The morphology of a liquid-crystalline ABA triblock copolymer with polystyrene (PS) blocks (12 vol %) and a side chain nematic liquid crystalline B block has been studied by TEM and temperature dependent SAXS measurements. Above the clearing temperature (T c = 122 °C) the morphology is characterized by a body-centered cubic (bcc) lattice of polystyrene spheres. The transition to the nematic phase induces a reversible transition to a morphology of hexagonally packed cylinders by coalescence of the PS spheres along the [1,1,1] direction of the bcc lattice.

BackgroundAs several new tibial osteotomy plates recently appeared on the market, the aim of the present study was to compare mechanical static and fatigue strength of three newly designed plates with gold standard plates for the treatment of medial knee joint osteoarthritis.MethodsSixteen fourth-generation tibial bone composites underwent a medial open-wedge high tibial osteotomy (HTO) according to standard techniques, using five TomoFix standard plates, five PEEKPower plates and six iBalance implants. Static compression load to failure and load-controlled cyclic fatigue failure tests were performed. Forces, horizontal and vertical displacements were measured; rotational permanent plastic deformations, maximal displacement ranges in the hysteresis loops of the cyclic loading responses and dynamic stiffness were determined.ResultsStatic compression load to failure tests revealed that all plates showed sufficient stability up to 2400 N without any signs of opposite cortex fracture, which occurred above this load in all constructs at different load levels. During the fatigue failure tests, screw breakage in the iBalance group and opposite cortex fractures in all constructs occurred only under physiological loading conditions (<2400 N). The highest fatigue strength in terms of maximal load and number of cycles performed prior to failure was observed for the ContourLock group followed by the iBalance implants, the TomoFix standard (std) and small stature (sm) plates. The PEEKPower group showed the lowest fatigue strength.ConclusionsAll plates showed sufficient stability under static loading. Compared to the TomoFix and the PEEKPower plates, the ContourLock plate and iBalance implant showed a higher mechanical fatigue strength during cyclic fatigue testing. These data suggest that both mechanical static and fatigue strength increase with a wider proximal T-shaped plate design together with diverging proximal screws as used in the ContourLock plate or a closed-wedge construction as in the iBalance design. Mechanical strength of the bone-implant constructs decreases with a narrow T-shaped proximal end design and converging proximal screws (TomoFix) or a short vertical plate design (PEEKPower Plate). Whenever high mechanical strength is required, a ContourLock or iBalance plate should be selected.

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Background. The objective of the present study was to compare mechanical strength and stability of the newly designed spacer plate with the gold standard plate for the treatment of medial knee joint osteoarthritis. Materials and Methods. Ten fourth-generation tibial bone composites underwent a medial open-wedge high tibial osteotomy (HTO) according to standard techniques, using five TomoFix plates and five Contour Lock plates. Static compression load to failure and load-controlled cyclical fatigue failure tests were performed. Forces and horizontal displacements were measured; plastic deformations and dynamic stiffness were determined. Results and Discussion. In all samples, rotation of the tibial head and fracture of the opposite cortex were observed. Behaviors of the specimens under static loading were comparable between groups. Cyclic testing revealed lateral significant higher stiffness until failure for the Contour Lock compared to the TomoFix plate. No visible implant failure was observed in any group. Conclusion. Considering the static analysis, both plates offered sufficient stability under physiologic loads of up to 3000 N. The Contour Lock plate-fixated specimens showed a higher stability during the cyclic testing, supposedly due to the wider distance between the fixation screws.

The purpose of this study was to evaluate the reliability of a new developed device to measure tibial rotation, the Rotameter. Thirty healthy subjects (15 males, 15 females, 24 years) were examined with the Rotameter measurement device. External and internal rotation was performed at an applied torque of 5, 10 and 15 Nm by two independent examiners in order to test the inter-observer reliability. The patients were measured again after a mean of 31 +/- 43 days by the same examiners to test the intra-observer reliability. Statistical analysis was performed using the intra-class correlation coefficient. The Pearson Correlation coefficient was used to compare the measurements of the left with the right side of the participants. In the measurements, a high inter- and intra-observer reliability was found at 5, 10 and 15 Nm of applied torque for the external rotation, internal rotation and the rotational range (internal + external rotation). Comparison of the left and the right knee of the same participant also revealed high correlations in the Pearson correlation coefficient at all applied torques. In conclusion, the Rotameter testing device for the measurement of tibial rotation showed a high inter-observer and intra-observer reliability. It is easy to perform and might be used in a wide field as a non-invasive instrument to objectively determine rotational stability and to investigate the restoration of the rotational stability after surgical procedures.

The purpose of this study was the correlation of the results of a new measurement device for tibial rotation (Rotameter) in comparison with the measurements of a knee navigation system as standard method. In a biomechanical laboratory study, all soft tissues were removed from 20 human cadaveric knees leaving only the intact capsule and the bone. Specific tracers were bicortically fixed in the bone in order to measure tibial rotation using a knee navigation system. The knees were fixed to a custom-made inside-boot to rule out undesirable rotation of the reconstruction inside the Rotameter measurement device. Internal and external rotation values were measured at an applied torque of 5, 10 and 15 Nm. The different methods to evaluate tibial rotation were compared using the Pearson correlation coefficient. The correlations were deemed to be reliable if a value of >or=0.80 was achieved. At 5 Nm of applied torque, high correlations for the internal rotation, external rotation and the entire rotational range were found in the Pearson correlation coefficient between the Rotameter testing device in comparison with the knee navigation system as invasive reference method. These results were also confirmed at an applied torque of 10 and 15 Nm. In conclusion, the Rotameter testing device showed high correlations compared with the knee navigation system as an invasive standard method. It might be used as a non-invasive and easy alternative to investigate tibial rotation.

Noninvasive measurement of tibiofemoral rotation might be useful to detect anterior cruciate ligament tears and to evaluate the restoration of rotational stability after anterior cruciate ligament surgery.

Summary:Honeycomb composite structures are used in airplanes, railway cars and vehicles. The sandwich panels consist of two stiff face sheets of aluminium, which are bonded to a very lightweight honeycomb core of aluminium. Compared to normal plates, sandwich panels have a very high stiffness and simultaneously a low weight. The core of these structures is mainly subjected to shear stresses.The shear stresses depend strongly on the angle of the load application. The distribution and the level of the shear stresses are investigated using analytical calculations. The load direction which induces highest stresses in the honeycomb core is derived. This direction is not the W-direction, which is the most compliant one.When doing finite element simulations of honeycomb cores, often the core is homogenized in order to reduce the calculation time. In this article, some equations are derived in order to calculate the real shear stresses from the shear stresses of the homogeneous core.The equations are validated by finite element simulations and partially by tests. Three-point bending tests and additionally some Food Cart Roller Tests were conducted in order to test the panels in different angles.