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Modern developments of biomedical applications demand a better understanding of mechanical behaviour of soft biological tissues. As human soft tissues demonstrate a significant structural and functional diversity, characterisation of their mechanical behaviour still remains a challenge. Limitations related with implementation of mechanical experiments on human participants lead to a use of finite-element models for analysis of mechanical responses of soft tissues to different loads. This study focuses on parameters of numerical simulation considered for modelling of indentation of a human lower limb. Assessment of the effect of boundary conditions on the model size shows that at a ratio of its length to the tissue's thickness of 1.7 for the 3D model this effect vanishes. The numerical results obtained with models employing various sets of mechanical parameters of the first-order Ogden scheme were compared with original experimental data. Furthermore, high sensitivity of the resulting reaction forces to the indenting direction is demonstrated for cases of both linear and angular misalignments of the indenter. Finally, the effect of changes in material parameters and their domain on their contribution to the reaction forces is discussed with the aim to improve our understanding of mechanical behaviour of soft tissues based on numerical methods. The undertaken research with its results on minimal requirements for finite-element models of indentation of soft tissues can support inverse analysis of their mechanical properties and underpin orthopaedic and medical procedures. [ABSTRACT FROM AUTHOR]

Pressure ulcers are localized damage to the skin and underlying tissues caused by sitting or lying in one position for a long time. Stresses within the soft tissue of the thigh and buttocks area play a crucial role in the initiating mechanism of these wounds. Therefore, it is crucial to develop reliable finite element models to evaluate the stresses caused by physiological loadings. In this study, we compared how the choice of material model and modeling area dimension affect prediction accuracy of a model of the thigh. We showed that the first-order Ogden and Fung orthotropic material models could approximate the mechanical behavior of soft tissue significantly better than neo-Hookean and Mooney–Rivlin. We also showed that, significant error results from using a semi-3D model versus a 3D model. We then developed full 3D models for 20 participants employing Ogden and Fung material models and compared the estimated material parameters between different sexes and locations along the thigh. We showed that males tissues are less deformable overall when compared to females and the material parameters are highly dependent on location, with tissues getting softer moving distally for both men and women. [ABSTRACT FROM AUTHOR]

Plantar soft tissue stiffening in diabetes leads to a risk of developing ulcers. There are relatively few studies providing methods for quantifying the mechanical properties of skin and fat in the plantar tissue of diabetic patients. Previous studies used linear or non-linear single layer deformable models or linear multi-layer models. This study aimed to investigate the mechanical properties of plantar soft tissue using multi-layer, non-linear models to estimate more accurate mechanical properties in the plantar tissues of diabetic patients. Ten healthy young (HY) subjects, ten healthy old (HO) subjects, and ten old diabetic patients (DB) volunteered for the study. Indentation tests were performed at two sites in the heel. The subjects underwent computed tomography (CT) to measure the respective thicknesses of the skin and fat at the indentation sites. Subject-specific finite element models were created to estimate the parameters of the first-order Ogden forms of the skin and fat. The initial shear modulus for the fat layer μ F in DB, HO, and HY were 4.68 MPa (±0.87), 2.71 MPa (±1.25), and 2.27 MPa (±0.87), respectively. The initial shear modulus for the skin layer (μ S) in DB, HO, and HY were 5.86 MPa (±2.51), 7.05 MPa (±1.94), and 14.58 MPa (±1.98), respectively. The DB had stiffer fat tissue than the normal subjects in the same age group but had the same soft skin. These aspects can cause different mechanical stress conditions in a diabetic foot than in a normal foot under the same mechanical loading, making the diabetic foot vulnerable to the initiation of mechanical breakdowns such as ulcers. [ABSTRACT FROM AUTHOR]

Fractures about the tibial tubercle are uncommon fracture patterns, seen most often in adolescent males as they approach skeletal maturity. Compartment syndrome has a high association with these fractures requiring close monitoring, and a heightened level of suspicion. Tibial tubercle fractures are typically stratified using the Ogden classification. The type of intra-articular involvement and degree of displacement guide appropriate treatment. This report highlights a 14-year-old male patient who suffered a type IV tibial tubercle fracture with a unique Salter–Harris II, or transitional, component posteriorly that was unable to be closed reduced and developed compartment syndrome. He underwent fasciotomy, open reduction, and temporary external fixation. Once the status of the soft tissues improved, he underwent staged open reduction and internal fixation with skin grafting. The patient's fracture and soft tissues healed and he currently ambulates without assistance or pain, and has returned to all desired activities including competitive sports. [ABSTRACT FROM AUTHOR]