Conventional Alignment Research Articles

Dynamic Response Analysis of Orthogonal and Skewed Slabs to Touch-off Explosion: Investigating Comparative Efficacy and Damage Mechanisms

Abstract Skewed slabs, deviating from conventional orthogonal alignment, pose distinctive structural hurdles. Despite their aesthetic allure and spatial efficiency, their incorporation entails intricate challenges in design, analysis, and construction. Within structural frameworks, slabs are pivotal elements susceptible to devastating impacts from contact explosions, like those triggered by suitcase or parcel bombs, in numerous engineering scenarios. The events like the Beirut explosion in 2022 and the Tianjin blast in 2023 serve as poignant reminders of the urgent need to grasp and address these dangers effectively. Slabs, whether arranged orthogonally or skewed, are fundamental in various engineering frameworks. Despite their key role in load support, slabs are highly vulnerable to damage from explosions, particularly contact blasts like suitcase bombs. Understanding slab behavior under such conditions is crucial for bolstering structural resilience and devising effective defense strategies against potential threats. This research endeavors to contribute to defense technology by examining the dynamic response of both orthogonal and skewed slabs to contact explosions, furnishing indispensable insights aimed at fortifying structural security in diverse environments. The blast is emulated through the utilization of the Eulerian-Lagrangian method, employing the Finite Element Analysis (FEA) technique with the aid of the Abaqus software. Slabs featuring various degrees of skew, including 15°, 30°, and 45°, are under scrutiny, and their comparative efficacy is evaluated against the benchmark of an orthogonal slab. The performance of the orthogonal slab is validated by comparing it to data from previous experiments published in academic literature. The findings revealed that with an escalating skew angle, there’s a reduction in perforation dimensions alongside a rise in peripheral damage. Furthermore, the hierarchical order of damage severity among configurations corresponds to the angles: 15° > 30° > 45°, highlighting critical considerations for structural resilience.

Carbon dots induced homeotropic alignment in a negative dielectric nematic liquid crystal material

Abstract Recently, doping guest materials such as quantum dots (QDs) into liquid crystals (LCs) has been of great interest since their addition substantially enhances the properties of LC and opens new avenues for scientific advancement. Here, we report the induction of homeotropic alignment in cells without alignment layers of the negative dielectric nematic liquid crystal, N-(4-Methoxybenzylidene)-4-butylaniline (MBBA) by doping with carbon dots (CDs ∼2.8 ± 0.72 nm). The CDs-MBBA composites (CDs concentration: 0.002, 0.01, 0.03, 0.1 and 0.3 wt%) were investigated using optical polarising microscopy, electro-optical and dielectric techniques. Polarizing optical micrographs and voltage dependent optical transmission revealed the induced homeotropic alignment for all the composites under investigation. Interestingly, the least concentrated sample, 0.002 wt% exhibited partial homeotropic alignment. However, due to light leakage, the optical transmission value below threshold voltage was relatively higher than the rest of the composites. MBBA is a negative dielectric material, hence the application of a voltage across the cell was able to switch the alignment from a dark to a bright state for all composites. However, above a certain voltage (>threshold voltage), the bright state produced some instabilities. The value of dielectric permittivity was observed to decrease with increasing concentration, confirming the effect of CDs in producing homeotropic alignment in MBBA. Measurements as a function of temperature were conducted to examine the thermal stability of the induced alignment. The alignment was found to be stable throughout the nematic phase of MBBA. The induction of such alignment without conventional alignment (i.e., rubbing of polyimides) technique can be helpful in addressing the evolving display demands by making liquid crystal displays (LCDs) and other display devices cost effective.

Fractional Talbot Lithography for Predesigned Large-Area Liquid-Crystal Alignment

To address the increasing demands for cost-effective, large-area, and precisely patterned alignment of liquid crystals, a fractional Talbot lithography alignment technique was proposed. A light intensity distribution with a double spatial frequency of a photomask could be achieved based on the fractional Talbot effect, which not only enhanced the resolution of lithography but also slashed system costs with remarkable efficiency. To verify the feasibility of the alignment method, we prepared a one-dimensional polymer grating as an alignment layer. A uniform alignment over a large area was achieved thanks to the perfect periodicity and groove depth of several hundred nanometers. The anchoring energy of the alignment layer was 1.82 × 10−4 J/m2, measured using the twist balance method, which surpassed that of conventional rubbing alignment. Furthermore, to demonstrate its ability for non-uniform alignment, we prepared polymer concentric rings as an alignment layer, resulting in a liquid-crystal q-plate with q = 1 and α0 = π/2. This device, with a wide tuning range (phase retardation of ~6π @ 633 nm for 0 to 5 V), was used to generate special optical fields. The results demonstrate that this approach allows for the uniform large-area orientation of liquid-crystal molecules with superior anchoring energy and customizable patterned alignment, which has extensive application value in liquid-crystal displays, generating special optical fields and intricate liquid-crystal topological defects over a large area.

Effect of doping with carbon dots on the alignment and dielectric properties of nematic liquid crystal 4-cyano-4′-pentylbiphenyl in ITO sample cells without conventional alignment layers for low-cost display applications

The melding of nanomaterials with liquid crystalline materials is at the frontier of scientific research due to the transformative impact of nanoparticles on the functionalities of host liquid crystal materials. Here, we report the effect of doping of carbon dots (CDs) in the nematic liquid crystal (NLC), 5CB (4-cyano-4′-pentylbiphenyl) in indium tin oxide (ITO) sample cells without alignment layers (i.e., unaligned ITO (U-ITO) sample cells) using polarizing optical microscopy and dielectric spectroscopic techniques. Polarizing optical microscopy reveals largely dark optical textures under crossed polarizers confirming vertical alignment of Pure 5CB in U-ITO sample cells. However, defects present in the texture pose severe constraints on the use of induced vertical alignment in U-ITO sample cells for device applications. To improve the quality of vertical alignment, CDs of size 2.8 nm at concentrations of 0.03, 0.05 and 0.1 wt% are doped into 5CB. Optical texture studies show the quality of induced vertical alignment of the 0.03 wt% composite is better than pure 5CB and other composites. Frequency-temperature dependent dielectric studies verify the induced vertical alignment by observation of the short-axis molecular relaxation. The stability of the vertical alignment throughout the nematic phase of 5CB is confirmed through temperature dependent dielectric and optical texture studies. The induced vertical alignment of 5CB in U-ITO sample cells could be attributed to the stronger LC-LC interaction than the ITO-LC interaction. The improvement in the quality of vertical alignment of CDs-5CB composites could be due to the CDs influencing LC-LC and ITO-LC interactions. Finally, the effect of CDs on the increasing dc electrical conductivity of 5CB in U-ITO sample cells is investigated. Our results clearly indicate that CD-5CB composites would be useful in cost-effective display and other photonic devices devoid of alignment layers.

A Novel Device for Micro-Droplets Generation Based on the Stepwise Membrane Emulsification Principle.

This paper presents a novel design of the device to generate microspheres or micro-droplets based on the membrane emulsification principle. Specifically, the novelty of the device lies in a proposed two-layer or stepwise (by generalization) membrane structure. An important benefit of the stepwise membrane is that it can be fabricated with the low-cost material (SU-8) and using the conventional lithography technology along with a conventional image-based alignment technique. The experiment to examine the effectiveness of the proposed membrane was conducted, and the result shows that microspheres with the size of 2.3 μm and with the size uniformity of 0.8 μm can be achieved, which meets the requirements for most applications in industries. It is noted that the traditional membrane emulsification method can only produce microspheres of around 20 μm. The main contribution of this paper is thus the new design principle of membranes (i.e., stepwise structure), which can be made by the cost-effective fabrication technique, for high performance of droplets production.

A New Angle-Calibration Method for Precise Ultra-Short Baseline Underwater Positioning

Ultra-short baseline (USBL) underwater positioning systems are widely used in marine scientific research and ocean engineering. Angle misalignment is a main error that reduces the accuracy of USBL underwater positioning. The conventional angle-calibration method assumes that the transponder position obtained by USBL positioning is an errorless coefficient matrix. However, errors inevitably exist in the estimation of the transponder’s position via USBL positioning, and the precision varies at different epochs. Ignoring the error in the transponder’s position will significantly reduce the precision of the angle misalignment estimation. In this paper, a new angle-calibration method is proposed for precise USBL underwater positioning. The angle alignment model is derived by treating the transponder’s position obtained by USBL positioning as an observation, and the stochastic model is then established according to the bearing angles. Robust estimation is likewise applied to further improve the precision of the angle misalignment estimation. To verify the performance of the proposed method, a sea experiment was performed. The results show that the new method has high calibration accuracy and robustness. The estimation precision of this method is improved by 0.0457°~0.6896° in heading, 0.0125°~0.8072° in roll, and 0.0077°~0.9436° in pitch, compared with that of the conventional angle alignment method.

A Practical Approach to Alignment and Error Feedback Control for Long-Span Arch Bridges

The accurate installation of long-span arch bridges’ arch ribs remains a challenge due to the complex calculations required for cable forces and arch rib displacements, as well as the significant influence of environmental and construction loads. In this study, we propose a practical approach to alignment and error feedback control for long-span arch bridges. Cable forces were optimized using multiple control objectives based on influence matrix principles. The impact of temperature on the next segment to be installed was analyzed using the metastatic GM(1, 1) model and fitting results. Several tunable parameters were employed to account for parameter errors and environmental interference. These parameters were adjusted based on the deviations between practical and theoretical alignments for different arch rib segments, achieving a model output of an offset-free-tracking arch rib structure. This technology was applied to monitor the construction of the Tian’e Longtan Grand Bridge. Compared to conventional alignment control approaches, the proposed method achieved excellent arch ring alignment after the closure of the high-accuracy arch rib and cable release, as well as effective control of cable force uniformity and tower deviation. Field measurement data indicate that the closing deviation of the arch ring is only 3 mm. This study provides a valuable reference for the construction control of long-span arch bridges.

Comprehensive assessment of global spinal sagittal alignment and related normal spinal loads in a healthy population

Abnormal postoperative global sagittal alignment (GSA) is associated with an increased risk of mechanical complications after spinal surgery. Typical assessment of sagittal alignment relies on a few selected measures, disregarding global complexity and variability of the sagittal curvature. The normative range of spinal loads associated with GSA has not yet been considered in clinical evaluation. The study objectives were to develop a new GSA assessment method that holistically describes the inherent relationships within GSA and to estimate the related spinal loads.Vertebral endplates were annotated on radiographs of 85 non-pathological subjects. A Principal Component Analysis (PCA) was performed to derive a Statistical Shape Model (SSM). Associations between identified GSA variability modes and conventional alignment measures were assessed. Simulations of respective Shape Modes (SMs) were performed using an established musculoskeletal AnyBody model to estimate normal variation in cervico-thoraco-lumbar loads.The first six principal components explained 97.96% of GSA variance. The SSM provides the normative range of GSA and a visual representation of the main variability modes. Normal variation relative to the population mean in identified alignment features was found to influence spinal loads, e.g. the lower bound of the second shape mode (SM2-2σ) corresponds to an increase in L4L5-compression by 378.64 N (67.86%).Six unique alignment features were sufficient to describe GSA almost entirely, demonstrating the value of the proposed method for an objective and comprehensive analysis of GSA. The influence of these features on spinal loads provides a normative biomechanical reference, eventually guiding surgical planning of deformity correction in the future.

Coronal Plane Alignment Classification of Arthritic Knees in a South Indian Population and Functional Outcome Comparison Post-mechanical Alignment Total Knee Arthroplasty.

Mechanical alignment has always been considered as the gold standard in total knee arthroplasty (TKA), but various other coronal alignment strategies have been proposed to enhance native knee kinematics and thus elevate patient satisfaction levels. Coronal plane alignment of the knee (CPAK) classification introduced by MacDessi is a simple yet comprehensive system to classify knees based on their coronal plane alignment. It categorizes knees into nine phenotypes based on medial proximal tibial angle (MPTA) and lateral distal femoral angle (LDFA). This study investigates the distribution of classification of primary arthritic knees (CPAK) types among arthritic knees in the South Indian population and compares the functional outcomes following total knee arthroplasty (TKA) using traditional mechanical alignment among various CPAK types. The research, spanning from September 2021 to August 2023, encompasses a comprehensive analysis of 324 patients with 352 knees in the first part and 48 patients with 72 knees in the second part of the study who underwent TKA, incorporating demographic data and radiological evaluations. Results indicate a predominant distribution of CPAK type 1, followed by type 2 and type 4 among the South Indian population. In the functional outcomes analysis, regardless of CPAK type, patients exhibited significant improvements in Knee Injury and Osteoarthritis Outcome Score (KOOS), Oxford Knee Score (OKS), and visual analog scale (VAS) scores post-operatively. CPAK distribution among the South Indian population is comparable to other Indian study and studies with an Asian population, but varies with studies among the White population. Significant improvement of functional outcome among all CPAK types signifies the robust nature of conventional mechanical alignment strategy. Thus, our study serves as an initial exploration into the knee phenotype of the South Indian population and findings contribute to ongoing research on optimal alignment strategies in knee arthroplasty, paving the way for future, more extensive studies in this dynamic field.

A rapid alignment method for high-precision rotational INS within group affine

In this paper, a rapid alignment method for high-precision rotation inertial navigation system (RINS) within group affine is proposed based on the Lie group theory. The proposed method can effectively solve the ultimate contradiction of initial alignment: speed and accuracy. It meets the requirements of fast response and high accuracy of high-precision RINS. We abandon the conventional coarse alignment + fine alignment scheme and realize a linear Kalman filter alignment method with arbitrarily initial misalignment based on the Earth-centered Earth-fixed frame RINS mechanization and the Lie group theory. Subsequently, considering the error characteristics of RINS two-position alignment, new left-invariant error model and observation model satisfying the group affine property are constructed to improve the convergence speed and accuracy of alignment. It is verified that the method can complete the initial alignment of arbitrary large misalignment and reach the ultimate accuracy in a short time, and the land vehicle navigation test shows that the proposed alignment method can complete the initial alignment of arbitrary misalignment in 5 min under the swaying disturbance and achieve better pure inertial navigation accuracy compared with the traditional scheme.

Tunable electronic and optical properties of BAs/WTe2 heterostructure for theoretical photoelectric device design

The geometric structure of the BAs/WTe2 heterojunction was scrutinized by employing ab initio calculations grounded on density functional theory. Multiple configurations are constructed to determine the equilibrium state of the heterojunction with optimal stability. The results show that the H1-type heterojunction with interlayer distance of 3.92 Å exhibits exceptional stability and showcases a conventional Type-II band alignment, accompanied by a direct band gap measuring 0.33 eV. By applying external electric field and introducing strain, one can efficaciously modulate both the band gap and the quantity of charge transfer in the heterojunction, accompanied by the transition of band alignment from Type-II to Type-I, which makes it expected to achieve broader applications in light-emitting diodes, laser detectors and other fields. Ultimately, the heterojunction undergoes a transformation from a semiconducting to a metallic state. Furthermore, the outstanding optical characteristics inherent to each of the two monolayers are preserved, the BAs/WTe2 heterojunction also serves to enhance the absorption coefficient and spectral range of the material, particularly within the ultraviolet spectrum. It merits emphasis that the optical properties of the BAs/WTe2 heterojunction are capable of modification through the imposition of external electric fields and mechanical strains, which will expand its applicability and potential for future progression within the domains of nanodevices and optoelectronic apparatus.

Accurate surgical posterior tibial slope alteration can be achieved in total knee arthroplasty regardless of surgeon skill level or local soft tissue thickness-A retrospective radiograph-based study.

To retrospectively report on the impact of local soft tissue thickness and surgeon skill level on the accuracy of surgical posterior tibial slope (PTS) alteration achieved in patients undergoing total knee arthroplasty (TKA) utilising lateral knee radiographs. Pre- and postoperative radiographs of 82 patients undergoing primary TKA using conventional mechanical alignment technique were measured by two observers and subjected to quality criteria for accurate measurement of the PTS. All patients underwent a standardised surgical approach for PTS alteration: cruciate-retaining (CR) cases with preoperative PTS ≤ 10° were set for reconstruction of the preoperative PTS. Cases indicated for posterior-stabilised (PS) design and/or with a preoperative PTS > 10° were set for 3° of postoperative PTS. Pretibial subcutaneous fat (PSF) and surgeon skill level were analysed for their predictive quality regarding the accuracy of surgical PTS alteration achieved. The overall mean postoperative PTS was significantly lower than the preoperative values (6.2°, SD 2.7 vs. 7.7°, SD 3.2; p = 0.002103). Neither local soft tissue thickness, namely PSF, nor surgeon skill level was found to be a predictor of the accuracy of surgical PTS alteration achieved. Among cases set for PTS reconstruction, 25.9% and 42.6% achieved a postoperative PTS within ±1° and ±2° of preoperative values, respectively. In patients with a PTS > 10° or those indicated for PS design, slope reduction was achieved with a mean postoperative PTS of 6.5°. Furthermore, 14.3% and 32.1% of cases were within ±1° and ±2° of 3, respectively. This study demonstrates that accurate surgical alteration of the PTS is possible in TKA regardless of local knee soft tissue thickness or surgeon skill level. This proves the clinical feasibility of both targeted reduction as well as reconstruction of the PTS in TKA. Level III, retrospective cohort study.

Liquid Crystal-Filled 60 GHz Coaxially Structured Phase Shifter Design and Simulation with Enhanced Figure of Merit by Novel Permittivity-Dependent Impedance Matching

This work serves as the first simulation investigation to tackle the liquid crystal (LC)-filled coaxially structured continuously variable phase shifter at 60 GHz, wherein the LCs act as single tunable dielectrics fully occupying the millimeter-wave (mmW) power transmitted (i.e., free of leakage or interference). Impedance and effective dielectric constant computations are settled, followed by the quantification of the interplay between the dielectric thickness and the dielectric constant (Dk) for a controlled 50 Ω impedance. Geometry’s aspect ratio (AR) effects are exploited for the coaxially accommodating topology filled with mmW-tailored LCs with an operatable Dk range of 2.754 (isotropic state) to 3.3 (saturated bias state). In addition to the proposed structure’s noise-free advantages, a novel figure of merit (FoM) enhancement method based on Dk-selection-based impedance matching is proposed. The optimum FoM design by simulation exhibits a 0–180.19° continuously variable phase shift with a maximum insertion loss of 1.75871 dB, i.e., a simulated FoM of 102.46°/dB when the LC-filled coaxial geometry is 50 Ω and matched with the Dk of 2.8, corresponding to the dielectric thickness of 0.34876 mm and line length of 15.92 mm. The envisioned device fabrication and assembly processes are free of the conventional polyimide alignment agent and the related thermal and electrical concerns. Significant cost reduction and yield improvement can hence be envisaged. The topology can also serve as a test structure for broadband characterizations of LC materials and new electro-optical effects.

Systematic review and meta-analysis of long term outcomes and innovations in Total Knee Arthroplasty: KINEMATIC, PERSONALIZED KNEE vs.CONVENTIONAL.

Kinematic alignment is an emerging approach for total knee arthroplasty, with the aim to restore patient's individual pre-arthritic joint kinematics. In this systematic review and meta-analysis, we compared the kinematic alignment with the conventional mechanical alignment for total knee arthroplasty. We searched PubMed, Web of Science, Cochrane Library, and Scopus on June 2, 2024. We screened the retrieved studies for eligibility. Then extracted the data from the included studies, and then pooled the data as mean difference (MD) or odds ratio (OR) with a 95% confidence interval using Review Manager Software (ver. 3.5). There was no significant difference between KA and MA in the different reported scores: combined KSS score at 6 months (P = 0.23) and 1 years (P = 0.60), KSS Patient satisfaction (P = 0.33), KSS function score (P = 0.07), Oxford score at 6 months (P = 0.45) and 2 years (P = 0.41), KOOS score (P = 0.26). Moreover, there was statistically significant difference in range of motion for flexion and extension at 1 and 2 years, incision length, the length of hospital stay, or the duration of surgery. Although kinematic alignment showed slightly better clinical outcomes than mechanical alignment, the difference between the two techniques is not statistically significant.

The Coronavirus Anxiety Scale: Cross-national measurement invariance and convergent validity evidence.

Coronavirus Anxiety Scale (CAS) is a widely used measure that captures somatic symptoms of coronavirus-related anxiety. In a large-scale collaboration spanning 60 countries (Ntotal = 21,513), we examined the CAS's measurement invariance and assessed the convergent validity of CAS scores in relation to the fear of COVID-19 (FCV-19S) and the satisfaction with life (SWLS-3) scales. We utilized both conventional exact invariance tests and alignment procedures, with results revealing that the single-factor model fit the data well in almost all countries. Partial scalar invariance was supported in a subset of 56 countries. To ensure the robustness of results, given the unbalanced samples, we employed resampling techniques both with and without replacement and found the results were more stable in larger samples. The alignment procedure demonstrated a high degree of measurement invariance with 9% of the parameters exhibiting noninvariance. We also conducted simulations of alignment using the parameters estimated in the current model. Findings demonstrated reliability of the means but indicated challenges in estimating the latent variances. Strong positive correlations between CAS and FCV-19S estimated with all three different approaches were found in most countries. Correlations of CAS and SWLS-3 were weak and negative but significantly differed from zero in several countries. Overall, the study provided support for the measurement invariance of the CAS and offered evidence of its convergent validity while also highlighting issues with variance estimation. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Generalization Beyond Feature Alignment: Concept Activation-Guided Contrastive Learning.

Learning invariant representations via contrastive learning has seen state-of-the-art performance in domain generalization (DG). Despite such success, in this paper, we find that its core learning strategy - feature alignment - could heavily hinder model generalization. Drawing insights in neuron interpretability, we characterize this problem from a neuron activation view. Specifically, by treating feature elements as neuron activation states, we show that conventional alignment methods tend to deteriorate the diversity of learned invariant features, as they indiscriminately minimize all neuron activation differences. This instead ignores rich relations among neurons - many of them often identify the same visual concepts despite differing activation patterns. With this finding, we present a simple yet effective approach, Concept Contrast (CoCo), which relaxes element-wise feature alignments by contrasting high-level concepts encoded in neurons. Our CoCo performs in a plug-and-play fashion, thus it can be integrated into any contrastive method in DG. We evaluate CoCo over four canonical contrastive methods, showing that CoCo promotes the diversity of feature representations and consistently improves model generalization capability. By decoupling this success through neuron coverage analysis, we further find that CoCo potentially invokes more meaningful neurons during training, thereby improving model learning.

Accuracy of Conventional Instrumentation is Dependent on Alignment Philosophy Using the Identical Surgical Technique in Total Knee Arthroplasty.

The objective of this prospective study was to assess the precision of restoring the anatomical tibial obliquity, as measured by the medial proximal tibial angle (MPTA) on conventional X-rays, in relation to the surgical technique employed. Specifically, the study aimed to compare the accuracy of tibial obliquity restoration between kinematic alignment (KA) and conventional mechanical alignment (MA) in total knee arthroplasty (TKA). Two-hundred-and-sixty patients underwent either mechanically aligned TKA (n = 139) or kinematically aligned TKA (n = 121) using conventional instrumentation (CI). Pre- and postoperative X-rays were measured twice by two observers, with a 2-week interval. Inter- and intraclass correlations were calculated, and postoperative tibial obliquity was compared to the preoperative anatomy. In the group of 139 patients with mechanically aligned TKA, no cases with an MPTA deviation greater than 1 degree from 90 degrees were observed. Sixteen percent of the cases (n = 22) had a deviation of 0 to 1 degree. The remaining 84% of the cases (n = 117) had their MPTA of 90 degrees achieved. In the group of 121 patients with kinematically aligned TKA, no cases had a deviation greater than 1 degree compared with the preoperative MPTA. Thirty-one percent of the cases (n = 37) had a deviation of 0 to 1 degree with respect to preoperative MPTA. The remaining 69% of the cases (n = 84) had their tibial obliquity restored. Mechanically aligned TKA revealed statistically significant smaller deviations of accuracy compared to kinematically aligned TKA (p = 0.005). The inter- and intraclass correlations indicated substantial agreement of all measurements (intraclass correlation coefficient [ICC] < 0.90). Both mechanically aligned and kinematically aligned TKA demonstrated satisfactory outcomes in terms of restoring tibial obliquity or a neutral MPTA of 90 degrees using CI. However, MA showed superior results regarding precision compared to KA. When starting with kinematical alignment using CI, the surgeons should be aware that the learning curve according to accuracy differs to MA. It was a Prospective Level II study.

Increased accuracy in component positioning using an image-less robotic arm system in primary total knee arthroplasty: a retrospective study.

Robotic-assisted total knee arthroplasty (RTKA) and navigated total knee arthroplasty (NTKA) have shown improved knee alignment and reduced radiographic outliers. Recent studies have proven that conventional mechanical alignment may not be the optimal goal for every patient. The aim of this study was to compare the accuracy of the planned implant positioning of a novel image-less robotic technique with an established navigated technique (NTKA). The study is a retrospective analysis of prospectively collected data that compared the implant positioning and lower-limb alignment of 86 image-less RTKA with 86 image-less NTKA. Radiographic analysis was performed to evaluate the lower-limb overall alignment, femoral and tibial components positioning in the coronal and sagittal planes. Outliers were evaluated with a cutoff of ± 3°. No difference was noted between the two groups for radiographic outliers within ± 3° from neutral (p = 0.098). The mean hip-knee-ankle angle deviation from target was 1.3° in the RTKA group compared to 1.9° in the NTKA (p < 0.001). Femoral sagittal deviation (femoral component flexion) was smaller in the RTKA group (0.9° vs 1.9°; p < 0.001). Similarly, tibial coronal deviation (0.8° vs 1.5°; p < 0.001) and tibial sagittal deviation (tibial slope) were smaller in the RTKA group compared to the NTKA group (0.9° vs 1.7°; p < 0.001). The RTKA group reported a substantial and significant reduced error from the planned target angles for both tibial and femoral components. No difference in terms of radiographic outliers was noted between navigation and robotic assistance.

Micro Electromechanical System Navigation Assists Femoral Extramedullary Alignment Osteotomy in Total Knee Arthroplasty: A Single-Blind Randomizing Study.

A micro-electromechanical system (MEMS) was developed based on spatial alignment and navigation technology to assist femoral extramedullary alignment osteotomy (FEAO) in total knee arthroplasty (TKA). The system can locate and adjust the femoral distal condylar osteotomy (FDCO) to obtain a better femoral prosthesis placement. It is a portable navigation device and provides an innovative approach for FDCO. Sixty patients who suffered from severe knee osteoarthritis who underwent unilateral TKA from May 14, 2021 to May 30, 2022 were randomly divided into a MEMS-FEAO group and a conventional femoral intramedullary alignment osteotomy (FIAO) group, with 30 cases in each group for a controlled retrospective study. The hip-knee-ankle angle (HKAA) of the lower limb was measured before and after surgery, the femoral valgus angle (FVA) was measured preoperatively, and the femoral prosthesis valgus angle (FPVA) and the femoral prosthesis flexion angle (FPFA) were measured postoperatively following computed tomography imaging protocols. Measurement data is statistically described as mean ± standard deviation c. The count data is described by frequency (constituent ratio) using the rank sum test. A total of 6.7% (2/30) of FEAO compared to 20.0% (6/30) of FIAO cases were postoperative deviations where the HKAA exceeded ±3° of neutral alignment (p < 0.05). The postoperative HKAA was 178.74° ± 1.56° versus 176.64° ± 3.39° (p < 0.05), the HKAA deviation was 1.25° ± 1.56° versus 3.36° ± 3.40° (p < 0.05), and the FPFA was 4.85° ± 2.46° versus 6.60° ± 1.86°(p < 0.05). Therefore, the differences were all statistically significant between the two groups. However, the FPVA was -0.59° ± 2.73° versus -0.80° ± 2.85° (p > 0.05), and there was no statistical significance between the two groups. The MEMS-FEAO system can improve the accurate alignment and can be utilized as a locator to obtain the best femoral prosthesis placement in TKA and significantly reduce the rate of poor force line of the lower limb.

Accuracy and outcome of a handheld accelerometer-based navigation device compared to conventional alignment method in total knee arthroplasty in a Chinese population

Background Total knee arthroplasty (TKA) is a successful procedure in treatment of degenerative disease of the knee, and optimal component placement is essential for long-term implant survival. The purpose of this study was to compare the accuracy of the accelerometer-based KneeAlign 2 (KA2) navigation system against conventional methods for accurate positioning of the femoral and tibial components in TKA in a Chinese population. Methods A total of 123 (37 conventional and 86 KA2) cases of elective primary TKA were reviewed. Hip-knee-ankle (HKA) angle, mechanical lateral distal femoral angle (mLDFA), and anatomical lateral distal femoral angle (aLDFA) were measured from hip-to-ankle EOS radiographs. Accuracy of conventional alignment and KA2 navigation system was assessed by measuring the difference between intraoperative goal and postoperative radiographic measurements of the components for each respective case. Results There was no significant difference between conventional alignment methods and KA2 navigation in achieving a neutral mechanical alignment of the lower limb. KA2 navigation was significantly more accurate than conventional alignment methods for optimal positioning of the tibial component in both the coronal and sagittal plane, while no significant difference between the two groups was appreciated in the positioning of the femoral component in the coronal plane. Conclusions TKA using the accelerometer-based KA2 system was found to offer a high degree of accuracy in component alignment, and in particular, significantly improved tibial component alignment in comparison with conventional alignment methods in a Chinese population. However, no significant improvements were observed in neutral mechanical axis of the lower limb alignment and femoral component placement in the coronal plane.