Quantitative Assessment of the Influence of Tensile Softening of Concrete in Beams under Bending by Numerical Simulations with XFEM and Cohesive Cracks

Results of the numerical simulations of the size effect phenomenon for concrete in comparison with experimental data are presented. In-plane geometrically similar notched and unnotched beams under three-point bending are analyzed. EXtended Finite Element Method (XFEM) with a cohesive softening law is used. Comprehensive parametric study with the respect to the tensile strength and the initial fracture energy is performed. Sensitivity of the results with respect to the material parameters and the specimen geometry is investigated. Three different softening laws are examined. First, a bilinear softening definition is utilized. Then, an exponential curve is taken. Finally, a rational Bezier curve is tested. An ambiguity in choosing material parameters and softening curve definitions is discussed. Numerical results are compared with experimental outcomes recently reported in the literature. Two error measures are defined and used to quantitatively assess calculated maximum forces (nominal strengths) in comparison with experimental values as a primary criterion. In addition, the force—displacement curves are also analyzed. It is shown that all softening curves produce results consistent with the experimental data. Moreover, with different softening laws assumed, different initial fracture energies should be taken to obtain proper results.

A COMPARATIVE STUDY ON FUNCTIONAL OUTCOME OF UNSTABLE INTERTROCHANTERIC FRACTURE IN ELDERLY TREATED WITH BIPOLAR HEMIARTHROPLASTY AND DYNAMIC HIP SCRE

Trochanteric hip fractures in elderly patients have beneted from advances in internal xation. Early failure of internal xation occurs however in a number of cases. The failure after internal xation had been due to initial fracture pattern, communication, sub-optimal fracture xation and poor bone quality. The aim of this prospective comparative study is to analyze the short term follow up results of unstable Intertrochanteric fractures in elderly treated with bipolar hemiarthroplasty and dynamic hip screw (DHS) xation.

The outcome of the uncemented acetabular component in delayed total hip arthroplasty following acetabular fractures

Aims After failed acetabular fractures, total hip arthroplasty (THA) is a challenging procedure and considered the gold standard treatment. The complexity of the procedure depends on the fracture pattern and the initial fracture management. This study’s primary aim was to evaluate patient-reported outcome measures (PROMs) for patients who underwent delayed uncemented acetabular THA after acetabular fractures. The secondary aims were to assess the radiological outcome and the incidence of the associated complications in those patients. Methods A total of 40 patients underwent cementless acetabular THA following failed treatment of acetabular fractures. The postoperative clinical and radiological outcomes were evaluated for all the cohort. Results The median (interquartile range (IQR)) Oxford Hip Score (OHS) improved significantly from 9.5 (7 to 11.5), (95% confidence interval (CI) (8 to 10.6)) to 40 (39 to 44), (95% CI (40 to 43)) postoperatively at the latest follow-up (p < 0.001). It was worth noting that the initial acetabular fracture type (simple vs complex), previous acetabular treatment (ORIF vs conservative), fracture union, and restoration of anatomical centre of rotation (COR) did not affect the final OHS. The reconstructed centre of rotation (COR) was restored in 29 (72.5%) patients. The mean abduction angle in whom acetabular fractures were managed conservatively was statistically significantly higher than the surgically treated patients 42.6° (SD 7.4) vs 38° (SD 5.6)) (p = 0.032). We did not have any case of acetabular or femoral loosening at the time of the last follow-up. We had two patients with successful two-stage revision for infection with overall eight-year survival rate was 95.2% (95% CI 86.6% to 100%) with revision for any reason at a median (IQR) duration of follow-up 50 months (16 to 87) months following THA. Conclusion Delayed cementless acetabular THA in patients with previous failed acetabular fracture treatments produces good clinical outcomes (PROMS) with excellent survivorship, despite the technically demanding nature of the procedure. The initial fracture treatment does not influence the outcome of delayed THA. In selected cases of acetabular fractures (either nondisplaced or with secondary congruency), the initial nonoperative treatment neither resulted in large acetabular defects nor required additional acetabular reconstruction at the time of THA. Cite this article: Bone Jt Open 2021;2(12):1067–1074.

Risk Factors for Aseptic Revision of Operatively Treated Ankle Fractures

Background: Early revision rates within 12 months after ankle fracture open reduction internal fixation (AF-ORIF) are fairly low; however, they remain relevant given the volume of ankle fractures occurring annually. Understanding these rates is complex because reoperation due to technical or mechanical complications is typically reported alongside soft tissue–related problems such as symptomatic hardware, wound dehiscence, or infection. There are limited data identifying risk factors specifically for revision of ankle fracture fixation in the absence of soft tissue complications. Understanding variables that predispose to aseptic technical and mechanical failure without this confounder may provide insight and improve patient care. Methods: A retrospective cohort study was performed at 2 large academic medical centers. Research Patient Data Registry (RPDR) data available from 2002 to 2019 were used to identify patients who underwent aseptic revision of AF-ORIF within 12 months (n = 33). A control group (n = 100) was selected by identifying sequential patients who underwent AF-ORIF not requiring revision within 12 months. Multiple factors were recorded for all patients in both cohorts. Each fracture was also evaluated according to the Ankle Reduction Classification System (ARCS) of Chien et al,8 which categorizes biplanar talar displacement in relation to a central tibial plumb line into 1 of 3 grades: A (0-2 mm), B (3-10 mm), and C (>10 mm). Adapted from its original purpose of grading reduction quality, we applied ARCS to pre-reduction radiographs to assess initial fracture displacement. All variables collected were compared in univariate analysis. Variables that achieved significance in univariate comparisons were included as candidates for multivariable analysis. Results: Final multivariable logistic regression modeling demonstrated the following factors to independently predict the need for aseptic revision surgery: documented falls in the early postoperative period (aOR, 298; 95% CI, 15.4, 5759; P < .001), movement-altering disorders (aOR, 81.7; 95% CI, 4.12, 1620; P = .004), a nonanatomic mortise (medial clear space [MCS] > superior clear space [SCS]) on immediate postoperative imaging (aOR, 38.4; 95% CI, 5.53, 267; P < .001), initial coronal plane tibiotalar displacement >10 mm and sagittal plane tibiotalar dislocation (ARCS-C) (aOR vs ARCS-A, 25.8; 95% CI, 2.81, 237; P = .004), substance abuse (aOR, 15.7; 95% CI, 2.66, 92.8; P = .002), and polytrauma (aOR, 12.3; 95% CI, 2.02, 74.8; P = .006). Conclusion: In this investigation we found a notable increase in risk for revision surgery after AF-ORIF for patients who had one of the following: (1) falls in the early postoperative period, (2) movement-altering disorders, (3) a nonanatomic mortise (MCS > SCS) on immediate postoperative imaging, (4) more severe initial fracture displacement, (5) substance abuse, or (6) polytrauma. Identifying these factors may allow surgeons to better understand risk and counsel patients, and may serve as future targets for intervention aimed at improving patient safety and outcomes after ankle fracture ORIF. Level of Evidence: Level III, retrospective cohort study.

Propagation of Cryogenic Thermal Fractures from Unconfined PMMA Boreholes

In cryogenic fracturing, a rock surface exposed to cryogenic fluids undergoes a large thermal gradient, and the resultant local tensile stress overcomes rock strength and initiates fractures. This study investigates the development of cracks generated from the cryogenic treatment of a borehole under no external confining stress on specimens. The experiments were performed on transparent PMMA specimens to observe fracture proliferation around boreholes. Liquid nitrogen was flowed through the boreholes to cool the borehole surface. The results show that initial fracture growth is characterized by abrupt starts and stops, and as the fracture propagates outward, the growth appears more continuous. In an early stage, horizontal/radial fractures and vertical fractures are the defining patterns. Horizontal fractures tend to be separated by a specific exclusion distance (i.e., spacing between cracks). While distinct horizontal/vertical fractures and exclusion distance manifest themselves at an early stage, fractures resulting from fracture interactions and curvatures can develop into complex shapes at later stages. Cryogenic thermal loading induces distinctively curved fractures. The tendency of curvature may prevent greater penetration. An increase in the borehole pressure during liquid nitrogen flow, however, can lessen fracture tortuosity and facilitate radial propagation. A high flow pressure and rate are also advantageous in that they accelerate cooling and fracture propagation.

Study on the Fracture Toughness of Polypropylene–Basalt Fiber-Reinforced Concrete

To study the hybrid effects of polypropylene fiber and basalt fiber on the fracture toughness of concrete, 13 groups of notched concrete beam specimens with different fiber contents and mass ratios were prepared for the three-point bending test. Based on acoustic emission monitoring data, the initiation cracking load and instability load of each group of specimens were obtained, and the fracture toughness parameters were calculated according to the double-K fracture criterion. The test results show that the basalt fiber-reinforced concrete has a greater increase in initial fracture toughness, and the toughness of coarse polypropylene fiber-reinforced concrete is more unstable. Moreover, after the coarse polypropylene fiber content reaches 6 kg/m3 and the basalt fiber content reaches 3 kg/m3, increasing the content will not significantly improve the fracture toughness of the concrete. The polypropylene–basalt fiber will produce positive and negative effects when mixed, and the mass ratio of 2:1 was optimal. Finally, the fitting analysis revealed that the fracture process of polypropylene–basalt fiber-reinforced concrete (PBFRC) can be objectively described by the bilinear softening constitutive curve improved by Xu and Reinhardt.

Osteoporotic fractures and subsequent fractures: imminent fracture risk from an analysis of German real-world claims data

Purpose In osteoporosis, prior fracture is a strong predictor of subsequent fracture. This study aimed to assess the imminent risk of subsequent fracture following an initial fracture in osteoporosis patients in Germany, and to identify clinical and demographic characteristics that are independently associated with subsequent fracture risk. Methods In this retrospective, observational cohort study using German real-world claims data, male and female patients aged ≥ 50 years with osteoporosis who experienced an initial (“index”) hip/femur, vertebral, forearm/wrist/hand or shoulder/upper arm fracture between 2010 and 2014 were included. The incidence and timing of subsequent fractures during a 1-year follow-up period were analyzed. Independent risk factors for subsequent fracture were identified by multivariate regression analysis. Results A total of 18,354 patients (mean age: 77 years; standard deviation: 9.8) were included. Of these, 2918 (15.9%) suffered a subsequent fracture during the 1-year follow-up period. The incidence of subsequent fracture was higher following an index vertebral fracture (18.0%) than after an index forearm/wrist/hand fracture (14.1%) or index hip/femur fracture (12.1%). Subsequent 1-year fracture incidence was generally higher in older patients. Index fracture type, age, epilepsy/use of antiepileptics, and heart failure were all independently associated with subsequent fracture risk. Conclusion Osteoporosis patients in Germany are at imminent risk of subsequent fracture during the first year following an initial fracture. They should be targeted for immediate post-fracture treatment to reduce the risk of further fractures, especially in the presence of specific risk factors such as old age or index vertebral fracture.

Petrographic and Mechanical Analyses of Selected Granitic Rock Deposits in Ado-Ekiti, South-West Nigeria.

In this study, the petrographic and mineralogy of selected granitic rocks on their physical and mechanical strength were evaluated. Granitic rock samples sourced from seven locations were analyzed to investigate their mineral micro-texture and compositions using petrographic examination and X-ray diffraction (XRD) analysis respectively. Mechanical properties including compressive strength and hardness of the examined rocks were performed following ASTM D7012–10 and EN 1534 standards. Their physical properties in term of specific gravity, porosity and water absorption were examined following ASTM C97/C97M. Results show that the predominant minerals in rock samples are quartz and kaolinite. Stress-strain curve displays plastic fragmentation after initial fracture in most granitic rock samples with rock samples from Olorunda Zone 9 and Olorunda Zone 2 exhibiting superior plastic deformation over a wide strain elongation. Their physical properties were within the acceptable range for construction applications.

The Biomechanical Role of the Fibula in Lower Limbs: A Fracture Mechanics Analysis

BackgroundFibular grafting is widely used in the treatment of various bone nonunions and defects because of its good therapeutic effects. Furthermore, partial fibular resection has been used as a treatment for fibular tumors, injuries, and other conditions. The fibula plays important roles in the biomechanics of the lower limbs. Some experts have used cadaver specimens to study these aspects. In this study, the biomechanical effects of the fibula in lower limbs were researched through mechanics analysis.MethodsWe randomly collected knee joint computed tomography (CT) scans from eight adults, including three left knees and five right knees. The DICOM formatted CT scan images were imported into Mimics software. The tibia and fibula were extracted with the CT-bone function in Mimics software, and 3D models of the tibia and fibula were obtained. Each model was imported into 3-MATIC and LS-DYNA software to smooth the surface, perform meshing, define material properties, and set the failure parameters, interface properties, vertical loads and boundary conditions. The tibial fractures in both models were calculated to evaluate the biomechanical role of the fibula in the lower leg.ResultsThe validity of the model was verified, and the fibular load condition was similar to those previously reported. In the model with fibular support, the fracture load of the tibia was 78.27±3.36 KN, the initial fracture time was 0.69±0.01 s, and the complete fracture time was 0.75±0.01 s. The fibula carried approximately 7% of the load on the lower leg. In the fibular defect model, the fracture load of the tibia was 72.71±3.25 KN, the initial fracture time was 0.54±0.02 s, and the complete fracture time was 0.62±0.01 s.ConclusionsThe fibula play an essential biomechanical role in lower limb load-bearing and therefore is worthy of clinical attention. We believe that LS-DYNA can be used as an effective tool for the study of fracture mechanics.

POS0167 SECONDARY PREVENTION OF VERTEBRAL FRACTURES IN REAL PRACTICE

Background:Vertebral fractures increases the risk of new fractures and deaths. There are different antiresorptive medications to prevent a secondary fracture, as bisphosphonates, teriparatide or denosumab, but little is known about the effects of secondary fracture appearance in real life.Objectives:To evaluate the appearance of new vertebral fractures depending on the treatment used for secondary prevention.Methods:We conducted a prospective descriptive study of patients with a first diagnosis of vertebral fracture from 2010 to 2017 and assessed the subsequent finding of new fractures. We selected patients with at least 3 years of secondary prevention with antiresorptive drugs or with sequential treatment (anabolic followed by, at least, 1 year with antiresorptive drugs), and excluded those who experienced new fractures within the first 6 months of treatment.Results:A total of 400 patients were selected from an initial base of 1018 patients. The average age of onset of the first fracture was 69.7 years, 84% of female patients and 16% of female patients. 38.5% suffered dorsal fractures, 33.75% lumbar fractures and 27.75% dorsolumbar fractures. We classified the secondary prevention strategies according to the different therapeutic options, as we can see in Table 1.We analysed the association between the appearance of new vertebral fracture corrected by sex with the age of the initial fracture its location. No association was found.We also performed a multivariate Bayesian model of logistic regression, in order to analyze the association between the appearance of new vertebral fracture and factors as the age of the initial fracture, its sex and the pharmacologic option used as secondary prevention. No statistically significant differences were observed between the different antiresorptive treatments and their efficacy as a secondary prevention of vertebral fractures. However, there was a tendency for a smaller occurrence of new fractures in patients undergoing sequential treatment. On the other hand, similar results were observed between denosumab and oral bisphosphonates, observing somewhat worse data with zoledronate (figure 1), probably due to patients under zoledronate treatment showed high osteoporotic risk and worse prognosis.Pharmacologic optionPatients (%)New fractures (%)Denosumab192 (48%)10 (5.21%)Teriparatide (up to 2 years) + Denosumab (at least 1 year)86 (21.5%)0 (0%)Oral bisphosphonate (alendronate, risedronate or ibandronate)58 (14.5%)3 (5.17%)Zoledronate33 (8.25%)4 (12.12%)Teriparatide (up to 2 years) + oral bisphosphonate (at least 1 year)28 (7%)2 (7.14%)Teriparatide (up to 2 years) + Zoledronate (at least 1 year)3 (0,75%)0 (0%).Conclusion:No differences between the different secondary prevention options in terms of the appearance of new fractures were observed.Disclosure of Interests:None declared