## 3 Biomechanical FEA Studies for Proximal Humerus Fractures  
According to the recent literature, most proximal humerus fracture studies using FEA tend to investigate factors involving open reduction and internal fixation (ORIF) treatment with a locking plate [5; 28; 29; 30; 31; 33], due to the popularity of the treatment in the last few years, and also because of the high failure rate it has. Biomechanical studies turn around this treatment, investigating either the bone behavior or the effects of the locking plate configuration (Table 1); in any case, the interaction of both is relevant. The predominant studies are those that evaluate the effect of a parameter, be it the bone or the locking plate; for example, the locking plate position [29], the screw hole style [5], and the insertion angle of the screws [31], among others. Each of these studies aims for treatment optimization and/or failure risk prediction. There are also other types of proximal humerus fracture studies, such as those \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Reference** & **Study’s Aim** & **Type of Fracture** & **Mechanical Test** \\ \hline \multirow{8}{*}{[PERSON] et al. [31]} & Optimize the proximal & \multirow{4}{*}{3-part} & \multirow{4}{*}{Abduction and flexion} \\  & humerus open reduction and & & \\  & internal fixation (ORIF) & & \\  & treatment locking plate by & & \\  & changing the orientation of the & & \\  & plate screws. & & \\ \hline \multirow{3}{*}{[PERSON] et al. [3]} & Predict performance load and & \multirow{3}{*}{2-part} & \multirow{3}{*}{Compression} \\  & baseline location of an & & \\  & anatomical neck fracture using & & \\  & finite element analysis (FEA). & & \\ \hline \multirow{4}{*}{[PERSON] et al. [30]} & Investigate and quantify the & \multirow{4}{*}{3-part} & \multirow{4}{*}{Abduction and flexion} \\  & effect of ORIF locking plate & & \\  & screw configuration on failure & & \\  & risk prediction of the fracture & & \\  & fixation. & & \\ \hline \multirow{4}{*}{[PERSON] et al. [29]} & Investigate the effect of the & \multirow{4}{*}{3-part} & \multirow{4}{*}{Abduction and flexion} \\  & position (proximal-distal) & & \\  & variations of the ORIF locking & & \\  & plate on failure risk prediction & & \\  & of the fracture fixation. & & \\ \hline \multirow{4}{*}{[PERSON] et al. [28]} & Optimize the proximal & \multirow{4}{*}{2-part} & \multirow{4}{*}{Bending} \\  & humerus locking plate & & \\  & parametric design by & & \\  & determining the orientation of & & \\  & the inferomedial ORIF locking & & \\  & plate screws. & & \\ \hline \multirow{4}{*}{[PERSON] et al. [33]} & Develop and evaluate an FEA & \multirow{4}{*}{3-part} & \multirow{4}{*}{Bending} \\  & technique to approximate the & & \\  & behavior of a threaded screw & & \\  & using a cylinder in ORIF. & & \\ \hline \multirow{4}{*}{[PERSON] et al. [5]} & Investigate the effect of the & \multirow{4}{*}{2-part} & \multirow{4}{*}{Compression} \\  & screw hole style design on the & & \\  & locking plate stress & & \\  & distribution in ORIF. & & \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Comparison of characteristics from recent studies of the proximal humerus, considering the objective of the study, type of fracture evaluated, and mechanical test applied. who study the nature of a fracture itself, like the research by [PERSON] et al. [3]. A comparison is presented in Table 1.  
Since a proximal humerus fracture can be presented in several forms, it is difficult to consider them all in one specific study, mainly due to the scope of the projects. That is why almost all studies of this type are limited to a single fracture pattern. Today, the majority of researchers are investigating proximal humerus 3-part fractures [15; 29; 30; 31; 33; 46], because of the actual recurrence of the pattern in the clinical field [2; 17; 36; 47; 48]. The 3-part fracture (AO/OTA 11B1.1) mostly involves the surgical neck and greater tuberosity.