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11.1 INTRODUCTION 217

FIG. 11.3 Femoral fractures according to Winquist and Hansen’s classification.

Despite the high number of designs, techniques, and materials, the intramedullary anterograde reamed nail with a
static combination of screws continues to be the reference treatment of fractures of femurs located between the 2 and 5
Wiss zones [4, 14, 15], depending on the success of the treatment, the characteristics of the fracture, the body habits of
the patient, the associated lesions, and the experience of the surgeon using this technique [7].
Experimentation with artificial bones or corpses in the lab, or with experimental animals, trying to study the bio-
mechanical behavior of various types of osteosyntheses in different fractures, is an important aid to clinical practice for
determining the therapeutic indication appropriate for every type of fracture. In this field, there are many studies of all
kinds of variables in terms of models of nails, techniques, and types of fracture, but the results are inconclusive and
sometimes divergent, particularly regarding their application to human clinical practice, which must be corroborated
with clinical studies. Research in experimental animals presents application difficulties due to anatomical differences
and load conditions, including complex application studies on cadaver bone or plastic anatomical models [16].
Due to differences between experimentation in vivo and in vitro, finite element (FE) models have emerged as a pow-
erful tool that simulates different biological systems in both physiological and pathological conditions, although there
are few articles studying the behavior of intramedullary nails in femoral bone. With regard to fractures of the femur
and biomechanical behavior of the different osteosynthesis techniques, experimental works studying multiple vari-
ables have been developed [17]. The location and type of fracture is a factor of utmost importance. The most studied
fractures have been supracondylar or distal femoral fractures because of their greater complexity, greater number of
complications, and multiple treatment options. Traditionally, their treatment has been based on plates associated with
dynamic screws, screws, or monoblock sheets; however, due to the lateral location of the plate, frequent medial col-
lapses in unstable fractures are produced [18]. For this reason, retrograde intramedullary nails have been designed
specifically to treat this type of fracture in an attempt to improve the biomechanical behavior of the fracture and
implant, and minimize surgical aggression; however, this type of fracture is still subject to breakage of the implants
at the level of the holes of the unplaced screws [19]. Nevertheless, in biomechanical experimental studies using artificial

I. BIOMECHANICS