Search Results (3,476)

Background/Objectives: Rigid interfragmentary compression is essential for primary bone healing following fractures, osteotomies, and arthrodeses of the foot and ankle. Evidence on the clinical performance of the MAX Variable Pitch Compression (VPC) Screw System (Zimmer Biomet, Warsaw, IN, USA) remains limited. This post-market, retrospective cohort study evaluated its safety, performance, and patient-reported outcomes. Methods: A single-center, consecutive series of patients treated with the MAX VPC Screw System for foot or ankle fractures, osteotomies, or arthrodeses between March 2018 and October 2023 was analyzed. The primary endpoint was radiographic and clinical bone union or joint fusion at 6–8 weeks and ≥18 months. Secondary endpoints included adverse events and functional outcomes using the Foot and Ankle Ability Measure (FAAM). Results: A total of 214 procedures were included (27 fractures, 80 osteotomies, 107 arthrodeses). Union was assessed in 209 procedures (97.7%) at 6–8 weeks and in 82 procedures (38.3%) at ≥18 months. Union rates were 86.1% at 6–8 weeks and 98.8% at ≥18 months. Early union was higher in arthrodeses (91.5%) than in fractures/osteotomies (80.6%). Adverse events occurred in 13.1% of procedures, 67.9% of which were device-related; no recurrent mechanical failures were observed. Mean FAAM scores were 92.3 (ADL) and 78.8 (Sports) for arthrodeses and 94.3 and 85.8, respectively, for fractures/osteotomies, at a mean FAAM follow-up of 2.9 years. Conclusions: The MAX VPC Screw System demonstrated high bone-union rates, favorable functional outcomes, and a moderate number of device-related complications. These results support its clinical use in foot and ankle surgery. However, the retrospective, single-center design limits generalizability, and prospective multicenter trials are warranted to confirm these findings. Full article

Melamine polyphosphate (MPP) is a widely employed additive-type flame retardant for polyamide 6. Generally, a higher loading of MPP leads to improved flame retardancy of polyamide 6 composites. Nevertheless, excessive addition tends to cause problems such as flame-retardant migration, leakage, and exudation. Against this background, this work focuses on covalently grafting melamine polyphosphate onto the surface of carbon nanotubes via a facile chemical reaction, with the aim of alleviating the migration and leakage of the flame retardant in the polyamide 6 matrix. Carbon nanotubes (CNTs) were surface modified with a silane coupling agent (KH560) to obtain CNTs bearing epoxy groups (CNT-KH560). Subsequently, a ring-opening addition reaction was conducted between the CNT-KH560 and melamine polyphosphate (MPP) yielding carbon nanotubes with surface-bonded flame-retardant MPP (CNTM). Polyamide 6 composite slices (PA6/CNTM) were prepared via twin-screw extrusion blending and compounding and then by hot-press molding into test specimens. The modified carbon nanotubes were characterized using Fourier transform infrared spectroscopy, scanning electron microscopy, and thermogravimetric analysis. The results confirmed the successful grafting of MPP onto the carbon nanotube surface, with a grafting degree of 9.1 g/100 g measured. The flame retardancy of the PA6/CNTM composites were evaluated through UL 94 vertical burning and limiting oxygen index (LOI) tests and cone calorimeter. These flame retardancy results indicated that when the content of flame-retardant-modified carbon nanotubes was 10 wt%, the PA6/CNTM10 composites achieved UL 94 V-2 and the limiting oxygen index increased from 24.5% of pure PA6 to 29.1%. The PHRR value of pure PA6 decreased from 750 kW/m² to 614 kW/m². This design of surface-grafted flame retardant provides a new strategy for the preparation and application of high-performance polyamide 6 flame-retardant composites. Full article

(1) Background and introduction: High-demand lumbosacral fusions are often supplemented with sacral-alar-iliac (SAI) screws. The idealized SAI trajectory was estimated to traverse 35 mm of sacrum before crossing the sacroiliac (SI) joint. However, there is debate on how much osseous purchase SAI screws achieve. The goal of this study was to determine the amount of osseous engagement achieved using a porous fusion–fixation screw (PFFS) when placed in a stacked SAI configuration. (2) Materials and methods: We retrospectively reviewed 40 consecutive patients who underwent sacropelvic fixation with stacked PFFS at our institution from 1 June 2022 to 30 June 2023, using intraoperative computed tomography (CT)-based computer navigation. A snapshot of each screw was taken and the length of purchase within the sacrum and ilium was measured on the axial image along the anterior and posterior aspect of each screw. Nineteen patients did not have adequate images available for review and were excluded. (3) Results: The overall mean anterior sacral engagement was 38.6 mm (±8.2 mm), which was found to be statistically significantly greater than the hypothesized threshold of 35 mm (p < 0.001), while posterior sacral engagement was 28.1 mm (±8.6 mm), which was not found to be statistically significantly greater than the hypothesized threshold of 35 mm (p = 1). The mean difference in sacral engagement between the anatomical location for the cephalad screws was 10.3 mm (p < 0.001) and 10.6 mm (p < 0.001) for the caudal screws. The total sacral surface area available for bone ingrowth for bilateral stacked PFFS was calculated to be 3338.3 mm², while the total iliac surface area available for bone ingrowth was 4364.8 mm². A mean difference in surface area availability between anatomical locations was −689.5 mm² (p < 0.001) for the sacrum and 689.5 mm² (p < 0.001) for the ilium. (4) Discussion and conclusions: The SAI trajectory screws in this cohort of patients achieved approximately 39 mm of sacrum engagement anteriorly and 28 mm posteriorly. This is consistent with prior estimates based on the idealized SAI pathway through the sacrum. PFFSs allow for simultaneous sacropelvic fixation and SI joint fusion, which may reduce the incidence of de novo SI joint pain in patients with long fusion constructs. Full article

The topic of improving the strength and performance properties of secondary polyamide materials as part of their functional modification is a very relevant area of expanding the possibilities of secondary use of plastic waste. The article aims to conduct a systematic study of the combined modification of polyamide waste agglomerate by six different types of carbon materials to improve their technological and strength properties. PA6 waste agglomerate from polyamide clothing items, tights, socks, and various carbon materials were studied: masterbatch for polyamides MW-PA CB10, brown coal humic substances, coke residue from pyrolysis, a mixture of plastic waste, and finely dispersed coal enrichment waste. A sustainable polymer composite based on a modified agglomerate of PA6 waste was obtained by extruding pre-prepared raw materials in a single-screw extruder. The structural and morphological analysis of the studied carbon materials showed that, within the framework of the combined modification of polyamide-6 waste agglomerate, they should perform different functions related to their distinct morphology and chemical composition. Thus, humic substances can act as functional modifiers and compatibilizers due to their nanodispersity and a wide range of active chemical groups. In contrast, coke residue from pyrolysis and coal enrichment waste will act as a functional filler to improve the complex strength properties of sustainable polymer composites. As part of a study on the effect of modifying polyamide-6 waste agglomerate by carbon materials on its complex technological characteristics, it was demonstrated that humic substances enhance sustainable polymer composite’s technological properties by increasing the melting temperature and melt flow index while reducing density. The increase in the functional effect of humic substances is due to the growth of a wide range of active chemical groups (hydroxyl, carboxyl, peptide). During the initial oxidation of brown coal, the coke residue from pyrolysis and coal enrichment waste served as a filler, increasing the sustainable polymer composite’s density and melt flow index. As part of the study of the effect of modification by carbon materials on the complex strength characteristics of polyamide-6 waste agglomerate, it was shown that all carbon materials studied, except for coke residue, improve the strength characteristics of polyamide-6 waste agglomerate. The optimal content of different types of humic substances is 0.5% wt., while the sustainable polymer composite’s impact strength and breaking stress during bending increase with the increase in the functionalization of humic substances during the oxidation of brown coal. It has been shown that the combination of small amounts of oxidized humic substances at the level of 0.5% by weight, as a functional additive with a masterbatch MW-PACB10 in an amount of 2–3.5%wt., provides materials with increased impact strength from 23 to ~48 kJ/m² and bending fracture stress from 115 to ~135 MPa, which allows returning secondary PA6 waste to the “traditional areas of primary PA6” in the manufacture of general technical parts and products. Full article

To address the issues of large overshoot, slow response, poor stability, and suboptimal control performance of traditional PID algorithms caused by the nonlinear relationship between the rotational speed and output flow rate of micro screw pump motors, this study proposes a PID parameter optimization method based on an improved spider wasp optimizer algorithm. First, this method incorporates the Tent chaotic mapping into the Spider Wasp Optimizer algorithm (SWO) to enhance initial population diversity, integrates differential evolution strategies to accelerate convergence, and employs Levy flight to boost local search capabilities, thereby balancing global exploration with local exploitation. Subsequently, comparative validation using 12 benchmark functions demonstrates that the improved algorithm (ISWO) outperforms SWO, PSO, SA, GOOSE, and CPO across metrics including mean, standard deviation, and Wilcoxon rank-sum test. Finally, integrating ISWO with PID control yields ISWO-PID, applied to a screw pump model. Simulation results demonstrate superior optimization efficiency and control performance: runtime was reduced by over 60% compared to benchmark algorithms, with enhanced system robustness and adaptability. Full article

Background: Reverse shoulder arthroplasty (RSA) relies on secure baseplate fixation to the glenoid. This carries a risk of suprascapular nerve (SSN) injury during peripheral screw insertion. Although fixed safe zones have been described, it remains unclear whether these scale with scapular morphometry or whether common screw positions confer differential SSN risk. Methods: Twenty cadaveric shoulders (ten pairs) were dissected. The superior safe zone (distance from the supraglenoid tubercle to SSN at the suprascapular notch) and posterior safe zone (distance from the glenoid rim to SSN at the spinoglenoid notch) were measured. Scapular dimensions (height, spine length, width) were measured. In ten shoulders, simulated RSA baseplate fixation was performed with superior screws placed at 11, 12, or 1 o’clock and posterior screws at 8, 9, or 10 o’clock. Screw lengths were based on glenoid depth. Cortical breach and SSN proximity were recorded. Linear regression assessed relationships between scapular dimensions and safe zones. Results: The superior safe zone (mean 2.9 ± 0.5 cm) significantly correlated with scapular dimensions (r = 0.78–0.86; p < 0.0001). All superior screws remained intraosseous across configurations. The posterior safe zone (1.9 ± 0.6 cm) showed no correlation. Posterior cortical breach occurred in 50% of specimens across all tested positions and was associated with smaller scapular spine length (p = 0.027). No significant difference in SSN proximity was observed between posterior screw positions. Conclusions: Scapular dimensions predict the superior, but not posterior, safe zone. Scapulae with shorter spine lengths demonstrated increased risk of posterior cortical breach, independent of screw position. These findings establish anatomical scalability of the superior safe zone and suggest that scapular morphometry may inform preoperative RSA planning; however, prospective validation is needed before routine clinical implementation. Full article

SSRMS refers to a Space Station Remote Manipulator System. The robotic arm of the Wentian module can complete tasks such as supporting astronauts’ extravehicular activities, installing and maintaining payloads, and inspecting the space station. The seven-joint SSRMS manipulator is critical for space missions. This study aims to build its kinematic model via screw theory. It simplifies SSRMS to right-angle rods, defines joint screw axes, twist coordinates, and initial pose matrix. Using the PoE (Product of Exponentials) formula, the 7-DOF forward kinematics equation is derived. In addition, it derives fixed joint angle for inverse kinematics, including analytical solutions and numerical solutions. It elaborates analytical solutions for fixing joints 1/7 and 2/6 and numerical solutions for fixing joints 3/4/5, solves all joint angles via kinematic decoupling, and addresses special cases. Experiments with China’s space station small arm parameters show the probability of meeting the accuracy threshold ${10}^{-4}$ is 99.79%, verifying model effectiveness, while noting singularity-related weak solving areas. This provides a reliable basis for subsequent inverse kinematics optimization. Full article

Background/Objectives: Dental implants are an established modality for oral rehabilitation, but their biomechanical success depends on controlling peri-implant strain, which is influenced by implant angulation, splinting, and length. This in vitro study evaluated the effects of these variables on strain and displacement under axial and oblique loading using digital image correlation (DIC). Methods: Three CBCT-derived mandibular models were 3D-printed and restored with screw-retained full-metal crowns. Group 1 compared parallel vs. angulated implants; Group 2 assessed splinted vs. non-splinted restorations; and Group 3 compared short (4.2 × 6.25 mm) vs. long (4.2 × 13 mm) implants. All specimens were loaded to 500 N at 0°, 15°, and 30° using a universal testing machine. Strain and displacement were analyzed with Istra 4D software and statistically evaluated using ANOVA and independent t-tests (α = 0.05). Results: Parallel implants exhibited progressively higher strain with load angle, peaking at 30° (p < 0.01), while angulated implants recorded their highest strain at 0° (p = 0.008), indicating better adaptation to oblique forces. Splinted restorations significantly reduced strain at 0° and 30° (p = 0.023) and lowered displacement across all inclinations (p = 0.0001). Short implants consistently produced greater strain and displacement than long implants (p < 0.02). Conclusions: Angulated implants mitigated strain under off-axis loading compared to parallel configurations. Splinting decreased strain and displacement, while longer implants consistently improved biomechanical performance. Optimal selection of implant orientation, splinting, and length may minimize peri-implant strain under functional loads. Findings are limited to in vitro conditions with static loading and a single implant system. Full article

To address the issues of narrow row spacing, complex terrain, and low fertilization efficiency in trenching and fertilizing operations for mountainous tea gardens, a dual-spiral integrated trenching and fertilizing machine was designed, and its key parameters were optimized using the discrete element method (DEM). The research aimed to improve the stability of trenching depth, uniformity of trench width, and fertilization accuracy to meet the needs of precision agriculture in tea gardens. A soil–tool interaction model was established using Extended Discrete Element Method (EDEM) simulation software, and the forward speed, spiral blade rotation speed, and spiral angle were optimized via the Box–Behnken design of response surface methodology. Simulation results showed that the optimal parameter combination was a forward speed of 0.37 m·s⁻¹, spiral blade rotation speed of 202.31 r·min⁻¹, and spiral angle of 23.13°, achieving a trenching depth stability coefficient of 98.12%, width uniformity coefficient of 97.44%, and soil coverage rate of 75.32%. After optimizing the fertilization device parameters, the coefficient of variation for fertilization uniformity decreased to 5.80%, the bilateral symmetry index approached 0, the target layer trenching rate reached 89.86%, and the fertilizer drift loss rate was only 3.00%. Prototype tests in tea gardens verified that the machine achieved a trenching depth stability coefficient of over 94.28% and fertilization uniformity of 94.29%, meeting the design requirements. This study provides an efficient trenching and fertilizing solution for hilly and mountainous tea gardens, promoting the transformation of trenching and fertilizing machinery from experience-driven to model-driven design. Full article

Variable cross-section rotors demonstrate significant potential for enhancing screw vacuum pump performance. This study proposes a variable-radius and variable-pitch screw rotor with a seven-segment fully smooth profile, accompanied by its parametric design methodology. Corresponding clearance design methods are provided, resulting in optimized clearance distribution. A thermodynamic model incorporating four leakage channels was developed. This model effectively simulates screw vacuum pump performance and has been experimentally validated. Systematic analysis was conducted on the effects of key parameters on pump geometric characteristics and performance, with comparative studies against two traditional constant cross-section rotors. Results demonstrate that the proposed design method enables rapid and precise generation of new 3D rotor models. The clearance optimization results validate the design expectations. The variable-radius design achieves cross-sectional variation, and its combination with variable pitch produces a dual internal compression effect, to which the variable radius contributes more significantly. With an increasing cone angle, the internal volume ratio rises significantly. Compared with conventional constant cross-section rotors, the rotor demonstrates superior performance in internal volume ratio, sealing characteristics, and structural integrity, notably cutting shaft power by 52.9% versus equal-pitch rotors. These findings provide an effective solution for developing high-performance screw vacuum pumps. Full article

Infiltrative lipomas involving the upper cervical spine present a significant surgical challenge, as the extensive muscular resection required for tumor control often leads to severe structural instability. This report describes the surgical treatment of an infiltrative lipoma that extensively invaded the cervical area in a 9-year-old dog. Following wide surgical debulking, a dual-plane stabilization strategy was employed. Ventral stabilization was attempted using standard C1–C2 transarticular screw fixation, while a modified dorsal stabilization technique anchored the occipital protuberance to the C2 spinous process using an ultra-high molecular weight polyethylene (UHMWPE) suture construct, combined with nuchal ligament reconstruction. Follow-up at 78 days revealed failure of the ventral implants, characterized by immediate improper positioning of the right screw and subsequent migration of the left screw. Despite these complications and confirmed tumor recurrence, the patient maintained normal neurological function and clinical cervical stability. This clinical course was suggestive of fibrous or early osseous union at the atlantoaxial joint. These findings suggest that the modified dorsal stabilization technique provided critical biomechanical support, effectively compensating for the compromised ventral fixation, and may represent a potential surgical option for managing extensive occipito-cervical instability in dogs. Full article

Background and Objectives: The management of periprosthetic tibial fractures distal to revision Total Knee Arthroplasty (TKA) presents a biomechanical challenge, often requiring extramedullary locking plates when long stems preclude nailing. While in femoral fractures the gap between the stem and plate is a well-documented stress riser, requiring implant overlap to prevent an inter-implant fracture, this specific biomechanical scenario has not been studied in the tibia, and it remains unclear if the femoral dogma of mandatory overlap applies to the straight, centrically loaded tibial anatomy. This study utilized Finite Element Analysis (FEA) to evaluate stress distribution in the tibial inter-implant gap. Materials and Methods: A comparative FEA was performed using a validated standardized tibia model simulating a healed distal fracture. Two cemented revision TKA constructs (50 mm and 80 mm stems) were modeled. These were paired with medial locking plates of varying lengths (10, 12, and 14 holes) to create different inter-implant distances. Eight distinct configurations, including non-plated controls, were subjected to physiological axial compression and three-point bending. Outcome measures included von Mises stress and total displacement. Results: The analysis revealed no significant stress concentration in the bone within the inter-implant zone across all plated models, regardless of the gap size. Instead, the addition of plates universally reduced bone stress compared to controls, effectively transferring load to the fixation hardware. Peak stresses were consistently observed in the proximal locking screws rather than the bone gap. The longest plates (14 holes) offered superior construct rigidity and stress distribution. Conclusions: Under the conditions evaluated in this preclinical finite element model, the tibia does not exhibit a biomechanical requirement for implant overlap to prevent stress risers. Our findings suggest that extramedullary fixation with the longest available anatomical locking plate represents a biomechanically plausible strategy for these fractures, even if an inter-implant gap remains. Full article

Parameter tuning for Active Disturbance Rejection Control (ADRC) in rolling mill hydraulic synchronization systems is critical for enhancing strip quality. Conventional manual trial-and-error methods often yield suboptimal results. This paper proposes a hybrid algorithm, WMA-PSO, integrating the Humpback Whale Migration Algorithm (WMA) with Particle Swarm Optimization (PSO) through an adaptive fusion weight strategy. This approach effectively balances global exploration and local exploitation, improving optimization accuracy and efficiency. Evaluation on the CEC-2005 benchmark suite shows that WMA-PSO outperforms several state-of-the-art algorithms. Simulation experiments on ADRC tuning in a rolling mill system demonstrate that the WMA-PSO-optimized controller achieves the smallest synchronization error and superior overall control performance compared to other methods. The results validate WMA-PSO as an effective tool for automated parameter tuning in complex industrial control systems. Full article

Objectives: Horizontal ridge augmentation remains a clinical challenge due to limitations in terms of spatial maintenance, graft stability and predictability of new bone formation. The umbrella-screw tent technique provides mechanical stability for particulate grafts, while adjuvants such as hyaluronic acid (HA) and polynucleotides (PN) may enhance biological remodeling. Evidence for this compound in implant-related bone augmentation is still scarce. Material and methods: In a single patient with a knife-edge alveolar ridge, augmentation was performed in regions 34 to 36 using the umbrella-screw tent technique. The defect was grafted with deproteinized bovine bone mineral (DBBM) mixed with hyaluronic acid (HA) and polynucleotides (PN), supplemented with platelet-rich fibrin (PFR) and covered with a resorbable collagen membrane. After six months, two implants were installed, and a biopsy was obtained by trepanation for histological and histomorphometric analysis. Results: Healing occurred without compromise, with no signs of infection or graft exposure. Horizontal bone gain averaged 4.5 mm, corresponding to a relative Target Performance Index (TPI-h) of 75%. Histomorphometric analysis revealed a total mineralized fraction of 76.4%, consisting of 36.1% newly formed bone and 40.3% residual DBBM particles. The xenogeneic granules were completely integrated into mature bone, with no signs of inflammation or foreign body reaction. Conclusion: The case report illustrates that the combination of DBBM with HA and PN, stabilized by the umbrella-screw tent technique, can lead to significant new bone formation and favorable graft integration. Although limited by its single-case design, the case report provides preliminary insights into the synergistic potential of HA and PN as biological enhancers in bone augmentation, warranting further controlled studies. Full article

The microstructural characteristics and fracture behavior of a magnetic pole screw were investigated here. The screw threads were produced by cold thread rolling. Microstructural analysis (OM, SEM, EBSD), mechanical testing (tensile, hardness, fastening), and fracture morphology observation were conducted. The results indicate that work hardening and microstructural deformation were introduced by the gradient plastic deformation in the screw thread. The elongated microstructure of ferrite and pearlite was obtained in the deformation zones, resulting in increased hardness and decreased plasticity. The thread root subsurface experienced severe localized indentation deformation and exhibited the highest hardness. The distinct forming stress states led to a notable difference in the hardened layer depth between the thread crest and root. The torsional overload fracture was initiated at the stress-concentrated thread root, where the work-hardened microstructure exhibited a limited capacity to accommodate large plastic deformation. The crack propagation was influenced by the gradient microstructure, following three primary propagation paths: transgranular through ferrite, along the ferrite–pearlite phase interface, and cracking through lamellar pearlite. The results provide theoretical support for material design and process optimization to achieve the production of high-performance screws with high strength and hardness at the thread surface and high plasticity in the center. Full article