Search Results (3,870)

Nanoparticle superlattices, periodic assemblies of nanoscale building blocks, offer opportunities to tailor mechanical behavior through controlled lattice geometry and interparticle interactions. Here, classical molecular dynamics simulations were performed to investigate the compressive responses of copper nanoparticle superlattices with face-centered cubic (FCC), hexagonal close-packed (HCP), body-centered cubic (BCC), and simple cubic (SC) arrangements, as well as disordered assemblies. The flow stresses span 0.5–1.5 GPa. Among the studied configurations, the FCC and HCP superlattices exhibit the highest strengths (~1.5 GPa), followed by the disordered assembly (~1.0 GPa) and the SC structure (~0.8 GPa), while the BCC superlattice exhibits the lowest strength (~0.5 GPa), characterized by pronounced stress drops and recoveries resulting from interfacial sliding. Atomic-scale analyses reveal that plastic deformation is governed by two coupled geometric factors: (i) the number of interparticle contact patches, controlling the density of dislocation sources, and (ii) their orientation relative to the loading axis, which dictates stress transmission and slip activation. A combined parameter integrating particle coordination number and contact orientation is proposed to rationalize the structure-dependent strength, providing mechanistic insight into the deformation physics of metallic nanoparticle assemblies. Full article

The deformation mechanism during the hot compression of PM nickel-based superalloy FGH99 and its micro-structural evolution, especially the evolution of γ’ phases, are the key factors affecting the final molding quality of aero-engine hot forged turbine disks. In this study, a new constitutive model of viscoplasticity with micro-structures as physical internal parameters were developed to simulate the hot compression behavior of FGH99 by incorporating the strengthening effect of the γ’ phase. The mechanical behavior of high-temperature (>1000 K) compressive deformation of typical superalloys under a wide strain rate (0.001~1 s⁻¹) is investigated using the Gleeble thermal-force dynamic simulation tester. The micro-structure after the hot deformation was characterized using EBSD and TEM. Work hardening as well as dynamic softening were observed in the hot compression tests. Based on the mechanical responses and micro-structural features, the model considered the coupled effects of dislocation density, DRX, and γ’ phase during hot flow. The model is programmed into a user subroutine based on the Fortran language and called in the simulation of the DEFORM-3D V6.1 software, thus realizing the multiscale predictive simulation of FGH99 alloy by combining macroscopic deformation and micro-structural evolution. The established viscoplastic constitutive model shows a peak discrepancy of 10.05% between its predicted hot flow stresses and the experimental values. For the average grain size of FGH99, predictions exhibit an error below 7.20%. These results demonstrate the high accuracy of the viscoplastic constitutive model developed in this study. Full article

This study examines the influence of layer thickness (0.9, 1.6, 2.4, and 4 mm) on the distribution of residual stress, microstructural evolution, and tensile properties of Cu18150/Al1060/Cu18150 multilayered composites fabricated via a combined cast-rolling and hot-rolling technique. The grain refinement, dislocation density, and residual stress gradients across the interfaces were characterized and analyzed using integrated electron backscatter diffraction and kernel average misorientation mapping. The results demonstrated that specimens with a lower layer thickness (0.9–1.6 mm) possess a significantly improved tensile strength of 351 MPa, which is mainly due to the significant grain refinement and the presence of compressive residual stresses at the region of the Al/Cu interfaces. However, tensile strength decreased to 261 MPa in specimens with thicker layers (4 mm), accompanied by improved ductility, e.g., elongation of 30%. This is associated with a reduction in the degrees of interfacial constraint and the formation of more homogeneous deformation structures that accommodate a larger strain. The intermediate layer thickness of 2.4 mm offers an optimal compromise, achieving a tensile strength of 317 MPa while maintaining balanced mechanical performance. These results emphasize the importance of layer thickness in controlling such stress profiles and optimizing the mechanical behavior of hybrid metal composites, providing useful guidance on the design and fabrication of superior structural-form materials. Full article

Open reduction and internal fixation (ORIF) for mandibular condyle fractures remains a controversial and challenging issue, with the exception of basal and low-neck fractures. Currently, there is a consensus that fractures causing irreparable malocclusion or dislocation, when the fracture line runs through the base or lower neck of the condyle, require ORIF. Due to the different characteristics of fractures, various surgical approaches and their modifications are available. The use of a minimally invasive intraoral approach during endoscope-assisted procedures is considered safer for the facial nerve and provides good esthetic results without facial scarring. This study aimed to compare two surgical approaches—retromandibular and intraoral—to examine post-operative outcomes and to guide surgical decision-making in the treatment of simple fractures of the base and low-neck condylar process of the mandible. Forty-nine patients (thirteen female, thirty-six male) were analyzed: eighteen were treated with the intraoral approach, and thirty-one with the retromandibular approach. There were no statistical differences in the duration of surgery, but intraoperative blood loss was significantly lower in patients treated endoscopically compared with those treated with an extraoral approach. Post-operative facial nerve and TMJ function were comparable in both groups. The endoscope-treated patients were at a higher risk of fracture non-union, but these findings should be considered with connection with the small sample size. The intraoral approach is a valuable option for basal or low-neck fractures but demands significant surgical experience due to its technical complexity. Full article

This study was focused on addressing the performance degradation in core microstructures of ultra-heavy steel plates (thickness ≥ 50 mm) caused by non-uniform cooling during thermo-mechanical controlled processing. Using microalloyed DH36 steel as the research subject, we systematically investigated the effects of cooling rate on the nucleation and growth of acicular ferrite and its consequent microstructure-property relationships through an integrated approach combining in situ observation via high-temperature laser scanning confocal microscopy with multiscale characterization techniques. Results demonstrate that the cooling rate significantly affects acicular ferrite formation, with the range of 3–7 °C/s being most conducive to acicular ferrite formation. At 5 °C/s, the acicular ferrite volume fraction reached a maximum of 74% with an optimal aspect ratio (5.97). Characterization confirmed that TiOx-Al₂O₃·SiO₂-MnO-MnS complex inclusions act as effective nucleation sites for acicular ferrite, where the MnS outer layer plays a key role in reducing interfacial energy and promoting acicular ferrite radial growth. Furthermore, the interlocking acicular ferrite structure was shown to enhance microhardness by 14% (HV0.1 = 212.5) compared to conventional ferrite through grain refinement strengthening and dislocation strengthening (with a dislocation density of 2 × 10⁸ dislocations/mm²). These results provide crucial theoretical insights and a practical processing window for strengthening-toughening control of heavy plate core microstructures, offering a viable pathway for improving the comprehensive performance of ultra-heavy plates. Full article

High-strength low-alloy (HSLA) steel is widely used in automotive industry for reduction of consumption and emissions. The microstructure and mechanical properties of two automotive HSLA steels with different strength grades were systematically investigated in present study. Microstructural characterization was conducted using optical microscopy (OM), scanning electron microscopy (SEM), and electron backscatter diffraction (EBSD), while mechanical properties were evaluated with Vickers hardness tester and tensile tests. Both steels exhibited a ferrite matrix with spheroidized carbides/pearlites. However, Sample A displayed equiaxed ferrite grains with localized pearlite colonies, while Sample B featured pronounced elongated ferrite grains with a band structure. Tensile testing revealed that Sample B had higher ultimate tensile stress and yield stress compared to Sample A. Texture analysis indicated that both steels were dominated by α-fiber and γ-fiber textures, with minor θ-fiber texture, resulting in minimal mechanical anisotropy between the rolling direction (RD) and transverse direction (TD). The quantitative assessment of strengthening mechanisms, based on microstructural parameters and experimental data, revealed that grain boundary strengthening dominates, with dislocation strengthening also contributing significantly. This work provides the first comprehensive quantification of individual strengthening contributions in automotive HSLA steels, offering critical guidance for developing further higher-strength automotive steels. Full article

Background: Pelvic injuries of the sacroiliac joint are unstable and require surgical intervention following high-energy trauma. In this study, we aimed to present the long-term clinical outcomes of patients with sacroiliac joint separation and sacroiliac fracture dislocation (crescent) injury. We compared the surgical interventions performed on the sacroiliac joint based on patient clinical data. Methods: By reviewing the records of 850 pelvic fractures treated in our clinic between 2000 and 2020, we identified 110 patients with sacroiliac joint injuries who were included in the study. The fractures were classified based on patient files and radiographs. The patients were categorized according to the surgical interventions performed on the sacroiliac joint into two groups: closed reduction with percutaneous iliosacral screws and open reduction with plates and screws. We further divided the patients who underwent open reduction and plate–screw fixation into anterior and posterior surgical approaches. Clinical outcomes were obtained by evaluating patients using a subjective pelvic scoring system. Additionally, complications observed after surgeries were investigated. Results: A total of 121 fractures from 110 patients were included in the study. Eleven of the patients had bilateral sacroiliac joint injuries, for which bilateral surgery was performed. The mean age of the patients at the time of injury was 35.15 years (range from 6 to 80 years). The mean follow-up period was 103.45 months (range from 16 to 253 months). According to the scoring system, the highest success rate was observed in plate–screw operations performed through the anterior approach to the sacroiliac joint, with excellent to good results in approximately 92% of patients. Both open reduction and internal fixation through the posterior approach and closed reduction and percutaneous iliosacral screw surgery yielded successful functional results, with no statistically significant difference between the methods (p = 0.880). Regarding complications, the most important problems were infections associated with plate–screw procedures using the posterior approach and neurologic injuries resulting from closed reduction screw surgery. Conclusions: Effective management of sacroiliac joint injuries requires surgical expertise and individualized treatment strategies. With appropriate technique and fixation, both open and closed surgical methods can achieve satisfactory anatomical reduction and functional outcomes. Although standardized treatment protocols may be developed, tailoring the approach to each patient is more important for optimal clinical success. Full article

The management of severely comminuted acetabular posterior wall fractures in young, active patients presents a significant surgical challenge. When anatomical open reduction and internal fixation (ORIF) is not feasible, primary total hip arthroplasty (THA) is often considered but is a suboptimal solution due to concerns over long-term implant survivorship and the inevitability of revision surgery. This single-patient technical note presents a novel joint-preserving technique for managing unreconstructible acetabular posterior wall fractures using with cement-augmented screw fixation via the Kocher–Langenbeck approach. A 28-year-old male sustained a left posterior hip dislocation with a comminuted acetabular posterior wall fracture involving >30% of the articular surface, alongside a tibial shaft fracture, following a high-energy motorcycle collision. Intraoperative assessment confirmed the posterior wall was unreconstructible, with six non-viable osteochondral fragments. A joint-preserving salvage procedure was performed. After debridement, a stable metallic framework was created using three screws anchored in the posterior column. Polymethylmethacrylate (PMMA) bone cement was then applied over this framework in its doughy phase, meticulously contoured to reconstruct the articular surface. The hip was reduced, and the tibia was fixed with an intramedullary nail. The patient was mobilized with weight-bearing as tolerated on postoperative day 3. At the 21-month follow-up, the patient reported no pain during daily activities and only mild discomfort during deep squatting. Radiographic and CT evaluations demonstrated a stable hip joint, concentric reduction, well-maintained joint space, and no evidence of implant loosening or osteolysis. Level of Evidence: V (Technical Note/single-patient Case report). For unreconstructible, comminuted fractures of the non-weight-bearing portion of the acetabular posterior wall in young patients, cement-augmented screw fixation offers a viable joint-preserving alternative to primary THA. This technique provides immediate stability, facilitates early mobilization, and preserves bone stock. While long-term outcomes require further study, this case demonstrates excellent functional and radiographic results at 21 months, presenting a promising new option for managing these complex injuries. Full article

Background/Objectives: Patellar instability is a common orthopedic condition affecting pediatric and adolescent populations, particularly during periods of rapid growth and increased sports participation. Recurrent patellar dislocation in skeletally immature patients is frequently associated with underlying anatomical risk factors such as patella alta, trochlear dysplasia, or increased tibial tubercle–trochlear groove distance. Methods: This narrative review summarizes the current evidence on the epidemiology, diagnostic approach, and arthroscopic management of patellar instability in skeletally immature patients. Results: Arthroscopy has become an essential tool in both the diagnosis and treatment of patellar instability, allowing for minimally invasive assessment of patellofemoral alignment, chondral pathology, and ligament integrity. It also enables precise surgical interventions such as physeal-sparing medial patellofemoral ligament reconstruction, which remains the preferred stabilization technique for patients with open physes due to its safety and efficacy. Emerging innovations, including robotic-assisted tunnel placement, bioengineered scaffolds for cartilage repair, and three-dimensional modeling for surgical planning, have the potential to improve outcomes and arthroscopic surgical precision in this population. Despite these advances, major challenges such as a lack of pediatric-specific outcome measures, variability in surgical indications and rehabilitation protocols, and limited long-term follow-up data remain. Conclusions: Optimizing outcomes in pediatric and adolescent patients with patellar instability requires individualized growth-aware strategies and multidisciplinary collaborations. By integrating technological innovation with patient-centered care, clinicians can continue to refine the arthroscopic management of patellofemoral instability in young patients. Full article

Background/Objectives: Modular dual mobility (MDM) cups are constituted by a cobalt-chromium liner inserted into a standard acetabular shell, allowing for intraoperative indication and supplementary screw fixation of the acetabular component. MDM could face mechanical and biological issues, with the associated risk of elevated blood metal ions levels and adverse local tissue reactions. Methods: This is a monocentric retrospective study on a consecutive series of 105 patients who underwent primary unilateral THA with the G7 Dual Mobility Acetabular System cup (Zimmer Biomet, Warsaw, IN, USA) from March 2019 to April 2023, and who were evaluated clinically and radiographically at a minimum two-year follow-up. All complications and revisions were recorded. Survivorship analysis with any revision surgery as endpoint was performed using Kaplan–Meier survival curves. Results: There were eighty-nine patients (follow-up rate 84.8%) who underwent clinical and radiographic follow-up. The mean follow-up was 2.5 ± 0.8 years. Revision-free survival was 98.0%. Three complications (2.8%) were recorded: one case of posterior dislocation, one periprosthetic joint infection and one post-traumatic periprosthetic femur fracture. Dislocation rate and infection rate were less than 1.0%. None of the patients were revised for adverse local tissue reactions. No cup loosening was observed. No cases of intraprosthetic dislocation, liner malseating or femoral notching were observed. Retroacetabular stress shielding was present in 43.0% of patients. Clinical scores significantly improved at the last follow-up compared with preoperative status (p < 0.0001): the final mean mHHS was 87.5 ± 5.3 and the final mean VAS was 0.5 ± 0.9. Conclusions: The Zimmer G7 modular dual mobility cup appears to be a safe and effective option and does not present specific implant-related mechanical and biological issues in primary total hip arthroplasty at a minimum two-year follow-up. Full article

Background/Objectives: Total hip arthroplasty (THA) is a widely accepted and effective intervention for advanced degenerative hip disease. However, prosthetic dislocation remains one of the most common postoperative complications. This study aimed to evaluate the biomechanical consequences of implant positioning variations and their influence on prosthetic stability. Methods: A three-dimensional finite element model (FEM) of the pelvis and hip joint was developed using SolidWorks Professional 2025, based on CT imaging of an anatomically normal adult. Multiple implant configurations were simulated, varying acetabular cup inclination and anteversion angles, femoral stem depth, and femoral offset. Muscle force vectors replicating single-leg stance conditions were applied according to biomechanical reference data. The mechanical performance of each configuration was quantified using the safety factor (SF), defined as the ratio of allowable material stress to calculated stress in the model. Results: The configuration with 45° cup inclination, 15° anteversion, standard femoral offset, and optimal stem depth demonstrated the highest SF values (9–12), indicating a low risk of mechanical failure or dislocation. In contrast, malpositioned implants—particularly those with low or high anteversion, excessive offset, or shallow stem insertion—resulted in a marked decrease in SF values (2–5), especially in the anterosuperior and posterosuperior quadrants of the acetabular interface. Conclusions: The findings underscore the critical importance of precise implant alignment in THA. Even moderate deviations from optimal positioning can substantially compromise biomechanical stability and increase the risk of dislocation. These results support the need for individualized preoperative planning and the use of assistive technologies during surgery to enhance implant placement accuracy and improve clinical outcomes. Full article

Objective: There is scarce reporting of radial head fracture epidemiology and patient characteristics beyond age and sex. This study aimed to describe demographic, socioeconomic, and injury pattern characteristics for people sustaining a radial head fracture admitted to trauma centers over a 15-year period. Methods: Analysis of Victorian Orthopaedic Trauma Outcomes Registry data was conducted to describe the demographic and case characteristics of patients with radial head fractures admitted to collaborating hospitals. Cohort and case characteristics were compared by center type (Level 1 vs. other trauma centers). Results: A total of 991 cases with a unilateral radial head fracture were recorded over 15 years, with 827 admitted to Level 1 trauma centers and 164 admitted to other centers. The mean age at time of injury was 48.7 years (SD 19.7), with male predominance (n = 621, 62.7%). Most patients resided in major cities (n = 824, 85.2%), were treated under the universal healthcare system (n = 546, 56.1%), and had no Charlson Comorbidity Index conditions (n = 738, 74.5%). A higher proportion of patients managed at Level 1 centers were male (65.7% vs. 47.6%), younger (mean 47.7 vs. 53.7 years), living in major cities (86.6% vs. 78.5%), and working prior to injury (71.3% vs. 57.1%). Over 85% of the cohort sustained concomitant injuries, with Level 1 centers receiving a higher proportion of multiple injury cases (87.8% vs. 73.2%). Elbow dislocations constituted the largest proportion of concomitant injuries (n = 257, 25.9%). Conclusions: This study has provided new insights into the demographic characteristics, comorbidity status, and associated injuries of radial head fracture populations admitted to Level 1 and other trauma centers, using long-established registry data. Full article

Background: Anterior shoulder dislocations are common in athletes, particularly in contact sports. Surgical stabilization reduces recurrence, but the optimal timing—early versus delayed—remains uncertain, especially for in-season athletes. Methods: A systematic search of PubMed, Embase, and Cochrane (2013–2023) yielded 945 articles; 15 met the inclusion criteria. Data were charted on procedure type, outcomes, follow-up, patient group, and timing of surgery. Search terms, e.g., ‘shoulder’, ‘athlete’, ‘anterior’ and ‘shoulder dislocation’, were used in a broad search protocol casting a wide net to maximize the likelihood of capturing all available data. Results: Surgery was superior to conservative care in lowering recurrence and enabling return-to-play, with arthroscopic and combined procedures most effective in high-contact sports. Conservative management carried higher instability risk. Evidence directly comparing early versus delayed surgery was scarce, and therefore inconclusive. Conclusions: Surgical stabilization remains the treatment with better outcomes compared to conservative treatment for young athletes. Still, athletes opt to delay surgery until postseason, with the impact of delaying surgery being unclear. Further research is needed to evaluate early versus delayed surgery regarding recurrence, joint damage, and return to sport. Full article

Introduction: Neck-preserving total hip arthroplasty (THA) has gained interest for conserving bone stock, restoring biomechanics, and facilitating revision surgery. The Nanos^® femoral stem, designed for metaphyseal fixation while preserving the femoral neck, represents a reliable alternative to conventional THA. This study reports 15-year clinical and radiographic outcomes of the Nanos implant. Materials and Methods: We retrospectively reviewed 53 patients (35 males, 18 females) who underwent THA with the Nanos stem between 2008 and 2010. Patients were stratified into two groups according to age: <50 years (n = 24) and ≥50 years (n = 29). The primary diagnosis was osteoarthritis (95%), with a few cases of avascular necrosis or dysplasia. Clinical evaluation included the Harris Hip Score (HHS) and the Western Ontario and McMaster Universities Arthritis Index (WOMAC). Radiographic assessment focused on implant stability, osteolysis, and heterotopic ossifications. Kaplan–Meier survival analysis was performed with revision for any reason as the endpoint. Results: At 15 years of follow-up, both groups showed significant improvement (p < 0.001). In patients <50 years, HHS increased from 53.3 to 94.8 and WOMAC decreased from 79.9 to 3.5. In patients ≥50 years, HHS improved from 47.5 to 95.2 and WOMAC from 81.5 to 3.2. Radiographs confirmed stable fixation without osteolysis. Complications included two dislocations and one cortical perforation requiring revision. Kaplan–Meier survivorship at 15 years was 100% (<50) and 96.6% (≥50). Conclusions: The Nanos stem provided excellent long-term outcomes with low complication and revision rates. It should be considered one of several reliable short-stem options for younger, active patients, offering durable function while preserving bone stock. Full article

Erosion wear is a major cause of surface degradation in metallic materials exposed to harsh marine environments. In this study, the erosion wear resistance of the 18Ni300 maraging steel repaired by underwater direct metal deposition (UDMD) is investigated. Results show that UDMD is successfully applied to repair the 18Ni300 samples in underwater environment. Full groove filling and sound metallurgical bonding without cracks are achieved, demonstrating its potential for underwater structural repair. Microstructural analyses reveal good forming quality with fine cellular structures and dense lath martensite in the deposited layer, attributed to rapid solidification under water cooling. Compared to in-air DMD, the UDMD sample exhibits higher surface microhardness due to increased dislocation density and microstructural refinement. Erosion wear behavior is evaluated at 30° and 90° impingement angles, showing that wear mechanisms shift from micro-cutting and plowing at 30° to indentation, crack propagation, and spallation at 90°. The UDMD samples demonstrate superior erosion wear resistance with lower mass loss, particularly at 30°, benefiting from surface work hardening and microstructural advantages. Progressive surface hardening occurs during erosion due to severe plastic deformation, reducing wear rates over time. The combination of refined microstructure, high dislocation density, and enhanced work hardening capability makes UDMD-repaired steel highly resistant to erosive degradation. These findings confirm that UDMD is a promising technique for repairing marine steel structures, offering enhanced durability and long-term performance in harsh offshore environments. Full article