Early functional results after Hemiarthroplasty for femoral neck fracture: a randomized comparison between a minimal invasive and a conventional approach

BACKGROUND: A minimal invasive approach for elective hip surgery has been implemented in our institution in the past. It is widely hypothesized that implanting artificial hips in a minimal invasive fashion decreases surgical trauma and is helpful in the rehabilitation process in elective hip surgery. Thereby geriatric patients requiring emergency hip surgery also could theoretically benefit from a procedure that involves less tissue trauma. METHODS: Sixty patients who sustained a fractured neck of femur were randomly assigned into two groups. In the minimal invasive arm, the so called “direct anterior approach” (DAA) was chosen, in the conventional arm the Watson-Jones-Approach was used for implantation of a bipolar hemi-arthroplasty. Primary outcome parameter was the mobility as measured by the four-item-Barthel index. Secondary outcome parameters included pain, haemoglobin-levels, complications, duration of surgery, administration of blood transfusion and external length of incision. Radiographs were evaluated. RESULTS: A statistically significant difference (p = 0,009) regarding the mobility as measured with the four-item Barthel index was found at the 5th postoperative day, favouring the DAA. Evaluation of the intensity of pain with a visual analogue scale (VAS) showed a statistically significant difference (p = 0,035) at day 16. No difference was evident in the comparison of radiographic results. CONCLUSIONS: Comparing two different approaches to the hip joint for the implantation of a bipolar hemi-arthroplasty after fractured neck of femur, it can be stated that mobilization status is improved for the DAA compared to the WJA when measured by the four-item Barthel index, there is less pain as measured using the VAS. There is no radiographic evidence that a minimal invasive technique leads to inferior implant position. Level of Evidence: Level II therapeutic study

Strukturwandel von Chalkogen-Polykationen unter Druck

Im Rahmen dieser Arbeit wurden die strukturellen Umwandlungen von Tellur- und Selen-Polykationen führenden Festkörpern unter dem Einfluss von hohem Druck untersucht. Einkristalle der zu untersuchenden Substanzen in geeigneter Größe von etwa 0,1 mm wurden nach Literaturvorschriften über Gasphasentransportreaktionen hergestellt. Die Kristalle wurden in einer Diamantstempelpresse hydrostatischem Druck bis etwa 65 kbar ausgesetzt. Als druckübertragendes Medium, welches mit den halogenhaltigen Kristallen nicht unter hydrolytischer Zersetzung reagiert, bewährte sich ein Gemisch aus Pentan/Isopentan. Die diskreten, wannenförmigen Te62+-Ionen der Normaldruckmodifikation von Te6(WOCl4)2 liegen oberhalb von 45 kbar als unendlicher Stapel von äquidistanten Te3+-Dreiringen vor. Bei einer erneuten Untersuchung gelang es, den Druckbereich der Umwandlung genauer zu bestimmen und die Vermutung der metallischen Leitfähigkeit der Hochdruckmodifikation mit einer theoretischen Rechnung zu stützen. Leitfähigkeitsmessungen unter Druck und bei verschiedenen Temperaturen zeigen allerdings, dass die Substanz unter allen untersuchten Bedingungen ein Halbleiter ist. Bei Te8(VOCl4)2 deutet sich bereits bei Normaldruck eine verkleinerte Elementarzelle an. Die diskreten Te84+-Ionen ordnen sich, sobald diese kleine Elementarzelle erreicht wird, zu äquidistanten Stapeln von quadratischen Te42+-Ionen um. Die vollständige Umwandlung zur verkleinerten Zelle wird bis 65 kbar nicht erreicht. Te7(WOCl4)Cl und Te7(WOBr4)Br enthalten das eindimensionale, gefaltete Band des (Te72+)n-Ions. Bei der ersten Hochdruckphase werden die vormals ebenen Te7-Einheiten zu einer flachen Schale gefaltet. Eine weitere Erhöhung des Drucks auf 63 kbar führte bei Te7(WOCl4)Cl zu der erwarteten Hochdruckphase mit äquidistanten Te72+-Polykationen und einer deutlich kleineren Elementarzelle mit nur noch zwei Formeleinheiten pro Zelle. Bei Te7(WOBr4)Br konnten die Strukturen der späteren Hochdruckphasen nicht bestimmt werden. Te6I2(WCl6)2 enthält das näherungsweise würfelförmige Te6I22+-Ion. Durch den vergleichsweise geringen Druck von 8 kbar wird eine Phasenumwandlung von P21/c nach A2/m induziert. Die Elementarzelle und die Anordnung der Moleküle bleiben bei der Phasenumwandlung nahezu erhalten, die Moleküle nehmen aber in der Elementarzelle der Hochdruckform Positionen mit höherer Lagesymmetrie ein. Se9(MoOCl4)2 enthält ein helixartiges (Se92+)n-Polykation, das mit nur zweibindigen Se-Atomen vom Zintl-Klemm-Konzept abweicht. Es zeigte sich oberhalb von 35 kbar eine Phasenumwandlung, welche lediglich eine Zellzentrierung einführt, aber an den Strukturbausteinen selbst kaum Veränderungen bewirkt.Structural change of chalcogen polycations under pressure This study is about high pressure phase transitions of mostly tellurium polycationic structures. Single crystals of roughly 0,1 mm size were produced via chemical transport reactions according to literature. Those were loaded in a diamond anvil cell and set under hydrostatic pressure up to 65 kbar. A 1:1-mixture of n-pentane and iso-pentane was used as pressure transmission medium. Discrete tub-shaped Te62+-ions at normal pressure in Te6(WOCl4)2 convert to infinite equidistant chain of Te3+-rings at 45 kbar. The transition pressure was determined more exactly and the assumption of metallic conductivity was supported with theoretical calculations. Temperature dependant conductivity measurements however showed semiconductivity for all tested pressures. Even at normal pressure Te8(VOCl4)2 indicates a much smaller unit cell. The discrete Te84+-ions form an infinite equidistant chain of quadratic Te42+-ions as soon as the transition is reached. The transition pressure is higher than 65 kbar and was not found yet. Te7(WOCl4)Cl and Te7(WOBr4)Br contain the one-dimensional, folded band of (Te72+)n-ions. The first high pressure transition leads to a conversion of the previously planar groups of Te7 units to a flat bowl. A further increase of pressure to 63 kbar converts Te7(WOCl4)Cl to the expected modification with a chain of equidistant parallel Te72+-units and decreased the unit cell to just 2 formula units per cell from 4 at normal pressure and 8 for the first transition. The structures of the two monoclinic higher pressure modifications of Te7(WOBr4)Br could not be determined. Te6I2(WCl6)2 contains the roughly cube-shaped Te6I22+-ion. A relatively low pressure of 8 kbar induces a transmission from space group P21/c to A2/m. The unit cell and the alignment of the molecules are very similar, the molecules just change to higher local symmetry. Se9(MoOCl4)2 contains a helical (Se92+)n-polycation, which differs from the Zintl-Klemm-concept. Pressures from 35 kbar on showed a new modification, which introduces a cell-centering, but does not change the structure fragments

Three-Phase Catalytic Hydrogenation of a Functionalized Alkyne: Mass Transfer and Kinetic Studies with in Situ Hydrogen Monitoring

Systematic studies of mass transfer interactions with intrinsic reaction kinetics were performed for the threephase selective hydrogenation of 2-methyl-3-butyn-2-ol (MBY) to 2-methyl-3-buten-2-ol (MBE) over a modified Pd/CaC${O}_{3}$ catalyst under solvent free conditions. Hydrogen concentration in the liquid phase (${C}_{H2,b}$) was monitored in situ during the catalytic reaction by means of the Fugatron” analyzer. Reactions were carried out in an autoclave at different stirring rates at two concentrations of hydrogen (5 and 13 mol ·${m}^{-3}$ For stirring speeds higher than 1500 rpm no influence of gas-liquid mass transfer was observed. Hydrogen liquid-solid (L-S) mass transfer was found to be negligible, whereas the MBY mass L-S transfer becomes important at high MBY conversions at high hydrogen concentration. Low stirrer speed caused the reaction rate and MBE selectivity to decrease. No internal mass transfer limitations were observed, and conditions for the kinetic regime were found. The kinetics modeled ollowed the Langmuir-Hinshelwood mechanism and was consistent with the experimental data

Reactor for continuous polymerization in a high viscosity medium

The title reactor, of simple construction and suppressing segregation and overheating, consists of a tube filled with static mixing elements, sepd. into a 1st segment which is sepd. by a recirculating pump from the 2nd and 3rd segments, which form a piston-flow reactor. Thus, the polymn. of styrene in such a reactor with the 1st segment and recycle loop at 158 Deg and recycle ratio 10 gave a 60% conversion to polystyrene [9003-53-6] with no.-av. mol. wt. 93,000, polydispersity 1.9, viscosity of the polymn. medium .apprx.10 Pa-s, and energy consumption 0.00073 kW-h/kg. [on SciFinder (R)

Early functional results after Hemiarthroplasty for femoral neck fracture: a randomized comparison between a minimal invasive and a conventional approach

Abstract Background A minimal invasive approach for elective hip surgery has been implemented in our institution in the past. It is widely hypothesized that implanting artificial hips in a minimal invasive fashion decreases surgical trauma and is helpful in the rehabilitation process in elective hip surgery. Thereby geriatric patients requiring emergency hip surgery also could theoretically benefit from a procedure that involves less tissue trauma. Methods Sixty patients who sustained a fractured neck of femur were randomly assigned into two groups. In the minimal invasive arm, the so called “direct anterior approach” (DAA) was chosen, in the conventional arm the Watson-Jones-Approach was used for implantation of a bipolar hemi-arthroplasty. Primary outcome parameter was the mobility as measured by the four-item-Barthel index. Secondary outcome parameters included pain, haemoglobin-levels, complications, duration of surgery, administration of blood transfusion and external length of incision. Radiographs were evaluated. Results A statistically significant difference (p = 0,009) regarding the mobility as measured with the four-item Barthel index was found at the 5th postoperative day, favouring the DAA. Evaluation of the intensity of pain with a visual analogue scale (VAS) showed a statistically significant difference (p = 0,035) at day 16. No difference was evident in the comparison of radiographic results. Conclusions Comparing two different approaches to the hip joint for the implantation of a bipolar hemi-arthroplasty after fractured neck of femur, it can be stated that mobilization status is improved for the DAA compared to the WJA when measured by the four-item Barthel index, there is less pain as measured using the VAS. There is no radiographic evidence that a minimal invasive technique leads to inferior implant position. Level of Evidence: Level II therapeutic study.</p

Motionless mixers for the design of multitubular polymerization reactors

Exptl. investigations of the thermal bulk polymn. of styrene (I) in pilot plants of different sizes were done. Each pilot plant consisted of a tubular recycle reactor connected in series with a tubular reactor, both completely filled with Sulzer motionless mixers. Kinetic, reactor, and viscosity models were verified at I conversions ?96%, temps. ?210 Deg, and polystyrene mol. wts. ?360,000. Scale-up studies were done which confirmed that multitubular reactors of special design could be applied for industrial polymn. processes. [on SciFinder (R)

Mechanical behavior of additively and conventionally manufactured 316L stainless steel plates joined by gas metal arc welding

Combining several additive manufactured (AM) parts to larger parts by welding may be required due the limited building volume of powder bed AM methods. Laser powder bed fusion (LPBF) has a great potential because it enables the production of nearly full-density components through AM processes; however, additional residual stresses and production defects are induced by LPBF. These residual stresses affect the residual stress state of welded AM parts. In combination with the production related defects, both alter the mechanical and—in particular—the fatigue behavior of these welded joints. In this study, various tests are performed to characterize the butt joints of 316L AM steel plates made by gas metal arc welding. To this goal, joints are produced with weld seams parallel and vertical to the layer orientation of AM plates. The results are compared to joints of conventionally rolled steel plates produced with the same welding parameter. The residual stress states in initial (unloaded) condition and after cyclic loading were determined by X-ray diffraction techniques for AM and rolled plates. Complex residual stress states were determined at the welds made of AM steel plates compared to the welds made of rolled steel plates; however, the residual stress level in the heat affected zone of the butt-welded AM steel plates was similar to the welds made of hot-rolled steel plates. After cyclic loading with a high load level, high residual stress relaxations were observed in the parent materials. The fatigue design curve for butt joints from international standards is exceeded by all three test series, but the fatigue strength of the butt joints made by LBPF and hot rolling vary significantly. This is thought to be related to differences between the AM and conventional joints in microstructure, static strength, residual stress level, and small crack-like defects that partially interact with stress concentrations at the weld transition