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Background: Debates persist over optimal pelvic girdle reconstruction after acetabular tumor resection, with surgeons grappling between modular and 3D-printed hemipelvic endoprostheses. We hypothesize superior outcomes with 3D-printed versions, yet scarce comparative research exists. This study fills the gap, examining biomechanics and clinical results retrospectively. Methods: From February 2017 to June 2021, we retrospectively assessed 32 patients undergoing en bloc resection for malignant periacetabular tumors at a single institution. Primary outcome: limb function. Secondary outcomes: implant precision, hip joint rotation center restoration, prosthesis-bone osteointegration, and complications. Biomechanical characteristics were evaluated through finite element analysis on pelvic defect models. Results: In the 3D-printed group, stress distribution mirrored a normal pelvis, contrasting the modular group with elevated overall stress, unstable transitions, and higher stress peaks. The 3D-printed group exhibited superior functional scores (MSTS: 24.3 ± 1.8 vs. 21.8 ± 2.0, p < 0.05; HHS: 79.8 ± 5.2 vs. 75.3 ± 3.5, p < 0.05). Prosthetic-bone interface osteointegration, measured by T-SMART, favored 3D-printed prostheses, but surgery time (426.2 ± 67.0 vs. 301.7 ± 48.6 min, p < 0.05) and blood loss (2121.1 ± 686.8 vs. 1600.0 ± 505.0 ml, p < 0.05) were higher. Conclusions: The 3D-printed hemipelvic endoprosthesis offers precise pelvic ring defect matching, superior stress transmission, and function compared to modular endoprostheses. However, complexity, fabrication expertise, and challenging surgical implantation result in prolonged operation times and increased blood loss. A nuanced consideration of functional outcomes, complexity, and patient conditions is crucial for informed treatment decisions. Level of evidence: Level III, therapeutic study (Retrospective comparative study). [ABSTRACT FROM AUTHOR]

Objective: This study aimed to evaluate the effects of 2 endoscopic spine surgeries on the biomechanical properties of normal and osteoporotic spines. Methods: Based on computed tomography images of a healthy adult volunteer, 6 finite element models were created. After validating the normal intact model, a concentrated force of 400 N and a moment of 7.5 Nm were exerted on the upper surface of L3 to simulate 6 physiological activities of the spine. Five types of indices were used to assess the biomechanical properties of the 6 models, range of motion (ROM), maximum displacement value, intervertebral disc stress, maximum stress value, and articular protrusion stress, and by combining them with finite element stress cloud. Results: In normal and osteoporotic spines, there was no meaningful change in ROM or disc stress in the 2 surgical models for the 6 motion states. Model N1 (osteoporotic percutaneous transforaminal endoscopic discectomy model) showed a decrease in maximum displacement value of 20.28% in right lateral bending. Model M2 (unilateral biportal endoscopic model) increased maximum displacement values of 16.88% and 17.82% during left and right lateral bending, respectively. The maximum stress value of L4-5 increased by 11.72% for model M2 during left rotation. In addition, using the same surgical approach, ROM, maximum displacement values, disc stress, and maximum stress values were more significant in the osteoporotic model than in the normal model. Conclusion: In both normal and osteoporotic spines, both surgical approaches were less disruptive to the physiologic structure of the spine. Furthermore, using the same endoscopic spine surgery, normal spine biomechanical properties are superior to osteoporotic spines. [ABSTRACT FROM AUTHOR]

Identification of the energy dissipation behavior of fiber metal laminate under low-velocity impact is necessary for understanding its impact response and damage mechanism, as the impact scenario is typical for energy conversion. In this paper, the glass fiber reinforced aluminum laminate (Glare) was tested under different impact energy to achieve typical low-velocity impact responses and damage patterns. By which the finite element model was built and verified to be effective, by employing the Johnson–Cook model for aluminum, Hashin's criteria and exponential damage evolution law based VUMAT subroutine for GFRP, and bi-linear traction–separation cohesive zone model for their interface. Based on the history energy outputs on internal energy, elastic strain energy, plastic deformation dissipated energy, and damage dissipated energy in the finite element model. The contributions of the constituents in the energy absorption aspect of Glare were firstly revealed. Furthermore, how the energy was dissipated by the laminate and by the constituents, i.e., the distributions of energy evolutions in laminate and constituent levels, were clarified. Finally, damage evolutions of individual layers and the failure sequence of the entire laminate were elaborated. The results achieved have specified the energy dissipation mechanism and its association with the impact response of Glare. • Energy evolutions of Glare under low-velocity impact were identified and associated with the impact response mechanism. • A fair amount of unrecovered elastic strain energy contributed primarily by the GFRP was reserved in Glare after impact. • The front and rear aluminum in Glare played dominant roles in energy absorption and damage evolution aspects, respectively. • Maximum delamination in Glare under low-velocity impact was less influenced by aluminum cracking and applied energy. [ABSTRACT FROM AUTHOR]

A large mode field fiber with bend-resistance is proposed to work at 1550-nm wavelength. After modulation by high refractive index rings introduced in the core and cladding, this fiber can ensure the single-mode operation under a tight bend radius of 10 cm. The finite element method with perfect matching layers (PML) is used to simulate the proposed fiber. Numerical results show that the effective mode area can reach up to 1518.814 μm2 with a 0.004073 dB / m low bending loss of the fundamental mode. The designed all-solid-state fiber has a symmetrical structure and takes no consideration of the bending direction. This fiber has potential applications in high-power lasers. [ABSTRACT FROM AUTHOR]