Abnormal Bone Morphology in Charcot-Marie-Tooth Disease

Background: Although long suspected, it has yet to be shown whether the foot and ankle deformities of Charcot-Marie-Tooth disease (CMT) are generally associated with abnormalities in osseous shape. Computed tomography (CT) was used to quantify morphologic differences of the calcaneus, talus, and navicular in CMT compared with healthy controls. Methods: Weightbearing CT scans of 21 patients (27 feet) with CMT were compared to those of 20 healthy controls. Calcaneal measurements included radius of curvature, sagittal posterior tuberosity-posterior facet angle, and tuberosity coronal rotation. Talar measurements included axial and sagittal body-neck declination angle, and coronal talar head rotation. Surface-mesh model analysis of the hindfoot was performed comparing the average of the CMT cohort to the controls using a CT analysis software (Disior Bonelogic 2.0). Means were compared with a t test ( P < .05). Results: CMT patients had significantly less talar sagittal declination vs controls (17.8 vs 25.1 degrees; P < .05). Similarly, CMT patients had less talar head coronal rotation vs controls (30.8 vs 42.5 degrees; P < .001). The calcaneal radius of curvature in CMT patients was significantly smaller than controls (822.8 vs 2143.5 mm; P < .05). CMT sagittal posterior tuberosity–posterior facet angle was also significantly different from that of controls (60.3 vs 67.9 degrees respectively; P < .001). Surface-mesh model analysis demonstrated the largest differences in morphology at the navicular tuberosity, medial talar head, sustentaculum tali, and anterior process of the calcaneus. Conclusion: This is the first study to quantify the morphologic differences in hindfoot osteology seen in CMT patients. Patients identified with osseous changes of the calcaneus, especially a smaller axial radius of curvature, may benefit from a 3-dimensional osteotomy for correction.

Investigation on the Site of Coronal Deformities in Hallux Valgus

BackgroundHallux valgus (HV) is a common foot deformity that is more prevalent in females, characterised by abnormal adduction of the first metatarsal (MT) and valgus deviation of phalanx on the transverse plane. Increasing evidence indicates that HV is more than a 2D deformity but a 3D one with rotational malalignment. Pronation deformity is seen during clinical examination for HV patients, but the exact origin of this rotational deformity is still unknown. Some attribute it first tarsometatarsal (TMT) joint rotation, while others attribute it to intra-metatarsal bony torsion. In addition, the correlation between the rotational and transverse plane deformity is inconclusive. Identifying the origin of the rotational deformity will help surgeons choose the optimal surgical procedure while also enhancing our understanding of the pathophysiology of Hallux valgus.ObjectiveThis study aims to (1) develop an objective method for measuring the first MT torsion and first TMT joint rotation; (2) investigate the exact location of the coronal deformity in HV; (3) investigate the relationship between the severity of deformity on the transverse and coronal planes as well as the correlation between deformity severity and foot function/symptoms in HV.MethodsAge-matched females with and without HV were recruited at Foot and Ankle Clinic of the Department of Orthopaedics and Traumatology. Computed tomography was conducted for all subjects with additional weight-bearing dorsal-plantar X-ray examination for HV subjects. Demographic information of all subjects was recorded, and foot function was evaluated. Intra-class correlation was used to explore the relationship between deformities on different planes and the deformity severity and functional outcomes, respectively. Independent t-test was used to compare joint rotation degrees and bone torsion degrees.ResultsHallux Valgus patients had more TMT joint rotation but not MT torsion compared to normal controls. TMT joint rotation is significantly correlated with foot functions. No relationship was found between the coronal rotation and the 1,2-intermetatarsal angle (IMA) or Hallux valgus angle (HVA) on the transverse plane.ConclusionOur results indicate that coronal deformities in HV may originate from TMT joint rotation. In addition, the severity of the TMT joint coronal rotation correlates with worse foot function; thus, multi-plane assessment and examination will be important for more precise surgical correction in the future.

The Hip Center Rule Can be Used to Decide if Measured Pelvic Incidence is Accurate

Study Design Simulation study. Objective Pelvic incidence (PI) should be considered during surgical planning. The ideal patient position with both hip centers perfectly aligned for a lateral radiograph is rarely obtained. It has been suggested that a radiograph with axial and coronal rotation up to 20° is acceptable to obtain a measured PI within 6 degrees of the actual PI. We seek to: (1) evaluate the effect of variations in PI and patient malpositioning on measured vs true PI, and (2) determine whether the presence of one hip center within the bony acetabular rim of the contralateral hip can serve as a simple clinical decision rule on the accuracy of measured PI. Methods Published anthropometric three-dimensional pelvic landmark coordinates were used in this study. Radiographic projections were generated using linear algebra for combinations of axial and coronal rotation from −20° to +20°. True and measured PIs were compared. Results Rotation to 20° cannot be uniformly accepted as decision rule. Pelvises with higher PIs are more sensitive to malpositioning with greater PI deviation with smaller amounts of rotation. Diagnostic performance of the hip center rule demonstrated a sensitivity of 25.58% and a specificity of 100.00%. Conclusions Rather than assessing the quality of radiographs for PI measurement by magnitude of malpositioning, we recommend clinicians use the “hip center rule.” As long as at least one hip center is contained within the bony acetabular rim of the contralateral hip, there is high confidence that measured PI will be within 6° of true PI.

First Metatarsal Pronation Stratified by Tibial Sesamoid Position on Coronal Plane: A Study Based on Weight-Bearing Computed Tomography

Backgrounds: Few studies analyzed the coronal rotation of first metatarsal in hallux valgus patients with weightbearing computed tomography (WBCT). The purpose of this study is to investigate the association between hallux valgus parameters and first metatarsal head rotation in the coronal plane.Methods: Retrospective review of full standing WBCT scans were taken by PedCAT. A group of 123 patients with 216 feet, that intermetatarsal angle (IMA) >9 degrees and hallux valgus angle (HVA) >15 degrees, were included. 27 feet of 17 female included in control group. Measurements of forefoot hallux valgus parameters included IMA, HVA, distal metatarsal abduction angle (DMAA), metatarsal adduction angle (MAA), first metatarsal coronal rotation angle (α-angle), tibial sesamoid position (TSP) on dorsoplantar view, and sesamoid grading in the coronal plane. The differences of HVA, IMA, MAA, DMAA and α-angle in control and study group were compared by Wilcoxon rank test and student t test. Spearman correlation test was performed between α-angle and other parameters. General linear regression analysis was used to predict relationship parameters and α-angle.Results: The mean α-angle in the control group was 11.33±6.16 (range ,0-20) degrees, with the 95% confidence interval (CI) for the mean from 8.90 degrees to 13.77 degrees. The mean of α-angle in the study group was 23.75±6.32 (range,9-39) degrees, with the 95% CI from 22.90 degrees to 24.59 degrees. In the hallux valgus group, there were positive correlations between α-angle and IMA (Spearman’s correlation coefficient (rs) 0.137, P=0.044), DMAA (rs=0.176, P=.010) and TSP (rs=0.218, P=0.001). General linear regression analysis showed that α-angle was correlated with TSP (P<0.001). 208 hallux valgus feet (96.3%) had more pronation than the control group, whereas 8 feet (3.7%) had no or less pronation. Comparing the control and study subjects with the same TSP, means of α-angle showed significant difference, P=0.005.Conclusion: A large portion of hallux valgus patients had the first metatarsal pronation, which was positive correlated to TSP, IMA, and DMAA, and did not correlated to HVA and Smith grading. TSP is a useful predicting factor to α-angle changing. Level of Evidence: Level Ⅲ，Retrospective Cohort study

Evidence of a strong relationship between hemispheric asymmetry in solar coronal rotation and solar activity during solar cycle 24

ABSTRACT In this paper, we report evidence of a very strong and statistically significant relationship between hemispheric asymmetry in the solar coronal rotation rate and solar activity. Our approach is based on the cross-correlation of the hemispheric asymmetry index (AI) in the rotation rate with annual solar activity indicators. To obtain the hemispheric asymmetry in the solar rotation rate, we use solar full disc (SFD) images at 30.4-, 19.5- and 28.4-nm wavelengths for the 24th solar cycle, that is, for the period from 2008 to 2018, as recorded by the Solar Terrestrial Relations Observatory (STEREO) space mission. Our analysis shows that the hemispheric asymmetry in rotation rate is high during the solar maxima from 2011 to 2014. However, hemispheric asymmetry decreases gradually on both sides (i.e. from 2008 to 2011 and from 2014 to 2018). The results show that the AI leads sunspot numbers by ∼ 1.56 yr. This is a clear indication that hemispheric asymmetry triggers the formation of sunspots in conjunction with the differential rotation of the Sun.

Plasma and magnetic field dynamics in the young solar wind

&lt;p&gt;Parker Solar Probe (PSP) has completed four encounters with the Sun since launch, three with a perihelion of 35.7 solar radii and one at 27.9 solar radii in January of this year.&amp;#160; More than a factor of two closer to the Sun than any previous mission, observations by the spacecraft are already revealing a surprisingly dynamic and non-thermal solar wind plasma near the Sun.&amp;#160; An overview of initial findings related to the solar wind and coronal plasmas will be presented, including the discovery of large-amplitude velocity spikes, highly non-thermal distribution functions, and large non-radial flows of plasma near the Sun observed by the Solar Wind Electrons Alphas and Protons (SWEAP) Investigation plasma instruments and the FIELDS Investigation electromagnetic field instruments.&amp;#160; Once PSP dropped below a quarter of the distance from the Sun to the Earth, SWEAP began to detect a persistent and growing rotational circulation of the plasma around the Sun peaking at 40-50 km/s at perihelion as the Alfv&amp;#233;n mach number fell to 3. &amp;#160;This finding may support theories for enhanced stellar angular momentum loss due to rigid coronal rotation, but the circulation is large, and angular momentum does not appear to be conserved, suggesting that torques still act on the young wind at these distances. &amp;#160;PSP also measured numerous intense and organized Alfv&amp;#233;nic velocity spikes with strong propagating field reversals and large jumps in speed. &amp;#160;These field reversals and jets call for an overhaul in our understanding of the turbulent fluctuations that may, by energizing the solar wind, hold the key to its origin.&lt;/p&gt;

Differential rotation of the solar corona and its importance for helioseismology

&lt;p&gt;It is shown that the solar corona rotates differentially at all heliocentric distances up to the source surface. As the distance increases, the differential rotation gradient decreases, and the rotation becomes more and more rigid. At small distances, the corona at latitudes above $\approx \pm 40^{\circ}$ rotates faster than the photosphere at the same latitudes. The type of the rotation depends also on the phase of the activity cycle. The differential rotation gradient is the largest in the vicinity of the cycle minimum. It is shown that time variations in the coronal rotation characteristics are associated with the tilt of the magnetic equator of the Sun. Based on the concept that the differential rotation of the corona reflects the rotation of deep subphotospheric layers, we compared the changes in the coronal rotation characteristics with distance with the helioseismic data and showed their satisfactory agreement. The results obtained allow us to suggest that the rotation of the solar corona can be used as indicator of the differential rotation of subphotospheric layers and calculate the nature of some current sheets in heliosphere/&lt;/p&gt;

Systematic regularity of solar coronal rotation during the time interval 1939–2019

ABSTRACT The temporal variation of solar coronal rotation appears to be very complex and its relevance to the 11-year solar activity cycle is still unclear. Using the modified coronal index for the time interval from 1939 January 1–2019 May 31, the systematic regularities of solar coronal rotation are investigated. Our main findings are as follows. (1) From a global point of view, the synodic coronal rotation period with a value of 27.5 days is the only significant period at periodic scales shorter than 64 days. (2) The coronal rotation period exhibits an obvious decreasing trend during the time interval considered, implying that the solar corona accelerates its global rotation rate in the long run. (3) Significant periods of 3.25, 6.13, 9.53 and 11.13 years exist in coronal rotation, providing evidence that coronal rotation should be connected with the quasi-biennial oscillation, the 11-year solar cycle and the 22-year Hale cycle (or magnetic activity reversal). (4) The phase relationship between the coronal rotation period and solar magnetic activity is not only time-dependent but also frequency-dependent. For a small range around the 11-year cycle band, there is a systematic trend in phase and a small mismatch in this band causes the phase to drift. The possible mechanism for the above analysis results is discussed.

The Magellanic System: the puzzle of the leading gas stream

ABSTRACT The Magellanic Clouds (MCs) are the most massive gas-bearing systems falling into the Galaxy at the present epoch. They show clear signs of interaction, manifested in particular by the Magellanic Stream, a spectacular gaseous wake that trails from the MCs extending more than 150° across the sky. Ahead of the MCs is the ‘Leading Arm’ usually interpreted as the tidal counterpart of the Magellanic Stream, an assumption we now call into question. We revisit the formation of these gaseous structures in a first-infall scenario, including for the first time a Galactic model with a weakly magnetized, spinning hot corona. In agreement with previous studies, we recover the location and the extension of the Stream on the sky. In contrast, we find that the formation of the Leading Arm – that is otherwise present in models without a corona – is inhibited by the hydrodynamic interaction with the hot component. These results hold with or without coronal rotation or a weak, ambient magnetic field. Since the existence of the hot corona is well established, we are led to two possible interpretations: (i) the Leading Arm survives because the coronal density beyond 20 kpc is a factor ≳10 lower than required by conventional spheroidal coronal X-ray models, in line with recent claims of rapid coronal rotation; or (ii) the ‘Leading Arm’ is cool gas trailing from a frontrunner, a satellite moving ahead of the MCs, consistent with its higher metallicity compared to the trailing stream. Both scenarios raise issues that we discuss.