Wide-blocky veins explained by dependency of crystal growth rate on fracture surface type: Insights from phase-field modeling

Vein microstructures contain a wealth of information on coupled chemical and mechanical processes of fracturing, fluid transport, and crystal growth. Numerical simulations have been used for exploring the factors controlling the development of vein microstructures; however, they have not been quantitatively validated against natural veins. Here we combined phase-field modeling with microtextural analysis of previously unexplained wide-blocky calcite veins in natural limestone and of the fresh fracture surface in this limestone. Results show that the wide-blocky vein textures can only be reproduced if ~10%–20% of crystals grow faster than the rest. This fraction corresponds to the amount of transgranularly broken grains that were observed on the experimental fracture surfaces, which are dominantly intergranular. We hypothesize that transgranular fractures allow faster growth of vein minerals due to the lack of clay coatings and other nucleation discontinuities that are common along intergranular cracks. Our simulation results show remarkable similarity to the natural veins and reproduce the nonlinear relationship between vein crystal width and vein aperture. This allows accurate simulations of crystal growth processes and related permeability evolution in fractured rocks.

Large spinal intraosseous arteriovenous fistula: case report

Here the authors report the case of a fresh vertebral body fracture with a large spinal intraosseous arteriovenous fistula (AVF). A 74-year-old woman started to experience low-back pain following a rear-end car collision. Plain radiography showed diffuse idiopathic skeletal hyperostosis (DISH). Sagittal CT sections revealed a transverse fracture of the L-4 vertebral body with a bone defect. Sagittal fat-suppressed T2-weighted MRI revealed a flow void in the fractured vertebra. Spinal angiography revealed an intraosseous AVF with a feeder from the right L-4 segmental artery. A fresh fracture of the L-4 vertebral body with a spinal intraosseous AVF was diagnosed. Observation of a flow void in the vertebral body on fat-suppressed T2-weighted MRI was important for the diagnosis of the spinal intraosseous AVF. Because conservative treatment was ineffective, surgery was undertaken. The day before surgery, embolization through the right L-4 segmental artery was performed using 2 coils to achieve AVF closure. Posterolateral fusion with instrumentation at the T12–S2 vertebral levels was performed without L-4 vertebroplasty. The spinal intraosseous AVF had disappeared after 4 months. At 24 months after surgery, the bone defect was completely replaced by bone and the patient experienced no limitations in daily activities. Given their experience with the present case, the authors believe that performing vertebroplasty or anterior reconstruction may not be necessary in treating spinal intraosseous AVF.

Nonunion with Breakage of Gamma Nail and Subsequent Fracture in the Ipsilateral Femur

We describe a rare case with breakage of gamma nail accompanied by nonunion of the original fracture and a subsequent new fracture in the ipsilateral femur. A 73-year-old woman suffered a subtrochanteric fracture of the femur, and the fracture was fixed with gamma nail at a previous hospital. However, fracture reduction was not adequately achieved and a large gap remained between the fracture fragments. The fracture demonstrated atrophic nonunion 10 months after surgery, and autologous bone grafting was performed at the same hospital. Two months after the second surgery, a breakage of the nail at the distal screw hole was observed. Twenty-six months after the second surgery, the patient fell and a fracture occurred at the level of the nail breakage. The atrophic nonunion site and fresh fracture site were very close thus demonstrating a segmental fracture. We exchanged the original gamma nail with a long gamma nail and performed autologous bone grafting at the nonunion site. Both the fresh fracture site and the nonunion site obtained bony union. This tragic chain of events was caused by inappropriate initial treatment and replacing the nail to a longer nail and autologous bone grafting were effective as salvage surgery.

CLINICAL OUTCOMES OF HOOK OF HAMATE FRACTURES AND USEFULNESS OF THE HOOK OF HAMATE PULL TEST

We report the usefulness of hook of hamate pull test (HHPT), described by Wright et al. in 2010, along with therapeutic outcomes of hook of hamate fractures. Eleven patients (two with fresh fractures and nine with nonunion) were studied. The fractures were diagnosed with HHPT for recently encountered 4 patients and a definitive diagnosis was made by a carpal canal view and a computed tomography (CT) scan. Treatment involved cast immobilization for one fresh fracture case, and bone fragment removal immediately over the hook for ten others. HHPT was positive in all the four cases. Union was achieved by conservative treatment, and hypothenar pain disappeared after surgery. Patients returned to work/sports two months postoperatively. HHPT was useful for diagnosing both fresh fractures and nonunion. If HHPT is positive, CT should be performed even if the fracture is obscure on a carpal canal view.

Performance and Analysis of Concrete in Sewer Environment: Anisotropy of Damage

The costs associated with the provision and maintenance of drinking water and wastewater infrastructure represents a significant financial demand worldwide. Maintenance costs are disproportionately high, indicating a lack of adequate durability. The aim of this paper is to study the degradation mode and the responsible factors of deterioration concrete pipe, used in the sewage’s city of Rennes (France). Thus, samples taken from different areas of the pipe (Raft, medium and roof) were analyzed using investigation methods in order to illustrate the internal and external rate of damage, caused by effluents and ground. In addition, chemical and mineralogical changes recorded were identified using scanning electron micrographs (SEM). In this research program, chemical and mechanical studies were performed by measuring the compressive and splitting tensile strengths. A phenolphthalein indicator solution is applied to a concrete specimen on a fresh fracture surface to determine the corrosion of steel reinforcement and the diseases advancement (pathologies depth). This study clearly shows the important anisotropy of both, internal and external damage. Finally, recommendations are proposed in line with the environment and possible approaches to sustainability assessment are also imposed.