Declination Angle Research Articles

Method and algorithm for determining the geographic coordinates of ground objects from an unmanned aerial vehicle

Introduction: As practice shows, the accuracy of determining the coordinates of objects is influenced by many factors associated with the presence of errors in measuring the angular coordinates of the optical system, the distance to the object and the presence of an inhomogeneous terrain. Purpose: Improving the accuracy of determining the geographic coordinates of ground objects from an unmanned aerial vehicle. Results: A method and an algorithm for determining geographic coordinates based on the use of a digital terrain model and optimization methods have been developed. The accuracy of calculating the coordinates of the object is increased by minimizing the error in measuring the declination angle, azimuth to the target and slant range. To confirm the analytical calculations, a field experiment was carried out with a car on the ground. At a considerable distance, at which the slant range was 900 m, several data freeze frames were taken. As a result of calculations, the geographical coordinates of the car were obtained in two ways (traditional and developed). Ultimately, the accuracy of calculating coordinates using the developed method is 4.8 times higher. Practical relevance: The method and algorithms for information processing proposed in the work will make it possible to create a number of hardware and software solutions for guidance and target designation systems.

The effects of depth perception viewing on hand–eye coordination in virtual reality environments

AbstractVirtual reality (VR) has been applied to many fields such as visualization, architecture, education, medical science, and sports simulation. Recent VR advancements allow direct manipulation of three‐dimensional (3D) objects in interactive displays, but problems of inefficiency in movement due to inaccuracy in depth perception have been reported. As human interaction in virtual environments (VE) is being realized, factors that may affect depth perception and movement need to be addressed. This study investigated the effects of viewing angle, stereo viewing technology, and visual cues on hand movement performance in a 3D movement task. Ten right‐handed participants performed continuous Fitts' pointing tasks using a computer mouse. Participants were asked to move a cursor to a target ball as quickly as possible. Fitts' law was employed to test effects to capture differences while the hand was moving in the 3D space under three factors, angle of declination, visual depth, and space cue and with varied index of difficulty (ID). Movement time (MT), error rate, and throughput (TP) were recorded as dependent variables. This study found significant effects of angle of declination, visual depth, space cue, and ID. This study investigated the effectiveness of hand movements in 3D environments for a further immersive VE using a two‐dimensional (2D) mouse. Potential applications of this research include the design of interactive 3D display interfaces in which fast and accurate selection is required and the manipulation of 3D objects in 3D environments may be expected.

Abrasive Waterjet (AWJ) Forces-Potential Indicators of Machining Quality.

The necessity of monitoring the abrasive waterjet (AWJ) processes increases with the spreading of this tool into the machining processes. The forces produced on the workpiece during the abrasive waterjet machining can yield some valuable information. Therefore, a special waterjet-force measuring device designed and produced in the past has been used for the presented research. It was tested during the AWJ cutting processes, because they are the most common and the best described up-to-date AWJ applications. Deep studies of both the cutting process and the respective force signals led to the decision that the most appropriate indication factor is the tangential-to-normal force ratio (TNR). Three theorems concerning the TNR were formulated and investigated. The first theorem states that the TNR strongly depends on the actual-to-limit traverse speed ratio. The second theorem claims that the TNR relates to the cutting-to-deformation wear ratio inside the kerf. The third theorem states that the TNR value changes when the cutting head and the respective jet axis are tilted so that a part of the jet velocity vector projects into the traverse speed direction. It is assumed that the cutting-to-deformation wear ratio increases in a certain range of tilting angles of the cutting head. This theorem is supported by measured data and can be utilized in practice for the development of a new method for the monitoring of the abrasive waterjet cutting operations. Comparing the tilted and the non-tilted jet, we detected the increase of the TNR average value from 1.28 ± 0.16 (determined for the declination angle 20° and the respective tilting angle 10°) up to 2.02 ± 0.25 (for the declination angle 30° and the respective tilting angle of 15°). This finding supports the previously predicted and published assumptions that the tilting of the cutting head enables an increase of the cutting wear mode inside the forming kerf, making the process more efficient.

Effects of receiver parameters on the optical efficiency of a fixed linear-focus Fresnel lens solar system with sliding adjustment

To effectively eliminate optical end loss for small-scale linear solar concentrators, a fixed linear-focus Fresnel lens solar system (FLFS) with triangle cavity receiver is described and the principle is provided. The effects of the receiver parameters including receiver position f, solar declination angle δ, solar hour angle ω, internal surface absorptivity αab and end plane reflectivity ρr on the end loss ratio (μoel) and relative optical efficiency (ηre−opt) of the proposed system have been studied by the control variable method and Monte Carlo ray tracing (MCRT) method which is implemented by software TracePro®. Significance tests of critical factors are conducted to assess the effect of receiver parameters. These results revealed that the FLFS could effectively solve the problem of optical end loss of linear solar concentrators. When f=650 mm and δ= 0°, 8°, 16°, and 23°27′, the corresponding average ηre−opt at ω from 0° to 60° are 0.9459, 0.9422, 0.9145, and 0.8144, respectively. As δ increases, reducing f can ensure the system operates at a high-efficiency state. The ηre−opt shows a positive relationship with αab and no relationship with ρr. δ occupies the greatest significant influence on ηre−opt, which is followed by ω, αab and f.

Effects of Receiver Parameters on Solar Flux Distribution for Triangle Cavity Receiver in the Fixed Linear-Focus Fresnel Lens Solar Concentrator

The objective of the study is to investigate and optimize the solar flux uniformity of a fixed linear-focus Fresnel lens solar concentrator using a triangle cavity receiver. The effects of receiver parameters including the vertical distance from the cavity opening plane to the Fresnel lens f, receiver internal surface absorptivity αab, end reflection plane reflectivity ρr, solar declination angle δ and solar angle ω on the uniformity factor (UF) of a triangle cavity receiver were carried out. The effects of receiver parameters are evaluated with a significance test of critical factors. The results showed that the increase in f and δ would result in an increase in the UF. The average UF with f = 600, 625, 650, 675 and 700 mm, respectively, are 0.5030, 0.5858, 0.6337, 0.6576 and 0.6784 for ω in range of 0–60°. Moreover, the UF increases as αab decreases when other receiver parameters are constant for the δ of 0–8°. The ρr has a limited effect on the UF until δ becomes relatively larger and ω becomes relatively smaller. Furthermore, ω effects are most significant on the UF, followed by δ, f and αab. Setting a suitable f is the most economical and effective way to improve the UF.

Qualitative study of musculoskeletal tissues and their radiographic correlates in diabetic neuropathic foot deformity

BackgroundDiabetes mellitus (DM) with peripheral neuropathy (PN) results in foot deformity increasing ulceration, joint dislocation, and amputation risk. This study describes the frequency and severity of foot and ankle musculoskeletal abnormalities and their relationship to radiographic alignment in people with DMPN with (DMPN + MCD) and without (DMPN − MCD) medial column deformity (MCD) compared to age- and body mass index-matched controls without DMPN or MDC. MethodsDMPN + MCD (n = 11), DMPN − MCD (n = 12), and controls (n = 12) were studied. A radiologist scored foot and ankle magnetic resonance images (MRI) for abnormalities in tendons/fascia, ligaments, muscles, joints, and bones. Higher scores represent greater abnormalities. Foot alignment was measured from lateral weightbearing radiographs. Frequency of abnormalities between groups and relationships between abnormalities and foot alignment in the combined group (n = 35) were examined. ResultsDMPN + MCD had higher total muscle, joint, and bone scores compared to controls and higher total joint scores than DMPN − MCD. DMPN − MCD had higher total muscle scores than controls. DMPN + MCD higher bone and joint scores were driven by increased frequency of osteophytes, cartilage damage, focal bone marrow edema, new bone formation, and subchondral cysts. Significant correlations included cuboid height and total bone and joint scores (ρ = −0.37 and ρ = −0.40, respectively) and talar declination angle and total joint score (ρ = 0.38). ConclusionHigh contrast resolution MRI allowed identification of structural lesions of the foot affecting the cartilage surfaces, bone marrow, and soft tissue supports in patients with DMPN + MCD. As expected, the presence of bone and joint lesions on MRI were strongly associated with DMPN + MCD; surprisingly, although the sample is small, lesions of the soft tissue supports were not associated with MCD. While MRI is not done routinely to investigate MCD, opportunistic use of the information from MRI done for the common clinical indications may allow early identification of the structural lesions associated with MCD and facilitate early, aggressive therapy. Level of evidenceIII.

Halluks Valgus Deformitesinin Tanımlanmasında Tripod İndeksin Etkinliği : Retrospektif Bir Çalışma

Aim: The aim of this study is to investigate the effectiveness and reliability of the Tripod Index (TI) in defining hallux valgus (HV) deformity and accompanying deformities and evaluating the treatment outcome. Material and Methods: Fifty and fifty two patients were included to the study who underwent Chevron (group 1) and proximal dome (group 2) osteotomy, respectively. Preoperative and postoperative hallux valgus angle (HVA), intermetatarsal angle (IMA), Meary angle (MA), talar declination angle (TDA), calcaneal tilt angle (CIA), talar head opening (THU) and TI were measured. Then, the relationship between TI and other angular variables was evaluated. Results: There was no significant difference between the mean age, body mass index (BMI), side and gender of the patients in both groups. The mean values of HVA and IMA differed between two groups both pre- and postoperatively. The preoperative TDA, THU and MA values were significantly higher in group 2. The preoperative mean CIA was significantly higher in group 1. The preoperative value of the TI was significantly higher in group 2. There was a significant decrease in all angular parameters in group 2 postoperatively. There was a significant decrease in mean HVA, IMA and TI postoperatively in group 1. There was strong correlation between TI and IMA, THU, CIA, TDA and MA, and moderate correlation with HVA in both groups. Conclusion: TI can provide partial data on the transverse and sagittal plane deformity of the first metatarsal deformity in HV with a single radiograph. Additionally, it can be a guiding measurement in evaluating the need for calcaneal shift osteotomy in pes planovalgus deformities accompanying HV. However, it is insufficient to define complex HV deformity alone.

Pre and Postoperative Analysis of Flatfoot Reconstruction Sparing the Talonavicular Joint

Surgical correction of a flatfoot deformity is controversial. The purpose of our study was to evaluate the structural radiographic changes of the flatfoot deformity while maintaining the mobile adapter of the foot. We conducted a retrospective analysis of 56 patients that underwent this procedure comparing their pre- to postoperative angular changes during a follow-up period. The mean age of our study cohort was 53.6 (range, 20-77) years and mean follow-up period was 23 (range, 4-73) months. Radiographic union was achieved in 48 patients (86%). Forty-six patients (82%) had all required radiographs completed through final follow-up visit. We illustrated statistically significant changes to the talonavicular, Meary, talocalcaneal, calcaneal inclination, and talar declination angles, and navicular height at 3 months and final follow-up. This study suggests surgical correction of the flatfoot deformity that fused the subtalar but spared the talonavicular joint appears to achieve and maintain radiographic angular changes and achieve union.

Error Analysis of Accelerometer- and Magnetometer-Based Stationary Alignment

This paper revisits the stationary attitude initialization problem, i.e., the stationary alignment, of Attitude and Heading Reference Systems (AHRSs). A detailed and comprehensive error analysis is proposed for four of the most representative accelerometer- and magnetometer-based stationary attitude determination methods, namely, the Three-Axis Attitude Determination (TRIAD), the QUaternion ESTimator (QUEST), the Factored Quaternion Algorithm (FQA), and the Arc-TANgent (ATAN). For the purpose of the error analysis, constant biases in the accelerometer and magnetometer measurements are considered (encompassing, hence, the effect of hard-iron magnetism), in addition to systematic errors in the local gravity and Earth magnetic field models (flux density magnitude, declination angle, and inclination angle). The contributions of this paper are novel closed-form formulae for the residual errors (normality, orthogonality, and alignment errors) developed in the computed Direction Cosine Matrices (DCM). As a consequence, analytical insight is provided into the problem, allowing us to properly compare the performance of the investigated alignment formulations (in terms of ultimate accuracy), as well as to remove some misleading conclusions reported in previous works. The adequacy of the proposed error analysis is validated through simulation and experimental results.

Association between Proximal Tibiofibular Joint Morphology and Knee Alignment in Osteoarthritis Patients

This study aimed to determine whether proximal tibiofibular joint (PTFJ) morphology was related to knee alignment in osteoarthritis (OA) patients. Methods: 67 OA patients were enrolled in this study. The morphology of the PTFJ including articular shape type, articular surface area, joint inclination, relative articular height, and joint declination were measured from 3D models. The knee alignment of each subject was characterized as varus, normal, or valgus according to the femorotibial angle (FTA). The FTA was measured on weight-bearing X-rays. Multinomial logistic regression analysis was used to evaluate the association between PTFJ morphology and knee alignment. Results: there were significant differences between varus, valgus, and normal FTA groups in terms of shape type (p = 0.021), inclination of the PTFJ (p = 0.025), relative articular height (p = 0.019), and PTFJ declination angle (p = 0.011). A higher relative articular height (OR: 0.608, 95% CI: 0.205–0.998, and p = 0.017) and lower declination angle (OR: 0.632, 95% CI: 0.601–0.887, and p =0.019) were found to be associated with an increased likelihood of having a valgus FTA rather than a varus FTA. Conclusion: our results indicate that PTFJ morphology is associated with knee alignment.

Radiographic measurements have limited effect in dynamic plantar pressures in hallux valgus patients.

Radiographic measurements are the gold standard in the management for preoperative surgical planning of hallux valgus deformity. Plantar pressure technology is a tool that is not commonly used to evaluate and manage hallux valgus patients, and few studies have reported the correlation of plantar pressure measurements and radiography. A prospective cohort study was designed to analyze plantar pressure measurements and radiographic variables. The inclusion criteria were age over 18 years old, and diagnosis of hallux valgus requesting surgical correction because of discomfort, pain or difficulty with shoe wear. Plantar pressure measurements were performed using a platform. Radiographic data were obtained according to the guidelines of the AOFAS Committee on Angular Measurements. A total of 114 patients met the inclusion criteria. Mean age of the patients was 50 years, and 94 patients (82.5%) were women. We found significant correlations between dynamic plantar pressure measurements and HVA, DMAA, and MDA. Mean pressure under third metatarsal head was the most associated plantar pressure measurement with hallux valgus angle and metatarsal declination angle. However, this association showed signs of weakness. Hallux valgus angle and metatarsal declination angle had a minimal influence on plantar-loading parameters. Pressure values did not discriminate the magnitude of HV deformity. Others factors responsible for the observed plantar pressures pattern should be addressed.

Modification of thin carbon films by UVc light

We modified single- and few-layer nano-sized graphene films deposited by pulsed laser deposition (PLD) on ∼300-nm-thick SiO2/Si substrates. The samples were irradiated by a UVC lamp (wavelength of 254 nm) for 15 and 30 minutes in air atmosphere. The light was directed almost parallel (about 2 - 2.5 arcdeg declination angle) to the films’ surface. The influence of the modification was evaluated by ellipsometry and X-ray photoelectron and Raman spectroscopies. The results showed that the irradiation caused an increase of the C-O/C-OH bond and a decrease or the complete disappearance of the -C=O/-COOH bond. The structural quality of the graphene films was improved moderately after a 15-min UVC treatment.

Characterization of Machined Surface Topography Based on the Normal Declination Angle of Microfacets.

It is important to characterize surface topography in order to study machined surface characteristics. Due to the features of periodicity and randomness of machined surface topography, the existing topographical parameters may not describe its features accurately. A novel characterization method called the normal declination angle of microfacet-based surface topography is thus proposed for this task. The topography of machined surfaces is measured and the data on the normal declination angle are obtained. Then, surface topography is analyzed via the distribution of the normal declination angle. The lognormal distribution characterization model of machined surface topography is established, and the accuracy of the model is verified by error analysis. The results show that the calculated results of the present characterization model are generally consistent with the distribution of the normal declination angle, where the maximal root mean square errors (RMSE) is 4.5%. Therefore, this study may serve as an effective and novel way to describe the characteristics of the machined surface topography.

Long-term photometric signature study of two GEO satellites

Geostationary earth orbit satellites have been extensively used for unique high-orbit stationary characteristics. Long-term precise investigation is an important issue in the observation of GEO satellites, since it can provide valuable information on the satellites’ operation state, discrimination and early warning analysis. Ground-based optical-electronic devices play a significant role in the observation. 4-month photometric signature variation of two satellites is presented based on the successive observations using the 1.56-meter telescope of Shanghai Astronomical Observatory (SHAO). It can be concluded that the long-term brightness change mainly results from the sun declination angle and regular orbit maneuver. Moreover, the solar panel offsets of the two satellites are analyzed and found to be approximately 4 degrees. Estimation of photometric accuracy reaches 0.15 mag for the application of CCD drift-scan optical-electronic technique.

Quantifying Global and Random Uncertainties in High Resolution Global Geomagnetic Field Models Used for Directional Drilling

SummaryTotal field strength, declination, and dip angle of the Earth's magnetic field, in conjunction with gravity, are used by magnetic-survey tools to determine a wellbore's location. Magnetic field values may be obtained from global models that, depending on the model, have a wide range of spatial resolution at the Earth's surface from large scale (3000 km) to small scale (28 km). The magnetic field varies continuously in both time and space, so no model can fully capture the complexity of all sources; hence, there are uncertainties associated with the values provided. The SPE Wellbore Positioning Technical Section/Industry Steering Committee on Wellbore Surveying Accuracy (ISCWSA) published their original measurement-while-drilling (MWD) error model in 2000. Such models and uncertainties define positional error ellipsoids along the wellbore, which assist the driller in achieving their geological target, in addition to aiding collision avoidance. With the recent update to Revision 5 of the ISCWSA error model, we have reassessed the uncertainties associated with our latest high-resolution global magnetic field model.We describe the derivation of location-specific global and random uncertainties for use with predicted geomagnetic values from high-resolution models within magnetic MWD survey-tool-error models. We propose a sophisticated approach to provide realistic values at different locations around the globe; for example, we determine separate errors for regions where the models have high spatial resolution from aeromagnetic data compared to regions where only satellite data are available.The combined uncertainties are freely available via a web service with which the user can also see how they vary with time. The use of the revised uncertainty values in the MWD-error model, in most cases, reduces the positional error ellipsoids and allows better use of the increased accuracy from recent improvements in geomagnetic modeling. This is demonstrated using the new uncertainty values in the MWD-error model for three standard ISCWSA well profiles. A fourth theoretical well offshore Brazil where the vertical magnetic field is weak shows that with drillstring interference correction relying on the more uncertain magnetic dip, the positional error ellipsoids can increase. This is clearly of concern for attaining geological targets and collision avoidance.

ПОВЫШЕНИЕ ЭФФЕКТИВНОСТИ РАБОТЫ АВТОГРЕЙДЕРОВ НА ОСНОВЕ СОВЕРШЕНСТВОВАНИЯ РАБОЧИХ ЭЛЕМЕНТОВ

The research considers methods of motor graders rise of efficiency by perfecting constructions of cutting elements and working organs on the basis of rise of a resource of their work. The work contains a research of interdependence of parameters of motor graders working organs by statistical methods with the purpose of detection of the basic tendencies of their development. The basic directions of designing of motor graders working organs and most perspective constructions are detected by a method of analysis of patent solutions. The formulas for account of resistance of ground to cutting by a knife with one direct and two sloping cutting edges with allowance for an angle of declination of a knife and its wear are deduced. The regularities of a wear of the cutting elements of a blade are investigated, its influence to efficiency of work and on parameters of working organs design is detected. The maximum size of wear is determined. The requirements to motor graders working equipment are defined on the basis of conducted researches, the new constructions of multiple use knives and order of their sequential replacement are developed in correspondence with the research work. It ensures the raise of efficiency of the machine by 10…15 per cent and it increases resource of knives in comparison with a traditional construction 3…4 times as much.

Subtalar distraction arthrodesis for calcaneal malunion - comparison of structural freeze-dried versus autologous iliac bone graft.

This study aims to analyze the outcomes of subtalar distraction arthrodesis (SDA) for calcaneal malunion using structural freeze-dried iliac allograft (FDIA) compared to using autologous iliac bone (AIB). We retrospectively evaluated 57 consecutive cases (51 patients) of calcaneal malunion between March 2006 and December 2017. All patients were followed for an average of 22.8 months. All cases were treated by SDA using structural FDIA (17 cases, group 1), or AIB (40 cases, group 2). The outcome measures included the American Orthopaedic Foot and Ankle Society ankle-hindfoot (AOFAS) scores, visual analog scale (VAS) pain scores, and radiographic measurements. The mean postoperative 3, 6, and 12 months of AOFAS scores and VAS pain score were significantly better in group 2 than those in group 1 (p < 0.05, for all). There were 3 cases (17.6%) of nonunion in the group 1, whereas the group 2 had 2 cases (5.0%), which did not shown significant difference between two groups (p=0.492). Although the mean pre-, postoperative, and final follow-up radiologic parameters in both groups were similar, (p > 0.05, for all) the difference of talocalcaneal height, talocalcaneal angle, and talar declination angle from postoperative to final follow-up were significantly bigger in the group 1. (p < 0.05, for all). Although union rate was not significantly different between the two groups, we obtained more favorable clinical and radiologic outcomes in the autologous iliac bone group. Using FDIA without any orthobiological agent for SDA, there were significant more loss of radiological parameters due to inferior incorporation and biomechanical properties. When considering the SDA for calcaneal malunion, routine use of FDIA without any orthobiological agents as an interpositional graft for SDA is not recommended.

Modelling of Electromagnetic Fields for Shielding Purposes Applied in Instrumentation Systems

In any sensory system, the Electromagnetic (EM) shielding of the channel-carrying signal is a fundamental technique to provide a noise-immune measurement system. Severe failures and uncertainty may occur if the external EM fields interfered with the measurements. Typically, the shielding is realized by enclosing the channel-carrying signal with thinconductive hollow structures. However, with such structures, it is required to provide access to the interior components from the outside, for wires' connections, or better heat dissipation. This can be considered as a weakness in such the external magnetic fields can penetrate through the shielding structure. In this paper, the EM shielding effectiveness is considered for long hollow-cylinder structures with slots. The induced eddy current in thin-conductive shielding systems with slots together with the magnetic fields at different conditions are modeled. The objective is to determine the impact of the integrated slots along with the structure. The influence of the slots' sizes (α) and position relative to the excitation magnetic field (i.e., the declination angle (β)) are investigated to evaluate the shielding effectiveness by means of the determination of the shielding factor. The results reveal the inherent relationship between the shield parameters and shielding effectiveness. The shielding effectiveness deteriorates by the slots' integration within the shielding surface. However, decreasing the size of the slots improves the shielding, significantly, towards the shielding effectiveness of the continuous cylindrical structure. Additionally, utilizing the symmetry in the structure positioning the slots in the direction perpendicular to the magnetic field flux improves the shielding effectiveness, drastically. Such a model can be considered to evaluate the degree of effectiveness or success of integrating opening slots within the shielding structure, which can be applied to different types of instrumentation systems specifically at the sensor-electronics interface.

Calculation of the Incidence Angle Modifier of a Linear Fresnel Collector: The Proposed Declination and Zenith Angle Model Compared to the Biaxial Factored Approach

Calculation of the Incidence Angle Modifier of a Linear Fresnel Collector: The Proposed Declination and Zenith Angle Model Compared to the Biaxial Factored Approach

Is Distraction Bone Block Arthrodesis better than Subtalar Arthrodesis for Malunited Calcaneal Fractures with Subtalar Arthritis? A Retrospective Case Series

To compare the clinicoradiological outcome between in situ and distraction bone block arthrodesis in patients with malunited calcaneal fracture. Patients presenting with painful subtalar joint arthritis between January 2015 and March 2018 were included after thorough clinical and radiological evaluation. In situ group I had 22 patients and distraction group II had 14. All patients were evaluated at final follow-up for functional outcome with American Orthopaedic Foot and Ankle Society (AOFAS) ankle-hindfoot score, and radiological parameters including talocalcaneal height (TCH), calcaneal pitch (CP), lateral talocalcaneal angle (LTCA), and talar declination angle (TDA). Mean follow-up was 19.26 months for in situ and 12.91 months for distraction group. AOFAS ankle-hindfoot score improved postoperative in both groups, but the difference between the groups was not significant ( p value = 0.371). Statistically significant improvement was observed in radiological parameters of talocalcaneal height ( p value = 0.006), calcaneal pitch ( p value = 0.025), lateral talocalcaneal angle ( p value = 0.078), and talar declination angle( p value = 0.02) in the distraction group. Distraction arthrodesis restores hindfoot radiological parameters better compared to the in situ group; however, there is no significant difference in functional outcome between the groups. Sundararajan SR, Ramakanth R, Shreeram V, et al. Is Distraction Bone Block Arthrodesis better than Subtalar Arthrodesis for Malunited Calcaneal Fractures with Subtalar Arthritis? A Retrospective Case Series. J Foot Ankle Surg (Asia Pacific) 2021;8(1):3–7.