Determination of a new uniform thorax density representative of the living population from 3D external body shape modeling

Abstract

Body segment parameters (BSP) for each body׳s segment are needed for biomechanical analysis. To provide population-specific BSP, precise estimation of body׳s segments volume and density are needed. Widely used uniform densities, provided by cadavers׳ studies, did not consider the air present in the lungs when determining the thorax density. The purpose of this study was to propose a new uniform thorax density representative of the living population from 3D external body shape modeling. Bi-planar X-ray radiographies were acquired on 58 participants allowing 3D reconstructions of the spine, rib cage and human body shape. Three methods of computing the thorax mass were compared for 48 subjects: (1) the Dempster Uniform Density Method, currently in use for BSPs calculation, using Dempster density data, (2) the Personalized Method using full-description of the thorax based on 3D reconstruction of the rib cage and spine and (3) the Improved Uniform Density Method using a uniform thorax density resulting from the Personalized Method. For 10 participants, comparison was made between the body mass obtained from a force-plate and the body mass computed with each of the three methods. The Dempster Uniform Density Method presented a mean error of 4.8% in the total body mass compared to the force-plate vs 0.2% for the Personalized Method and 0.4% for the Improved Uniform Density Method. The adjusted thorax density found from the 3D reconstruction was 0.74g/cm(3) for men and 0.73g/cm(3) for women instead of the one provided by Dempster (0.92g/cm(3)), leading to a better estimate of the thorax mass and body mass.

Analysis of Center of Mass and Gravity-Induced Vertebral Axial Torque on the Scoliotic Spine by Barycentremetry

“…1), and patients who did not respect this position were excluded. This significantly limits the uncertainty of the gravity line position, as was confirmed by validation studies on healthy subjects and scoliotic patients, which reported an uncertainty of the GL position lower than 9 mm [10,14].…”

“…For each vertebra, the body segment above it (ie, the sum of the slices above it) was characterized by calculating its volume. Using the estimation of the density values proposed by Dempster [13] and by Amabile for the torso [14], its mass and center of mass (COM segment ) were also computed. The subject's arms were included in the model, although their position was not personalized, and their weight was shared by the T2 and T3 vertebrae.…”

Three- dimensional reconstruction of the thorax in the mongoose (Herpestes ichneumon)

“…The lung volume and capacity were higher in male mongoose than in female was parallel to the morphometric measurements of the lungs, which had greater values in the former compared to the latter (Guyton, 1986). Amabile et al (2016) assessed the 3D reconstruction model of the human thorax and found the thorax and lung volumes to be greater in males than in females. However, there was no significant difference observed in human fetal lung volumes due to genders (Szpinda et al, 2015).…”

Spinopelvic sagittal alignment of patients with transfemoral amputation

“…Pelvic tilt (PT): angle between the line connecting the center of the femoral heads and the middle of the sacral plate and the vertical. Sacral slope (SS): angle between the sacral plate line and the horizontal [11,13]; c OD-HA, adapted from Amabile et al [20]: angle between the line joining the most superior point of dentiform apophyse of C2 (OD) and the middle of acetabulum centers (HA) with the vertical, which is an invariant parameter in the young and in the elderly general populations [20,22]. In a balanced posture, the head is over the pelvis and the OD-HA is close to zero; d Sagittal vertical axis: SVA, adapted from Diebo et al [32]: posteroanterior distance between the C7 plumb line and the posterosuperior point of the sacral plate.…”

“…In the general population, it is now accepted that a misalignment could induce an imbalanced or noneconomical posture, causing an increase in the loads on the spinal structures. Subsequently, it can cause a overuse of trunk muscles to compensate the imbalance [5][6][7][8][9][10][11]. Thus, changes in the spinal posture can lead to pain due to premature lesions of structures and muscular efforts.…”