Cement Distribution Research Articles

A novel and convenient method to evaluate bone cement distribution following percutaneous vertebral augmentation

A convenient method to evaluate bone cement distribution following vertebral augmentation is lacking, and therefore so is our understanding of the optimal distribution. To address these questions, we conducted a retrospective study using data from patients with a single-segment vertebral fracture who were treated with vertebral augmentation at our two hospitals. Five evaluation methods based on X-ray film were compared to determine the best evaluation method and the optimal cement distribution. Of the 263 patients included, 49 (18.63%) experienced re-collapse of treated vertebrae and 119 (45.25%) experienced new fractures during follow-up. A 12-score evaluation method (kappa value = 0.652) showed the largest area under the receiver operating characteristic curve for predicting new fractures (0.591) or re-collapse (0.933). In linear regression with the 12-score method, the bone cement distribution showed a negative correlation with the re-collapse of treated vertebra, but it showed a weak correlation with new fracture. The two prediction curves intersected at a score of 10. We conclude that an X-ray-based method for evaluation of bone cement distribution can be convenient and practical, and it can reliably predict risk of new fracture and re-collapse. The 12-score method showed the strongest predictive power, with a score of 10 suggesting optimal bone cement distribution.

Robot-guided percutaneous kyphoplasty in treatment of multi-segmental osteoporotic vertebral compression fracture

To evaluate the safety and effectiveness of robot-guided percutaneous kyphoplasty (PKP) in treatment of multi-segmental thoracolumbar osteoporotic vertebral compression fracture (OVCF). A clinical data of 63 cases with multi-segmental thoracolumbar OVCF without neurologic deficit treated with PKP between October 2017 and February 2019 were analyzed retrospectively. The patients were divided into robot-guided group (33 cases) and traditional fluoroscopy group (30 cases). There was no significant difference in gender, age, fracture segment, bone mineral density, and preoperative visual analogue scale (VAS) score, midline vertebral height, and Cobb angle between the two groups ( P>0.05). The time to establish the tunnel, the times of fluoroscopy, the dose of fluoroscopy, the deviation of puncture, the distribution of bone cement, the leakage of bone cement, the puncture angle, and the postoperative VAS score, midline vertebral height, and Cobb angle were recorded and compared. The patients in two groups were followed up 11-13 months (mean, 12 months). Compared with traditional fluoroscopy group, the time to establish the tunnel, the times and dose of fluoroscopy in robot-guided group were significantly lower, the deviation of puncture was slighter, the distribution of bone cement was better, and the puncture angle was larger, the differences between the two groups were significant ( P<0.05). There were 8 segments (9.3%, 8/86) of bone leakage in robot-guided group and 17 segments (22.6%, 17/75) in traditional fluoroscopy group, the difference between the two groups was significant ( χ 2=5.455, P=0.020). There was no significant difference in VAS score, the midline vertebral height, and Cobb angle between the two groups at 2 days after operation and last follow-up ( P>0.05). Robot-guided PKP in treatment of multi-segmental thoracolumbar OVCF can shorten the operation time, improve the accuracy of puncture, reduce the times and dose of fluoroscopy, reduce the leakage of bone cement, and achieve better cement distribution.

The effect of sulfur- and carbon-codoped TiO2 nanocomposite on the photocatalytic and mechanical properties of cement mortars

This study has established the impact of a nano-ТіО 2 P25 modifier and a nanocomposite based on titanium dioxide, doped with sulfur and carbon dioxide (ТіО 2 /S,C), on the photocatalytic, mechanical properties and the structural formation of cement mortars. The paper reports the results of the particle size distribution of the Portland composite cement and the ТіО 2 nano additives; a comprehensive assessment of the particle size distribution has been performed both in terms of volume and specific surface. It has been proven that the ТіО 2 /S,C nanocomposite is characterized by the extremely high surface activity, which determines the photocatalytic properties of the surface of cement mortars. The comparison of the mechanical properties of cement mortars modified by titanium dioxide nano additives has been carried out. An experimental study has confirmed the improved photocatalytic properties of the cement mortar surface in the visible spectrum through the doping of the nano-sized titanium dioxide with carbon and sulfur. A combination of the ТіО 2 nano additives and the superplasticizers of polycarboxylate type leads to the increased strength of the modified samples in proportion to a hardening age. Given the high surface activity of the ТіО 2 /S,C nanocomposite's particles, the cement paste hydration products deposit at their surface, thereby forming such conglomerates with them that seal the microstructure of the cement matrix. It has been shown that using a nanocomposite based on the modified titanium dioxide decreases the indicators of free energy while the surface of the cement mortar acquires hydrophobic properties, which contributes to the processes of self-cleaning. Thus, there is a reason to argue about the feasibility of using the ТіО 2 /S,C nanocomposite to improve the photocatalytic, self-cleaning, mechanical, and hydrophobic properties of cement mortars

The effect of bone cement distribution on the outcome of percutaneous Vertebroplasty: a case cohort study

BackgroundTo analyze the effect of different types of bone cement distribution after percutaneous vertebroplasty (PVP) in patients with osteoporotic vertebral compression fracture (OVCF).MethodsOne hundred thirty seven patients with single level OVCF who underwent PVP were retrospectively analyzed. The patients were divided into two groups according to bone cement distribution. Group A: bone cement contacted both upper and lower endplates; Group B: bone cement missed at least one endplate. Group B was divided into 3 subgroups. Group B1: bone cement only contacted the upper endplates; Group B2: bone cement only contacted the lower endplates; Group B3: bone cement only located in the middle of vertebral body. The visual analogue scale (VAS) score at 24 h post operation and last follow-up, anterior vertebral height restoration ratio (AVHRR), anterior vertebral height loss ratio (AVHLR), local kyphotic angle change and vertebral body recompression rate were compared.Results24 h post operation, the pain of all groups were significantly improved. The average follow-up time was 15.3 ± 6.3 (6–24) months. At last follow-up, the VAS score of group A was lower than that of group B. There were 14 cases (10.2%) of adjacent vertebral fracture, 5 cases (8.6%) in group A and 9 cases (11.4%) in group B. There were 9 cases (6.6%) of cement leakage, 4 cases (6.9%) in group A and 5 cases (6.3%) in group B. At last follow-up, there were 16 cases (11.7%) of vertebral body recompression, including 3 cases (5.2%) in group A and 13 cases (16.5%) in group B. There was no significant difference in AVHRR between two groups. Local kyphotic angle change was significant larger in group B. At last follow-up, AVHLR in group B was higher than that in group A. Analysis in subgroup B revealed no significant difference in VAS score, local kyphotic angle change, vertebral recompression rate, AVHRR or AVHLR.ConclusionsIf the bone cement fully contacted both the upper and lower endplates, it can better restore the strength of the vertebral body and maintain the height of the vertebral body, reduce the risk of the vertebral body recompression and long-term pain.

Investigation of pore-scale CaCO3 distributions and their effects on stiffness and permeability of sands treated by microbially induced carbonate precipitation (MICP)

Physical properties of MICP-treated sands are controlled by CaCO3 distributions in pore space, which remain relatively unexplored. CaCO3 can deposit at the particles’ contact area (contact-cementing), coat sand particles (grain-coating), or create a cementation bridge between soil grains (matrix-supporting). The objectives of this paper are to determine the dominant CaCO3 distributions in pore space and investigate the effects of CaCO3 distributions on the small-strain stiffness (measured by S-and P-wave velocities) and permeability of MICP-treated sands. To achieve these objectives, cemented-sand and uncemented-sand models combined with three ideal CaCO3 distributions (contact-cementing, grain-coating, and matrix-supporting) were used to estimate the S-and P-wave velocities. In order to determine the dominant CaCO3 distributions in pore space, the calculated values from the models were then compared with experimental data. It was concluded that the dominant CaCO3 distributions were a combination of grain-coating and matrix-supporting. The effects of CaCO3 distributions at pore space on the variation of permeability were estimated using Kozeny-Carman and Panda-Lake models with three pore-scale cement distributions (pore-lining, pore-filling, and pore-bridging). The comparison between laboratory-measured and calculated permeability from the pore-filling Panda-Lake model for seven types of sands demonstrated a relatively good match with a maximum difference of one order of magnitude. The comparison suggests the pore-filling Panda-Lake model can be used for estimating the permeability of the MICP-treated sands.

Testing the impact of discoplasty on the biomechanics of the intervertebral disc with simulated degeneration: An in vitro study

Percutaneous Cement Discoplasty has recently been developed to relieve pain in highly degenerated intervertebral discs presenting a vacuum phenomenon in patients that cannot undergo major surgery. Little is currently known about the biomechanical effects of discoplasty. This study aimed at investigating the feasibility of modelling empty discs and subsequent discoplasty surgery and measuring their impact over the specimen geometry and mechanical behaviour. Ten porcine lumbar spine segments were tested in flexion, extension, and lateral bending under 5.4 Nm (with a 200 N compressive force and a 27 mm offset). Tests were performed in three conditions for each specimen: with intact disc, after nucleotomy and after discoplasty. A 3D Digital Image Correlation (DIC) system was used to measure the surface displacements and strains. The posterior disc height, range of motion (ROM), and stiffness were measured at the peak load. CT scans were performed to confirm that the cement distribution was acceptable. Discoplasty recovered the height loss caused by nucleotomy (p = 0.04) with respect to the intact condition, but it did not impact significantly either the ROM or the stiffness. The strains over the disc surface increased after nucleotomy, while discoplasty concentrated the strains on the endplates. In conclusion, this preliminary study has shown that discoplasty recovered the intervertebral posterior height, opening the neuroforamen as clinically observed, but it did not influence the spine mobility or stiffness. This study confirms that this in vitro approach can be used to investigate discoplasty.

Clinical Efficacy of Different Bone Cement Distribution Patterns in Percutaneous Kyphoplasty: A Retrospective Study

Bone cement distribution patterns in percutaneous kyphoplasty (PKP) is the key factor in keeping the vertebral stabilization and curative effect. However, the same cement volume can result in different bone cement distribution patterns and can thereby lead to different clinical outcomes. Therefore we investigated associations between cement distribution patterns and the occurrence rates of recompression in cemented vertebrae after PKP for patients with osteoporotic vertebral compression fractures (OVCFs). The study focuses attention on the influence of compact and dispersive cement distribution patterns in PKP for patients with OVCFs. A retrospective cohort study. An affiliated people's hospital of a university. According to different cement distribution patterns, patients were assigned to 4 groups. The demographic data, radiographic data, and clinical outcomes were compared between the 4 groups. The Visual Analog Scale (VAS) and Oswestry Disability Index (ODI) were evaluated before and 2 days after PKP. Moreover, the relationships between bone cement and clinical outcomes were analyzed. The epidemiologic data, clinical outcomes, and complications of the 4 groups were assessed. Comparisons of the radiologic and clinical results of the 4 groups were made pre- and postoperatively. Anterior height of fractured vertebrae (AH), the kyphotic Cobb angle, and the volumetric cubage index of the fractured vertebrae were measured. A total of 104 subjects were retrospectively analyzed and followed up (median age, 75.01 ± 8.42 years; age range, 56-94 years). The mean procedure duration was 61.26 ± 23.05 minutes (range, 30-140 minutes). The mean follow-up was 12.1 ± 2.2 months (range, 2-15 months). Statistically, there was no significant difference in terms of gender, age, body mass index, and bone mineral density (P > 0.05). The incidence of cement leakage was significantly lower in group A than those in the other groups. The total amount of bone cement injected into 104 cases (104 vertebral bodies in total) was 848.5 mL, and the amount of bone cement injected into a single vertebral body was 7.94 ± 1.38 mL. The amount of bone cement injection in each group was the lowest (6.80 ± 1.66 mL) in group D, followed by (7.94 ± 1.38 mL) group B, and the highest (8.96 ± 1.68 mL) in group A, with a statistically significant difference between the 4 groups (P < 0.05). No serious complications were observed during the follow-up periods. The AH and Cobb angle improved significantly for the 4 groups (P < 0.05). The VAS score decreased from 3.55 ± 0.54, 3.53 ± 0.65, 3.40 ± 0.58, and 3.40 ± 0.66 preoperatively to 0.18 ± 0.39, 0.23 ± 0.41, 0.20 ± 0.40, and 0.15 ± 0.36 at 48 hours postoperatively. The ODI score dropped from 35.65 ± 4.54, 36.45 ± 4.72, 34.12 ± 4.86, and 35.65 ± 4.34 preoperatively to 15.47 ± 1.32, 15.32 ± 1.34, 15.23 ± 1.26, and 15.73 ± 1.17 at 48 hours postoperatively. Our estimation of the vertebral body volume is imprecise. In addition, the number of subjects with OVCFs was small in this retrospective study. The volume of the fractured vertebra was not calculated accurately. Significant associations between cement distribution patterns and bone cement leakage affected the clinical outcome in patients after PKP. A higher incidence of bone cement leakage was observed in patients with treated vertebrae exhibiting a single-dispersive or single-compact pattern. Percutaneous kyphoplasty, osteoporotic vertebral compression fracture, bone cement distribution patterns.

Effect of unilateral pulsed jet lavage prior to vertebroplasty on the intravertebral pressure and cement distribution

BackgroundPercutaneous vertebroplasty is the most common treatment for osteoporotic vertebral compression fracture. However, the morbidity of vertebroplasty-related complications, such as cement leakage, remains high. We tested a new technique of unilateral pulsed jet lavage and investigated its effect on the intravertebral pressure and bone cement distribution.MethodsThirty lumbar vertebrae (L1-L5) from six cadaver spines were randomly allocated into two groups (with and without irrigation). Prior to vertebroplasty, pulsed jet lavage was performed through one side of the pedicle by using a novel cannula with two concentric conduits to remove the fat and bone marrow of the vertebral bodies in the group with irrigation. The control group was not irrigated. Then, standardized vertebroplasty was performed in the vertebral bodies in both groups. Changes in the intravertebral pressure during injection were recorded. Computed tomography (CT) was performed to observe the cement distribution and extravasations, and the cement mass volume (CMV) was calculated.ResultsDuring cement injection, the average maximum intravertebral pressure of the unirrigated group was higher than that of the irrigated group (4.92 kPa versus 2.22 kPa, P < 0.05). CT scans showed a more homogeneous cement distribution with less CMV (3832 mm3 vs. 4344 mm3, P < 0.05) and less leakage rate (6.7% vs. 46.7%, P < 0.05) in the irrigated group than in the control group.ConclusionsUnilateral pulsed jet lavage can reduce intravertebral pressure and lower the incidence of cement leakage during vertebroplasty. An enhanced bone cement distribution can also be achieved through this lavage system.

Clinical observation of two bone cement distribution modes of percutaneous vertebroplasty in the treatment of thoracolumbar K\xfcmmell\u2019s disease

BackgroundIn recent years, percutaneous vertebroplasty (PVP) has provided a new option for the treatment of Kümmell’s disease (KD). This retrospective study aimed to investigate the differences in clinical characteristics, clinical efficacy, and related complications between two types of bone cement distribution patterns in the PVP treatment of KD.MethodsA total of 63 patients with KD from January 2016 to February 2018 who received PVP treatment were examined at least 24 months. According to X-ray distribution modes of bone cement after PVP treatment, they were divided into 2 groups: blocky group (30 cases) and spongy group (33 cases). Clinical features and disease severity preoperatively, and clinical efficacy and related complications postoperatively were statistically compared between the two groups.ResultsThe two groups were followed for at least 24 months. The duration of disease, age, Cobb angle, and vertebral compression rate preoperatively were significantly higher in the blocky group than in the spongy group (P < 0.05, respectively). The height of vertebral anterior margin and BMD were significantly lower in the blocky group than in the spongy group (P < 0.05, respectively). The amount of bone cement injected was significantly greater in the blocky group than in the spongy group (P = 0.000). VAS and ODI of the two groups were significantly reduced at the first day, the first year, and the last follow-up postoperatively (all P = 0.000) and were maintained at the last follow-up. VAS and ODI postoperatively decreased significantly in the spongy group compared with the blocky group (P = 0.000). The correction degrees of kyphosis and vertebral compression postoperatively in the two groups were significantly corrected, but gradually decreased over time (P < 0.05), and these correction degrees were significantly higher in the blocky group than in the spongy group, and the postoperative losses were also more serious.ConclusionsThe disease was more serious in the blocky group than in the spongy group. The amount of bone cement, correction degrees of postoperative kyphosis and vertebral compression were significantly higher in the blocky group than in the spongy group, but its postoperative losses of the correction degrees of kyphosis and vertebral compression were also more serious. However, for pain relief and functional recovery, the spongy group was superior to the blocky group. Therefore, the spongy distribution pattern should be formed during the injection of bone cement to obtain better therapeutic effect.

Percutaneous Vertebroplasty with Side-Opening Cannula or Front-Opening Cannula in the Treatment of Kummell Disease?

ObjectiveTo explore the effect of bone cement distribution, cement leakage, and clinical outcomes with side‐opening cannula for bone cement injection in percutaneous vertebroplasty (PVP) in treatment of Kummell disease.MethodsA prospective study of patients with Kummell disease undergoing PVP was conducted from April 2012 to September 2017. In total, 43 patients (11 males, 32 females) with Kummell disease who received bilateral PVP were included in the study. The patients were divided into front‐opening cannulas (FOC) group with front‐opening cannulas and side‐opening cannulas (SOC) group with side‐opening cannulas. All patients were followed up for 6 months. The patient general information such as gender, age, bone density, compression ratio, operative time, and location of fracture vertebrae were recorded. Visual analogue scale (VAS), Oswestry Disability Index (ODI), bone cement distribution, radiation exposure time, bone cement leakage rate and vertebral height, and kyphosis angle were measured and compared for two groups before surgery, 1 day and 6 months after surgery.ResultsA total of 43 patients were enrolled, including 11 males and 32 females, aged 61–84 years. The bone density (T value) was 2.5 ± 0.6 in FOC group and 2.4 ± 0.6 in SOC group (P > 0.05). The compression ratio and operative time were 36.1% ± 13.0%, 39.3 ± 7.9 min in FOC group and 35.2% ± 13.7%, 40.0 ± 10.7 min in SOC group (P > 0.05). There was no significance between FOC and SOC groups in the location of fracture vertebrae. All patients underwent at least 6 months of follow‐up. At 6 months postoperatively, the VAS and ODI were significantly higher in the FOC group (3.0 ± 0.8, 35.7% ± 2.1%) than in the SOC group (1.3 ± 0.4, 18.6% ± 2.4%) (P < 0.05). The cement leakage rate of the SOC group was 4.8%, which was lower than that of the FOC group (31.8%, P < 0.05), and the bone cement distribution ratio was higher than that of the FOC group (63.1% ± 7.9% vs 40.5% ± 8.6%, P < 0.05). At 6 months after operation, the height of the anterior and posterior vertebral bodies of the patients in the SOC group restored better than the FOC group (anterior SOC: FOC 5.1 ± 0.5 mm vs 4.5 ± 0.5 mm; posterior SOC: FOC 0.6 ± 0.1 mm vs 0.3 ± 0.1 mm, P < 0.05), and the kyphosis correction was more obvious than patients in FOC group (SOC: FOC 8.5° ± 1.4° vs 4.6° ± 0.8°, P < 0.05).ConclusionPercutaneous vertebroplasty with side‐opening cannula is safe and effective in avoiding bone cement leakage, improving bone cement distribution, and restoring vertebral height.

Sources of Ca2+ in the major carbonate cements in Eocene sandstones and conglomerates: Evidence from Sr isotopes, Sr/Ca ratios, and rare-earth elements

Different sources of calcium have important effects on the formation and distribution of carbonate cements. On the basis of identifying all possible sources of calcium, comprehensive quantitative analyses of Sr, C, and O isotopic values and trace elements (including rare-earth elements) were conducted to determine the Ca2+ sources and their changes in the same type of carbonate cements at different vertical positions in the same reservoirs. Ferroan calcite and ankerite were the major types of carbonate cements. Ca2+ in ferroan carbonate cements in the sandstones near the mudstone-sandstone (M-S) interfaces was derived primarily from diagenetic fluids mixed with Ca2+ originating from the transformation of smectite to illite and from original sedimentary water in the adjacent mudstones. However, Ca2+ in the ferroan carbonate cements in the sandstones away from the M-S interfaces originated from the transformation of smectite to illite, the dissolution of carbonate minerals, and original sedimentary water in source rocks. The gradual change of Ca source of the same type of ferroan carbonate cements indicates the diversity of migration direction of diagenetic paleo-fluid in the same period. During the transformation of smectite to illite, concentration gradients were created from mudstones to sandstones. Ca2+, Mg2+, Fe2+, and other cations in the mudstones diffused to the adjacent sandstones and provided sources of ferroan carbonate cements at the edge of the sandstones. Pore water with Ca2+, Mg2+, Fe2+, CO32−, and other cations in the source rocks was collectively charged into sandstones during oil emplacement and promoted the precipitation of ferroan carbonate cements in residual pore water. Due to oil emplacement and material supplied by the adjacent mudstones, the content of ferroan carbonate cements in the sandstones was lower, and the reservoir porosity was higher at a greater distance from the M-S interfaces. However, in thick-bedded sandstones, due to lack of material supply from the adjacent mudstones, Ca2+, Mg2+, Fe2+, and CO32− in the ferroan carbonate cements were mainly derived from source rocks. As a result, no significant changes were observed in the content of ferroan carbonate cements and reservoir porosity in the vertical direction.

Reliability of two different measuring techniques with computer tomography for penetration and distribution of cement in the proximal tibia after total knee arthroplasty

BackgroundTo evaluate the reliability of two different techniques for measuring penetration and distribution of the cement mantle in the proximal tibia after total knee arthroplasty (TKA) with Computer Tomography (CT) in vivo.MethodsStandardized CT scans of the proximal tibia were taken 1 to 2 years after total knee arthroplasties implanted with a surface cementing technique. These prospectively acquired transversal CT images of the surface of the proximal tibia were divided into four quadrants and were assessed once manually and once with a numerical computing program (MATLAB® Update 2, The MathWorks, Inc.) based on Hounsfield Units by one of the researchers. The assessments were repeated by the same and a second researcher. The ratio cement/trabecular bone was calculated 1, 3 and 5 mm distal of the tibia tray per quadrant. Kruskall-Wallis tests with multiple pairwise comparisons (Dunn’s test) were used to determine differences between the quadrants. Intra- and inter-rater reliability as well as the inter method reliability were assessed with the Intraclass Correlation Coefficient (ICC) per level of depth and with Bland-Altman plots.ResultsA total of 92 CT scans were included. The intra- and inter-rater reliability of the manual method ranged from 0.22 and 0.52. The intra- and inter-rater reliability of the matlab method varied between 0.98 to 0.99.The median percentage cement measured with the matlab method 1 mm underneath the tibial tray varied between 82 and 88%; at 3 mm depth between 38 and 54% and at 5 mm between 15 and 25%. There was significantly (p < 0.05) less cement in the antero-medial quadrant compared to the antero-lateral and postero-lateral quadrant at 3 mm and 5 mm depth.ConclusionsDistribution and penetration of cement in the proximal tibia in a total knee arthroplasty can be measured reliably with CT in combination with the matlab method presented in this manuscript. This method can be used for clinical purposes as well as for scientific research.Trial registrationMETC-nr: 06–104 Dossier NL14807.098.06/versie 06.

Risk factors for postoperative residual back pain after percutaneous kyphoplasty for osteoporotic vertebral compression fractures.

To determine the incidence of and risk factors for residual back pain in osteoporotic vertebral compression fracture (OVCF) patients after percutaneous kyphoplasty (PKP) treatment, we performed a retrospective analysis of prospective data. Patients who underwent bilateral PKP and met this study's inclusion criteria were retrospectively reviewed. Back pain intensity was assessed using a visual analogue scale (VAS) after surgery. Residual back pain was defined as the presence of postoperative moderate-severe pain (average VAS score ≥ 4), and the variables included patient characteristics, baseline symptoms, radiological parameters and surgical factors. Univariate and multivariate logistic regression analyses were performed to identify risk factors. A total of 809 patients were included, and residual back pain was identified in 63 (7.8%) patients. Of these patients, 52 patients had complete data for further analysis. Multivariate logistic regression analysis showed that risk factors for back pain included the presence of an intravertebral vacuum cleft (OR 2.93, P = 0.032), posterior fascia oedema (OR 4.11, P = 0.014), facet joint violations (OR 12.19, P < 0.001) and a separated cement distribution (OR 2.23, P = 0.043). The incidence of postoperative residual back pain was 7.8% among 809 OVCF patients following PKP. The presence of an intravertebral vacuum cleft, posterior fascia oedema, facet joint violations and a separated cement distribution were identified as independent risk factors for residual back pain.

Grain-scale failure mechanism of porous sandstone: An experimental and numerical FDEM study of the Brazilian Tensile Strength test using CT-Scan microstructure

Many widely used numerical models of rock fracture based on mesoscale laboratory test characterisation of effective ‘intact’ strength parameters neglect microstructure effects. They therefore cannot explain grain boundary and pore effects on crack propagation and consequently are inadequate for models of rock destruction that exploit point and indentation stresses. Understanding deep drilling processes involving drill-bit buttons and/or water-jetting where rock loading is concentrated in domains with fewer mineral grains will therefore require models with microstructure. To investigate microscale failure mechanisms of granular rocks in diverse scenarios, we target a porous sandstone and introduce a novel workflow consisting of a computerized tomography (CT) based microstructure construction approach and a complementary mechanical numerical approach. The construction approach extracts the realistic rock microstructure and transforms the large voxel number CT-scan data into significantly fewer triangular elements. The finite-discrete element method (FDEM) with grain-based model (GBM) is adopted to solve the mechanics. The microscale failure mechanism of sandstone during the Brazilian test was thoroughly analysed using the numerical results together with the post failure CT-scan test data. The build-up of compressive and tensile stress chains, micro-crack nucleation, local relaxation, chain switching and final crack-path development exploiting pores was illustrated, revealing the micro-to-macro failure mechanism in time and space. Fracture paths in the specimens during Brazilian tensile test were dominated by the pores and the inter-grain boundaries. The tensile strength of the inter-grain joints was estimated to be at least 3.67 times the mesoscale specimen's intact tensile strength, while the pores account for 72.76% of the fracture path. The influence of the cementation distribution and microscale discontinuities was investigated with numerical cases.

The Use of SpineJack Intravertebral Implant for the Correction of Recurrent Vertebral Fracture After Kyphoplasty

This report presents a case of short-term symptomatic failure with continued vertebral collapse after a T12 kyphoplasty for an acute fracture in a severely osteoporotic elderly patient. The original trajectory of the unilateral balloon and subsequently injected bone cement failed to fill the fracture, allowing further vertebral collapse that resulted in a rapid return of pain. Within 30 days, a titanium intravertebral body implant, SpineJack® (Stryker Corp, Kalamazoo, MI), combined with injection of polymethylmethacrylate (PMMA) bone cement, was placed in the collapsed area. This provided both sagittal and coronal partial correction of the collapse, fuller distribution of bone cement throughout the fractured vertebrae, and rapid reduction of pain. which was found to have been maintained at the long-term follow-up. The article reviews the technical issues causing failure of vertebral augmentation (VA) as well as the advantage of providing a permanent internal scaffolding to ensure stabilization of any fracture, especially where there is a high risk for progressive instability, such as the thoracic-lumbar junction.

Analisis Risiko Potensi Bahaya dan Pengendaliannya Dengan Metode HIRADC pada PT. IGASAR Kota Padang Sumatera Barat

&lt;p&gt;PT IGASAR was one of the companies affiliated with PT Semen Padang with business activities in the fields of engineering, cement distribution, transportation, heavy equipment rental, cement-based building materials industry, manufacturing, general contractor, and developer. Some work accidents were still found in activities at this company. It was essential to making hazard identification, risk assessment, and determined the type of control in some areas. There are work accidents in PT IGASAR in as many as five cases in 2017 - 2018. One way was to use the Hazard Identification Risk Assessment Determine Control (HIRADC) Method. A risk analysis was done by looking at the opportunities and the severity of the hazards. Based on the results of the risk analysis, it was found that activities that were low risk, very high risk was absent while the medium risk was 100%. The risk control measures include the provision of personal protective equipment, the rule of safety signs, equipment maintenance, and the creation of road area boundaries.&lt;/p&gt;

Unilateral percutaneous kyphoplasty for lumbar spine: A comparative study between transverse process-pedicle approach and conventional transpedicular approach.

Anatomical differences of unilateral percutaneous kyphoplasty (PKP) between transverse process-pedicle approach (TPPA) and conventional transpedicular approach (CTPA) are not well discussed. To investigate the anatomical distinctions of unilateral PKP between TPPA and CTPA, we have discussed the unilateral PKP through a 3-dimensional-computed tomography database.Five hundred lumbar spines from 100 patients have been retrospectively collected and unilateral CTPA and TPPA were simulated. Distance between the entry point and the midline of the vertebral body (DEM), the puncture inclination angle (PIA), and the success rate (SR) of puncture were measured and compared.The male presented with significantly larger DEM than the female. The TPPA group presented with larger DEM than the CTPA group according to different level, the difference was 1.5 ± 1.1 mm to 3.8 ± 2.3 mm. The PIAs in the TPPA group were larger than that in the CTPA group. The SR including 1 side SR and bilateral SR was 72.0% in the CTPA group and 98.0% in the TPPA group. Compared with CTPA group, the SR in TPPA group was significantly higher for L1 to L4 no matter in the left, right side and female patients.The TPPA group presented with more lateral entry point, larger PIAs and higher SRs than that in the CTPA group. PKP surgery through a TPPA was safer and could provide a more symmetrical distribution of bone cement than the CTPA group.

Risk of New Fractures in Vertebroplasty for Multiple Myeloma. A Retrospective Study.

Vertebroplasty is a percutaneous minimally invasive procedure indicated for vertebral collapse pain treatment. Among the known complications of the procedure is the augmented risk of new vertebral fractures. There are no specific studies in this patient population describing the risk of new vertebral fractures after vertebroplasty. This study analyzed risk factors associated with new vertebral fractures after vertebroplasty in patients with multiple myeloma. Observational retrospective study in patients with multiple myeloma. The data collection took place from January 1, 2010, to December 30, 2017, at the National Cancer Institute. Clinical data and procedural variables such as cement volume, cement leaks, fracture level, number of treated vertebrae, pedicular disease, and cement distribution pattern, with two years follow-up, were analyzed with the Wilcoxon test, and a logistic regression model was used to identify risk factors related to new vertebral fractures. A confidence interval of 95% was used for analysis. At one-year follow-up, 30% of fractures were reported after vertebroplasty, most of them at low thoracic and lumbar level (50% adjacent level). Vertebroplasty was most commonly performed at the thoracolumbar and lumbar area. We demonstrated a 70.7% median numerical rating scale reduction at one-year follow-up; a significant decrease in opioid consumption occurred only during the first month. Pedicle involvement, disc leakage, cement volume, thoracolumbar and lumbar level, and number of treated vertebrae by intervention are important risk factors when performing vertebroplasty. Prospective randomized studies are needed to evaluate these factors in this specific population.

Effect of cement particle size distribution on properties of cement mixed with polycarboxylate superplasticizer

The particle size distribution of cement under different milling time was studied, and the effects of different particle size distributions on the polycarboxylate superplasticizer dosage of the paste and the bleeding property of the paste were researched, and the early hydration exothermic rule of cement was investigated with the hydration heat meter. The results show that with the increase of ball milling time, the particle size distribution of cement is close to the direction of small particle size. With the same paste fluidity, the dosage of polycarboxylate superplasticizer increased and the bleeding rate of cement paste decreased with the increase of cement fine particle components. Under the same condition, with the increase of cement fine particle content, the hydration reaction speed is accelerated and the degree of hydration is relatively high.

Factors affecting the performance of microbial-induced carbonate precipitation (MICP) treated soil: a review

Soil stabilization technology based on microbial-induced carbonate precipitation (MICP) has gained widespread interest in geotechnical engineering. MICP has been found to be able to improve soil strength, stiffness, liquefaction resistance, erosion resistance, while maintaining a good permeability simultaneously. MICP processes involves a series of biochemical reactions that are affected by many factors, both intrinsically and externally. This paper reviews various influential factors for MICP process, including bacterial species, concentration of bacteria, temperature, pH, composition and concentration of cementation solution, grouting strategies, and soil properties. Through this comprehensive review, we find that: (1) the species and strains of bacteria, concentration of bacteria solution, temperature, pH value, and the cementation solution properties all affect the characteristics of formed calcium carbonate, such as crystal type, appearance and size, which consequently affect the cementation degree and distribution in geomaterials; (2) the condition with temperature between 20 and 40 °C, pH between 7 and 9.5, the concentration of the cementation solution within 1 mol/L, and high bacteria concentration is optimal for applying MICP in soil. Under the optimal condition, relatively low temperature, high pH value, and low concentration of cementation solution could help retain permeability and vice versa; (3) the effective grain size ranging from 10 to 1000 µm. MICP treatment works most effectively for larger size, well-graded sand; (4) the multi-phase, multi-concentration or electroosmotic grouting method can improve the MICP treatment efficiency. The grouting velocity below 0.042 mol/L/h is beneficial for improving the utilization ratio of cementation solution. The recommended grouting pressure is generally between 0.1 and 0.3 bar for MICP applications in sand and should not exceed 1.1 bar for silty and clayey soils.