Osman İyIbilgin

Introduction: The purpose of this study was to perform biomechanical pull-out comparisons between composite bone blocks and additively manufactured bone models using locked plate and screw systems. The hypothesis posited that the mean pull-out force of the 3D-printed models would demonstrate non-inferior pull-out strength compared to standard composite bones within a clinically acceptable 15% margin. A standardized pull-out mechanism was developed to evaluate its biomechanical reliability and its potential as a customizable alternative. Materials and methods: The study compared three groups: standard composite (Sawbones) blocks and two types of additively manufactured polylactic acid (PLA) blocks (grid and gyroid infill pattern), each measuring the same dimensions with 30% infill and mimicking a Sawbones block with 2 mm cortical thickness. A 6-hole LC-DCP titanium plate was fixed onto bone block models with dimensions of 29 × 170 × 42 mm using four screws, each measuring 36 mm in length, which were inserted perpendicularly and tightened to the same torque levels. Steel cables placed under the plate were connected to a mechanical testing setup, and pull-out tests were conducted to evaluate fixation strength. Seven replicate specimens were fabricated to ensure repeatability and reliability of the results. Results: Mean pull-out forces were 1784.4 ± 79.9 N for Sawbones, 1698.5 ± 134.3 N for Grid PLA ( n = 7), and 1908.7 ± 335.2 N for Gyroid PLA ( n = 7). Statistical analysis using a one-sample t-test showed that both 3D-printed models were non-inferior to the standard Sawbones model within a clinical acceptance margin of 15% ( p < 0.05). Conclusions: Additively manufactured models exhibit mechanical pull-out performance that is statistically non-inferior to traditional composite bone block models. These findings confirm that 3D-printed PLA-based grid and gyroid structures serve as reliable, cost-effective alternatives for orthopaedic mechanical research without compromising mechanical integrity.

Pediatric supracondylar humerus fractures are among the most common elbow injuries in children and require stable fixation to prevent complications. Kirschner (K) wire osteosynthesis is a widely used technique; however, the optimal wire configuration remains a subject of debate. This study aims to investigate the effects of three different K-wire configurations (crossed, medial-parallel, and lateral-parallel) on the fixation stability of pediatric supracondylar humerus fractures using finite element analysis (FEA). A three-dimensional finite element model of a pediatric humerus with a supracondylar fracture was constructed. Each of the three K-wire configurations was virtually applied to the model. To replicate physiological conditions, force (Z-axis) and moment (X- and Y-axes) components were applied under various loading scenarios, both individually and in combination. Mechanical parameters, including displacement, stress distribution, and rigidity, were analyzed for each configuration. The crossed K-wire configuration demonstrated superior structural stability compared to both medial-parallel and lateral-parallel configurations. It exhibited lower displacement values and more favorable stress distribution, particularly under rotational loading conditions, indicating higher mechanical resistance. The findings suggest that the crossed K-wire configuration provides enhanced fixation stability and may be the most effective technique for the surgical treatment of pediatric supracondylar humerus fractures. Additionally, this study confirms the utility of finite element analysis as a robust and reliable method for evaluating the biomechanical performance of orthopedic fixation methods.

In this study, the deformation behavior of armor (plate) systems composed of high-strength ballistic steels MARS 190 and MARS 240 arranged in various thicknesses and combinations was investigated under different projectile impact velocities and angles using both experimental methods and the finite element method (FEM). In the experimental stage, four different plate configurations were prepared: single steel plate, double steel plates, steel–rubber–steel, and steel–air gap–steel combinations. These configurations were subjected to ballistic impacts at varying velocities. For each configuration, the level of deformation, energy absorption capacity, and structural integrity were analyzed. The same test scenarios were modeled numerically using FEM, and the simulation results were validated through comparison with the experimental findings. Upon validating the analysis model, the number of composite plate models was increased. The results highlight the influence of impact velocity and plate composition on deformation behavior, revealing that multilayered and gapped structures effectively optimize energy distribution. The performance of different combinations of MARS 190 and MARS 240 materials was comparatively evaluated, and recommendations for effective armor design were provided. This study aims to contribute to engineering applications concerning the design of ballistic protection systems and material selection.

Additive manufacturing has revolutionized the production industry by enabling the fabrication of complex geometries. In recent years, significant advancements have been made in 3D printing using metal filament, particularly with materials such as 316L stainless steel. Known for its high strength, corrosion resistance, and ductility, 316L stainless steel is well suited for demanding applications in the medical, marine, and aerospace industries. However, secondary processes such as debinding and sintering can lead to changes in the dimensions and mechanical properties of the final product. This study investigates the effect of layer thickness on the mechanical properties of 316L stainless steel produced through additive manufacturing. Samples were produced with varying layer thicknesses (100, 200, 300, and 400 µm) and tested for tensile strength, hardness, and density. The results indicate that tensile strength increases with decreasing layer thickness. The highest tensile strength (432 MPa) and hardness (213 Hv) were observed at a layer thickness of 100 µm. Additionally, phase analyses and microstructural examinations were conducted. The primary phases identified in the samples were face-centered cubic (FCC) austenite and body-centered cubic (BCC) ferrite (δ). In this study, the manufacturing parameters with 316L filament have been optimized, and their impact on the mechanical properties has been examined.

Different types of plates are available to allow insertion of screws for internal fixation of long bone fractures. The aim of the study was to determine the effect of the insertion of screws at different angles on a long bone to the pull-out strength. Using 3D printed bone models, we tested the pull-out strength of screws in long bones at insertion angles between 0 and 40° with both finite element analysis and on printed models experimentally and compared the results. Test samples and cortical screws used were modeled with SolidWorks software and analyzed with Ansys software. As the screw insertion angle increases, the pull-out forces on the test specimens increase from 61.14 ± 3.5 N at 0° to 273 ± 6.8 N at 40° with an exception of a small drop between 15 and 20° from 235.4 ± 6.2 to 233 ± 6.9 N. Both methods showed an increase in the pull-out strength of screws as the insertion angle increases. This might be applicable in the clinical practice of bone fixation. Further studies on plate and screw fixation are needed to complement the findings.

El titanio (Ti) y sus aleaciones se encuentran entre los materiales más utilizados en aplicaciones biomédicas. Además de ser biocompatibles, estos materiales tienen una baja densidad, una alta resistencia a la corrosión y unas propiedades mecánicas notables. Es muy difícil producir piezas con geometría compleja utilizando métodos convencionales de pulvimetalurgia (PM) ya que este método se basa en dar forma a polvos bajo fuerzas uniaxiales utilizando moldes. La Inyección Aglutinante (Binder Jetting) es un tipo de técnica de fabricación aditiva que no necesita moldes para dar forma a los polvos. Este estudio se centra en comparar las propiedades de las piezas porosas de CP-Ti producidas con PM e Inyección Aglutinante. Las piezas se sinterizaron durante 120 min en una atmósfera de argón a 1200 °C. Después de la sinterización, se alcanzaron valores de densidad relativa de aproximadamente el 94% y el 92% en las muestras producidas por PM y con la impresora 3D, respectivamente. También se observó que la muestra producida con una presión de compactación de 25 MPa tiene una dureza de 317 ± 10 HV0.05 y un límite elástico bajo compresión de 928 MPa, mientras que la pieza producida con la impresora 3D tiene una dureza de 238 ± 8 HV0. 05 y un límite elástico bajo compresión de 342 MPa. Aunque la dureza y resistencia de las muestras producidas con la impresora 3D fueron menores que las de PM, sus propiedades son adecuadas para producir implantes que reemplacen las estructuras óseas.

Triboloji, makinelerde, birbiri ile çalışan parçalarda ve yüzeylerde sıklıkla karşılaşılan sürtünme, aşınma ve yağlama konularını inceleyen araştırma alanları arasında yeralmaktadır. Biyotriboloji ise, tribolojik etkilerin canlılar üzerindeki uygulamaları olarak tanımlanabilir. Bu kavram, özellikle implant tasarımı, imalatı ve uygulamaları sırasında göz önünde bulundurulması gereken en önemli etkenler arasında yer almaktadır. Canlılar üzerinde uygulanması ve geliştirilmesi planlanan implantların tasarımları çok iyi olsa bile, biyotriboloji konusundaki testler ve analizler gerçekleştirilmeden başarı elde edilmesi mümkün olmamaktadır. Bu nedenle, biyotriboloji konusunun daha iyi anlaşılması ve bu alanda çalışan araştırmacılara ışık tutarak yol göstermesi amacıyla bu makale hazırlanmıştır. Makalede, son 20 yılda biyotriboloji konusunda gerçekleştirilmiş teorik ve deneysel çalışmalar incelenerek değerlendirilmiş ve geleceğe bakış sunulmuştur.