## 1 Introduction  
In medical practice, nails are used to treat various types of limb fractures. Femoral nails are used to treat fractures of the proximal and distal femur. This article presents an analysis of nails used to treat proximal femoral fractures located in the vicinity of the pelvis. It also draws significance to the usage of short reconstructive nails in the treatment of specific proximal femur fractures. The examined nails are manufactured by Medin (Nove Mesto na Morave, Czech Republic) and Tantum (Neumunster, Germany). It drawson previous theoretical and practical studies concerning the proximal femur [1; 2]. In the AO classification, the fractures in this region are _fractura mediocervicalis femoris_ AO 31B3 and _fractura subtrochanterica femoris_ AO 32A3 [3]. These are among the most frequent fractures of long bones, human trauma and they present the greatest risk to the elderly population. A substantial majority of patients with these fractures are over the age of 50, and cases occur among women 2-3 times more frequently than among men [4]. For these reasons, it is beneficial to conduct stress-deformation analyses and to assess the suitability of femoral nails for clinical treatment. The nails currently in use differ primarily in their design (collo-diaphyseal angle 120-135\({}^{\circ}\), see Figure 1a) and also depending on the producer and the materials used (compatibility with the human body). The femur (see Figure 1) is the largest and heaviest bone in the human body. The proximal part of the femur consists mainly of the almost spherical femoral head (caput femoris), which is seated within the acetabulum of the pelvis; the femoral neck (collum femoris), which forms the neck-shaft angle (collo-diaphyseal angle) with the main axial length of the femur (usually 125-135\({}^{\circ}\)); and the eminences of the greater and lesser trochanter (trochanter major and trochanter minor) and the adjacent areas, where the muscle attachments are located [1]. The anteversion of the femoral neck to the frontal anatomical plane is approximately 15\({}^{\circ}\). Proximal femoral fracture (PFF) is one of the most common types of long bone fracture and it presents a particular risk to elderly patients. We know that PFFs account for a large proportion of hospitalisations and possible complications among trauma cases [2]. More precise classifications of these fractures have been developed, facilitating practical description and enabling different treatment centres to share their clinical experiences. Historically, one of the best-known classifications of trochanter fractures was developed by [PERSON] [5], who divides them primarily into stable and unstable fractures and into several types. Figure 2a shows a classification of a fracture based on this system compared with the equivalent AO classification. Figure 1: (**a**) Anatomy of femur bone (a—lnia intertrochanterica; b—trochanter major; c—caput femoris; d—fovea capitis femoris; e—collum femoris; f—tuberositas glutea; g—trochanter minor; h—tuberculum adductorium; i—epicondyl medialis; j—condylus medialis; k—facies patellaris; l—condylus lateralis; m—epidocondyl lateralis; n—proximal end; o—diaphysis; p—distal end). (**b**) Proximal femur placed in acetabulum (X-ray snapshot). Femoral neck fractures have been described by numerous authors. One of the most frequently used classifications is by [PERSON] [6], who divides fractures into four grades: I. incomplete, II. complete but non-displaced, III. complete and partially displaced and IV. complete and fully displaced. Another classification of PFFs (and other fractures) is the international AO/OTA system, developed by the Swiss AO (Arbeitsgemeinschaft fur Osteosyntheesfragen) and the OTA (Orthopedic Trauma Association). This system uses numbers and letters to designated fracture types. PFFs are denoted by numbers from 31 upwards [3].