Augmentation of mechanical properties in osteoporotic vertebral bones--a biomechanical investigation of vertebroplasty efficacy with different bone cements

Recent clinical trials have reported favorable early results for transpedicular vertebral cement reinforcement of osteoporotic vertebral insufficiencies. There is, however, a lack of basic data on the application, safety and biomechanical efficacy of materials such as polymethyl-methacrylate (PMMA) and calciumphospate (CaP) cements. The present study analyzed 33 vertebral pairs from five human cadaver spines. Thirty-nine vertebrae were osteoporotic (bone mineral density < 0.75 g/cm2), 27 showed nearly normal values. The cranial vertebra of each pair was augmented with either PMMA (Palacos E-Flow) or experimental brushite cement (EBC), with the caudal vertebra as a control. PMMA and EBC were easy to inject, and vertebral fillings of 20-50% were achieved. The maximal possible filling was inversely correlated to the bone mineral density (BMD) values. Cement extrusion into the spinal canal was observed in 12% of cases. All specimens were subjected to axial compression tests in a displacement-controlled mode. From load-displacement curves, the stiffness, S, and the maximal force before failure, Fmax, were determined. Compared with the native control vertebrae, a statistically significant increase in vertebral stiffness and Fmax was observed by the augmentation. With PMMA the stiffness increased by 174% (P = 0.018) and Fmax by 195% (P = 0.001); the corresponding augmentation with EBC was 120% (P = 0.03) and 113% (P = 0.002). The lower the initial BMD, the more pronounced was the augmentation effect. Both PMMA and EBC augmentation reliably and significantly raised the stiffness and maximal tolerable force until failure in osteoporotic vertebral bodies. In non-porotic specimens, no significant increase was achieved.

Privacy in the Post-NSA Era: Time for a Fundamental Revision?

Big Brother Watch and others have filed a complaint against the United Kingdom under the European Convention on Human Rights about a violation of Article 8, the right to privacy. It regards the NSA affair and UK-based surveillance activities operated by secret services. The question is whether it will be declared admissible and, if so, whether the European Court of Human Rights will find a violation. This article discusses three possible challenges for these types of complaints and analyses whether the current privacy paradigm is still adequate in view of the development known as Big Data.

Surgical capping of superior semicircular canal dehiscence

Surgical plugging and resurfacing are well established treatments of superior semicircular canal dehiscence, while capping with hydroxyapatite cement has been little discussed in literature. The aim of this study was to prove the efficacy of the capping technique. Charts of patients diagnosed with superior semicircular canal dehiscence were reviewed retrospectively. All patients answered the dizziness handicap inventory, a survey analyzing the impact of their symptoms on their quality of life. Capping of the dehiscent canal was performed via the middle fossa approach in all cases. Ten out of 22 patients diagnosed with superior semicircular canal dehiscence were treated with surgical capping, nine of which were included in this study. No major perioperative complications occurred. In 8 out of 9 (89 %) patients, capping led to a satisfying reduction of the main symptoms. One patient underwent revision surgery 1 year after the initial intervention. Scores in the dizziness handicap inventory were lower in the surgically treated group than in the non-surgically treated group, but results were not statistically significant (P = 0.45). Overall, capping is a safe and efficient alternative to plugging and resurfacing of superior semicircular canal dehiscence.

In-situ X-ray micro-diffraction studies of heterogeneous interfaces between cementitious materials and geological formations

In the present study the challenge of analyzing complex micro X-ray diffraction (microXRD) patterns from cement–clay interfaces has been addressed. In order to extract the maximum information concerning both the spatial distribution and the crystal structure type associated with each of the many diffracting grains in heterogeneous, polycrystalline samples, an approach has been developed in which microXRD was applied to thin sections which were rotated in the X-ray beam. The data analysis, performed on microXRD patterns collected from a filled vein of a cement–clay interface from the natural analogue in Maqarin (Jordan), and a sample from a two-year-old altered interface between cement and argillaceous rock, demonstrate the potential of this method.

Dentinhaftung von Zementen. Der Haftverbund von Zementen mit Dentin in Kombination mit verschiedenen indirekten Restaurationsmaterialien

Einleitung: Die Anzahl zahnärztlicher Zemente sowie Restaurationsmaterialien steigt stetig. Die richtige Zementwahl für einen zuverlässigen Haftverbund zwischen Restaurationsmaterial und Zahnsubstanz ist von Interesse für den Kliniker. Ziel der vorliegenden in vitro-Studie war es daher, den Dentinhaftverbund von verschiedenen Zementen in Kombination mit verschiedenen indirekten Restaurationsmaterialien zu untersuchen. Material und Methoden: Zylindrische Probekörper aus sechs Restaurationsmaterialien (Goldlegierung, Titan, Feldspat-Keramik, Leuzit-Glaskeramik, Zirkon sowie Komposit) wurden an einem Ende plangeschliffen und sandgestrahlt. Die Zylinder aus Feldspat-Keramik und Leuzit-Glaskeramik wurden zusätzlich mit Flusssäure geätzt und silanisiert. Die Zylinder wurden anschliessend mit acht Zementen auf plangeschliffenes Dentin extrahierter menschlicher Zähne zementiert (ein Zink-Phosphatzement (DeTrey Zinc), ein konventioneller Glasionomerzement (Fuji I), ein kunststoffmodifizierter Glasionomerzement (Fuji Plus), ein "etch-&-rinse" Kompositzement (Variolink II), zwei "self-etch" Kompositzemente (Panavia F2.0 und Multilink) und zwei "self-adhesive" Kompositzemente (RelyX Unicem Aplicap und Maxcem)). Nach einwöchiger Wasserlagerung bei 37°C wurden die Dentinhaftwerte der Zylinder (n=8 pro Gruppe) mittels Scherkraft-Test gemessen. Zusätzlich wurde das Frakturmuster unter dem Lichtmikroskop bestimmt. Die Haftwerte wurden mittels zweifaktorieller ANOVA und einem post hoc-Test analysiert (Signifikanzniveau α = 0.05). Resultate: Sowohl das Restaurationsmaterial wie auch der Zement hatten einen statistisch signifikanten Effekt auf den Haftverbund. Der Zink-Phosphatzement sowie beide Glasionomerzemente zeigten die niedrigsten Haftwerte. Die höchsten Haftwerte wurden mit beiden "self-etch" und einem der zwei "self-adhesive" Kompositzementen erzielt. Im Allgemeinen variierte das Frakturmuster deutlich je nach Zement und Restaurationsmaterial. Schlussfolgerungen: Der Dentinhaftverbund wurde stärker vom Zement beeinflusst als vom Restaurationsmaterial. Die Kompositzemente erzielten im Grossen und Ganzen die höchsten Haftwerte.

Influence of screw augmentation in posterior dynamic and rigid stabilization systems in osteoporotic lumbar vertebrae: a biomechanical cadaveric study.

STUDY DESIGN Biomechanical cadaveric study. OBJECTIVE To determine whether augmentation positively influence screw stability or not. SUMMARY OF BACKGROUND DATA Implantation of pedicle screws is a common procedure in spine surgery to provide an anchorage of posterior internal fixation into vertebrae. Screw performance is highly correlated to bone quality. Therefore, polymeric cement is often injected through specifically designed perforated pedicle screws into osteoporotic bone to potentially enhance screw stability. METHODS Caudocephalic dynamic loading was applied as quasi-physiological alternative to classical pull-out tests on 16 screws implanted in osteoporotic lumbar vertebrae and 20 screws in nonosteoporotic specimen. Load was applied using 2 different configurations simulating standard and dynamic posterior stabilization devices. Screw performance was quantified by measurement of screwhead displacement during the loading cycles. To reduce the impact of bone quality and morphology, screw performance was compared for each vertebra and averaged afterward. RESULTS All screws (with or without cement) implanted in osteoporotic vertebrae showed lower performances than the ones implanted into nonosteoporotic specimen. Augmentation was negligible for screws implanted into nonosteoporotic specimen, whereas in osteoporotic vertebrae pedicle screw stability was significantly increased. For dynamic posterior stabilization system an increase of screwhead displacement was observed in comparison with standard fixation devices in both setups. CONCLUSION Augmentation enhances screw performance in patients with poor bone stock, whereas no difference is observed for patients without osteoporosis. Furthermore, dynamic stabilization systems have the possibility to fail when implanted in osteoporotic bone.

Die Rechtstellung der Synagogengemeinden in Preussen und die Reichsverfassung : ein Beitr. zur Revision der bisherigen Gesetzgebung

von Ismar Freund

Hygrical shrinkage stresses in tiling systems: Numerical modeling combined with field studies

To track down potential sites of material failure in the tile–mortar–substrate systems, locations and intensities of stress concentrations owing to drying-induced shrinkage are investigated. For this purpose, mechanical properties were measured on real systems and used as input parameters for numerical modeling of the effect of shrinkage of substrate and/or mortar using the finite element code Abaqus. On the base of different geometrical set-ups we demonstrate that stress concentrations in the mortar can become critical when (i) substantial mortar shrinkage occurs, (ii) substrate shrinkage can accumulate over considerable spatial distances, particularly (iii) in situations where the mortar layer is not separated from the substrate by a flexible waterproofing membrane. Hence material failure in the system tile–mortar–substrate can be prevented (or reduced) by (i) an application of the tiles after the major stages of substrate shrinkage, (ii) the use of elasto-plastic deformable tile adhesives which can react elastically on local stress concentrations, (iii) the implementation of flexible membranes, and (iv) a reduction of the field size by the installation of flexible joints.

Die früheren und gegenwärtigen Verhältnisse der Juden in den sämmtlichen Landestheilen des Preußischen Staates : eine Darst. u. Revision d. gesetzl. Bestimmungen über ihre staats- u. privatrechtlichen Zustände ; mit Benutzung der Archive der Ministerien des Innern und der Justiz

von Ludwig von Rönne u. Heinrich Simon

Incidence and causative agents of chemical eye injuries in Switzerland

CONTEXT Chemical eye injuries are ophthalmological emergencies with a high risk of secondary complications and severe visual loss. Only limited epidemiological data for such injuries are available for many countries. PATIENTS AND METHODS We performed two independent studies. The cause of chemical eye injuries was assessed with a prospective questionnaire study. Questionnaires were sent to all ophthalmologists in Switzerland. A total of 163 patients (205 eyes) were included, between December 2012 and October 2014. Independent of the questionnaire study, the incidence of chemical eye injuries was assessed with a retrospective cohort study design using the database of the mandatory accident insurance. RESULTS Ophthalmological questionnaires revealed that plaster/cement (20.5%), alkaline (12.2%) and acid (10.2%) solutions caused the highest number of chemical injuries. Only 2% of all injuries were classified as grade III and none as grade IV (Roper-Hall classification). The official toxicological information phone-hotline was contacted in 4.3% of cases. Using data from the accident insurance, an incidence of chemical eye injuries of about 50/100 000/year was found in the working population. CONCLUSION Here, we present data on the involved agents of chemical eye injuries in Switzerland, and also the incidence of such injuries in the working population. This may also help to assess the need for further education programs and to improve and direct preventive measures.

Assessment of the Breakaway Torque at the Posterior Pelvic Ring in Human Cadavers

PURPOSE To enhance the diminished screw purchase in cancellous, osteoporotic bone following the fixation of posterior pelvic ring injuries by iliosacral screws an increased bone-implant contact area using modificated screws, techniques or bone cement may become necessary. The aim of the study was to identify sites within the pathway of iliosacral screws requiring modifications of the local bone or the design of instrumentations placed at this site. MATERIALS AND METHODS The breakaway torque was measured mechanically at the iliosacral joint ("ISJ"), the sacral lateral mass ("SLM") and the center of the S1 ("CS1"), at a superior and an inferior site under fluoroscopic control on five human cadaveric specimens (3 female; mean age 87 years, range: 76-99) using the DensiProbe™Spine device. RESULTS The measured median (range) breakaway torque was 0.63 Nm (0.31-2.52) at the "iliosacral joint", 0.14 Nm (0.05-1.22) at the "sacral lateral mass", 0.57 Nm (0.05-1.42) at the "S1 center." The "sacral lateral mass" breakaway torque was lower than compared to that at the "iliosacral joint" (p < .001) or "S1 center" (p < .001). The median (range) breakaway torque measured at all superior measurement points was 0.52 Nm (0.10-2.52), and 0.48 Nm (0.05-1.18) at all inferior sites. The observed difference was statistically significant (p < .05). CONCLUSIONS The lateral mass of the sacrum provides the lowest bone quality for implant anchorage. Iliosacral screws should be placed as superior as safely possible, should bridge the iliosacral joint and may allow for cement application at the lateral mass of the sacrum through perforations.

Virtual Patients in continuing medical education and residency training: a pilot project for acceptance analysis in the framework of a residency revision course in pediatrics.

AIM Virtual patients (VPs) are a one-of-a-kind e-learning resource, fostering clinical reasoning skills through clinical case examples. The combination with face-to-face teaching is important for their successful integration, which is referred to as "blended learning". So far little is known about the use of VPs in the field of continuing medical education and residency training. The pilot study presented here inquired the application of VPs in the framework of a pediatric residency revision course. METHODS Around 200 participants of a pediatric nephology lecture ('nephrotic and nephritic syndrome in children') were offered two VPs as a wrap-up session at the revision course of the German Society for Pediatrics and Adolescent Medicine (DGKJ) 2009 in Heidelberg, Germany. Using a web-based survey form, different aspects were evaluated concerning the learning experiences with VPs, the combination with the lecture, and the use of VPs for residency training in general. RESULTS N=40 evaluable survey forms were returned (approximately 21%). The return rate was impaired by a technical problem with the local Wi-Fi firewall. The participants perceived the work-up of the VPs as a worthwhile learning experience, with proper preparation for diagnosing and treating real patients with similar complaints. Case presentations, interactivity, and locally and timely independent repetitive practices were, in particular, pointed out. On being asked about the use of VPs in general for residency training, there was a distinct demand for more such offers. CONCLUSION VPs may reasonably complement existing learning activities in residency training.

Beschluß der Plenar-Sitzung des Studenten-Ausschusses und der Commandanten und Hauptleute der akademischen Legion: Zu der in der akademischen Legion vorzunehmenden Revision hat Folgendes zur Richtschnur zu dienen ...

Welsch (Projektbearbeiter): Bekanntgabe der Bestimmungen über die Berechtigung zur Mitgliedschaft in der Wiener Akademischen Legion

Management of pelvic discontinuity in revision total hip arthroplasty: a review of the literature

Pelvic discontinuity is a complex problem in revision total hip arthroplasty. Although rare, the incidence is likely to increase due to the ageing population and the increasing number of total hip arthroplasties being performed. The various surgical options available to solve this problem include plating, massive allografts, reconstruction rings, custom triflanged components and tantalum implants. However, the optimal solution remains controversial. None of the known methods completely solves the major obstacles associated with this problem, such as restoration of massive bone loss, implant failure in the short- and long-term and high complication rates. This review discusses the diagnosis, decision making, and treatment options of pelvic discontinuity in revision total hip arthroplasty.