## 1 Introduction  
Fracture of the proximal humerus is becoming one of the most common injuries among the elderly and is related to osteoporosis, which deteriorates the microstructure of the bone and decreases its bone mass [1; 2; 3; 4; 5]. Fracture risk will increase with population aging [6; 7; 8]: the changes that come with the biological aging process make the elderly more susceptible to suffering a fracture, given that falls are the major risk factor for this group, along with osteoporosis [9; 10; 11; 12].  
The treatment for this type of fracture is still debatable, due to the fracture/patient factors involved in the treatment decision process, and the high complication rates of surgical treatments. The stability and displacement of the fracture, the bone mineral density, the fracture pattern, and the age and comorbidities of the patient are some of the factors to consider for the proper selection of treatment [3; 4; 13; 14; 15]. The potential poor outcomes of surgical treatments include non-union, varus collapse, screw-cut, loss of reduction, avascular necrosis, and the need for reoperation [14; 16; 17].  
Therefore, computational biomechanical studies have become more common, which try to solve and validate the different aspects of fracture treatments and enhance their outcomes through finite element analysis (FEA), providing a fast and low-cost experimentation technique and, most importantly, helping to prevent premature failures through fracture/treatment behavior analysis via three-dimensional (3D) models. An FEA can provide information on realistic bone behavior in specific scenarios through a three-dimensional simulation, as long as the mesh parameters, constraints, and mechanical properties are properly selected, especially for the bone [18; 19].  
Nevertheless, discrepancies exist between studies due to the lack of standards for the characterization of the bone model, including in proximal humerus studies. Each researcher uses different bone material properties and natures; for instance, there are studies were the orthotropic nature is preferred for the bone [20; 21], while others use the isotropic nature [3; 5; 22; 23; 24; 25; 26; 27; 28], even when anisotropy is the actual nature of bone tissues. The research papers also differ in their modeling technique. Some researchers consider the bone as a solid and \"homogeneous\" model, without distinguishing between the different bone tissue [25; 26], while other studies use a threshold to separate cancellous and cortical bone in order to maintain real bone structure in their model [3; 5; 20; 29; 30; 31]. What is more, each researcher uses dissimilar meshing parameters for their FEA bone models--crucial parameters for the accuracy of outcomes, which vary from the type of element to the element's edge length.  
Hence, this article aims to review the most used bone characterization techniques for the proximal humerus in FEA biomechanical studies, analyzing the different aspects of the modeling process, from bone geometry simplification to the most used mesh parameters. The strengths and limitations of these FEA characterization techniques will also be reviewed, starting from the most basic knowledge you must possess about the proximal humerus to be able to apply them, and considering how to achieve the best and closest-to-reality results from an FEA through the use of revised techniques.