However, the Young’s modulus error was associated with the stiffness properties (p < 0.01), whereas shear wave speed was associated with none of them . A detailed procedure can reliably assess the AS muscle stiffness. None of the sociodemographic or body composition features assessed were correlated with SWE errors. However, baseline stiffness seems to be associated with Young’s modulus error.Shear-wave elastography (SWE) is an imaging method that can be used to estimate shear wave speed and the Young’s modulus based on the measured shear wave speed under certain conditions. Up to date, no research has analyzed whether body composition factors contribute to ultrasound attenuation, refraction, reflection, and, consequently, SWE measurement errors. Therefore, this study aimed to analyze the association between demographic and body composition features with SWE errors for assessing the anterior scalene stiffness (which is a key structure in patients with neck pain and nerve compressive syndromes). Demographic , body composition , and anterior scalene muscle stiffness (Young’s modulus and shear wave speed) data were collected from a sample of asymptomatic subjects. After calculating the absolute SWE differences between trials and the reliability estimates, a correlation matrix was generated to quantify the association among all the variables. A total of 34 asymptomatic subjects  were included in the analyses. Test–retest reliability was excellent for assessing the Young’s modulus and shear wave velocity . No significant associations were found between age, height, weight, body mass index, body fat, lean mass, or water volume with SWE errors ( There is a growing body of scientific research focused on the evaluation of muscle stiffness due to its potential as a discriminative factor between asymptomatic individuals and clinical populations ,2,3,4. TIn such cases, fibrotic processes occur, which involve the excessive formation of connective tissue between skeletal muscle fibers, leading to the development of muscle scars . By evalUltrasound elastography is used for acquiring tissue elasticity information in this context. It serves as an adjunct to B-mode ultrasound imaging (US) in order to detect early stages of disease when no morphological abnormalities can be depicted with grey-scale . HoweverOn the other hand, shear wave elastography utilizes mechanical shear waves produced by the compressive acoustic waves used for acquiring the B-mode images, as shear wave propagation velocity depends on tissue stiffness. In contrast with strain elastography, this is an absolute unit expressed in m/s, which can be algebraically transformed to calculate the Young’s modulus in kPa to calculate the absolute pressure needed to deform a tissue . Due to the differences in physics principles, SWE overcomes several limitations of strain elastography. Strain elastography is highly subjective since the external and internal forces are difficult to standardize, the magnitude of the stiffness difference between two areas is unknown, and longitudinal assessments are limited . HoweverA previous study  analyzinAs the anterior scalene (AS) muscle is a key location with high clinical relevance, as most of the thoracic outlet syndromes result from neurovascular compression in the interscalene space  ,20, it iTherefore, the aims of this study were to calculate the test–retest reliability of a novel procedure for estimating the AS muscle stiffness using SWE and to analyze the association between the stiffness metrics error  with participants’ characteristics, including sociodemographic , body composition , and stiffness features .Between October 2022 and March 2023, a diagnostic accuracy designed cross-sectional observational study was conducted for assessing the test–retest reliability of a novel procedure targeting the AS muscle stiffness assessment, and the association between SWE errors with participants’ characteristics was conducted at a private university located in Ávila (Spain). In order to enhance the quality of this research, the writing adhered to the Reporting Reliability and Agreement Studies (GRRAS) guidelines  and the After posting local announcements around the campus, a sample consisting of asymptomatic volunteers was recruited through convenience sampling. Volunteers between the ages of 18 and 65 who had not experienced any neck pain symptoms in the past year were considered eligible for participation. No strict limits for weight, height, body mass index, or body composition metrics were imposed to improve the results’ generalizability. Those participants reporting previous history of whiplash, taking medication that may alter the muscle tone (such as muscle relaxants), underwent any surgical procedure, having any neuropathic condition , or demonstrating severe degenerative radiologic findings were excluded from the study. All participants meeting the eligibility requirements were asked to read and sign an informed written consent prior to their participation in the data collection.n = 50 + number of variables), as this calculation has demonstrated acceptable validity and power in detecting associations and conducting factor analyses [The minimum sample size for this study was estimated following the guidelines presented by Harris for correlation-based designs , an InBody 270 bioimpedance device  was used. This device was selected since the literature described an almost perfect correlation between the bioimpedance scores with Gold Standard methods such as dual-energy X-ray absorptiometry and excellent reliability . A laborA single examiner with +10 years of experience in the use of musculoskeletal US and clinical practice conducted all US measurements using a Logiq E9 device with a 6–15 MHz ML-6-15-D linear transducer . The console settings were standardized for all the imaging acquisitions . This examiner performed two measurements (each one spaced by 2 h) in order to obtain reliability estimates and analyze the correlation of test–retest error with body composition and sociodemographic features.The procedure followed to acquire the images was based on the study conducted by Valera-Calero et al. . ParticiFor acquiring the Young’s modulus and the shear wave velocity, the width and height of the region of interest was adjusted to completely cover the AS muscle. Finally, the AS muscle was carefully contoured, avoiding the inclusion of bone, nerve roots, or surrounding fascia, as illustrated in p < 0.05. All statistical analyses were run using the Statistical Package for the Social Sciences  for Mac, setting a two-tailed significance level of p > 0.05) was verified using histograms and Shapiro–Wilk tests. Next, the sociodemographic, body composition, and US characteristics of the overall sample were examined using descriptive statistics . Additionally, all features were reported independently for both sexes, SWE characteristics were reported by gender and side. The Student’s t-test was used to analyze between-group differences in the mean difference with a 95% confidence interval, considering the differences statistically significant if p < 0.05.First, normality of the data distribution , (4) the standard error of measurement , and (5) the minimal detectable changes  [Subsequently, test–retest reliability analyses were conducted by calculating (1) the mean average and standard deviation of both attempts for each SWE metric, (2) the absolute error between both trials (Young’s modulus error and shear wave speed error), (3) the intraclass correlation coefficients (ICCmes SEM) .Finally, a correlation matrix was constructed using Pearson’s correlation coefficients for two purposes: (1) for assessing the direction  and strength  paired associations , (2) ideOut of the 38 individuals who expressed interest in participating in the study, 2 were excluded due to a history of traumatic injury (whiplash-associated disorders) within the previous year, and 2 were lost for the second measurement. As a result, 34 asymptomatic volunteers were included in the data collection, analyzing both left and right sides of all participants. This resulted in a total of 68 AS muscles being examined, a total of 136 US images.p > 0.05), but men were significantly taller than women (p < 0.001). Despite these similarities, body composition features differed significantly between sexes. Males had less body fat mass (p < 0.01) and greater lean mass and water volume  than women. Regarding the SWE metrics, both genders demonstrated similar AS stiffness (p > 0.05). No significant side-to-side asymmetries were found for Young’s modulus nor shear wave velocity .Test–retest reliability estimates for assessing AS muscle stiffness are summarized in p > 0.05) and multiple associations among demographic characteristics with body composition (identifying multicollinearity and shared variance in most of the variables). Thus, no significant associations were found between muscle stiffness and SWE errors with height, weight, body mass index, water volume, lean mass, or fat mass (p > 0.05). In contrast, significant associations were observed between Young’s modulus errors and AS stiffness , whereas no associations were found between shear wave speed errors and stiffness values .Finally, the Pearson’s correlation matrix assessing the association among demographic characteristics, body composition features, muscle stiffness, and SWE errors is presented in Up to the authors’ knowledge, this is the first study investigating the association between demographic and body composition features with SWE errors. However, this is not the first study analyzing the test–retest reliability of SWE for quantifying the AS stiffness  or aiminFrom a total of two published studies found assessing the AS stiffness properties, only one focused on the test–retest reliability , whereasIn addition, the image acquisition procedure differed significantly from the one presented in this study. The description provided by Bedewi et al.  was limiThe study conducted by Kuo et al.  providedResearch analyzing morphological characteristics of the AS muscle is also scarce . The proWhile the primary aim of this study was to assess test–retest reliability and the association between SWE errors and specific features, the sample size calculation may not provide sufficient statistical power to consider the obtained scores as normative values. However, a discussion about the AS stiffness scores obtained among the studies may be of interest. This comparison is feasible despite the demographic differences among the studies, as our results, in agreement with Bedewi et al.  and Kuo Finally, it is important to highlight significant differences regarding the associations between the B-mode US and SWE errors with demographic, body composition, and anthropometric features. Varol et al. found age to be one of the most important contributors to B-mode US measurement errors for assessing cross-sectional area, circularity, aspect ratio, roundness, and mean echo intensity  characteristics of the lumbar multifidus  and the It is important to acknowledge several limitations of this study. One such limitation is our restriction of the sample to asymptomatic individuals. Therefore, we cannot be certain whether the reliability estimates obtained would apply to patients experiencing neck pain or thoracic outlet syndrome symptoms, especially considering that certain clinical populations have demonstrated histological changes that may impede the visualization of muscle boundaries ,39,40. AThis study found that a detailed procedure considering the participants’ positioning and transducer placement for locating and measuring the AS muscle stiffness demonstrated excellent reliability in asymptomatic subjects. Intra-examiner reliability was good to excellent for assessing both the Young’s modulus and shear wave speed. In addition, sociodemographic characteristics and body composition features showed no association with SWE test–retest errors. In contrast, baseline stiffness showed a significant association with SWE errors. Further research including clinical populations is needed to confirm the reliability estimates obtained in this study, analyze the discriminative capacity of SWE to detect clinical populations, and investigate the association between the AS muscle stiffness with clinical severity.


Valle de Ricote . PPL was assessed by the Spanish Perceived Physical Literacy Instrument for adolescents (S-PPLI). To assess adherence to the MedDiet, the Mediterranean Diet Quality Index in children and adolescents (KIDMED) was applied. Results: In unadjusted analyses, adolescents with medium or high PPL were more likely to have optimal adherence to the MedDiet . These findings remained significant after adjusting for sex, age, socioeconomic status, body mass index, energy intake, overall sleep duration, physical activity, and sedentary behavior . Conclusions: PPL could play a relevant role in the adoption of healthy eating habits among adolescents. Adolescents with low or medium PPL were less likely to report optimal adherence to the MedDiet. Adolescents with high PPL seem to consume more fruits, vegetables, fish, pulses, nuts, and dairies (for breakfast). Conversely, these adolescents tend to skip breakfast less, as well as to consume less commercially baked goods or pastries at this meal.Purpose: The objective of the current study was to analyze the relationship between perceived physical literacy (PPL) and adherence to the Mediterranean Diet (MedDiet) and its specific components in a sample of Spanish adolescents. Methods: In this cross-sectional study, we examined a sample of 845 adolescents (58.1% boys) aged 12–17 years from the  Physical literacy refers to the inclination, self-assurance, physical proficiency, awareness, and comprehension that people cultivate to sustain a suitable level of physical engagement throughout their lifetime ,2. SimilConversely, the Mediterranean diet (MedDiet), a predominantly plant-focused dietary regimen that is gaining global popularity, is regarded as one of the most beneficial diet patterns for health . StudiesTo our knowledge, no previous study has examined the relationship between physical literacy and eating healthy habits . However, physical activity  has alsValle de Ricote in the Region of Murcia. Data were collected during the 2021/2022 academic year. Of the initial 1378 adolescents (100.0%) from the EDHLA study, 383 (27.8%) were eliminated from the study due to insufficient information about their adherence to the MedDiet. Furthermore, additional participants were excluded because of incomplete data regarding PPL , body mass index , and energy intake . Therefore, a sample of 845 adolescents (58.1% boys) was examined in this secondary cross-sectional study. To be involved in this study, parental or guardian consent was secured in written form for the chosen teenage participants. They were furnished with an informative document detailing the study’s objectives, as well as the assessments and surveys that would be administered. Additionally, the adolescents themselves were requested to provide their consent to take part.This is a secondary cross-sectional study that used data from the Eating Healthy and Daily Life Activities (EHDLA) study. The comprehensive approach of the EHDLA study has been documented elsewhere . The subThis research adhered to the principles outlined in the Declaration of Helsinki and received approval from the Ethics Committee at the University of Murcia (ID 2218/2018), as well as from the Ethics Committee of the Albacete University Hospital Complex and the Albacete Integrated Care Management (ID 2021-85) for studies involving human participants.Perceived physical literacy (PPL) was assessed by the Spanish Perceived Physical Literacy Instrument for adolescents (S-PPLI), which was previously validated for Spanish youth . The PerAdherence to the MedDiet was assessed using the Mediterranean Diet Quality Index in children and adolescents (KIDMED) . This inAdolescents provided self-reported information about their sex and age. The Family Affluence Scale (FAS-III) was used to assess their socioeconomic status, which involved summing up responses from six items related to their family’s possessions and amenities  . The resH test (for continuous variables) or chi-square test . Furthermore, we used the chi-square test to examine the relationship between PPL status and adherence to the MedDiet and the different components of the KIDMED. Given that no interaction between sex and adherence to the MedDiet (p = 0.397) was found, we decided to examine both boys and girls together. To examine the association between the S-PPLI score and KIDMED score or adherence to the MedDiet among adolescents without any parametric assumptions on the nature of the relationship, generalized additive models (GAMs) were used. The GAM is a flexible model that can capture nonlinear connections in data without requiring a predefined mathematical structure. Restricted maximum likelihood (REML) for smoothness selection was applied [edf) of GAM. Regarding PPL status , an analysis of covariance was conducted to estimate the association with the KIDMED score , applying a nonparametric bias-corrected and accelerated (BCa) bootstrap method with 1000 samples. Likewise, to determine the odds ratio (OR) and the 95% confidence interval (CI) of the association between PPL status  and adherence to the MedDiet , we conducted binary logistic regression analyses. For both types of analyses, we applied a correction for multiple comparisons by using the false discovery rate p-value method developed by Benjamini and Hochberg [p-value < 0.05.For categorical variables, the descriptive data are presented as both the number (n) and the percentages (%) of observations in each category. For continuous variables, the descriptive data are presented as the median and interquartile range (IQR) of the values. Visual methods  and Shapiro–Wilk’s test were used to check normality of the variables. Associations between study variables and PPL status (tertiles) were tested using the Kruskal–Wallis  applied , with a  applied . To quanHochberg . Models The main characteristics of the adolescents examined based on their PPL status are displayed in p < 0.05 for all). Adolescents with high PPL showed a higher proportion of fruit, vegetable, fish, pulse, nut, and dairy consumption (for breakfast) in comparison with their counterparts with medium or low PPL . Conversely, adolescents with high PPL reported a lower proportion of skipping breakfast and commercially baked goods or pastries’ consumption (for breakfast) compared to those with medium or low PPL (p < 0.05 for both).p < 0.001), upon examining the figure and edf, we observed a nonlinear relationship between the S-PPLI score and the KIDMED score . Furthermore, for the KIDMED score, we found a significant range between 13 and 31 points on the S-PPLI score, indicating that a score within this range was inversely associated with the KIDMED score. Another significant range was observed at >34 points on the S-PPLI, showing the opposite direction compared to the significant range between 13 and 31 points on the S-PPLI. This suggests that a score within this range was associated with the KIDMED score. Regarding adherence to the MedDiet, given that the edf that was obtained is close to 1, it is close to being a linear term . Additionally, a significant range was found between 9 and 33 points on the S-PPLI, indicating that the score was inversely associated with optimal adherence to the MedDiet among participants within this range of values. Additionally, for participants with an S-PPLI score > 33 points, an opposite direction was observed compared to the significant range between 9 and 33 points on the S-PPLI. This indicates an association between the score and adherence to the MedDiet in adolescents within this range.BCa bootstrapped 95% CI based on PPL status are shown in BCa bootstrapped 95% CI 6.8–7.4), followed by those with medium PPL  and those with low PPL . Significant differences were found between low PPL and medium PPL, as well as between low PPL and high PPL (p = 0.003 for both).The estimated marginal means of KIDMED scores and their p-adjusted = 0.003; high PPL: OR = 2.90, 95% CI 2.03–4.17, p-adjusted < 0.001). These findings remained significant after adjusting for sex, age, socioeconomic status, body mass index, energy intake, overall sleep duration, physical activity, and sedentary behavior  (< 0.001) B, indicaIn general, our results indicate that higher PPL is related to greater adherence to the MedDiet, with higher consumption of some specific Mediterranean dietary components ), as well as with lower odds of skipping breakfast and consuming commercially baked goods or pastries for breakfast. There is limited empirical evidence linking PPL and health outcomes, but the literature supports an association between the greater physical domain of physical literacy and more desirable health outcomes. A review by Cornish et al.  found thFirst, one possible reason may lie in the tendency of healthy behaviors to cluster together. The scientific literature has shown how healthy behaviors  tend to cluster together among youths ,10,11,12Second, physical literacy involves setting and achieving physical goals , which could also explain these results. Young people who are proficient in physical activities might extend their goal-oriented mindset to their dietary choices, recognizing that the MedDiet can complement their physical goals and, thus, adhere to it more consistently ,32,33. FThird, engaging in physical activities can influence appetite regulation. Adolescents who are physically active might develop a better sense of hunger and satiety cues, which can help them adhere to the portion control and balanced eating approach of the MedDiet. In this sense, desirable movement behavior profiles, which include physical activity, sedentary behaviors, and sleep, have been associated with better appetite control and improved eating habits , as wellFourth, a higher level of physical literacy often includes knowledge about nutrition and its impact on overall health and performance. In this sense, a large study among Italian adults showed that nutrition knowledge is a driver of adherence to the MedDiet . TherefoDespite the findings obtained, this study must be interpreted while bearing in mind certain limitations. As a result of employing a cross-sectional approach in this study, it is not possible to establish a direct causal link based on the results. Additional research employing diverse methodologies, such as experimental approaches, is necessary to investigate whether heightened levels of PPL are associated with greater adherence to the MedDiet among adolescents. Nonetheless, while clinical trials are necessary to establish a direct cause-and-effect relationship between dietary patterns and sleep, as well as to uncover the underlying mechanisms, existing data suggest a reciprocal connection between these lifestyle factors ,12,43. LPPL could play a relevant role in the adoption of healthy eating habits among adolescents. Adolescents with low or medium PPL were less likely to report optimal adherence to the MedDiet. Adolescents with high PPL seem to consume more fruits, vegetables, fish, pulses, nuts, and dairies (for breakfast). Conversely, these adolescents tend to skip breakfast less and consume less commercially baked goods or pastries at this meal. These findings could be used to consider physical literacy in interventions aimed at increasing adherence to healthy eating habits in adolescents.


As a result, we have doubts about the accuracy of our published results".The Editors decided to retract this paper to avoid further damage to the scientific community. The Brazilian Journal of Medical and Biological Research remains vigilant to prevent misconduct and reinforces the Journal’s commitment to good scientific practices.


Additionally, the wave speed ratio, i.e. the ratio of systolic and diastolic speed, correlates to a pressure–volume derived index of contractility, i.e. preload-recruitable stroke work . Measuring wave speed ratio might thus provide a non-invasive index of contractility during ischemia/reperfusion injury.Ultrasound-based shear wave elastography is a promising technique to non-invasively assess the dynamic stiffness variations of the heart. The technique is based on tracking the propagation of acoustically induced shear waves in the myocardium of which the propagation speed is linked to tissue stiffness. This measurement is repeated multiple times across the cardiac cycle to assess the natural variations in wave propagation speed. The interpretation of these measurements remains however complex, as factors such as loading and contractility affect wave propagation. We therefore applied transthoracic shear wave elastography in 13 pigs to investigate the dependencies of wave speed on pressure–volume derived indices of loading, myocardial stiffness, and contractility, while altering loading and inducing myocardial ischemia/reperfusion injury. Our results show that diastolic wave speed correlates to a pressure–volume derived index of operational myocardial stiffness (R = 0.75,  This is essential for increasing our understanding of cardiovascular pathophysiology and improving treatment of multiple cardiac disorders.Myocardial stiffness changes dynamically throughout the cardiac cycle and is closely intertwined with the electromechanics and hemodynamics of the heart. During diastole, the heart relaxes and myocardial stiffness is low to accommodate ventricular filling, whereas during systole the heart contracts, increasing myocardial stiffness, to generate the pressure build up before ejection. It has been shown that characterization of the time-varying myocardial elastance using pressure–volume measurements can provide insights into cardiac function2. The fundamental principle of this technology is to image the propagation of acoustically induced vibrations along the cardiac wall, hence representing the propagation of a mechanical wave. The propagation speed of this wave is related to the intrinsic tissue stiffness, and higher speeds are measured in stiffer tissues3. By repeating a SWE measurement multiple times throughout the cardiac cycle, it is possible to construct a time-varying wave speed curve of which its characteristics are related to the myocardial stiffness dynamics4. Indeed, the magnitude of the wave speed in diastole reflects passive myocardial stiffness: diastolic wave speed correlates to other stiffness parameters derived from the end-diastolic pressure–volume relationship5 and the end-diastolic stress–strain relationship7. The magnitude of the wave speed in systole has been put forward as a measure for contractility, as it correlated strongly with end-systolic pressure during beta-adrenergic stimulation2. Next to the magnitude of the wave speed, the dynamics of the wave speed curve also offered insights into the isovolumic relaxation time constant5.Ultrasound-based shear wave elastography (SWE) has been proposed as non-invasive method for measuring the dynamics of myocardial stiffness2, whereas other studies showed that an increase in ventricular or intra-myocardial pressure affected wave propagation speed in a Langendorff-prepared set-up9. We therefore hypothesized that increased ventricular pressure can induce an apparent stiffening of the myocardium due to the intrinsic material non-linearity. There is also inconclusiveness on the use of systolic wave speed as measure for contractility during ischemia/reperfusion (I/R) injury, as both a decrease6 and increase in systolic wave speed7 have been reported. To elucidate the aforementioned uncertainties, the objective of this work was to investigate the relation between diastolic and systolic wave speeds and indices of loading, myocardial stiffness, and contractility derived from PV loops. We therefore applied transthoracic SWE in a pig model where we altered loading of the heart and induced myocardial I/R injury.It should be noted that all previously mentioned studies measured dynamic stiffness variations in an ex vivo or open-chest animal setting to bypass the limited SWE image quality of transthoracic recordings. To investigate whether previous findings hold in an intact heart with realistic loading conditions, it is essential to perform closed-chest SWE measurements in combination with pressure–volume (PV) recordings. These measurements can also sort out the remaining uncertainties in literature how other factors such as loading but also a combination of contractility and intrinsic stiffness (in for example an infarct) affect SWE measurements in diastole and systole. A preload independence of diastolic and systolic wave speed measurements has been suggested10, which focused on wave speed measurements after mitral valve closure.All animal procedures were approved by the local Ethical Committee for Animal Experimentation (ECD) of UZ Leuven, and were performed according to the ethical standards formulated by the European Commission (2016/63/EU). The procedures were written up following the ARRIVE guidelines. Thirteen Yorkshire-Landrace pigs  in supine position were anesthetized with an intramuscular injection of tiletamine/zolazepam (4 mg/kg) and xylazine (2.5 mg/kg). Anesthesia was maintained by intravenous infusion of propofol (0.17 mg/kg/h) and remifentanil (0.3 mg/kg/min), while pigs were mechanically ventilated. Vital signs, including heart rate, oxygen saturation, and arterial blood pressure, were monitored. It should be noted that the animals were the same as in our previous studyThe effects of hemodynamic alterations and an I/R injury on SWE and PV measurements in the pig model were investigated. Hemodynamic alterations entailed: (i) a decrease of preload by inflating the 8-F balloon catheter  by 2–5 ml in the vena cava inferior, (ii) an increase of afterload by inflating another 8-F balloon catheter by 2–5 ml in the descending aorta, and (iii) an increase of preload by rapidly administering 500 ml of saline intravenously. Measurements were taken when the pressure–volume loops stabilized. After the hemodynamic interventions, an I/R injury was induced by inflating a coronary angioplasty balloon  positioned in the proximal left anterior descending (LAD) coronary artery for 60–100 min. The coronary angioplasty balloon was then deflated and removed, and the tissue re-perfused for 40 min before the last measurement was performed. The timeline of these interventions is schematically shown in Fig. Left ventricular (LV) anatomy was quantified on B-mode images in the parasternal long-axis view using a GE Vivid E95 ultrasound scanner . More specifically, LV end-diastolic volume (EDV) and end-systolic volume (ESV) were derived from the measured LV diameter in the corresponding phase in the cardiac cycle using the Teichholz formula. These volumes are plugged into the volume calibration procedure of the pressure–volume analysis described in Sect. 2.5. Ejection fraction (EF) was subsequently derived from EDV and ESV. Septal wall thickness (IVSd) was calculated as the average of the measured wall thickness at basal and mid-ventricular level, corresponding to the region in which SWE measurements were performed. All measurements were performed using EchoPac software v202 .Transthoracic SWE measurements were performed in a parasternal long-axis view with a Verasonics Vantage 256 ultrasound research system . The first five pigs were scanned with a P4-2 phased array probe , whereas the other measurements were performed using a P4-2V phased array probe . One SWE sequence consisted of 1.5–2 s recording time in which multiple individual SWE acquisitions were performed at intervals of 28 ms (34 SWE acquisitions per second), as illustrated in the first row of Fig. 11. Second, a high-intensity focused ultrasound beam (center frequency of 2 MHz) was applied for 800 µs with a focal point depth set to the mid-septal wall. The resulting shear wave propagation was consecutively recorded at a minimal frame rate of 6.2 kHz using diverging wave imaging. Reference and tracking frames were acquired using a pulse-inversion harmonic transmission scheme (center frequency of 2 MHz) with a sliding window to maintain the frame rate. The radio frequency (RF) data together with the ECG signal were saved for offline processing.One SWE acquisition consisted of first acquiring 20 reference frames using ultrafast ultrasound, i.e. diverging wave imaging12 was subsequently used to compute the axial particle velocities in the IQ frames. To reduce the effect of noise, a Gaussian spatial smoothing filter of 1.9° by 2.0 mm was applied to the autocorrelation frames before taking the complex angle. Gross motion and high frequency noise were subsequently reduced by applying a 6th-order 75–750 Hz bi-directional Butterworth bandpass filter.Analytic in-phase and quadrature (IQ) image data were then obtained by offline beamforming the RF data using the Verasonics software in Matlab R2019a . A one-lag autocorrelator13 failed due to the limited signal-to-noise ratio. Resulting shear wave speed dynamics for three SWE sequences at one intervention stage is demonstrated in the last row of panels in Fig. 14—one positively inclined line, one horizontal line representing the systolic speed, one negatively inclined line and another horizontal line representing the diastolic speed  measurements, a 5-F pressure–volume Millar catheter  was placed in the LV under fluoroscopic guidance. Pressure, volume and ECG were registered at a sample rate of 1000 Hz using the MPVS Ultra Pressure–Volume loop acquisition system (Millar Instruments Inc.) and Labchart 7 Pro analysis software . For pressure calibration, the catheter was calibrated in a 37° water tank at the start of each experiment and its calibration was re-evaluated at the end of the experiment. For the total volume calculation, only the catheter-segments inside the left ventricle were considered, i.e. showing a counter-clockwise pressure–volume loop progression. Subsequently, a linear regression was performed between the voltages measured with the Millar catheter and the volumes measured with echocardiography in Sect. 2.3 considering end-diastole and end-systole of all interventions in one animal. This regression equation allowed to convert voltage data into volume data in a robust manner.End-diastolic pressure (EDP): pressure at onset of positive deflection of dP/dt ;End-systolic pressure (ESP): pressure for which the ratio of pressure and volume is maximal;End-diastolic pressure–volume relationship (EDPVR): an exponential relationship was assumed with the following equation1515—and operating chamber stiffness dP/dV, i.e. the slope of the tangent to the EDPVR at .With end-diastolic pressure EDP, end-diastolic volume EDV and fitting constants C, β, D and E. The fitting constants are obtained by performing a nonlinear least squares fitting procedure considering the end-diastolic PV-data during preload reduction. We considered two measures of chamber stiffness: exponential coefficient β—often used to represent diastolic chamber propertiesPreload recruitable stroke work (PRSW): the slope of a robust linear regression between stroke work (SW) and EDV during preload reduction gives information about contractility. PRSW provides a load-independent measure of the contractility of the heart, and has shown to be a more robust and clinically useful index than end-systolic elastance17.The relevant cardiac cycles of the PV-data to analyze are selected based on the maximum of the cross-correlation function between the ECG of the PV analysis and the ECG of the SWE measurements. From the PV-data during these selected cardiac cycles, the following relevant parameters are extracted using Matlab R2021b  with − 172% during preload decrease, resulting in negative pressures. This can be expected from a severe preload reduction in healthy hearts, where the blood is sucked into the ventricle. The end-diastolic volume (EDV of 73 ml at baseline) significantly changed during preload decrease (− 40%), afterload increase (+ 12%) and preload increase (+ 16%). Loading changes also significantly affected end-systolic pressure (ESP of 98 mmHg at baseline) during preload decrease (− 51%) and afterload increase (+ 25%); and end-systolic volume (ESV of 29 ml at baseline) during afterload increase (+ 31%). All changes in operational chamber stiffness dP/dV during loading interventions were significant: − 86%, + 41% and + 78% during preload decrease, afterload increase and preload increase, respectively.p < 0.05) after the reperfusion period. This corresponded with a significant operational chamber stiffness dP/dV change of + 188% and + 169% after the infarction and reperfusion phase, respectively. The I/R injury also resulted in a significantly thicker septal wall (+ 44% in IVSd), and a significant lower contractility (− 54% in PRSW).The I/R injury increased myocardial stiffness: the exponential coefficient of the EDPVR (β) increased by 62% after the ischemia period and further increased by 93% (dia and SWSsys) from the piecewise linear model fit is depicted in Fig. SWE measurements were successful in 7 out of the 13 pigs (success rate of 54%). In these 7 pigs, 93 of the 126 SWE sequences (74%) were considered for further analysis. Representative examples of shear wave speed variability in an SWE sequence due to the observer, heartbeat and anatomic M-mode line placement are shown in Fig. The diastolic wave speed for the different interventions is summarized in Fig. p < 0.01). The linear regressions during the loading interventions are tabulated in Table p < 0.01 in Fig. p < 0.01), operational chamber stiffness dP/dV  and stiffness constant β R = 0.50; p = 0.03). Diastolic wave speed is more sensitive to changes in intrinsic stiffness than in loading, as reflected by the larger slope of the regression line  and not PRSW in Fig. 2) than for the diastolic measurements, probably due to the limited sensitivity of the manual wave speed estimator to detect differences in speed (ΔSWSdia = 0.37 m/s vs. ΔSWSsys = 1.27 m/s). No significant correlation was found between systolic wave speed and measures of contractility during I/R injury.Systolic wave speed significantly correlated with only one measure of contractility during loading interventions: ESP in Fig. The ratio of the systolic and diastolic wave speed for the different interventions is depicted in Fig. p = 0.017 in Fig. p = 0.044 in Fig. During loading interventions, a moderate statistically significant correlation was found between the speed ratio and ESP  recordings throughout the entire cardiac cycle to invasive pressure–volume (PV) measurements for evaluating the myocardial stiffness dynamics in vivo. A moderate feasibility of the SWE-method was shown (success rate of 54%) and wave speed estimations varied 19.4% in diastole and 20.0% in systole on average. By performing a robust estimate of wave speed, this study linked diastolic wave speed to a pressure–volume loop-derived index of operational myocardial stiffness, i.e. dP/dV. Operational myocardial stiffness takes into account the stiffening effect due to increased ventricular pressure, stressing the importance of hemodynamic loading for diastolic wave speed. The ratio of systolic and diastolic wave speed correlated to pressure–volume loop-derived indices of contractility, i.e. end-systolic pressure (ESP) and preload-recruitable stroke work (PRSW). Measuring this ratio might thus provide a non-invasive index of contractility during I/R injury.18) needs to be studied in the future.The feasibility of SWE depends on three important factors: the amplitude of the acoustically induced vibrations, the quality of the images in which the vibrations are tracked, and the quality of the tracking algorithm itself to cope with underlying tissue motion. Transthoracic application of SWE to the heart poses extra difficulties as (i) cardiac phased array probes have a relatively small footprint and thus limited excitation strength and image quality, and (ii) cardiac tissue is moving relatively fast, challenging tracking algorithms but also push beam settings for powerful shear wave excitation throughout the cardiac cycle. This explains in part our moderate success rate of 54% (7/13 pigs). Some of the SWE acquisitions in the other 6 ‘unsuccessful’ pigs did reveal shear wave propagation but were not included in our analysis as there were only consistent SWE results for maximal 2 out of the 6 interventions. Especially at the start of our pig experiment, there were more ‘unsuccessful’ pigs as the experimental set-up gradually improved . Future work should investigate the feasibility of SWE in a systematic manner while varying the set-up and sequence settings, but this was outside the scope of this work. For example, the effect of using a more accurate but computationally more expensive tissue motion estimator than Kasai’s algorithm  to investigate qualitatively the dynamic stiffness variations across the cardiac cycle. The success rate increases tremendously when applying SWE at one time point during the cardiac cycle (end-diastole) according to previous clinical studies: 77.5% in healthy children21 and 91.3% in healthy adults22. Recently, some preliminary results have been reported on the dynamic stiffness variations in healthy children, but feasibility rate of these measurements is currently unknown23. Technical improvements are currently ongoing to increase the feasibility of SWE: optimization of filters to suppress background motion20, improvements in the imaging sequence, such as ultrafast harmonic coherent compound imaging24, or development of a new ultrasound transducer with a better mechanical focus for shear wave excitation25.Our reported feasibility is higher than the success rate of our dynamic SWE experiments in open-chest pigs26). The variability in wave speed estimation might arise from the dependence of the wave propagation on the ventricular morphology, the stress state (ventricular pressures) and the myocardial fiber orientation27. Furthermore, different acquisitions or heartbeats contribute to the natural physiological variability of the wave speed. Also, experimental settings such as the selected protocol, the number of observers, and the selected wave speed estimator will affect wave speed estimation. We accounted for part of this variability by performing wave speed estimation for the total 10 M-mode lines across the septal wall drawn by 2 observers and subsequently fitting a piecewise linear model to the speed data of multiple heartbeats and acquisitions 5. Our study confirms this earlier research: the change in the stiffness constant β of the EDPVR increased after the ischemia period  and increased even further after the reperfusion period , which was reflected in the change of diastolic wave speed after ischemia injury  and reperfusion injury (2.5 m/s). Furthermore, our work showed a significant correlation between diastolic wave speed and stiffness constant β in Fig. p = 0.04). Literature does not report any correlations between diastolic wave speed and stiffness parameters, however a clinical study in hypertrophic cardiomyopathy patients22 showed a significant correlation between diastolic wave speed and fibrosis markers in cardiac magnetic resonance: T1 post-contrast  and late gadolinium enhancement .Diastolic wave speed has been suggested as measure for myocardial stiffness by several studies through estimating the significance level of an infarcted vs. non-infarcted group in comparison to the significance of changes in other stiffness parameters: the stiffness constant of the end-diastolic stress–strain relation15, however it does not provide insights into the stiffness dynamics. Operational chamber stiffness, where a change in pressure is considered relative to a change in volume (or dP/dV), allows to assess the local slope of the EDPVR at a specific filling pressure and thus increases when pressure increases due to the non-linear ESPVR. Therefore, we considered dP/dV next to stiffness constant β in this study in order to describe any stiffness changes due to loading and/or intrinsic stiffness alterations. As tabulated in Table p < 0.01 for loading and R = 0.68; p < 0.01 for stiffness interventions). Furthermore, the correlation was even stronger when considering all interventions , and the low sample size of our study. Furthermore, the effect of material nonlinearity can also be observed from the changes of the wave speed as a function of time during diastole in Figs. The results of our statistical analysis on the group level suggests a preload independence of diastolic wave speed, which is in correspondence with other studies30 for which diastolic speed no longer depended on wall thickness in a multivariate linear analysis for their (unreported) shear wave frequencies.Next to loading, wall thickness may also affect the measured wave propagation speed in thin-walled media, as the wave might become guided due to the thin walls. When considering an analytical model describing wave propagation in a plate, i.e. a Lamb wave, an increased thickness can result in an increased wave speed for a specific frequency , as can be seen from the strong correlation with ESP in c. However, systolic wave speed increased significantly after ischemia injury  increase after 1–2 h ligation of the LAD7.Systolic wave speed has been put forward as a measure for contractility in literature, because of its excellent correlation with ESP during isoproterenol stimulation32. We hypothesized that both mechanisms affect systolic wave speed in an opposing manner, and it is therefore unsure what the net resulting effect is. This study therefore investigated the ratio of the systolic and diastolic wave speed as potential index of contractility: the wave speed ratio moderately correlated with measures of contractility for loading interventions  when considering both type of interventions simultaneously in Fig. In theory, an acute myocardial infarction is associated with an elevated myocardial stiffness and decreased contractility33. Furthermore, it should be noted that the same considerations as for diastolic wave speed measurements are valid concerning the effect of loading and wall thickness.The sensitivity of the use of wave speed ratio as non-invasive index of contractility needs to be further investigated in a larger clinical study as the current study only explored a limited number of animals (n = 7) and the induced changes in contractility are larger than what is reported in cardiac disease, e.g. PRSW altered + 17.5% in hypertension and − 6.9% in heart failure with preserved ejection fractionIt should be noted that SWE assesses systolic and diastolic ventricular properties in a local region (~ 3 cm) of the septal wall, whereas pressure–volume loop analysis provides functional measures of the left ventricular chamber as a whole. In this study, interventions were chosen such that they resulted in global alterations of left ventricular function or in local  changes via LAD occlusion. Therefore, the local SWE measurements in the septal wall strongly correlated with the global pressure–volume measures. SWE measurements in different regions and walls of the heart can offer us insights into the regional differences of systolic and diastolic ventricular properties.PRSW and EDPVR were not measured during preload decrease and afterload increase as this required insertion of a second balloon in the vena cava inferior and execution of two interventions at the same time. Also, right ventricular pressure was not measured even though this pressure also affects the resulting stresses and strains in the septal wall, and consequently wave speed. It is however unsure how much right ventricular pressure alters in case of an acute septal infarct.34, for which an analysis in the Fourier domain is necessary. This type of analysis was not possible in current work due to limited SNR, but should ideally be considered in future work. We refrained from converting the wave propagation speed value into a stiffness value, because the myocardium is not an unbounded homogeneous isotropic linear elastic medium, which is required for the well-known conversion in SWE.In this study, the wave propagation speed reported is rather a group speed, as it represents the speed of a pulse comprising multiple frequencies (50–500 Hz), but this does not strictly align with the textbook-definition of group speedsppa,0.3 = 403 W/cm2 for a push beam with a focal depth of 60 mm and push voltage of 60 V). Acoustic safety can however be guaranteed through ECG gating or programming scanner off time after every SWE acquisition to reduce the spatial peak temporal average acoustic intensity. Acoustic safety of dynamic shear wave measurements has recently been demonstrated by Malik et al.23 in healthy volunteers and hypertrophic cardiomyopathy patients. Concerning SWE data processing, diastolic and systolic wave speeds were now derived from a piecewise linear model, as suggested by Hollender et al.14, but this model might need to be tuned to account for higher end-diastolic wave speeds (see Fig. As current study presented animal experiments, SWE measurements did not fulfill the FDA guidelines concerning acoustic safety for human exams (MI = 2.2 and IThis work related diastolic and systolic wave speed to pressure–volume loop derived indices of loading, myocardial stiffness and contractility in a closed-chest pig model. Diastolic wave speed was linked to operational myocardial stiffness, with a larger sensitivity to changes in intrinsic stiffness than in loading. The ratio of systolic and diastolic wave speed was related to measures of contractility. Our findings indicate that shear wave elastography might provide a non-invasive alternative to pressure–volume recordings in order to map the cardiac stiffness dynamics in vivo.Supplementary Information.


P < 0.05). There was more inflammatory cell infiltration in the left graft, and the right graft had obvious proliferation of hepatocytes and mature bile duct cells. Left grafts were more prone to apoptosis than right grafts (P < 0.05). In conclusion, growth of the right graft is superior to the left; after double liver transplantation, perfusion blood flow and apoptosis may be the reason contributing to the volume differences in dual grafts.Dual-graft liver transplantation (DGLT) expands the pool of donors, ensures the safety of the donors, and treats a potential small for size syndrome (SFSS). However, some of the recipient graft showed atrophy. The cause and mechanism of the unbalanced proliferation and atrophy of dual grafts after clinical DGLT have not been clarified. We established and optimized the rat model of DGLT to explore the causes of growth unbalance. Continuously and dynamically observed bilateral graft volume and portal vein blood flow change by magnetic resonance imaging (MRI) and ultrasound (US). We detected liver function indexes: alanine aminotransferase (ALT), aspartate aminotransferase (AST), lactate dehydrogenase (LDH), total bilirubin (TBIL), direct bilirubin (DBIL), and indirect bilirubin (IBIL). Liver samples from receptors were obtained for morphology, and apoptosis was measured by RT-PCR and western blot. Optimization of the model improved the 7-day survival rate from former 58.3% to 87.5%, and the 30-day survival rate was 68.8%. The volume of the right graft gradually increased, and the left graft atrophied during the 30-day observation period. The portal blood flow of the left graft gradually decreased until the 30th day (0.13 ± 0.01 ml/s) compared with the sham group (0.63 ± 0.05 ml/s), and the right graft significantly increased on the 30th day (0.75 ± 0.11ml/s). The liver function initially increased and then recovered. The total volume (12.52 ± 1.60 ml vs 4.47 ± 0.08 ml) and weight (12.09 ± 1 g vs 4.91 ± 0.18 g) of the graft increased significantly compared to pre-transplantation and reached the level of the sham operation group on the 30th day. The volume and weight of the right graft increased more than those of the left graft (  For many end-stage hepatobiliary diseases, liver transplantation is the most effective treatment strategy –3. HowevBased on this problem, Lee achieved the first dual-graft liver transplantation (DGLT) in 2001 . FurtherThe present study was approved by the Laboratory Animal Protection and Use Committee of Lanzhou University of China (ID:2016-D42), and all experiments were conducted according to the government and international guidelines regarding animal experimentation. Animal suffering was minimized, and the total number of rats was limited so that few were utilized for easy control and experimentation and to avoid wastage.All SD (Sprague Dawley) rats were provided by Lanzhou Veterinary Research Institute of the Chinese Academy of Agricultural Sciences under the production license number SYXK (Gan) 2015-0001 [laboratory animals use license number SYXK (Gan) 2018-0003]. All animals were housed under standard conditions with a 12-h light/dark cycle, with free movement permitted, a constant temperature and humidity, and ad libitum access to water and food. The rats were allowed to acclimatize to the new environment for ≥3 days, and each rat was fasted for 12 h before surgery. After the experiment, all rats were euthanized by cervical dislocation, and respiratory movements and heartbeats were monitored to verify that the rats had demised.A total of 96 SPF male SD rats, 8–10 weeks old, weighing 270 g–300 g, were randomly divided into transplantation groups  and sham groups . The transplantation group (n = 72) randomly used two donors and one recipient for transplantation, and the dual right upper lobes (45%–50% of the recipient liver weight) were transplanted in one recipient. There were 12 recipients assigned to collect specimens and perform hemodynamic, morphological, and serological monitoring, while the other 12 recipients were observed until the 30th day after the operation for survival analysis. The sham group (n = 24) was used to mobilize the liver by the division of the hepatic ligaments. There were 12 rats in the sham group designated for specimen collection, and the remaining 12 rats were used for survival analysis.Basic data of the dual-graft liver transplantation rat model are depicted in The entire surgical process is shown in Dual- graft volume data in dual grafts on the 1st, 3rd, 7th, and 30th days post transplantation were acquired on a Siemens Verio 3.0 T scanner .Ultrasonic detection of portal vein velocity , portal vein diameter (PVD), and portal vein blood flow  on the 1st, 3rd, 7th, and 30th days after transplantation was executed . Because the hepatic artery was ligated during the transplantation process, the hepatic artery hemodynamics could not be measured.Preoperatively and 3, 7, and 30 days after operation, alanine aminotransferase (ALT), aspartate aminotransferase (AST), lactate dehydrogenase (LDH), total bilirubin (TBIL), direct bilirubin (DBIL), and indirect bilirubin (IBIL) were determined at 25°C by standard enzymatic techniques .After the observation period, liver tissues from the rat model dual grafts were collected and weighed using an electronic balance scale, and volumes were measured by incorporating the use of a measuring cylinder.Specimens were fixed in 10% buffered formaldehyde phosphate for at least a day for tissue evaluation and were subsequently dehydrated and embedded in paraffin wax to cut sections at a thickness of 4 µm. The growth status of bilateral grafts was evaluated. Morphologic parameters were recorded by routine histology.−ΔΔCT). The primers were purchased from the Beijing Genomics Institute , and the primer sequences are shown in RNA was isolated using TRIzol (Invitrogen). A Reverse Transcription Reagent kit with gDNA Eraser  was used to perform reverse transcription. Real-time polymerase chain reaction (PCR) was performed using an ABI 7500 Sequence Detection System  with SYBR Green I . Data were analyzed using the comparative method  was added to each sample, ground thoroughly with liquid nitrogen, and centrifuged at 13,000 rpm/min for 10 min. The supernatant was collected and stored in aliquots at −80°C until analysis by western blot analysis. The protein concentration was measured by a BCA protein assay system. Protein samples were separated by 10%–12% SDS-PAGE and transferred to PVDF membranes. The blots were blocked with 5% skimmed milk in Tris-buffered saline containing 0.1% Tween 20 (TBST) for 1 h at room temperature and then incubated at 4°C overnight with primary antibodies against GAPDH , Fas , caspase-8 , caspase-9 , granzyme b , and caspase-3 . After being washed in TBST three times, the membranes were incubated with a horseradish peroxidase-conjugated secondary antibody  for 1 h at room temperature. Finally, the membranes were washed three times for 5 min each with TBST. The specific protein bands were visualized using Super Signal West Pico Chemiluminescent Substrate and imaged using a VersaDoc imaging system .P < 0.05 was considered to indicate statistically significant differences.The data are shown as the means ± standard deviations (SD). Group comparisons of normally distributed data were performed with unpaired Student’s t test (two-tailed) or one-way ANOVA. Statistical analysis was performed using SPSS 19.0 , and The model’s stability, sustainability, and rigidity were improved by increasing the rat’s body anatomic mass, moderate bile duct length, pruning Y-blood vessels, and “triangle method” anastomosis Figure 2The volume of the dual grafts was continuously observed by MRI. The results showed that the volume of the right graft gradually increased, and the left graft firstly increased before the 7th day and then decreased until the 30th day Figure 42 , the portal vein blood flow was calculated. The results showed that the PVF of the left graft gradually decreased until the 30th day, while right graft decreased slightly before the 7th day but increased significantly on the 30th day 30th day Figure 5P < 0.05). ALT, AST, TBIL, DBIL, IBIL, and LDH all peaked on day 3 and then decreased continuously. Moreover, the liver function parameters recovered, while LDH increased again drastically on the 30th day.ALT, AST, TBIL, DBIL, IBIL, and LDH are significant indexes for liver function evaluation. Blood samples from the sham-operated group and transplanted group on the 3th, 7th, and 30th days were obtained. The results are shown in P < 0.05) (P < 0.05)  Atrophy of the cadaveric liver as a donor may be associated with the long preservation time and impaired liver function . (2) Theperation . (3) Forperation , 23.To explore the cause of volume unbalance of dual grafts, we used US to detect PVF of dual grafts in the receptor and found that there were PVF differences in dual grafts. The PVF was consistently decreased in the left graft. In the right graft, although the PVF decreased on the 3th  and 7th  days after surgery, it was still more than the left, and the right graft PVF increased on the 30th day, which may be a contributing factor to volume differences in dual grafts. Broering et al. and Kaihara et al. believed that the growth of the dual grafts is related to the distribution of PVF and that larger grafts have an advantageous growth and preferentially obtain more blood from the ipsilateral portal vein, smaller grafts obtain less PVF, and proliferation is slower. The larger-volume graft seizes blood flow from the small graft, which is called the “blood stealing phenomenon” , 23. SomApoptotic indicators of the left graft were higher than the right graft. In the right graft, the apoptosis level decreased except caspase-9 that decreased on the 7th day and increased on the 30th day. In the left graft, Fas, caspase-8, caspase-9, and granzyme b decreased on the 7th day and increased on the 30th day, which was consistent with the volume change of the grafts and peaked on the 7th day, potentially explaining that the volume changes may be related to apoptosis. However, we did not compare the left and right grafts by western blotting.Serological changes of liver function showed the worst liver function on the 3th day after transplantation and then gradually recovered on day 7 and day 30, which was similar to the changes of apoptosis indicators. However, LDH increased again drastically on the 30th day. In fact, after day 7, we also performed two additional time points at day 15 and day 25, but the changes were not significant, and we considered that continuous anesthesia might be the cause of the changes in LDH.In addition, we measured the mass and volume of the dual graft on the 30th day. Compared with the grafts before transplantation, the total mass and volume of the transplantation group reached the level of the sham operation group and even slightly exceeded the sham operation group. Furthermore, with later observations, we found that many rats have unilateral graft atrophy, and even though the left graft diminished, the receptors were healthy. Therefore, although atrophy was not the expected result, it did not seem to affect the survival of the rats.Although the animal model was successfully established and optimized in this study, the transplantation mode was all dual right liver lobe, which was different from the complex liver lobe combination pattern of the clinical scene and only initially reproduced the graft atrophy scenario after clinical DGLT. Secondly, the mechanism exploration is also very shallow, and the model observation time is not long enough. The operation is also complicated, and it is difficult to popularize this model for the study of liver transplantation. In addition, although some patients have unilateral graft atrophy after DGLT, the survival rate of most patients is tremendously good and no uncurable complications can be pinpointed , 38, simThe raw data supporting the conclusions of this article will be made available by the authors, without undue reservation.The animal study was approved by Lanzhou University Second Hospital Institutional Animal Care and Use committee. The study was conducted in accordance with the local legislation and institutional requirements.Contributions: (I) Conception and design: HC and YZ; (II) Administrative support: HC; (III) Experiment: DW, YM, and BG; (IV) Provision of study materials: DW and XL; (V) Collection and assembly of data: DW, YY, and YZ; (VI) Data analysis and interpretation: All authors; (VII) Manuscript writing: DW; (VIII). All authors contributed to the article and approved the submitted version.


Arthralgia or joint pain is a heterogeneous condition including organic and nonorganic joint pain. It is common in older populations, particularly in females. There is evidence that menopausal changes are associated with increased prevalence of arthralgia. While physical activities have been recommended to mitigate osteoarthritis (OA) and arthralgia, sport participation also carries risk factors due to excessive loading of some joints and possible injuries. The aim was to evaluate the association of training patterns, prior injuries, and severity of menopausal symptoms with arthralgia in female Masters weightlifters.n=868, 30-78 years) from 30 countries completed an online survey including joint pain for different anatomical sites, weightlifting training and performance, sport history, and menopausal symptoms. Logistic regression models were used to estimate the association of training patterns, prior sport participation, and menopausal symptom severity with arthralgia separately for shoulders, spine, hips, knees, ankles, elbows, and hands.Competitive female Masters weightlifters (p=0.03), knees , and hands/wrists , but prior strength training was protective for arthralgia in the shoulders . Prior injuries and psychological menopausal symptom severity were associated with an increased risk for arthralgia (p<0.01).Arthralgia was most reported in knees (38.8%), shoulders (29.8%), hands/wrists (28.8%), and hips (24.9%). The prevalence of arthralgia was 51.5% in pre-menopausal women, 62.4% in women post natural menopause and 73.3% in women post medical or surgical menopause. Lifting heavier weights was associated with arthralgia in hips (OR=1.05, Arthralgia was common in competitive female weightlifters. Training frequency was not associated with arthralgia, but lifting heavier weights relative to age and body mass was. Prior injuries and menopausal symptoms were associated with arthralgia, but prior strength training was protective of arthralgia in the shoulders. Athletes, coaches and sports medicine professionals should be aware that prevalence of polyarthralgia increases in post-menopausal athletes. Arthralgia or joint pain is a heterogeneous condition and is inclusive of osteoarthritis (OA), degenerative joint disease, and organic and nonorganic causes of joint pain. Its prevalence may be underestimated since not all symptomatic individuals seek medical help for diagnosis . It is aPhysical activities have been recommended for improving OA to increase strength, joint stability, proprioception, flexibility, and reduce pain –8. SportArthralgia and OA increases with age and are more common in women , 13. MenThere is a significant gap in the literature investigating arthralgia in female athletes, in particular its association with menopausal status or menopausal symptom severity. The objectives of this study were to evaluate prevalence and determinants for arthralgia for different anatomical sites in competitive female Masters weightlifters. We expected that prevalence of arthralgia would be more common in shoulders, knees, and wrists compared to other joints due to the demands of this sport. Our hypothesis was that training patterns (frequency and load), sport history, and severity of menopausal psychological symptoms would be associated with this condition.n=1) or currently pregnant (n=3). To account for the possibility of male participants, missing responses to age of menstruation or prior pregnancies were excluded (n=22). Since the focus was on active Olympic-style weightlifters, missing best snatch or clean and jerk in the last 6 months (n=18) was also an exclusion criterion. This resulted in an analysis data set of 868 females [A cross-sectional study design was employed. An online survey was completed by 912 female weightlifters, ages 30 to 79, from 30 countries. The survey was distributed by the International Masters Weightlifting Association (IMWLA) to the National Masters Chairs. They then used email or social media to widely communicate the study to the female members in their organization. In addition, the survey was advertised in Olympic-style weightlifting interest groups via Facebook and Instagram. The survey was available in four languages , translated and tested by native speakers. Data collection was conducted in Spring 2022. The study protocol was reviewed and determined to be exempt by the Michigan State University Human Research Ethics Committee (STUDY00007512). Inclusion criteria were female Masters weightlifters, globally. The Masters age groups start at 35 years in international competitions, but in some countries, the Masters age also encompasses 30 to 34 years, hence this study included female weightlifters ages 30 and older. Exclusion criteria were younger than 30 years  to represent the performance level. SHMF standardizes performances with respect to body mass and age . SHMF waThe Menopausal Rating Scale (MRS)  was usedP-values less than 0.05 were considered statistically significant. The study was reported according to the STROBE statement [Continuous variables were summarized with mean ± standard deviation, categorical variables with counts and percentages. Proportions of females with arthralgia prior and post menopause were compared with Fisher’s exact test. Logistic regression models were used to estimate the effect of age, training hours, training load , and severity of menopausal symptoms on arthralgia. The psychological subscale of the menopausal symptom rating scale was included, since depressed mood had been shown previously to be associated with arthralgia . The somtatement .The mean age of the respondents was 43.6 years. The majority started weightlifting before age 35 51.9%), but 11.2% indicated starting weightlifting after age 50 , and 73.8% visited health professionals in the last six months for problems with bones, joints, or muscles. Joint pain was mostly reported in knees (38.8%) followed by shoulders 29.8%), hands/wrists (28.8%), and hips (24.9%)  and in hips , knees , elbows , and hands/wrists . Prior participation in strength sports  was protective of arthralgia in shoulders . Older age was associated with arthralgia overall , in knees  and hands/wrists .Severity of psychological menopausal symptoms and prior injuries were associated with arthralgia Table . Prior pp=0.03 compared to pre-menopause), and 73.3% in medical or surgical menopause (p<0.01 compared to pre-menopause). In a 2021 survey of 976 Masters weightlifters  from six countries participated in an online survey about injuries and training [p<0.01) . There is a significant gap in the literature investigating female athletes. Prior studies often focused on OA in male athletes [Arthralgia was common among female weightlifters at all ages, and arthralgia increased with age, namely 41% at ages 35-44, 50% at ages 45-50, and 54% for respondents older than 60. The most common sites of joint pain were knees (39%), shoulders (30%), hands/wrists 29%), and hips (25%). It is important to note that the prevalence of joint pain at these anatomical sites was similar in community-dwelling females at approximately 58 years of age, drawn from clustered random samples in urban areas in Scotland [9%, and hathletes , 28, andathletes . The preathletes . HoweverParticipation in prior strength sports  was not a risk factor for arthralgia and could even be protective for shoulder joint pain. Participation in high impact sports and participation in competitions at a younger age were not associated with arthralgia in female weightlifters. This is in contrast to other studies where prior participation in high impact sports was a risk factor for OA .Higher training load was a risk factor for arthralgia of the knees, hips, elbows, or hands. Prior injuries at the shoulders, spine, hips, knees, ankles were also risk factors for arthralgia at these joints. Studies have shown that joint-level factors such as injury, malalignment and abnormal loading of the joints are risk factors for arthralgia or OA , 30. RepMenopausal status was significantly associated with arthralgia. The proportion of athletes with arthralgia was 52% for pre-menopausal females, 62% for females undergoing natural menopause, and significantly higher with 73% in females undergoing medical or surgical menopause. To our knowledge differentiating between natural and medical or surgical menopause has not been considered before. The cumulative incidence of self-reported polyarthralgia increased in females at a faster rate after age 50 compared to males which could indicate a potential menopausal effect. Several studies have noted that joint pain or OA increases around the time of menopause –35, but Strengths of this study were the large number of female weightlifters from 30 countries and considering determinants for arthralgia at different anatomical sites. There is a significant gap in the literature studying female athletes despite large participation rates. This was an online survey of joint pain in the last six months and prior injuries were self-reported and thus responses may suffer from recall bias. However, information on joint pain was collected through different questions such as own experience, visiting health professionals because of joint pain, or diagnosis by health professionals. The question about prior injuries in specific joints was accompanied by a question of at which age such an injury first occurred, but there was no information about the severity and duration of injuries. Study participants differed in years of experience and their sport history, thus those with longer exposure to the sport or participation in competitive sports at younger ages would be more likely to have experienced an injury or have cumulative stress on joints. Information on weekly hours of training and maximum weight achieved in the past six months was collected, but specific training load was not available. Future longitudinal studies in Masters weightlifters with more detailed information about training intensity would be useful to understand cumulative stress on specific joints and injuries requiring surgery or length of recovery until resumption of weightlifting or retirement from the sport.Age, BMI, and heavier weights lifted were associated with polyarthralgia. Prior strength training was protective of arthralgia in the shoulder joints, thus resistance exercises for isolated muscle groups may be beneficial. Menopausal status and severity of psychological menopausal symptoms (including depressive mood and anxiety) were associated with polyarthralgia. Athletes, coaches and sports medicine professionals should be aware that prevalence of polyarthralgia increases post-menopause, however it is not a contraindication to competitive weightlifting. Menopausal symptom severity needs to be considered in personalized training programs to avoid potential overtraining and possibly arthralgia. Strength exercises for isolated muscle groups may mitigate or protect against arthralgia. Individual weightlifting training programs should consider sport history and prior injuries to manage arthralgia.


Graft selection in anterior cruciate ligament (ACL) reconstruction is critical, as it remains one of the most easily adjustable factors affecting graft rupture and reoperation rates. Commonly used autografts, including hamstring tendon, quadriceps tendon and bone-patellar-tendon-bone, are reported to be biomechanically equivalent or superior compared to the native ACL. Despite this, such grafts are unable to perfectly replicate the complex anatomical and histological characteristics of the native ACL. While there remains inconclusive evidence as to the superiority of one autograft in terms of graft incorporation and maturity, allografts appear to demonstrate slower incorporation and maturity compared to autografts. Graft fixation also affects graft properties and subsequent outcomes, with each technique having unique advantages and disadvantages that should be carefully considered during graft selection. The primary goal of ACL-R is restoring antero-posterior and rotatory knee stability and function as closely as possible to the native joint. Despite advances in surgical techniques and rehabilitation, postoperative complications including graft rupture remain significant, yielding severe socioeconomic consequences and detrimental patient experience.Revision surgery rates average between 2 and 10% , 98, 128Graft choices in ACL-R are broadly divided into autograft and allograft tissue. Hamstring tendon autograft (HT) is the most commonly used autograft among ACL surgeons worldwide, followed by bone-patellar-tendon-bone (BPTB) and quadriceps tendon autograft (QT) . When avThe following review aims to highlight current concepts of graft choice in ACL-R and provide the most up-to-date evidence regarding the graft selection process for primary ACL-R. The first of two parts, this paper will discuss the anatomical, biomechanical, and histological properties as well as differences in graft incorporation and fixation techniques of the three most widely used autografts and allografts. The second part will focus on clinical outcomes, failure rates and complications associated with each graft option.Individualized graft choice is advised in modern ACL-R; no single graft is appropriate for all patients. When choosing the optimal graft for each patient, the surgeon must consider multiple patient-specific, physician-specific, and graft-specific factors. Such considerations include tissue availability, prior or concomitant injury, patient comorbidities, and surgeon experience. The optimal graft will offer an expeditious harvest with low morbidity, rapid graft integration, and mechanical and structural properties similar to the native ACL. Despite this, each graft option has unique anatomical and biomechanical characteristics with resultant advantages and disadvantages.Successful ACL-R necessitates reconstruction of native anatomy. A profound comprehension of ligamentous anatomy is the first step in the graft selection process.2 [3 [2, whereas a larger CSA (from 100 to 160 mm2) has been described for the tibial site [ACL-R is predominantly performed as a single-bundle procedure. Quantitative measurements of the native ACL are patient-dependent with length, cross-sectional area (CSA), and volume ranging from 26 to 38 mm , 42, 1182 , 124 and2 [3 , 123, reial site , 117.Histologically, the native ACL demonstrates a high percentage of fibroblasts, blood vessels, and elastic fibrils, with a relatively low ratio of collagen fibrils to interstitium. These characteristics facilitate ACL function during daily activity, as they allow for regeneration and enable the ligament to withstand multiaxial stresses and fluctuating tensile strains .There are several different autograft options available for ACL-R, the most prevalent of which include BPTB, QT and HS. In general, each graft should be at least 7 cm long and have a midsubstance CSA similar to the native ACL.The BPTB autograft represented historically the “gold standard” in ACL-R. The graft consists of an approximately 10 mm wide tendon strip obtained from the central third of the patellar tendon and includes two bone blocks, one each from the tibial tuberosity and the patella. Compared to HT it is more “flat” and has less collagen fibers compared to QT .Unlike the BPTB autograft, multiple configurations are described for the QT autograft. It can be harvested with or without a bone block and as an approximately 10 mm wide full-thickness graft, or a 12 × 5 mm partial-thickness graft . HistoloFor HT autograft, harvested from the semitendinosus and/or gracilis tendon, there is wide variability in graft configurations ranging from one to eight strands, with quadrupled hamstring being the most common . While B2) [2) [2) [When comparing the CSA of the BPTB (33 – 61 mm2) , 85, 1052) [2) , 57, 85, [2) [2) , 85, 105 [2) [2) .When comparing histological features of commonly used autografts, none can replace the complex ultrastructural characteristics of the native ACL , 46. TheAllografts can be generally subdivided into all-soft tissue and bone-tendon grafts. Soft tissue allografts include hamstring, tibialis anterior, tibialis posterior, peroneal tendon, and iliotibial band/fascia lata, while subtypes of bone-tendon allografts are BPTB, QT with patellar bone block, or Achilles tendon with calcaneal bone block. Similar to autograft options, BPTB allograft is the only allograft with bone blocks on either tendon side, and therefore the only option providing femoral and tibial bone-to-bone healing. While allografts have similar anatomical properties to their autograft correlates, the use of allograft offers the option of customizing graft size to the individual patient’s anatomy.When considering biomechanical studies of the native ACL and its respective graft options, it is important to recognize that numerous factors influence outcomes, including experimental testing variables , as well as patient or cadaver-specific factors  . It is tThe primary and secondary functions of the ACL are to prevent anterior translation and internal rotation of the tibia, respectively, in relation to the femur. Studies on structural properties of the native ACL report an age- and sex-dependent ultimate load to failure of 2160 ± 157 Newtons (N) in young adults . These vThe ultimate load to failure of BPTB autograft ranges from 319 to 4389 N, with the highest load reported in 15 mm-wide grafts . In clinSimilarly, the ultimate load to failure for a 10 to 12 mm-wide QT autograft ranges from 249 to 2186 N , 75, 111For HT autograft, graft configuration  correlates with graft size, which is in turn positively correlated with tensile strength . DependiIn a recent study by Hart et al. comparing the biomechanical properties of the three most common autografts, no statistically significant difference was found in ultimate load to failure among the graft options . Thus, iTo restore normal knee kinematics and physiologic joint forces the stiffness of the used graft should be similar to the native ACL. Supraphysiologic graft stiffness results in knee over-constraint and increased chondral stress, thereby increasing the risk of early onset osteoarthritis , 112.Values for native ACL stiffness are reported to be 242 ± 28 N/mm in young adults. As with ultimate load to failure, these values decrease with age to 180 ± 25 N/mm in patients over 60 .For BPTB grafts, stiffness is reported to range from 158 to 685.2 N/mm, with values between 324 and 543 N/mm for grafts of 10 mm width , 111. FoWhen comparing all three graft options, Hart et al.  found a In summary, graft stiffness is an important factor in graft choice for ACL-R. At time zero, none of the grafts can perfectly mimic the native ACL and little evidence exists thereafter. It seems that the HT graft has the highest tendency towards supraphysiologic stiffness.Modulus of elasticity for the native ACL is reported to be between 111 and 124 MPa , 84. ThiModulus, maximum stress, and failure strain for BPTB range from 184 to 337.8 MPa, 21.6 to 101.3 MPa, and 0.16 to 25%, respectively. For QT, the same values range from 153.0 to 255.3 MPa, 9.7 to 23.9 MPa, and 2.0 to 10.7%. HT values are reported to be as high as 144.8 to 904.0 MPa, 65.6 to 156.0 MPa, and 0.3 to 33.0%, respectively .As with autografts, the structural and mechanical characteristics of allografts differ depending on harvest site. Common allograft options frequently meet or exceed the biomechanical properties of the native ACL . For sinIn addition to donor characteristics, graft preservation techniques alter the properties of allograft tendon. These changes are important to recognize when considering the use of allograft. Gamma irradiation and electron beam (E-beam) are employed for inactivation of bacteria and other pathogens. Mixed effects have been reported for low-dose gamma irradiation (< 20 kGy), with little , 130 or Methods of preservation also influence tendon properties , 113. FrIn summary, fresh frozen allograft tissue may meet or exceed the biomechanical characteristics of the native ACL, however various sterilization and preservation methods alter histological and biomechanical graft properties. While low dose irradiation appears to have little influence on graft biomechanics, moderate- to high-dose irradiation and chemical processing have detrimental tissue effects and should be avoided when possible.Much of our current knowledge about graft incorporation derives from animal studies. It should be noted that animal studies carry potential bias, including time-dependent differences in soft tissue remodeling compared to humans. Furthermore, postoperative immobilization and physiotherapy, both recognized in optimizing graft incorporation, cannot often be performed in animals. Therefore, these studies should be used cautiously when treating and advising patients .Graft remodeling occurs within the first six months postoperatively and may continue for years , 131. DuGraft-to-bone integration is necessary for optimal healing and resemblance of the physiologic ACL . Early hAnimal studies also suggest that higher graft-to-bone contact area has positive effects on tendon–bone healing, especially in the early period after ACL-R , 23, 132With the advent of faster and more aggressive rehabilitation protocols, the primary aim of graft fixation is to provide stability of the graft within the bone tunnel until graft-to-bone incorporation is accomplished. Optimal graft fixation minimizes graft elongation, longitudinal (“bungee effect”) and transverse (“windshield wiper”) graft movement, as well as influx of synovial fluid into the bone tunnel by maximizing strength, stiffness, stability, and durability. Despite advancements in graft fixation methods, the fixation point remains the weakest link in the graft-to-bone interface and is therefore crucial to the success of ACL-R.Several direct and indirect methods of graft fixation have been described. Direct methods include absorbable and non-absorbable interference screws, cross pins, staples, washers, or hardware-free press-fit fixation, whereas indirect devices include fixed or adjustable suspensory cortical button fixation. At this point, there is no clear consensus regarding the “best” graft fixation method, as each option has advantages and disadvantages. Several recent meta-analyses , 82, 106Advantages of suspensory fixation include the ease and simplicity of technique, the possibility of a thicker graft with higher graft-to-bone contact area resulting in superior graft incorporation, as well as excellent fixation strength and stiffness , 77, 79.Hardware-free press-fit techniques have been reported, showing promising outcomes comparable to traditional techniques with low rates of tunnel enlargement , 44, 106Graft choice has a considerable influence on postoperative outcomes and remains an easily adjustable surgical factor affecting graft rupture and reoperation rates. When comparing anatomical, histological, and morphological features of commonly used grafts to the native ACL, none can perfectly replicate the complex characteristics of the native ACL. Biomechanically, however, both autograft and allograft show equivalent or increased characteristics compared to the native ACL and represent viable options for ACL-R. There further remains limited evidence as to the superiority of one graft in terms of maturation and incorporation, yet the available literature suggests that allograft may demonstrate slower graft incorporation and maturity compared to autograft tissue. Finally, methods of graft fixation have unique advantages and disadvantages that affect graft properties, and should be carefully considered when selecting the optimal graft for each patient.


The surface of zirconia-based dental ceramic restorations require preparation prior to adhesive cementation. The purpose of this study was to assess the influence of airborne-particle abrasion with different sizes of alumina particles  on the mechanical strength of zirconia-based ceramics’ frameworks and on the extent of phase transformations. A fracture resistance test was performed. The central surface of the frameworks was subjected to a load [N]. The identification and quantitative determination of the crystalline phase present in the zirconia specimens was assessed using X-ray diffraction. The Kruskal–Wallis one-way analysis of variance was used to establish significance (α = 0.05). The fracture resistance of zirconia-based frameworks significantly increases with an increase in the size of alumina particles used for air abrasion: 715.5 N for 250 μm alumina particles, 661.1 N for 110 μm, 608.7 N for 50 μm and the lowest for the untreated specimens (364.2 N). The X-ray diffraction analysis showed an increase in the monoclinic phase content after air abrasion: 50 μm alumina particles—26%, 110 μm—40%, 250 μm—56%, and no treatment—none. Air abrasion of the zirconia-based dental ceramics’ surface with alumina particles increases the fracture resistance of zirconia copings and the monoclinic phase volume. This increase is strongly related to the alumina particle size. Zirconia-based dental ceramics possess superior mechanical parameters to other types of dental ceramics. They are widely used in dentistry, particularly in prosthodontics, as the material for full-ceramic dental crowns and bridge frameworks, monolithic restorations, and implant suprastructures. However, the adhesive bonding of 3Y-TZP restorations  to resin cements is impaired by the structure and inertness of zirconia ,2,3. A nAlumina airborne-particle abrasion, besides its obvious advantages, may also cause defects in the topmost surface layer of 3Y-TZP, such as microscopic cracks, grooves, the plastic deformation of crystals, and the embedding of alumina particles ,19,20,21m), tetragonal (t), and cubic (c) phases. At room temperature, zirconia is composed of the monoclinic phase. It transforms into tetragonal upon heating above 1170 °C; at 2370 °C, it transforms into the cubic phase, and it melts above 2716 °C .To assess the presence of a monoclinic phase in the zirconia-based specimens after alumina air abrasion, the X-ray diffraction test (XRD) was conducted. The examined surface of specimens needed to be flat. Cuboid-shaped specimens with the dimensions 5 × 5 × 20 mm were designed in the computer software , processed to the milling device, and dry-machined . The specimens before the sintering step are shown in Specimens were randomly divided into four groups depending on the size of alumina particles used for air abrasion, respectively, 50 μm, 110 μm, and 250 μm . Specimens in one group were left untreated (the control group). Other specimens were air-abraded at a 45° angle, at a 13 mm distance, at a pressure of 3 bar, for 10 s .The identification and quantitative determination of crystalline phases present in zirconia specimens was conducted using the X-ray diffraction method  . The quaScans were performed using a Bragg–Brentano design in θ-θ mode with the parameters below;Incident beam: Co Kα radiation at 40 kV and 45 mA, a programmable divergence slit of ½ degree, a Soller slit of 0.04 rad, and a mask measuring 5 mm;Diffracted beam: semiconductor detector X’Celerator, a Soller slit of 0.04 rad, and a Kβ filter;A goniometer of five degrees of freedom: X-Y-Z-Phi-Chi;For the small-angle X-ray diffractograms, a 0.1 degrees/step and counting time of 100 s per step were used.The statistical analysis was performed with the Kruskal–Wallis one-way analysis-of-variance-by-ranks test, with a level of significance set at 0.05.p < 0.001). Also, the size of alumina particles significantly affected the fracture resistance of the zirconia frameworks (p < 0.001).The mean fracture resistance of zirconia-based frameworks values in N, and the standard deviations of all tested groups are shown in m content was 26%; for 110 µm, it was 40%; and for 250 µm, it was 44%.The XRD results are demonstrated in representative plots in This study rejected the null hypothesis that the airborne-particle abrasion with alumina particles of different sizes does not affect the fracture resistance of zirconia frameworks and the phase transformation induction in the surface layers of zirconia-based ceramics. The obtained results indicate that performing alumina air abrasion of the inner surface of zirconia frameworks results in a double increase of their fracture resistance. Moreover, the increase in the size of alumina particles entails an increase in the fracture resistance of zirconia frameworks. It is strongly related to the phase transformation toughening phenomenon. The XRD revealed that the air abrasion induced the tetragonal-to-monoclinic phase formation.2O3, at a pressure of 2.5 bar) is performed in comparison with the untreated specimens (1458.8 vs. 1015.9 MPa) [2O3, at a pressure of 4 bar) and the untreated specimens [In this study, the fracture resistance of zirconia-based ceramics frameworks was assessed by subjecting the specimens to a load until they fractured. There are different shapes of zirconia specimens recommended for this test in the literature on f.e. cylindrical specimens, specimens in the shape of FPRs (fixed prosthetic restorations), such as single crowns or bridges, cemented on abutments made of metal or other materials, with or without the imitation of periodontal ligaments, where the load is applied along the long axis or at different angles ,39,40,415.9 MPa) . Moqbel 5.9 MPa) . Also, S5.9 MPa) . Kelch e5.9 MPa) . Chintap5.9 MPa) . On the pecimens . The afoThe results of the XRD test obtained in the current investigation demonstrate that alumina air abrasion of the zirconia-based ceramics’ surface induces the phase transformation and the increase of the monoclinic phase volume. Such results are similar to those obtained by the other research studies, in which the monoclinic phase was also detected after performing the alumina air abrasion. Karakoca et al. detected a 9.44–14.5% monoclinic phase volume in the surface layers of zirconia after air abrasion with 110 µm alumina particles . Moqbel In the present study, we compared three different sizes of alumina particles used for air abrasion and their influence on the phase content in the zirconia surface—it is clear that the alumina particle size used for air abrasion significantly affects the monoclinic phase volume detected in the topmost layer of 3Y-TZP. Such observations are confirmed by Hallmann et al., Monaco et al., and Kelch et al. ,45,52,53The monoclinic phase volume present on the superficial layers of 3Y-TZP is a relatively small fraction; the exact transformation depth is bigger. In theresearch conducted, the examined maximum depth of zirconia was 21 µm, while in Chintapalli et al.’s studies, the penetration depth of the X-rays was 3 µm. This may be the reason for the higher values of the monoclinic phase volume obtained in the current study . ChintapIn the current study, it is demonstrated that the air abrasion with alumina particles of the surface of zirconia results in the increase of the mechanical strength of this material and the increase in the monoclinic phase content. Such observations are confirmed by the other authors. The rise of the mechanical strength of 3Y-TZP is explained as the result of compressive stresses that occur within the topmost layer of zirconia specimens as a result of the 4–5% monoclinic crystal volume increase ,43,48. AAssuming all the results obtained in this study, the alumina airborne-particle abrasion of 3Y-TZP results in an increase of the monoclinic phase volume in the topmost layers of zirconia and in an increase of the fracture resistance of zirconia-based frameworks. An increase of the size of alumina particles entailed an increase of the monoclinic phase volume and an increase of the mechanical strength of 3Y-TZP. According to the aforementioned research studies conducted by Cotič et al. and Inokoshi et al., alumina airborne-particle abrasion does not affect the reliability and stability of 3Y-TZP restorations over time despite the rise in the monoclinic phase content present in the alumina air-abraded specimens ,32. NeveAlumina airborne-particle abrasion of the zirconia surface results in an increase in the fracture resistance of zirconia-based dental ceramics frameworks. The fracture resistance increases with an increase of the alumina particle size.Alumina airborne-particle abrasion of the zirconia surface induces a phase transformation in the surface layers of zirconia. An increase of the alumina particle size entails an increase of the monoclinic phase presence in the surface layers of zirconia.