Antegrade anterior column acetabulum fracture fixation with cannulated compression headless screws-A biomechanical study on standardized osteoporotic artificial bone

PURPOSE Due to the increase in life expectancy and high-energy traumas, anterior column acetabular fractures (ACFs) are also increasing. While open reduction and internal fixation (ORIF) is still the standard surgical procedure, minimally invasive, percutaneous fixation of osteoporotic acetabulum fractures (AF) are growing in popularity. The aim of this biomechanical study was to evaluate the biomechanical competence following antegrade fixation with a standard screw versus a cannulated compression headless screw. METHODS Eight anatomical osteoporotic composite pelvises were given an anterior column fracture. Two groups of eight specimens each (n = 8) for fixation with either a 6.5 mm cannulated compression headless screw in group Anterior Acetabulum Canulated Compression Headless Screw (AACCH), or with a 6.5 mm partially threaded cannulated screw in group Anterior Acetabulum Standard Screw (AASS) where compared. Each specimen was biomechanically loaded cyclically at a rate of 2 Hz with monotonically increasing compressive load until failure. Motions were assessed by means of optical motion tracking. RESULTS Initial construct stiffness trended higher in group AACCH at 152.4 ± 23.1 N/mm compared to group AASS at 118.5 ± 34.3 N/mm, p = 0.051. Numbers of cycles and corresponding peak load at failure, were significantly higher in group AACCH at 6734 ± 1669 cycles and 873.4 ± 166.9 N versus group AASS at 4440 ± 2063 cycles and 644.0 ± 206.3 N, p = 0.041. Failure modes were breakout of the screws around the proximal entry point. CONCLUSION From a biomechanical perspective, group AACCH was associated with superior biomechanical competence compared to standard partially threaded cannulated screws and could therefore be considered as valid alternative for fixation of anterior acetabulum fractures

Mechanical assessment of two hybrid plate designs for pancarpal canine arthrodesis under cyclic loading

Pancarpal canine arthrodesis (PCA) sets immobilization of all three carpal joints via dorsal plating to result in bony fusion. Whereas the first version of the plate uses a round hole (RH) for the radiocarpal (RC) screw region, its modification into an oval hole (OH) in a later version improves versatility in surgical application. The aim of this study was to mechanically investigate the fatigue life of the PCA plate types implementing these two features–PCA-RH and PCA-OH. Ten PCA-RH and 20 PCA-OH stainless steel (316LVM) plates were assigned to three study groups (n = 10). All plates were pre-bent at 20° and fixed to a canine forelimb model with simulated radius, RC bone and third metacarpal bone. The OH plates were fixed with an RC screw inserted either most proximal (OH-P) or most distal (OH-D). All specimens were cyclically tested at 8 Hz under 320 N loading until failure. Fatigue life outcome measures were cycles to failure and failure mode. Cycles to failure were higher for RH plate fixation (695,264 ± 344,023) versus both OH-P (447,900 ± 176,208) and OH-D (391,822 ± 165,116) plate configurations, being significantly different between RH and OH-D, p = 0.03. No significant difference was detected between OH-P and OH-D configurations, p = 0.09. Despite potential surgical advantages, the shorter fatigue life of the PCA-OH plate design may mitigate its benefits compared to the plate design with a round radiocarpal screw hole. Moreover, the failure risk of plates with an oval hole is increased regardless from the screw position in this hole. Based on these findings, the PCA plate with the current oval radiocarpal screw hole configuration cannot be recommended for clinical use

Data on the coefficient of friction and its prediction by a machine learning model as a function of time for open-cell AlSi10Mg-Al2O3 composites with different porosity tested by pin-on-disk method

This data article presents the experimental data of the wear behavior of four types of open-cell AlSi10Mg materials and open-cell AlSi10Mg-Al2O3 composites with different pore sizes under dry sliding conditions tested by pin-on-disk method. The data include the coefficient of friction (COF) as a function of time for each material, as well as the predictions of COF using a machine learning model - Extreme Gradient Boosting. The data were generated to investigate the effect of pore size and reinforcement on the friction and wear properties of open-cell AlSi10Mg-Al2O3 composites, which are promising materials for lightweight and wear-resistant applications. The data can also be used to validate theoretical models or numerical simulations of wear mechanisms in porous materials, as well as to optimize the material design and processing parameters to enhance the wear resistance of open-cell AlSi10Mg materials. The data are available in DWF and XLSX format and can be opened by any text editor or spreadsheet software. The data article is related to an original research article entitled “Production and Tribological Characterization of Advanced Open-Cell AlSi10Mg-Al2O3 Composites”, where the details of the experimental methods, the microstructural characterization, and the analysis of the wear mechanisms are provided [1]

Mechanical Properties Assessments for Materials of High Porosity and Light Alloys with Predominant Embedded Phases

In the present contribution, upgrading the findings of previous works, [11], new models are proposed for evaluation of effective mechanical properties of light alloys regarded as multiphase composites. This study concerns three - phase composites with high volume fraction of non-matrix phases. The elastic properties assessments of such materials are calculated by analytical approach based on the variant of Differential Effective Medium (DEM) method. Here in the methodology from [10, 11] is further developed for two cases: composite type A and composite type B. The composite A consists of matrix and two inclusion phases. The matrix material is much softer than the inclusions material of the first kind and at it is much harder than the inclusions of second kind. The composite B is a closed cell porous material. It is assumed that the high porosity is induced by spherical pores of two sets very different by size: Di≫diDi≫di. At high volume fraction of pore space the average diameter of small pores is comparable to the inter-pores distance (cell’s wall). For assessment of the elastic moduli of both composites A an B a two-step homogenization procedures are applied. New yield conditions for the composites A and B are derived to define the initial plastic state of composites. Hill’s strain energy equivalent condition and leading role of matrix are taken into account describing the transition point from elastic to plastic state.This research is carrying out in the frame of KMM-VIN - European Virtual Institute. The financial support of BG FSI through the grant DH 07/17/2016 ‘New approach for structure and properties design of amorphous and nanostructured metallic foams’ is gratefully acknowledged

Wear Analysis of an Advanced Al–Al2O3 Composite Infiltrated with a Tin-Based Alloy

In this study, a hybrid material is produced, and the effect of different loads varying from 40 to 60 N against an EN-31 steel counter disk on its wear behavior under dry sliding conditions at room temperature is studied. The tribological behavior is studied via the pin-on-disk method and analyzed using primary wear parameters, such as the coefficient of friction (COF), mass wear, and specific wear rate. The obtained results are compared with the results for B83 babbitt under the same wear test conditions. Microstructural observation with scanning electron microscopy (SEM) is performed along with X-ray energy dispersive spectroscopy (EDX) for chemical analysis conduction. The results from the wear experiments indicate that the hybrid material possesses a lower COF, mass wear, and specific wear rate as well as a higher wear resistance in comparison to the B83 babbitt specimen when subjected to the same test conditions. The results from the wear experiments indicate that by applying different loads of 40, 50, and 60 N, the hybrid material possesses a lower mass wear, specific wear rate, and COF specifically at a load of 40 N in comparison to the B83 babbitt specimen under the same test conditions. It was also observed that by increasing the load under dry sliding friction, the hybrid material increases its mass wear and specific wear rate

Production and Tribological Characterization of Advanced Open-Cell AlSi10Mg-Al₂O₃ Composites

In this study, advanced open-cell porous AlSi10Mg-Al2O3 composites have been successfully fabricated by replication of NaCl space holders. The tribological behavior under dry sliding conditions at room temperature of composites with different pore sizes was studied via the pin-on-disk method, and wear parameters, such as the coefficient of friction (COF) and mass wear, were determined. Micro-hardness tests have been performed to investigate the change in mechanical properties after the processing of the composite materials. Microstructural observation was conducted by means of light microscopy and scanning electron microscopy (SEM) along with chemical micro-analysis using an X-ray energy-dispersive spectroscopy (EDS) system. The obtained results revealed that the investigated AlSi10Mg-Al2O3 composites possess lower COF and mass wear than the open-cell porous AlSi10Mg material when subjected to the same test conditions. Furthermore, it was also reported that the effect of pore size is insignificant to the COF, and in relation to mass wear, the composite material with the larger pores shows better results

Data on mechanical properties of open-cell AlSi10Mg materials and open-cell AlSi10Mg-SiC composites with different pore sizes and strain rates

This data article describes the stress-strain curves, energy absorption and energy absorption efficiency of open-cell AlSi10Mg materials and open-cell AlSi10Mg-SiC composites with different pore sizes and strain rates. The data were obtained by quasi-static compression loading up to 60% strain at strain rates of 0.01 and 0.001 s−1 according to ISO 13,314:2011 standard. The data can be used to compare the effects of pore size and strain rate on the compressive properties of the materials. The data are related to the research article entitled “Fabrication, Experimental Investigation and Prediction of Wear Behavior of Open-Cell AlSi10Mg-SiC Composite Materials” (Kolev, M., Drenchev, L., & Petkov, V. (2023). Fabrication, Experimental Investigation and Prediction of Wear Behavior of Open-Cell AlSi10Mg-SiC Composite Materials. Metals, 13(4), 814. MDPI AG. Retrieved from http://dx.doi.org/10.3390/met13040814)