Patella intraosseous blood flow disturbance during a medial or lateral arthrotomy in total knee arthroplasty: a laser Doppler flowmetry study

Patella complications are recognized sequelae of total knee arthroplasty (TKA). Disruption of blood flow to the patella and adjacent soft tissues during surgery may contribute to reduced viability of the bone and patella ligament tissue. The effect on genicular blood flow to the medial and lateral patella was compared for a medial (MA) and lateral arthrotomy (LA) during TKA. Laser Doppler flowmetry was used to measure both baseline and postarthrotomy flow in vivo for 16 primary TKA patients. Flow in the lateral patella was reduced approximately 20% for both MA and LA. Conversely, the use of MA resulted in substantial reduction in flow to the medial patella (53%) compared to the lateral approach (27%). A large standard deviation of scores was evident in all cases. Although there was a tendency for LA to disturb the patellar blood flow less, the difference was not significant. It was concluded that neither approach is superior regarding the blood flow preservation to the patella. Hence, a lateral approach might only have an advantage in knee joints that are likely to need a lateral release in combination with an MA—e.g., a valgus deformity or preoperative patella maltrackin

Combined spectral and temporal analysis of a Her X-1 Turn-On

Der 35 Tage Zyklus im akkretierenden Röntgenpulsar Her X-1 ist einer der deutlichsten Beobachtungs-Hinweise für eine geneigte, verbogene und präzedierende Akkretionsscheibe in einem Doppelsternsystem. Im September 1997 wurde die Quelle mit dem Röntgensatelliten RXTE mit hoher zeitlicher und spektraler Auflösung im Spektralbereich von 2-200 keV beobachtet. Die Beobachtung mit einer Gesamtlänge von 3 Tagen umfasst einen Turn-On des 35 Tage Präzessions-Zyklus der Akkretionsscheibe. Dies entspricht dem Zeitraum, zu dem der äußere Rand der Akkretionsscheibe die Sicht auf den Neutronenstern frei gibt. Diese Arbeit stellt die Ergebnisse einer zeitlichen und spektralen Analyse der Daten vor. Das phasengemittelte Kontinuum von Her X-1 während des Turn-On wird gut durch ein Partial Covering Modell beschrieben. Dieses Modell setzt sich zusammen aus einer stark absorbierten Power-Law-Komponente (alpha ungefähr 1.0) mit einem exponentiellen Abfall (E_cut ungefähr 21 keV) und einer zusätzlichen spektralen Komponente mit gleichem Verlauf die nicht absorbiert ist. Das Spektrum weisst eine Eisenfloureszenzlinie bei ungefähr 6.4 keV auf und zeigt eine schwache Zyklotronresonanzlinie bei 39.9 keV. Die Energieauflösung des PCA von RXTE ist zu niedrig, um eine systematische Variation der Eisenlinie mit der Zeit zu untersuchen. Aus der Linienlage der Zyklotronlinie lässt sich direkt eine Magnetfeldstärke von 4.1x10^12 Gauss ableiten. Die Rotationsperiode des Neutronensterns wurde aus den Daten bestimmt und ist in guter Übereinstimmung mit den Ergebnissen aus anderen Beobachtungen. Dies bestätigt die lang anhaltende Spin-Up Phase von Her X-1, die sich erst vor kurzer Zeit zu einem Spin-Down geändert hat. Eine Zerlegung des Pulsprofils in die Beiträge der beiden Neutronensternpole liefert ähnliche Ergebnisse für den Turn-On, wie die für das Pulsprofil im Main-On. Das beobachtete Pulsprofil wird bei hohen Energien von einem "Pencil Beam" Anteil dominiert, aber beinhaltet auch Anteile eines "Fan Beams". Die Änderungen des Pulsprofils und des Anteils an gepulstem Fluss zu Beginn des Turn-On sind konsistent mit der Form eines Main-On Pulsprofils, das durch photoelektrische Absorption und Thomson-Streuung beeinflusst ist. Die Entwicklung der Wasserstoffsäulendichte N_h und der Covering Fraction während des Turn-Ons kann durch ein einfaches geometrisches Modell erklärt werden, das eine Akkretionsscheibenkorona und den äusseren Rand der Akkretionsscheibe mit einbezieht. Das Modell kann auch die beobachtete Entwicklung des Pulsprofils in den unterschiedlichen Energiebereichen erklären. Zusätzlich wurden die zeitliche Signatur einer streuenden heissen Korona auf gepulste und gerichtete Emission untersucht und die Ergebnisse dargestellt. Ein Vergleich der Ergebnisse der Simulation mit den beobachteten Pulsprofilen unterstützt das geometrische Modell des Turn-Ons.The 35 day cycle of the accreting X-ray pulsar Her X-1 provides one of the best evidences for an inclined, warped, and precessing accretion disk in a binary system. In 1997 September the source was observed with the X-ray satellite RXTE with high temporal and spectral resolution in the energy band of 2-200 keV. The 3 days long observation covers a full turn-on of the 35 day precession cycle of the accretion disk, which is the time when the outer edge of the disk frees the line of sight to the neutron star. In this thesis I present results of the temporal and spectral analysis of the data. The phase averaged continuum spectrum of Her X-1 during the turn-on is well described by a partial covering model, which combines a heavily absorbed power-law spectral component (alpha approx. 1.0) with an exponential cut-off (E_cut approx. 21 keV) and a similar spectral component which is not affected by absorption. The spectrum shows a strong signature of iron flourescent emission at approx. 6.4 keV and a weak Cyclotron resonant scattering feature at 39.9 keV. The energy resolution of the PCA on-board of RXTE is too low for a systematic study of a variation of the iron line with time. The energy of the CRSF indicates a magnetic field strength of 4.1x10^12 Gauss which confirms recent findings. The spin period of the neutron star was determined from the data and is in agreement with other observations. This confirms the long spin-up period of Her X-1 which only recently changed to a spin-down. A decomposition of the pulse profile into the contribution of the two neutron star poles gives similar results for the turn-on as for the main-on pulse profile. The observed pulse profile is dominated by a "pencil beam" component at high energies, but shows a signature of a "fan beam" component as well. The changes in shape of the pulse profile and the pulsed flux ratio towards the beginning of the turn-on are consistent with the shape of a main-on pulse profile which is modified by photoelectric absorption and Thomson scattering. The evolution of the absorbing column N_h and the covering fraction during the turn-on can be explained by a simple geometric model which includes an accretion disk corona and the influence of the outer accretion disk rim. This model can also explain the observed pulse evolution in different energy bands. In addition the temporal signature of a partially ionized corona on beamed and pulsed emission is simulated and the results presented. These results in turn are used to simulate the influence of a scattering hot corona on pulsed emission. Comparing the results of the simulations with the observed pulse profiles supports the presented geometric model of the turn-on

Validation of Compton Scattering Monte Carlo Simulation Models

Several models for the Monte Carlo simulation of Compton scattering on electrons are quantitatively evaluated with respect to a large collection of experimental data retrieved from the literature. Some of these models are currently implemented in general purpose Monte Carlo systems; some have been implemented and evaluated for possible use in Monte Carlo particle transport for the first time in this study. Here we present first and preliminary results concerning total and differential Compton scattering cross sections.Comment: 5 pages, 3 figures, to be published in the Proceedings of IEEE Nuclear Science Symposium 201

Dynamic plate osteosynthesis for fracture stabilization: how to do it

Plate osteosynthesis is one treatment option for the stabilization of long bones. It is widely accepted to achieve bone healing with a dynamic and biological fixation where the perfusion of the bone is left intact and micromotion at the fracture gap is allowed. The indications for a dynamic plate osteosynthesis include distal tibial and femoral fractures, some midshaft fractures, and adolescent tibial and femoral fractures with not fully closed growth plates. Although many lower limb shaft fractures are managed successfully with intramedullary nails, there are some important advantages of open-reduction-and-plate fixation: the risk of malalignment, anterior knee pain, or nonunion seems to be lower. The surgeon performing a plate osteosynthesis has the possibility to influence fixation strength and micromotion at the fracture gap. Long plates and oblique screws at the plate ends increase fixation strength. However, the number of screws does influence stiffness and stability. Lag screws and screws close to the fracture site reduce micromotion dramatically

First functionality tests of a 64 x 64 pixel DSSC sensor module connected to the complete ladder readout

The European X-ray Free Electron Laser (XFEL.EU) will provide every 0.1 s a train of 2700 spatially coherent ultrashort X-ray pulses at 4.5 MHz repetition rate. The Small Quantum Systems (SQS) instrument and the Spectroscopy and Coherent Scattering instrument (SCS) operate with soft X-rays between 0.5 keV - 6keV. The DEPFET Sensor with Signal Compression (DSSC) detector is being developed to meet the requirements set by these two XFEL.EU instruments. The DSSC imager is a 1 mega-pixel camera able to store up to 800 single-pulse images per train. The so-called ladder is the basic unit of the DSSC detector. It is the single unit out of sixteen identical-units composing the DSSC-megapixel camera, containing all representative electronic components of the full-size system and allows testing the full electronic chain. Each DSSC ladder has a focal plane sensor with 128 x 512 pixels. The read-out ASIC provides full-parallel readout of the sensor pixels. Every read-out channel contains an amplifier and an analog filter, an up-to 9 bit ADC and the digital memory. The ASIC amplifier have a double front-end to allow one to use either DEPFET sensors or Mini-SDD sensors. In the first case, the signal compression is a characteristic intrinsic of the sensor; in the second case, the compression is implemented at the first amplification stage. The goal of signal compression is to meet the requirement of single-photon detection capability and wide dynamic range. We present the first results of measurements obtained using a 64 x 64 pixel DEPFET sensor attached to the full final electronic and data-acquisition chain.Comment: Preprint proceeding for IWORID 2016, 18th International Workshop on Radiation Imaging Detectors, 3rd-7th July 2016, Barcelona, Spai

A Method for the Quantification of Intracellular Zidovudine Nucleotides

An assay to quantify the phosphorylation products of zidovudine (AZT) in peripheral blood mononuclear cells (PBMC) was developed. Extracts of PBMC were separated by high-performance liquid chromatography. Eluted AZT mono- (MP), di- (DP), and triphosphate (TP) were collected in separate portions. Treatment with alkaline phosphatase yielded equimolar amounts ofAZT, which after solid-phase enrichment were assayed by radioimmunoassay. Detection limit was 0.1 pmol/106 PBMC for each nucleotide. Recoveries of 102%-118% were observed. AZT nucleotides were measured in samples from three patients receiving 250 mg ofAZT every 12 h. Intracellular concentrations of AZT-MP after 1-2 h ranged from 0.9 to 1.4 pmol/106 PBMC and then declined to 0.3-1.1 pmol/106 PBMC after 4 h. AZT-DP and AZT-TP reached concentrations of 0.3-0.5 pmol/106 PBMC after 1-2 h and could not be detected after 4 h in any of the three patients. Duplicate determinations deviated by <20

Background Simulations of the Wide Field Imager of the ATHENA X-Ray Observatory

The ATHENA X-ray Observatory-IXO is a planned multinational orbiting X-ray observatory with a focal length of 11.5m. ATHENA aims to perform pointed observations in an energy range from 0.1 keV to 15 keV with high sensitivity. For high spatial and timing resolution imaging and spectroscopic observations the 640x640 pixel^2 large DePFET-technology based Wide field Imager (WFI) focal plane detector, providing a field of view of 18 arcsec will be the main detector. Based on the actual mechanics, thermal and shielding design we present estimates for the WFI cosmic ray induced background obtained by the use of Monte-Carlo simulations and possible background reduction measures.Comment: IEEE NSS MIC Conference 2011, Valencia, Spai

The interaction between the vastus medialis and vastus intermedius and its influence on the extensor apparatus of the knee joint

Although the vastus medialis (VM) is closely associated with the vastus intermedius (VI), there is a lack of data regarding their functional relationship. The purpose of this study was to investigate the anatomical interaction between the VM and VI with regard to their origins, insertions, innervation and function within the extensor apparatus of the knee joint.Methods: Eighteen human cadaveric lower limbs were investigated using macro-dissection techniques. Six limbs were cut transversely in the middle third of the thigh. The mode of origin, insertion and nerve supply of the extensor apparatus of the knee joint were studied. The architecture of the VM and VI was examined in detail, as was their anatomical interaction and connective tissue linkage to the adjacent anatomical structures.Results: The VM originated medially from a broad hammock-like structure. The attachment site of the VM always spanned over a long distance between: (1) patella, (2) rectus femoris tendon and (3) aponeurosis of the VI, with the insertion into the VI being the largest. VM units were inserted twice—once on the anterior and once on the posterior side of the VI. The VI consists of a complex multi- layered structure. The layers of the medial VI aponeurosis fused with the aponeuroses of the tensor vastus intermedius and vastus lateralis. Together, they form the two- layered intermediate layer of the quadriceps tendon. The VM and medial parts of the VI were innervated by the same medial division of the femoral nerve.Conclusion: The VM consists of multiple muscle units inserting into the entire VI. Together, they build a potential functional muscular complex. Therefore, the VM acts as an indirect extensor of the knee joint regulating and adjusting the length of the extensor apparatus throughout the entire range of motion. It is of clinical importance that, besides the VM, substantial parts of the VI directly contribute to the medial pull on the patella and help to maintain medial tracking of the patella during knee extension. The interaction between the VM and VI, with responsibility for the extension of the knee joint and influence on the patellofemoral function, leads readily to an understanding of common clinical problems found at the knee joint as it attempts to meet contradictory demands for both mobility and stability. Surgery or trauma in the anteromedial aspect of the quadriceps muscle group might alter a delicate interplay between the VM and VI. This would affect the extensor apparatus as a whole