ti6 Al4V alloy. These properties are a result of reduced local stresses and the influence of dislocations in the material structure [15]. Ti6 Al4V alloy powder is characterized by a spherical particle shape. This shape is obtained during the manufacturing process using the gas atomization method [16]. The particle shape provides good fluidity, which enables even layer distribution during printing, as well as a high application density. This translates into higher accuracy and uniformity of the manufactured products. Both parameters are important features in use for 3D printing technology. Particle sizes fall into two ranges, suitable for specific manufacturing methods. DMLS and EBM technologies use powder with gradations in the range 15-45 \(\upmu\)m, while powder metallurgy and thermal spraying use powder with gradations between 45 \(\upmu\)m-105 \(\upmu\)m. The shape and distribution of Ti6 Al4V powder particles are described in the literature [17; 18; 19; 20]. The most important advantage of using DMLS technology is the ability to design and manufacture a perfectly shaped device. It will meet the patient's needs and material requirements, while maintaining its mechanical properties [21].