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The Finite Element Method (FEM) can be used to analyze very complex geometries, such as the pelvis, and complicated constitutive behaviors, such as the heterogeneous, nonlinear, and anisotropic behavior of bone tissue or the noncompression, nonbending character of ligaments. Here, FEM was used to simulate the mechanical ability of several external and internal fixations that stabilize pelvic ring disruptions. A customized pelvic fracture analysis was performed by computer simulation to determine the best fixation method for each individual treatment. The stability of open-book fractures with external fixations at either the iliac crests or the pelvic equator was similar, and increased greatly when they were used in combination. However, external fixations did not effectively stabilize rotationally and vertically unstable fractures. Adequate stabilization was only achieved using an internal pubis fixation with two sacroiliac screws.

Objective. This study was to examine the influence of socioeconomic status on fitness and fatness in Spanish adolescents. Subjects and Methods. A total of 1 795 adolescents (833 boys) aged 12.5–18.5 years from the AVENA study participated in this study. The following physical fitness components were assessed: muscular strength (standing long jump), speed‐agility (4 × 10 m shuttle run) and cardiorespiratory fitness (20 m shuttle run). Total and central body fat was assessed using skinfold thickness and waist circumference, respectively. Both parents reported their educational and professional level. Results. Girls with higher paternal educational level and boys with higher either maternal or paternal professional level had higher muscular strength levels (all P<0.05). Speed‐agility and cardiorespiratory fitness were not associated with parental educational or professional levels in boys. In contrast, girls with higher paternal educational level or higher parental professional level had higher levels in both fitness components (all P<0.05). A higher maternal educational level was associated with lower total and central body fat in boys (all P<0.05), but not in girls. We observed a small effect size (Cohen's d∼0.2) in most of these associations. Conclusions. Our results suggest modest associations of high socioeconomic status with better fitness and fatness levels in Spanish adolescents. These associations greatly depend on the socioeconomic status and fitness parameters studied.

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The knowledge of the lumbar spine biomechanics is essential for clinical applications. Due to the difficulties to experiment on living people and the irregular results published, simulation based on finite elements (FE) has been developed, making it possible to adequately reproduce the biomechanics of the lumbar spine. A 3D FE model of the complete lumbar spine (vertebrae, discs, and ligaments) has been developed. To verify the model, radiological images (X-rays) were taken over a group of 25 healthy, male individuals with average age of 27.4 and average weight of 78.6 kg with the corresponding informed consent. A maximum angle of 34.40° is achieved in flexion and of 35.58° in extension with a flexion-extension angle of 69.98°. The radiological measurements were 33.94 ± 4.91°, 38.73 ± 4.29°, and 72.67°, respectively. In lateral bending, the maximum angles were 19.33° and 23.40 ± 2.39, respectively. In rotation a maximum angle of 9.96° was obtained. The model incorporates a precise geometrical characterization of several elements (vertebrae, discs, and ligaments), respecting anatomical features and being capable of reproducing a wide range of physiological movements. Application to disc degeneration (L5-S1) allows predicting the affection in the mobility of the different lumbar segments, by means of parametric studies for different ranges of degeneration.