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.

Experimental research of energy absorbing structures within helmet samples made with the additive manufacturing method - preliminary study.

PURPOSE: This study aimed to develop an energy-absorbing structure for bicycle helmets to minimize head injuries caused by collisions. The research team explored three geometric structures produced through additive methods and compares their energy absorption properties with a standard bicycle helmet made of Expanded Polystyrene (EPS) foam. METHODS: The study prepared samples of three geometric structures (a ball, a honeycomb and a conical shape) and a fragment of a bicycle helmet made of EPS foam with the same overall dimensions. Laboratory tests were conducted using a pneumatic hammer, piston compressor, anvil, triaxial accelerometer and data processing systems. Three crash tests were performed for each type of structure, and the anvil's maximum acceleration and stopping distance after the crash were analyzed. RESULTS: The study found that the energy absorption properties of the Polylactic Acid (PLA) material printed with the incremental method were comparable or better than those of the EPS material used in helmets. The geometric structure of the energy-absorbing material played a crucial role in its effectiveness. The most promising results were obtained for the ball samples. CONCLUSIONS: The study concluded that further research on energy-absorbing structures made using the Fused Deposition Modeling (FDM) method could be useful in the production of bicycle helmets. The results show that the geometric structure of the energy-absorbing material is a crucial factor in its effectiveness. The findings suggest that the ballshaped structure made with PLA material printed using the incremental method could be a promising design for bicycle helmets to minimize head injuries caused by collisions.

Rib kinematics analysis in oblique and lateral impact tests.

PURPOSE: Understanding thorax kinematics and rib breaking mechanisms in conditions of oblique and lateral impact is crucial in safety systems development. To increase knowledge level on this subject, simulation and experimental tests are necessary. The purpose of this study was to obtain single rib kinematics in the case of oblique and lateral impact conditions using numerical simulation approach. METHODS: Two impact tests using human body model of a 50th percentile man (THUMS v4.0.1 AM50) were performed in LS-Dyna R7.1.1. Impactor was a rigid cylinder with a diameter of 152 mm, and velocity equal to 6.7 m/s. Impact angle measured to sagittal plane was 30 and 90°, respectively in oblique and lateral impact case. RESULTS: Kinematics of ribs from 3rd to 6th were analyzed. Results shown significant similarities between oblique impact and kinematics of ribs tested in frontal impact conditions in the literature, with maximal costochondral joint displacement relatively to costovertebral joint varying from 65.4 mm (3rd rib) to 82.0 mm (5th rib). Deformation of rib in lateral impact conditions was different than during oblique impact test, with distinctive "flattening" approximately in the middle of the rib. Maximal relative displacement varies from 16.4 mm (6th rib) to 26.6 mm (5th rib) and its location depends on the analyzed rib. CONCLUSIONS: Oblique impact scenario may be simulated for the single rib on an experimental way using set-up of the frontal impact. Experimental simulation of the lateral impact for the single rib should not use the same set-up, as the kinematics analysis showed significant differences between simulated cases.

Variation in the human ribs geometrical properties and mechanical response based on X-ray computed tomography images resolution.

Computational models of the human body are commonly used for injury prediction in automobile safety research. To create these models, the geometry of the human body is typically obtained from segmentation of medical images such as computed tomography (CT) images that have a resolution between 0.2 and 1mm/pixel. While the accuracy of the geometrical and structural information obtained from these images depend greatly on their resolution, the effect of image resolution on the estimation of the ribs geometrical properties has yet to be established. To do so, each of the thirty-four sections of ribs obtained from a Post Mortem Human Surrogate (PMHS) was imaged using three different CT modalities: standard clinical CT (clinCT), high resolution clinical CT (HRclinCT), and microCT. The images were processed to estimate the rib cross-section geometry and mechanical properties, and the results were compared to those obtained from the microCT images by computing the 'deviation factor', a metric that quantifies the relative difference between results obtained from clinCT and HRclinCT to those obtained from microCT. Overall, clinCT images gave a deviation greater than 100%, and were therefore deemed inadequate for the purpose of this study. HRclinCT overestimated the rib cross-sectional area by 7.6%, the moments of inertia by about 50%, and the cortical shell area by 40.2%, while underestimating the trabecular area by 14.7%. Next, a parametric analysis was performed to quantify how the variations in the estimate of the geometrical properties affected the rib predicted mechanical response under antero-posterior loading. A variation of up to 45% for the predicted peak force and up to 50% for the predicted stiffness was observed. These results provide a quantitative estimate of the sensitivity of the response of the FE model to the resolution of the images used to generate it. They also suggest that a correction factor could be derived from the comparison between microCT and HRclinCT images to improve the response of the model developed based on HRclinCT images.

Occupant kinematics and shoulder belt retention in far-side lateral and oblique collisions: a parametric study.

In far-side impacts, head contact with interior components is a key injury mechanism. Restraint characteristics have a pronounced influence on head motion and injury risk. This study performed a parametric examination of restraint, positioning, and collision factors affecting shoulder belt retention and occupant kinematics in far-side lateral and oblique sled tests with post mortem human subjects (PMHS). Seven PMHS were subjected to repeated tests varying the D-ring position, arm position, pelvis restraint, pre-tensioning, and impact severity. Each PMHS was subjected to four low-severity tests (6.6 g sled acceleration pulse) in which the restraint or position parameters were varied and then a single higher-severity test (14 g) with a chosen restraint configuration (total of 36 tests). Three PMHS were tested in a purely lateral (90° from frontal) impact direction; 4 were tested in an oblique impact (60° from frontal). All subjects were restrained by a 3-point seatbelt. Occupant motion was tracked with a 3D optoelectric high speed motion capture system. For all restraint configurations, the 60° oblique impact angle was associated with greater lateral head excursion than the 90° impact angle. This unexpected result reflects the increased axial rotation of the torso in the oblique impacts, which allowed the shoulder to displace more relative to the shoulder belt and thus the head to displace more relative to the sled buck. Restraint engagement of the torso and shoulder was actually greater in the purely lateral impacts than in the oblique impacts. Pretensioning significantly reduced lateral head excursion (175 mm average in the low-severity tests across all restraint configurations).