Fracture Characteristics Research Articles

Analysis of Rock Mechanical Characteristics and Establishment of an Evaluation System for Coal Measures in the Longtan Formation, Guizhou Province.

The mechanical properties of coal measure rocks and their evaluation significantly impact the process and efficacy of coal measure exploration and development. This study focuses on the Guizhou Longtan Formation coal measure. The mechanical and fracturing characteristics of coal measure rock samples are analyzed via well coring, geophysical logging, and indoor experiments. Additionally, predictive models for rock mechanical parameters are developed, and an evaluation system for the Longtan Formation coal measure rock mass is established. The findings are as follows: (1) Coal measure rocks in Guizhou's Longtan Formation exhibit a relatively low elastic modulus and tensile strength, but a substantial variation in compressive strength. The triaxial compressive strength, elastic modulus, and residual strength increase nonlinearly with increasing confining pressure. As the confining pressure increases, the failure mode of the mudstone and siltstone transitions from primarily splitting failure to shearing failure. (2) Strong correlations are calculated between logging parameters and rock mechanical parameters and are used to construct three regression prediction models, yielding an average prediction accuracy of approximately 85% for rock mechanical properties. (3) Considering the rock mechanical properties, rock mass structure and stratigraphic characteristics, and the occurrence environment related to the characteristics of rock mass affecting coal measure gas development, eight evaluation indices are selected. The analytic hierarchy process-entropy weighting method is used to determine the weights of the comprehensive evaluation indices, and a coal measure rock mass evaluation system is established by utilizing gray clustering analysis. The evaluation results categorize the mudstone group (mudstone and silty mudstone) as Classes III-IV, the fine sandstone group as Classes I and II, and the siltstone group (muddy siltstone and siltstone) as Classes II and III. A comparative analysis with fuzzy comprehensive evaluation results and extenics theory evaluation results demonstrated a high level of consistency. These findings benefit coal measure rock mechanics classification and quantitative research on rock mechanics properties, providing a solid foundation for efficient coal measure gas exploration and development.

Fracture Evolution during CO2 Fracturing in Unconventional Formations: A Simulation Study Using the Phase Field Method

With the introduction of China’s “dual carbon” goals, CO2 is increasingly valued as a resource and is being utilized in unconventional oil and gas development. Its application in fracturing operations shows promising prospects, enabling efficient extraction of oil and gas while facilitating carbon sequestration. The process of reservoir stimulation using CO2 fracturing is complex, involving coupled phenomena such as temperature variations, fluid behavior, and rock mechanics. Currently, numerous scholars have conducted fracturing experiments to explore the mechanisms of supercritical CO2 (SC-CO2)-induced fractures in relatively deep formations. However, there is relatively limited numerical simulation research on the coupling processes involved in CO2 fracturing. Some simulation studies have simplified reservoir and operational parameters, indicating a need for further exploration into the multi-field coupling mechanisms of CO2 fracturing. In this study, a coupled thermo-hydro-mechanical fracturing model considering the CO2 properties and heat transfer characteristics was developed using the phase field method. The multi-field coupling characteristics of hydraulic fracturing with water and SC-CO2 are compared, and the effects of different geological parameters (such as in situ stress) and engineering parameters (such as the injection rate) on fracturing performance in tight reservoirs were investigated. The simulation results validate the conclusion that CO2, especially in its supercritical state, effectively reduces reservoir breakdown pressures and induces relatively complex fractures compared with water fracturing. During CO2 injection, heat transfer between the fluid and rock creates a thermal transition zone near the wellbore, beyond which the reservoir temperature remains relatively unchanged. Larger temperature differentials between the injected CO2 fluid and the formation result in more complicated fracture patterns due to thermal stress effects. With a CO2 injection, the displacement field of the formation deviated asymmetrically and changed abruptly when the fracture formed. As the in situ stress difference increased, the morphology of the SC-CO2-induced fractures tended to become simpler, and conversely, the fracture presented a complicated distribution. Furthermore, with an increasing injection rate of CO2, the fractures exhibited a greater width and extended over longer distances, which are more conducive to reservoir volumetric enhancement. The findings of this study validate the authenticity of previous experimental results, and it analyzed fracture evolution through the multi-field coupling process of CO2 fracturing, thereby enhancing theoretical understanding and laying a foundational basis for the application of this technology.

Study on the mixed fracture characteristics of concrete-rock Brazilian disks with different fracture angles

The fracture characteristics of cracked straight-through Brazilian discs for concrete-rock composites (CSTBD-CRC) with different fracture inclination angles (Mode I-II) were investigated to evaluate the stability of concrete reinforcement engineering. Acoustic emission (AE) and digital image correlation (DIC) techniques were employed to study crack propagation and fracture modes in CSTBD-CRC Brazil splitting tests, as well as the entropy evolution of AE and DIC. Additionally, 3D scanning technology and fractal theory were utilized to investigate the effect of the fracture mode on the fracture surface morphology. The results indicate that both the fracture energy and peak load of the CSTBD-CRC increase with increasing fracture inclination angle. Moreover, the section fractal dimensions of 0°, 10°, 15° and 25° samples are 2.01879, 2.01528, 2.01186, and 2.01072. Shear fracture mode increases as the dip angle increases and the fracture surface morphology decreases in fractal dimension. Notably, sharp increases in entropy values for both AE and DIC occurred at peak load, suggesting their use as failure criteria for CSTBD-CRC specimens. Furthermore, cracks were found to initiate at the tips of preexisting cracks within the concrete. The displacement in the x direction undergoes the most significant changes on both sides of the crack during crack growth, while the strain in the x direction experiences its greatest variations at the crack location.

Explosive stress wave propagation and fracture characteristics of rock-like materials with weak filling defects

Filling-type defects have a non-negligible effect on the propagation of explosive stress waves in rock. Combined with the new dynamic caustics experimental system and ANSYS/LS-DYNA numerical simulation platform, the research on the propagation characteristics of explosive stress wave and fracture characteristics of rock-like materials containing weak filling defects with different ductility has been carried out. Firstly, we analyzed the influence of weak filling on the propagation of blast-induced cracks, explored the “guiding” and “stopping” effects of weak filling on cracks, and analyzed the mechanical characteristics of crack propagation. Secondly, the effect of planar weak filling ductility on the damage degree of blasted medium was quantitatively evaluated. Thirdly, the influence of weak filling on the fluctuation characteristics of explosive stress wave was investigated. Then, the mechanical response behavior of the specimens was analyzed, and the results showed that the compaction and slip behaviour characteristics of the weak filling have some variability in degree, some continuity in time, some correlation in space and are affected by the ductility of the planar weak filling. In addition, the stress wave and weak filling interaction mechanism was elucidated. The conclusions of the analysis have positive reference value for understanding the explosion mechanics mechanism of defective rock masses.

Investigation of two collinear cracks in fiber reinforced composites under thermal loading

The objective of this paper is to explore the transient behaviors of fiber reinforced composites with two embedded collinear cracks subject to a sudden thermal shock. The orthotropic composites with both the vertically oriented and horizontally aligned fibers are examined to present a systematic comparison. By means of the integral transform methodology and singular integral equations, the thermal and elastic governing equations are solved numerically to determine the transient thermal process and stress intensifications around the crack tips. Parametric investigations are carried out for fiber volume fractions and crack distances. The findings would be beneficial to a more thorough knowledge of fibrous composites’ fracture characteristics under thermal shocks, which helps material design and structural optimization of the composites with fiber reinforcements.

Clinical decision making in the assessment and treatment of closed hand fractures: A scoping review.

Closed hand fractures represent a significant proportion of emergency department attendances, result in substantial health service utilisation and have a detrimental effect on quality of life. Increasingly, hand therapists in the United Kingdom provide first line fracture treatment. However, the knowledge and skills required to work in such an extended scope capacity have not been elucidated or standardised. This literature review synthesises and reports evidence for the knowledge requisite of clinicians to make evidence-based treatment decisions for patients with hand fractures. A systematic search was undertaken, using Embase, MEDLINE, PsychInfo and CINAHL electronic databases. Inclusion criteria were English language, full research reports of studies assessing of the reliability or validity of the decision-making process in hand fracture treatment published between 2013 and 2023. Data were summarised narratively. 15 studies met inclusion criteria; most assessed decision making for metacarpal fractures. Studies on imaging (n = 4) suggested the reliability of plain radiograph interpretation of hand fracture characteristics such as angulation is good and similar across various levels of experience. Agreement between surgeons and therapists in choosing surgical or nonsurgical treatment was generally good, but factors influencing decision making remained unclear. No evidence was identified that explored clinical assessment knowledge (subjective or objective patient factors) or the specific competencies required to treat hand fractures. There is limited evidence for the knowledge and skills required of clinicians for the competent assessment and treatment of hand fractures. Stakeholder consensus work is required to develop robust competencies and standardise practice.

Analysis of shear fracture characteristics and energy evolution of salt rock under real-time coupled thermo-mechanical conditions

Studying the shear fracture behavior of salt rock is of great importance for the identification of precursor information for geological disasters such as underground salt cavern caprock slippage, fault instability displacement, and zonal destruction of the surrounding rock. Despite its undeniable importance, research on the shear fracture characteristics of salt rock under real-time high-temperature and high-pressure triaxial conditions remains scarce. To address this research gap, this study employed a self-developed rock real-time high-temperature and high-pressure multi-field coupled triaxial universal testing machine to perform triaxial shear fracture tests on salt rock punch through shear (PTS) specimens across a wide range of confining pressures (0 to 25 MPa) and real-time temperatures (20 °C to 600 °C). Additionally, the internal pore fracture structures of the salt rock after different coupled thermo-mechanical (TM) treatments were examined using micro-computed tomography (MCT) and metallographic microscopy. The results reveal the complexity of fracture behavior in salt rock. At normal temperature and pressure, salt rock specimens primarily fractured into short rods and hollow cylindrical forms, with wing cracks appearing on the surfaces of the cylinders. Under high-temperature and high-pressure conditions, the salt rock exhibited more intense shear slippage phenomena, although the specimens did not undergo complete fracturing. Notably, the internal pore fractures in the salt rock under real-time coupled high-temperature and high-pressure displayed a competitive interaction between self-healing and thermal damage, leading to a significant nonlinear increase in mode II fracture toughness with temperature. Through the analysis of energy absorption and dissipation, this study further elucidates the shear fracture mechanism of salt rock under coupled TM conditions. Overall, the findings of this paper not only deepen our understanding of the mechanical behavior of salt rock under high-temperature and high-pressure conditions but also provide crucial theoretical support for the design and risk management of underground salt cavern projects.

Surgical versus conservative treatment for odontoid fractures in older people: an international prospective comparative study.

The optimal treatment for odontoid fractures in older people remains debated. Odontoid fractures are increasingly relevant to clinical practice due to ageing of the population. An international prospective comparative study was conducted in fifteen European centres, involving patients aged ≥55years with type II/III odontoid fractures. The surgeon and patient jointly decided on the applied treatment. Surgical and conservative treatments were compared. Primary outcomes were Neck Disability Index (NDI) improvement, fracture union and stability at 52weeks. Secondary outcomes were Visual Analogue Scale neck pain, Likert patient-perceived recovery and EuroQol-5D-3L at 52weeks. Subgroup analyses considered age, type II and displaced fractures. Multivariable regression analyses adjusted for age, gender and fracture characteristics. The study included 276 patients, of which 144 (52%) were treated surgically and 132 (48%) conservatively (mean (SD) age 77.3 (9.1) vs. 76.6 (9.7), P = 0.56). NDI improvement was largely similar between surgical and conservative treatments (mean (SE) -11 (2.4) vs. -14 (1.8), P = 0.08), as were union (86% vs. 78%, aOR 2.3, 95% CI 0.97-5.7) and stability (99% vs. 98%, aOR NA). NDI improvement did not differ between patients with union and persistent non-union (mean (SE) -13 (2.0) vs. -12 (2.8), P = 0.78). There was no difference for any of the secondary outcomes or subgroups. Clinical outcome and fracture healing at 52weeks were similar between treatments. Clinical outcome and fracture union were not associated. Treatments should prioritize favourable clinical over radiological outcomes.

Flexural and fracture characterization of UHPGC notched beam with various glass sand replacement ratios and steel fiber contents

The preparation process of quartz sand (QS) can cause serious environmental pollution, which is particularly important to find a new replacement material for QS in cement-based construction materials. In this study, an economical and environmentally friendly ultra-high performance glass sand concrete (UHPGC) was prepared by partially replacing QS in conventional ultra-high performance concrete (UHPC) with glass sand (GS) ground from waste glass. The effects of material composition characteristics including water-binder ratio (W/B), GS replacement ratio, and steel fiber content on the flexural and fracture characteristics of UHPGC notched beams were investigated based on response surface method (RSM) and acoustic emission (AE) monitoring. The results indicate that the GS replacement rate presents almost no effect on the tensile strength and flexural toughness of the specimens while reducing the water-binder ratio or increasing the steel fiber content can significantly improve the flexural tensile strength of UHPGC notched beams. UHPGC notched beams show the best performance when the W/B is 0.17, the steel fiber content is 3 %, and the GS replacement rate is 50 %. By analyzing and comparing the AE parameters and fracture modes, the discrepancies in flexural and fracture properties of UHPGC notched beams with variable material composition characteristics can be elucidated. Among them, the low water-binder ratio or high steel fiber content has a significant effect on the fracture characteristics and fracture process of the specimens, while the GS replacement rate exhibits negligible effect.

Comparison of Titanium versus Resorbable Intramedullary Nailing in Pediatric Forearm Fractures.

Pediatric forearm fractures, particularly involving the shaft or diaphysis, are common injuries typically resulting from accidental trauma during various activities. Traditional treatment involves closed reduction and casting; however, surgical intervention may be necessary in certain cases. The gold standard surgical approach utilizes elastic stable intramedullary nailing (ESIN), but a newer technique uses bioabsorbable intramedullary nails made of poly(lactic-co-glycolic acid) (PLGA). This study aims to compare the outcomes of these two surgical methods in pediatric diaphyseal forearm fractures. We retrospectively reviewed 86 patients who underwent operative treatment due to the diaphyseal fractures of the forearm in the Surgical Division, Department of Pediatrics, Medical School, University of Pécs, Pécs, Hungary between 2018 and September 2022. The mean age was 9.48 (ranging from 4 to 17). A total of 41 patients underwent surgery with PLGA implants (RESIN technique), while 45 patients were treated with titanium elastic nails (ESIN technique). Various factors including patient demographics, injury mechanisms, fracture characteristics, and complications were assessed. Both groups showed similar gender distribution, with a majority of fractures occurring in boys (the male-female ratio was 31:10 in the PLGA group, while in the titanium elastic nailing (TEN) group, this ratio was 29:16, with no statistical difference between the groups (p > 0.005). The average age of the patients treated with PLGA implants (8.439 years) was lower compared to those treated with titanium nails (10.422 years). A statistically significant difference was found regarding the average age of the two groups (p = 0.0085). Left-sided injuries were more prevalent in both groups (59% of the cases in the PLGA group and 69% in the TEN group, with no statistically significant difference, p = 0.716), and fractures typically involved both the radius and ulna. This represents 93% of the cases in the PLGA group and 80% in the TEN group. Regarding the involvement of bones, we also did not find a statistically significant difference (p = 0.123). The mechanisms of injury predominantly involved indirect force, such as falls (30 cases in the PLGA group and 27 cases in the TEN group), and no statistically significant difference was found (p = 0.139) regarding the mechanism of the injury. Complication rates were lower in the PLGA group (7%) compared to the titanium group (20%). The treatment of pediatric diaphyseal forearm fractures using PLGA implants appears to be a viable alternative to traditional titanium implants. Advantages include no need for secondary surgery and associated cost savings and reduced complication rate and stress associated with anesthesia and surgery. Prospective randomized trials are warranted to further validate these findings and explore long-term outcomes.

Microstructural Evolution and Mechanical Behaviors of Cf/Cm-SiC-(ZrxHf1−x)C Composites with Different Carbon Matrices

In this study, two types of porous Cf/Cm composites were obtained by introducing pyrolytic carbon (PyC) and pyrolytic carbon/furan resin carbon (PyC/FRC). Subsequently, Cf/Cm-SiC-(ZrxHf1−x)C composites with different carbon matrices were prepared by introducing SiC and (ZrxHf1−x)C matrices into the porous Cf/Cm composites via the reactive melt infiltration method, specifically termed as Cf/PyC-SiC-(ZrxHf1−x)C and Cf/PyC/FRC-SiC-(ZrxHf1−x)C composites. The microstructures of the porous Cf/Cm and Cf/Cm-SiC-(ZrxHf1−x)C composites with different carbon matrices were examined, and a comprehensive analysis was conducted on microstructural evolution and mechanical behaviors of the Cf/Cm-SiC-(ZrxHf1−x)C composites. The results indicate that both Cf/Cm-SiC-(ZrxHf1−x)C composites underwent similar microstructural evolution processes, differing only in terms of evolution kinetics and final microstructure. Differences in the pore structures of porous Cf/Cm composites, as well as in the reactivities of carbon matrices, were identified as primary influencing factors. Additionally, both Cf/Cm-SiC-(ZrxHf1−x)C composites exhibited “pseudo-ductile” fracture characteristics, with flexural strengths of 214.1 ± 8.8 MPa and 149.6 ± 12.2 MPa, respectively. In the Cf/PyC-SiC-(ZrxHf1−x)C composite, crack initiation during loading primarily originated from the ceramic matrix, while in the Cf/PyC/FRC-SiC-(ZrxHf1−x)C composite, failure initially arose from the residual FRC matrix. Excessive fiber corrosion and the presence of residual low-modulus FRC matrix resulted in lower mechanical performance.

Review of Incidence and Risk Factors for Spinal Fauctures in Canines

A survey was conducted to analyze vertebral fractures in dogs presented to the Madras Veterinary College Orthopaedic Outpatient Unit during a period of one and half year. A total of 24 cases were included, predominantly males with an average weight of 16 to 18 kilograms. The primary causes identified were road traffic accidents (n=15) and high-rise syndrome (n=9), affecting predominantly dogs aged 5 months to 2 years (n=14). Non-descript breeds were most commonly affected. Fractures were most frequently observed in the caudal thoracic vertebrae (T11 to L1). CT myelography revealed ventral displacement in cases of luxation, primarily affecting the thoracolumbar and lumbosacral regions. This study underscores the prevalence and characteristics of vertebral fractures in dogs, highlighting the need for prompt diagnosis and appropriate management strategies.

Study on mechanical properties and damage characteristics of acid corrosion in granite based on NMR technology

In acidic environments, rock masses are frequently subjected to severe chemical corrosion, resulting in the initiation of numerous geological engineering disasters. This study aimed to collect physical and mechanical parameters of granite exposed to prolonged acid corrosion and analyze fracture characteristics using acoustic emission (AE) techniques. Additionally, it examined the evolution of pore structure and damage mechanisms through the use of low-field nuclear magnetic resonance (NMR) and fractal theory. The results demonstrate a monotonic decrease in mass, volume, density, P-wave velocity, and S-wave velocity of granite with increasing corrosion time. Particularly notable is the phased reduction observed in uniaxial compressive strength and elastic modulus. The transition from brittle to ductile failure in corroded granite is accompanied by a gradual decrease in internal fracture strength. The trend in the correlation dimension reveals the relationship between the formation time of the main fracture surface and the pore structure. Additionally, total porosity and macropores (D, Da) exhibit significant fractal characteristics. The fractal dimension correlates positively with the damage variable and inversely with uniaxial compressive strength and elastic modulus. This indicates that more severe pore structure damage leads to a higher fractal dimension and lower mechanical performance. Among these, Da demonstrates higher sensitivity in characterizing rock mechanical properties. These findings provide important basis for evaluating the stability of granite geotechnical engineering in acidic environments.

A new device and calibration method for the fracture energy testing of single-particle impact

This study presents a piezoelectric fast load cell (PFLC) as a novel device for testing single particle fracture energy under impact and proposes a collision model for measurement and calibration. The research examined various models, modifying the long-rod model to create a more practical short-rod model describing the contact dynamics during collision processes. Through back-calculating the Young's modulus of glass beads, the optimized measurement settings are calibrated for practical use based on the short-rod model, which is corroborated by comparison with fracture probabilities obtained from the drop weight tests and PFLC. It was verified that the observed fracture characteristics of ore align with established principles of fracture mechanics, validating the testing approach. The PFLC offers a cost-effective and compact substitute to classic ultra-fast load cell (UFLC), potentially enhancing the adoption of advanced comminution models like the Tavares Model.

Specially Structured AgCuTi Foil Enables High-Strength and Defect-Free Brazing of Sapphire and Ti6Al4V Alloys: The Microstructure and Fracture Characteristics.

A novel AgCuTi brazing foil with a unique microstructure was developed, which could achieve strong vacuum brazing of Ti6Al4V (TC4) and sapphire. The brazing foil was composed of Ag solid solution (Ag(s,s)), Cu solid solution (Cu(s,s)), and layered Ti-rich phases, and had a low liquidus temperature of 790 °C and a narrow melting range of 16 °C, facilitating the defect-free joining of TC4 and sapphire. The sapphire/TC4 joint fabricated by using this novel AgCuTi brazing foil exhibited an outstanding average shear strength of up to 132.2 MPa, which was the highest value ever reported. The sapphire/TC4 joint had a characteristic structure, featuring a brazing seam reinforced by TiCu particles and a thin Ti3(Cu,Al)3O reaction layer of about 1.3 μm. The fracture mechanism of the sapphire/TC4 joint was revealed. The crack originated at the brazing seam with TiCu particles, then propagated through the Ti3(Cu,Al)3O reaction layer, detached the reaction layer from the sapphire, and finally penetrated into the sapphire. This study offers valuable insights into the design of active brazing alloys and reliable metal-ceramic bonding.

Development characteristics of natural fractures in tight sandstone reservoirs and their controlling factors: upper Triassic Xujiahe Formation, western Sichuan Basin

Development characteristics of natural fractures in tight sandstone reservoirs and their controlling factors: upper Triassic Xujiahe Formation, western Sichuan Basin

Mechanical and microstructure characterisation of 2.5D C/C-SiC composites applied for the brake disc of high-speed train

Carbon fibre reinforced silicon carbide (C/C-SiC) composite materials have attracted increasing attention in brake system of high-speed trains, due to their low density, high specific strength, thermal stability, and frictional wear performance. This study aims to explore the mechanical properties of the 2.5D C/C-SiC composites, in order to characterise its potential application to the friction braking system of high-speed trains. To comprehensively evaluate the mechanical performance of the 2.5D C/C-SiC composites, the chemical vapor infiltration (CVI) method was adopted to prepare novel samples with high densification and low content of residual Si. The mechanical properties and failure mechanisms of the composites were investigated under various loading conditions, including tension, compression, bending, and shear tests. The experimental results indicated that the 2.5D C/C-SiC composites exhibited superior mechanical properties, with average in-plane tensile strength, compressive strength, bending strength, and interlaminar shear strength reaching 127.67 MPa, 326.92 MPa, 355.74 MPa, and 9.77 MPa, respectively, which are 2–8 times higher than the mechanical properties of C/C-SiC composites in existing publications. Under different loading conditions, the composites demonstrated characteristics of ductile fracture, pseudo-plastic compression fracture, pseudo-plastic bending fracture, and brittle shear fracture. Both high fibre content and the formation of SiC structure were advantageous for enhancing the load-bearing performance of C/C-SiC composites. The outstanding mechanical properties of the 2.5D C/C-SiC composite render the brake disc highly resistant to deformation and cracking under high stress, thereby enhancing its durability and establishing it as the ideal material for the next generation of high-speed train brake discs.

Tensile deformation and failure of AlSi10Mg random cellular metamaterials

Cellular metamaterials are an emerging class of porous materials, in which the topology of the solid is precisely-engineered to achieve attractive combinations of properties. This work specifically examines the tensile response of a novel type of cellular metamaterials, in which pores of arbitrary elliptical shape are randomly-dispersed into an aluminum alloy matrix. Their porous mesostructure is generated numerically via a random sequential absorption algorithm, and is fabricated by laser powder bed fusion from AlSi10Mg powders. The results – obtained by means of digital image correlation combined with X-ray tomography – highlight the advantages offered by a random cellular topology. They are notably a low sensitivity to geometric imperfections (which inevitably result from manufacturing), coupled with the ability to delay long-wavelength strain localization, which is in turn responsible for failure. Structural disorder also leads to highly heterogeneous deformation patterns, which result from the interaction between geometric pores and promote void growth and coalescence during plastic straining. The presence of manufacturing defects exacerbates void interaction and promotes early plastic flow localization. Interestingly, experiments reveal that this class of porous solids effectively displays features of the ductile fracture of metals at the mesoscale. For example, void-sheeting is observed with increasing pore aspect ratio and is accompanied by large geometric distortions of the voids upon coalescence. Measured data for the pore strains are highly scattered and show a departure from McClintock’s model predictions for the voids within the fracture band. Collectively, this study highlights the potential offered by random porous metamaterials, which can be harnessed to revisit the complex mechanisms of ductile fracture at the mesoscale.

Risk factors for malalignment after intramedullary nail treatment of distal tibia fractures with associated fibula fractures

PurposeMalalignment of distal tibia fractures can lead to malunion/nonunion or alter the limb mechanical axis which may cause arthritis. Proposed methods to decrease malalignment include fibular fixation or multiplanar interlocking screws, however these remain controversial. This study aimed to identify factors associated with malalignment in distal tibial fractures with associated fibular shaft fractures.MethodsA retrospective review was performed of distal tibia fractures with associated fibular shaft fractures treated with intramedullary nailing at two level one trauma centers between 2015 and 2019. Cases involving malalignment (> 5° of deviation from anatomic axis on either coronal/sagittal axis) on final follow-up (minimum three months postoperatively) were compared to those without malalignment with regard to demographics, fracture characteristics, intraoperative characteristics, and complications.ResultsThe rate of malalignment was 13%. On multivariate analysis, multiplanar distal interlocking screw fixation (odds ratio [OR], 0.18; 95% confidence interval [CI] 0.03–0.92) was associated with a decreased rate of final malalignment, while nail diameter > 10 mm was associated with a higher rate (OR, 4.05; 95% CI 1.25–13.11). Fibular fixation was not associated with malalignment.ConclusionMultiplanar distal interlocking screws may protect against malalignment. Fibula fixation does not appear associated with a decreased rate of malalignment in distal tibia fractures treated with intramedullary nails.Level of EvidenceIII.

Upper-Extremity Injuries in a Level 1 Trauma Center Following Border Wall Height Increase

PurposeFrom 2018-2019, the height of over 400 miles of southern border wall was raised to 30 feet. Our aim was to evaluate the impact of the increase in border wall height on upper extremity injuries sustained via barrier fall. MethodsA retrospective review of patients admitted with upper extremity injuries sustained via border wall fall between January 2015 and December 2022 at a Level 1 trauma center serving the United States- Mexico border. Patients admitted between 2015-2018 were included in the pre-increase group, and those admitted between 2019-2022 were included in the post-increase group. Demographic data, injury severity metrics, fracture characteristics, operative treatments, hospital charges, and lengths of stay were compared. Results110 patients were identified, with 16 pre-increase and 94 post-increase. Following the barrier height increase, patients had higher injury severity scores. Radial fractures were most common pre- and post-increase and accounted for nearly a third of all fractures. Post-increase upper extremity trauma patients required more operative events (2.15 ± 2.10 vs. 1.44 ± 0.73 pre-increase). The average cost for each patient’s hospital stay also quadrupled after the increase in wall height ($397,632 ± $1,057,574 vs. $98,978 ± $84,169 pre-increase). ConclusionsThe increase in overall injury severity and costly inpatient treatment of upper extremity injuries among patients who fell from the border following construction has placed additional stress on an already strained healthcare system.