Purpose
The WARPS/STAID classification employs clinical assessment of presenting features and anatomic characteristics to identify two distinct subsets of patients within the patellofemoral ...instability population. The purpose of this study was to further define the specific demographics and the prevalence of risky pathoanatomies in patients classified as either WARPS or STAID presenting with recurrent patellofemoral instability. A secondary purpose was to further validate the WARPS/STAID classification with the Banff Patella Instability Instrument (BPII), the Marx activity scale and the Patellar Instability Severity Score (ISS).
Methods
A convenience sample of 50 patients with recurrent patellofemoral instability, including 25 WARPS and 25 STAID subtype patients, were assessed. Clinical data were collected including assessment of demographic risk factors (sex, BMI, bilaterality of symptoms, affected limb side and age at first dislocation) and pathoanatomic risk factors (TT-TG distance, patella height, patellar tilt, grade of trochlear dysplasia, Beighton score and rotational abnormalities of the tibia or femur). Patients completed the BPII and the Marx activity scale. The ISS was calculated from the clinical assessment data. Patients were stratified into the WARPS or STAID subtypes for comparative analysis. An independent
t
test was used to compare demographics, the pathoanatomic risk factors and subjective measures between the groups. Convergent validity was tested with a Pearson
r
correlation coefficient between the WARPS/STAID and ISS scores.
Results
Demographic risk factors statistically associated with a WARPS subtype included female sex, age at first dislocation and bilaterality. Pathoanatomic risk factors statistically associated with a WARPS subtype included trochlear dysplasia, TT-TG distance, generalized ligamentous laxity, patellar tilt and rotational abnormalities. The independent t test revealed a significant difference between the ISS scores: WARPS subtype (
M
= 4.4, SD = 1.1) and STAID subtype (
M
= 2.5, SD = 1.5);
t
(48) = 5.2,
p
< 0.001. The relationship between the WARPS/STAID and the ISS scores, measured using a Pearson r correlation coefficient, demonstrated a strong relationship:
r
= −0.61,
n
= 50,
p
< 0.001.
Conclusions
This study has demonstrated statistically significant evidence that certain demographics and pathoanatomies are more prevalent in each of the WARPS and STAID patellofemoral instability subtypes. There was no difference in quality-of-life or activity level between the subtypes. The WARPS/STAID score demonstrated convergent validity to the ISS and divergent validity to the BPII score and the Marx activity scale. This study has further validated both the WARPS/STAID classification and the ISS of patients that present with recurrent patellofemoral instability.
Level of evidence
III.
The tensile properties and the deformation microstructure of pearlitic steel (0.8 wt % C) have been quantified in wires drawn to strains in the range from 3.7 to 5.4, having a flow stress in the ...range from 3.5 to 4.5 GPa. With increasing strain the interlamellar spacing (ILS) decreases from about 20 to 10 nm and the thickness of the cementite lamellae decreases from about 2 nm to about 0.7 nm, representing a structure, which breaks up at large strains, decomposes and releases carbon to the ferrite lamellae. The dislocation density increases continuously with strain and reaches about 5 × 1016 m−2 at a strain of 5.4; the dislocations are stored as threading dislocations, as dislocation tangles and as cell boundaries with low to medium misorientation angles. An analysis of the evolution of microstructure and strength with increasing strain suggests that dislocation-based plasticity is a dominating mechanism in the wire and three strengthening mechanisms are applied: boundary strengthening, dislocation strengthening and solid solution hardening with their relative contributions to the total flow stress which change as the strain is increased. Based on linear additivity good correspondence between the calculated and the measured flow stress is observed over the strain range 0–5.4. However at large strains beyond 3.7 deviations are observed which are discussed in terms of the applied strength-structure relationships.
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•Relationship between dislocation annihilation and dislocation type is revealed.•The cause of almost no annihilation of edge dislocations is explained.•Reason for the failure of AlGaN and AlN layers ...to block dislocations is given.
In this work, we have found that there is a clear difference between the annihilation of screw dislocation and edge dislocation, and the density of edge dislocations remains almost unchanged during the growth from AlN to GaN. Through the transmission electron microscope (TEM), the internal mechanism of this phenomenon has been explored in this paper, which can be attributed to the failure of AlGaN buffer layer and AlN insertion layer to block the edge dislocation. The explanation proposed in this paper may provide new ideas to further reduce the dislocations in GaN-on-Si, improving the crystal quality.
Radial head dislocation with no associated lesions, is a relatively uncommon injury in children. In this case report, it is reported a case of anteromedial locked radial head dislocation in children, ...and we discuss its clinical presentation and pathogenetic mechanism of injury.
An 8-year-old girl fell off on her right forearm with her right elbow extended in hyperpronation. An isolated radio-capitellar dislocation was identified with no other fractures or neurovascular injuries associated. Elbow presented an extension-flexion arc limited (0°- 90°), and the prono-supination during general anesthesia shows "a sling effect" from maximal pronation (+ 55°) and supination (+ 90°) to neutral position of forearm. The radial head dislocation was impossible to reduce and an open reduction was performed using lateral Kocher approach. The radial head was found "button-holed" through the anterior capsule. The lateral soft tissues were severely disrupted and the annular ligament was not identifiable. Only by cutting the lateral bundle of the capsule was possible to reduce the joint. At 50 moths follow-up, patient presented a complete Range of motion (ROM), complete functionality and no discomfort or instability even during sport activities.
It is important to understand the pathogenic mechanisms of locked radial head dislocation in children. Some mechanism described are the distal biceps tendon or the brachialis tendon interposition. However even the anterior capsule can hinder reduction. A characteristic "sling-effect" of the forearm could be pathognomonic for capsular button-holing. Surgical release of the capsular bundle sometimes is the only way to reduce the dislocation and obtain a good outcome.
High threading dislocation (TD) density in GaN-based devices is a long unresolved problem because of the large lattice mismatch between GaN and the substrate, which causes a major obstacle for the ...further improvement of next-generation high-efficiency solid-state lighting and high-power electronics. Here, we report InGaN/GaN LEDs with ultralow TD density and improved efficiency on a sapphire substrate, on which a near strain-free GaN compliant buffer layer was grown by remote plasma atomic layer deposition. This "compliant" buffer layer is capable of relaxing strain due to the absorption of misfit dislocations in a region within ~10 nm from the interface, leading to a high-quality overlying GaN epilayer with an unusual TD density as low as 2.2 × 10(5) cm(-2). In addition, this GaN compliant buffer layer exhibits excellent uniformity up to a 6" wafer, revealing a promising means to realize large-area GaN hetero-epitaxy for efficient LEDs and high-power transistors.
The synergistic action of local elemental distribution, and in particular Re doping, with interfacial dislocations at the γ/γ′ interface is still one of the most considered and unclear issues during ...creep of nickel-based single-crystal superalloys. In order to investigate this problem, a detailed characterization of interfacial dislocations in a DD6 superalloy after creep loading for 12h at high temperature and low stress was carried out using transmission electron microscopy and high-angle annular dark field scanning transmission electron microscopy techniques. In addition, the local elemental distribution near dislocation core regions was determined by energy dispersive X-ray spectroscopy (EDS) mapping. It was found for the first time that three types of interfacial protrusions are formed at the γ/γ′ interface after creep loading for 12h under conditions of high temperature and low stress and demonstrated that the formation of these features originates from dislocation motion. Additionally, EDS mapping provides evidence for co-segregation of Re with Cr and Co at the tip of the protrusions. Based on this, a model concerning dislocation core structure and dislocation climb was proposed to explain the different morphology of the protrusions. The observations highlight the importance of the coupling between Re segregation and γ/γ′ interfacial dislocations for improving creep properties in nickel-based superalloys. The results of the study will be beneficial for the design of new high-temperature materials and for understanding the origin of the effect of Re additions in nickel-based single-crystal superalloys.
We have investigated the interface dislocations in InxGa1−xN/GaN heterostructures (0 ≤ x ≤ 0.20) using diffraction contrast analysis in a transmission electron microscope. The results indicate that ...the structural properties of interface dislocations depend on the indium composition. For lower indium composition (up to x = 0.09), we observed that the screw-type dislocations and dislocation half-loops occurred at the interface, even though the former do not contribute toward elastic relaxation of the misfit strain in the InGaN layer. With the increase in indium composition (0.13 ≤ x ≤ 0.17), in addition to the network of screw-type dislocations, edge-type misfit dislocations were generated, with their density gradually increasing. For higher indium composition (0.18 ≤ x ≤ 0.20), all of the interface dislocations are transformed into a network of straight misfit dislocations along the <10–10> direction, leading to partial relaxation of the InGaN epilayer. The presence of dislocation half-loops may be explained by a slip on basal plane; formation of edge-type misfit dislocations are attributed to punch-out mechanism.
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