Journal of biomechanics
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Journal of biomechanics · Jun 2021
Physiological articular contact kinematics and morphological femoral condyle translations of the tibiofemoral joint.
The changes of tibiofemoral articular cartilage contact locations during knee activities represent a physiological functional characteristic of the knee. However, most studies reported relative motions of the tibia and femur using morphological flexion axes. Few data have been reported on comparisons of morphological femoral condyle motions and physiological tibiofemoral cartilage contact location changes. ⋯ At 120° of flexion, the morphological measures of the lateral femoral condyle were more posteriorly positioned than those of the contact locations. The data showed that the morphological measures of femoral condyle translations and axial rotations varied with different flexion axes and did not represent the physiological articular contact kinematics. Biomechanical evaluations of the knee joint motion should include both morphological and physiological kinematics data to accurately demonstrate the functionality of the knee.
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Journal of biomechanics · Mar 2021
Bone cement augmentation of femoral nail head elements increases their cut-out resistance in poor bone quality- A biomechanical study.
The aim of this study was to analyze biomechanically the impact of bone cement augmentation on the fixation strength and cut-out resistance of Proximal Femoral Nail Antirotation (PFNA) and Trochanteric Fixation Nail Advanced (TFNA) head elements within the femoral head in a human cadaveric model with poor bone quality. Methodology: Fifteen pairs of fresh-frozen human cadaveric femoral heads were randomized to three sets of five pairs each for center-center implantation of either TFNA blade, TFNA screw, or PFNA blade. By splitting the specimens of each pair for treatment with or without bone cement augmentation, six study groups were created. ⋯ Augmented TFNA blades resulted in highest numbers of cycles to failure and loads at failure (30492; 4049 N) followed by augmented PFNA blades (30033; 4003 N) and augmented TFNA screws (19307; 2930 N), p = 0.11. Augmented TFNA screws showed similar numbers of cycles to failure and loads at failure compared to both non-augmented TFNA and PFNA blades, P = 0.98. From a biomechanical perspective, bone cement augmentation significantly increases the cut-out resistance of instrumented TFNA and PFNA head elements and is a valid supplementary treatment option to these nailing procedures in poor bone quality.
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Journal of biomechanics · Jan 2021
Biomechanical evaluation of the docking nail concept in periprosthetic fracture fixation around a stemmed total knee arthroplasty.
Intramedullary femoral nails provide an ideal mechanical axis for periprosthetic fracture fixation. Slotted nails allow a connection to a total knee arthroplasty (TKA) stem. This study aims to compare implant and construct stiffness, interfragmentary movement and cycles to failure between an antegrade slotted femoral nail construct docked to a TKA stem and a distal femoral locking plate in a human periprosthetic femoral fracture model. ⋯ Nail constructs provided significantly higher initial axial bending stiffness and cycles to failure (200 ± 83 N/mm; 16'871 ± 5'227) compared to plate constructs (93 ± 35 N/mm; 7'562 ± 1'064), P = 0.01. Relative axial translation at osteotomy level after 2'500 cycles was significantly smaller for nail fixation (0.14 ± 0.11 mm) compared with plate fixation (0.99 ± 0.20 mm), P < 0.01. From a biomechanical perspective, the docking nail concept offers higher initial and secondary stability under dynamic axial loading versus plating in TKA periprosthetic fracture fixation.
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Journal of biomechanics · Dec 2020
Assessment of mechanical properties of articular cartilage with quantitative three-dimensional ultrashort echo time (UTE) cones magnetic resonance imaging.
Conventional magnetic resonance imaging (MRI) is not capable of detecting signal from the deep cartilage due to its short transverse relaxation time (T2). Moreover, several quantitative MRI techniques are significantly influenced by the magic angle effect. The combinations of ultrashort echo time (UTE) MRI with magnetization transfer (UTE-MT) and Adiabatic T1ρ (UTE-AdiabT1ρ) imaging allow magic angle-insensitive assessments of all regions of articular cartilage. ⋯ Correlations between other UTE MRI measurements (T2*, T1, and T2mm) and mechanical properties were non-significant. The 3D UTE-AdiabT1ρ and UTE-MT sequences were highlighted as promising surrogates for non-invasive assessment of cartilage mechanical properties. MMF from UTE-MT modeling showed the highest correlations with cartilage mechanics.
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Journal of biomechanics · Dec 2020
Spring-loaded inverted pendulum modeling improves neural network estimation of ground reaction forces.
Inertial-measurement-unit (IMU)-based wearable gait-monitoring systems provide kinematic information but kinetic information, such as ground reaction force (GRF) are often needed to assess gait symmetry and joint loading. Recent studies have reported methods for predicting GRFs from IMU measurement data by using artificial neural networks (ANNs). To obtain reliable predictions, the ANN requires a large number of measurement inputs at the cost of wearable convenience. ⋯ Leave-one-subject-out cross-validation was performed with normalized root mean square error and r as quantitative measures of prediction performance. The vertical and anteroposterior (AP) GRFs obtained using both methods agreed well with the experimental data, but Method 2 yielded improved predictions of AP GRF compared to Method 1 (p = 0.005). These results imply that knowledge of the dynamic characteristics of walking, combined with a neural network, could enhance the efficiency and accuracy of GRF prediction and help resolve the tradeoff between information richness and wearable convenience of wearable technologies.