A personalized method for estimating centre of mass location of the whole body based on differentiation of tissues of a multi-divided trunk

Finite element method analysis of bone stress for variants of locking plate placement

This study investigates the optimal placement of locking plate screws for bone fracture stabilization in the humerus, a crucial factor for enhancing healing outcomes and patient comfort. Utilizing Finite Element Method (FEM) modeling, the research aimed to determine the most effective screw configuration for achieving optimal stress distribution in the humerus bone. A computer tomography (CT) scan of the humerus was performed, and the resulting images were used to create a detailed model in SOLIDWORKS 2012. This model was then analyzed using ANSYS Workbench V13 to develop a finite element model of the bone. Four different screw configurations were examined: 4 × 0°, 4 × 10°, 4 × 20°, 2 × 20°; 2 × 0°. These configurations were subjected to bending in the XZ and YZ planes, as well as tension and compression along the Z axis. The research identified the 2 × 20°+2 × 0° configuration as the most beneficial, with average stress values below 30 MPa and peak stress values below 50 MPa in 3-point bending at the first screw. This configuration consistently showed the lowest stress values across all loading scenarios. Specifically, stress levels ranged from 20 MPa to 50 MPa for bending in the XZ plane, 20 MPa-35 MPa for bending in the YZ plane, 20 MPa-30 MPa for extension in the Z-axis, and 18 MPa-25 MPa for compression in the Z-axis. The 4 × 10° and 4 × 20° configurations also produced satisfactory results, with stress levels not exceeding 70 MPa. However, the 4 × 0° configuration presented considerable stress during bending and compression in the Z-axis, with stress values exceeding 100 MPa, potentially leading to mechanical damage. In conclusion, the 2 × 20°; 2 × 0° screw configuration was identified as the most effective in minimizing stress on the treated bone. Future work will involve a more detailed analysis of this methodology and its potential integration into clinical practice, with a focus on enhancing patient outcomes in bone fracture treatment.

Comparison of body segment models for female high jumpers utilising DXA images

In motion analysis of sport competitions, the question is often about the most convenient choice for defining the segment endpoints when no visible landmarks can be used. The purpose of the present study was to determine the location of the body centre of mass (CoM) of female high jumpers by using a high accuracy reaction board and two different segment models: Dempster (1955) and de Leva (1996). Digitising the bony landmarks from the images of dual energy x-ray absorptiometry (DXA) and overhead digital camera were used to compare the digitising accuracy. The location of the CoM determined by a reaction board was 55.88 ± 0.52% of subjects' body height. The segment model of Dempster digitized from DXA images (56.66 ± 0.50%) differed from the reference values of reaction board (p = 0.004), whereas the model of de Leva (56.06 ± 0.61%) showed no significant difference. The model of de Leva adjusted for female subjects differed only slightly (0.32%), thus, providing appropriate model for female high jumpers. Since the digitised bony landmarks in the DXA images are obviously very close to the correct locations, the differences in results between the segment models and reaction board is most likely due to inaccuracies in the model itself and/or generalisation of one model to different body structures. When the segment landmarks were estimated without any markers on the body, the results did not differ much from the DXA results.

Basic inertial quantities including multi-segment trunk of fit, young males obtained based on personalized data

Up to now several researchers use values of basic inertial quantities of human body parts obtained for old cadavers. Taking into account the trunk researchers presented this body part often as one segment only and rarely as few-segment part. The purpose of this study was obtaining values of basic inertial quantities of body parts including five parts of the trunk for young, fit living males. Thirty young, fit males (age: 24 ± 4 years, height: 179 ± 6 cm, body mass: 74 ± 7 kg) were directly measured (circumferences and skin-fat folds) and photographed in order to use these data for Clauser et al. (parts of extremities) and Erdmann's (parts of trunk) methods for estimation of mass and location of centres of mass of body parts. These methods take into account personal data for estimating inertial quantities. Relative mass (according to the mass of the whole body) of trunk parts (sum of thorax + abdomen + pelvis but without shoulder girdle) of subjects investigated in this work was similar to that obtained by Dempster for old cadavers. Relative mass differed for shoulders and for lower extremities. Old subjects for both lower extremities had around 31-32% of the whole body mass and young subjects had almost 37%. Procedure for obtaining location of the whole body centre of mass for graphical method (summation of mas) was presented. Obtained data are very important for analyses of arched trunk, e.g. in high jumping, pole vault jumping, rhythmic gymnastics of young, fit athletes and also for models of young passengers in car-crash tests, for ergonomics and medical analyses and other purposes.

Predictive regression modeling of body segment parameters using individual-based anthropometric measurements

Body segment parameters such as segment mass, center of mass, and radius of gyration are used as inputs in static and dynamic ergonomic and biomechanical models used to predict joint and muscle forces, and to assess risks of musculoskeletal injury. Previous work has predicted body segment parameters (BSPs) in the general population using age and obesity levels as statistical predictors (Merrill et al., 2017). Estimated errors in the prediction of BSPs can be as large as 40%, depending on age, and the prediction method employed (Durkin and Dowling, 2003). Thus, more accurate and representative segment parameter inputs are required for attempting to predict modeling outputs such as joint contact forces, muscle forces, and injury risk in individuals. This study aims to provide statistical models for predicting torso, thigh, shank, upper arm, and forearm segment parameters in working adults using whole body dual energy x-ray absorptiometry (DXA) scan data along with a set of anthropometric measurements. The statistical models were developed on a training data set, and independently validated on a separate test data set. The predicted BSPs in validation data were, on average, within 5% of the actual in vivo DXA-based BSPs, while previously developed predictions (de Leva, 1996) had average errors of up to 60%, indicating that the new models greatly increase the accuracy in predicting segment parameters. These final developed models can be used for calculating representative BSPs in individuals for use in modeling applications dependent on these parameters.