Though treatable, osteoporosis continues as a substantially underdiagnosed and undertreated condition. Bone mineral density (BMD) monitoring will definitely aid in the prediction and prevention of medical emergencies arising from osteoporosis. Although quantitative computed tomography (QCT) is one of the most widely accepted tools for measuring BMD, it lacks the contribution of bone architecture in predicting BMD, which is significant as aging progresses. This paper presents an innovative approach for the prediction of BMD incorporating bone architecture that involves no extra cost, time, and exposure to severe radiation.  In this approach, the BMD is predicted using clinical CT scan images taken for other indications based on image processing and artificial neural network (ANN). The network used in this study is a standard backpropagation neural network having five input neurons with one hidden layer having 40 neurons with a tan-sigmoidal activation function. The Digital Imaging and Communications in Medicine (DICOM) image properties extracted from QCT of human skull and femur bone of rabbit that are closely associated with the BMD are used as input parameters of the ANN. The density value of the bone which is computed from the Hounsfield units of QCT scan image through phantom calibration is used as the target value for training the network.  The ANN model predicts the density values using the image properties from the clinical CT of the same rabbit femur bone and is compared with the density value computed from QCT scan. The correlation coefficient between predicted BMD and QCT density valued to 0.883. The proposed network can assist clinicians in identifying early stage of osteoporosis and devise suitable strategies to improve BMD with no additional cost. Osteoporosis is a progressive, systemic, and skeletal disease which is characterized by low bone mass and microarchitectural deterioration of bone tissue, leading to increased bone fragility and consequent increase in fracture risk . The peaThough osteoporosis is incurable, it remains markedly underdiagnosed and inadequately treated. Hence, early detection of impaired quality of bone is crucial in the prevention of osteoporotic fracture and helps in starting timely bone modulating therapies. Bone mineral density (BMD) plays a major role in evaluating the osteoporotic condition of a patient. The measurement of BMD is significant in diagnosing and therapy monitoring of osteoporosis as well as to predict fracture risk.Dual-energy X-ray absorptiometry (DEXA) of total hip, femoral neck, and lumbar spine is the most widely used tool for diagnosing osteoporosis. It is reported that DEXA scan provides defective diagnosis due to the involvement of cortical bone which can be a source in overestimation of BMD . AdditioT-score derived through CT attenuation number (Hounsfield units (HU)) from clinical CT images [T-score based on DEXA score is not accurate in majority of patients who sustain fragility [Recently, osteoporosis is being predicted from T images . Even thT images . But, T-ragility . From thragility . Furtherragility . It is rragility . Two-dimragility . Studiesragility . The rouragility .P is the relative frequency with which two pixels, one with intensity i and the other with intensity j, separated by a pixel distance (d) and at a particular angle (θ), occur within a given neighborhood. It is reported that 14 textural features can be measured from the probability matrix to extract the characteristics of texture statistics of images and out of which the texture features such as angular second moment (energy), contrast, correlation, entropy, and the inverse difference moment (homogeneity) have good correlation with mechanical properties of bone [The GLCM quantitatively measures the frequency of different combinations of pixel brightness values occurring in an image. Each element in the matrix represents the position of pixels in the image having similar gray level values. The matrix element  of bone , 20–22. ANN is a system that simulates the human brain which is suited for solving nonlinear problems , 23. ANNAccording to the authors' knowledge, no study has been published that employs image properties generated from the GLCM of a routine clinical CT scan taken for other purposes to predict osteoporosis using ANN. Through this paper, the authors intent to propose an ANN model developed for direct prediction of BMD from the second-order texture properties of a Digital Imaging and Communications in Medicine (DICOM) image of a routine clinical CT scan of an individual patient. In comparison to current methods that use topological properties of a patient, the proposed approach, if implemented, can be used to assess osteoporosis with high accuracy and at no additional expense.In the second stage, the GLCM matrix is formulated from DICOM images and five second-order texture properties such as energy, contrast, correlation, entropy, and homogeneity are estimated. The BMD values are extracted from the QCT images which are computed from the HU of the scan image through phantom calibration. The third stage trains the ANN model using the dataset which consists of five texture properties and the HU values extracted from the QCT. The QCT images of human skull supplied by Amrita Hospital, Ernakulam, were also used for training the network. In the final stage, the trained ANN is used to predict the BMD values using the texture properties extracted from clinical CT images.The stepwise procedure of sample preparation and data acquisition for training and testing the network are discussed in the following sections.Femur bone specimens of adult rabbit weighing ∼1.75–2.5 kg are used for this study. Published methods for storage and handling of bone specimens were strictly followed during this investigation . The speThe dataset used for training the neural network is gathered from the QCT scanning  conducted on 15 rabbit femur bone specimens prepared as per the procedure reported by Ahmed and Voort . The traThe QCT and clinical CT images obtained are analyzed for identifying bone tissues or region of interest (ROI) by calculating tissue distribution from the mean gray value or HU value. This is done by using a ROI tool in the software Sante-DICOM Viewer. The selected ROI of an image is saved as jpeg image. Energy, entropy, contrast, homogeneity, and correlation, which quantify the spatial relationship between pixels in the area under investigation (ROI), had the best correlate with BMD . The GLCEn) measures the number of repeated pairs in the image. It is computed as the sum of squares of entries in the GLCM and is given by:i, j are the spatial coordinates of the function P and Ng is the gray tone of the image.The parameter energy (Et) measures the randomness of gray level distribution within the image and is given by:The parameter entropy (The parameter contrast (Co) measures the local variations present in an image and is defined as:The parameter homogeneity (Ho) measures the uniformity of image and is defined as:C) property measures the linear dependency of gray levels of neighboring pixels and is given as:μxμy and σxσy are the mean gray tone values and standard deviation of gray tone values, respectively.The parameter correlation  activation function has strong gradient and big learning steps. The output of tanh is symmetric around zero leading to faster convergence.The tan-sigmoid  and is plotted against the predicted and target BMD values  of 0.19043, from the validation performance graph, also indicates a very good agreement in the predicted values of density. All curves, as shown in The accuracy of the trained network is further established using the matrix of texture properties extracted from the clinical CT images of nine rabbit femur bone specimens. The BMD values extracted from the QCT images of the same samples were depended for comparison. It is noted that the predicted BMD values of the rabbit femur bone specimens from the routine clinical CT image properties using the trained neural network are well within 90% as against the BMD values computed from QCT images. In this study, an approach based on image processing and ANN for predicting BMD from clinical CT image is presented. The network used in this study is a standard backpropagation neural network, which consists of an input layer with five neurons, an output layer with one neuron, and a hidden layer with 40 neurons. The five inputs are the texture properties such as energy, entropy, correlation, homogeneity, and contrast extracted from CT images and the output is BMD. The dataset used for training the neural network includes 300 sets of five texture features as the input data and the corresponding BMD values as the target data, extracted from QCT images of rabbit femur bone specimens and human skull supplied by Amrita Hospital, Ernakulam, India. The overall correlation coefficient for the training phase valued to 0.9715 indicates that the trained ANN model is converged and can predict BMD values.To the best of knowledge, no studies in predicting BMD from clinical CT image have been reported; however, the BMD computed from QCT has been compared with predicted values of the current network, as shown in The methodology limits the training dataset to human skull bone and rabbit femur. This work can be extended and generalized by considering bone image data (training data) in a wider age group, incorporating gender, bone images from varying human habitat.


Neurogenesis ceases in most regions of the mammalian brain before or shortly after birth, however, in a few restricted brain regions, the production of new neurons proceeds into adulthood. Neural stem cells (NSCs) in these neurogenic zones are integrated into niches that control their activity and fate. Most stem cells in the adult brain are mitotically inactive and these cells can remain quiescent for months or even years. One of the key questions is what are the molecular mechanisms that regulate NSC maintenance and differentiation. Notch signaling has been shown to be a critical regulator of stem cell activity and maintenance in many tissues including in the nervous system. In this mini-review we discuss the roles of Notch signaling and the functions of the different Notch receptors and ligands in regulating neurogenesis in the adult murine brain. We review the functions of Notch signaling components in controlling NSC quiescence and entry into cell cycle and neurogenesis. The mammalian brain is formed during embryogenesis and early postnatal life, with most neurons being born before birth. However, in the 1960s, the field of neurogenesis was revolutionized by the discovery that neurons are continually generated in distinct regions of the adult mammalian brain including in the cerebral cortex and the hippocampus . HithertAdult neural stem cells (NSCs) are the source of new neurons during adult neurogenesis. NSCs are specialized radial glia (RG) that reside in dedicated niches in the walls of the lateral ventricles (LV) forming the V-SVZ, and in the subgranular zone (SGZ) of the DG. V-SVZ NSCs give-rise to different interneuron populations that migrate to the olfactory bulb (OB) and the SGZ NSCs generate granule cells in the DG . NSCs inIn this review, we focus on the role of Notch signaling in the control of NSC activity and neurogenesis and address some of the unanswered questions about how this pathway plays different roles in the generation of neurons in the adult brain.NSCs in the adult V-SVZ and the SGZ niches share many similarities, however, they also have important differences in the organization, location and architecture of their niches and in their fate potentials that will be discussed below [for reviews see ].NSCs in the adult V-SVZ (B1 cells) are generated by RGs during embryonic development. The majority of the V-SVZ NSC precursors are generated as early as embryonic day 13.5 and remain quiescent through the late stages of embryogenesis until postnatal and adult stages of life . V-SVZ NNSCs of the V-SVZ are polarized with an apical cilium that projects through the ependymal (E cells) lining of the ventricles into the cerebrospinal fluid (CSF) of the LV, and a long basal process that contacts blood vessels. The V-SVZ NSCs organize the E cells into pinwheel structures . During In addition to the NSCs in the lateral wall (LW) of the LV, recently gliogenic stem cells have been identified in the lateral septal wall (LSW) , as wellLike the NSCs of the V-SVZ, the NSCs of the adult SGZ of the DG are formed during embryonic development. Their precursors acquire a radial morphology reminiscent of adult NSCs, localize to the SGZ of the DG and become quiescent during the early postnatal period . In contDG NSCs predominantly generate glutamatergic granule neurons and to a less extent astrocytes but not oligodendrocytes . The aduNotch1-4) and five canonical ligand  genes. Both the receptors and their ligands are type I transmembrane proteins, presented on the surface of cells and thus enabling direct cell-to-cell communication  as proproteins and are then proteolytically processed by a Furin-like protease and post-translationally modified to generate the mature heterodimeric receptor. The mature Notch receptors are expressed on the plasma membrane with the Notch extracellular domain (NECD) linked to the transmembrane-intracellular domain through a calcium bridge .Binding of a Notch to a ligand triggers the ubiquitination of the ligand, which results in endocytosis of the ligand and the bound NECD into the signal-sending cell. An endocytosis-mediated conformational change on the NECD reveals a proteolytic cleavage site for ADAM10/17 in the negative regulatory region (NRR) of the Notch receptor which facilitates the removal of the NECD. In the absence of a Notch/ligand interaction, the LNR (Lin-12/Notch Repeat) domains within the NRR prevent access and cleavage by ADAM proteases at the NECD, maintaining the Notch receptor in an inactive conformation . CleavagHes) and hairy and enhancer of split-related with YRPW motif (Hey) families  and are therefore important for NSC cell fate determination and neuronal differentiation , astrocytes (Notch1 and Notch2), neurons (Notch1 and Notch2), endothelial cells (Notch1 and Notch4) and vascular smooth muscle cells and pericytes (Notch3) . FurtherRbpj, the common downstream effector of all Notch receptors. Rbpj deletion in NSCs of the V-SVZ and SGZ of the adult mouse brain caused an initial transient increase in neurogenesis that is followed by a total depletion of the NSC pool and loss of neurogenesis in the long-term  in SGZ NSCs maintained qNSCs, blocked NSC entry into cell cycle, and decreased mitotic progenitor, NB and neuron production  in both the V-SVZ and SGZ . In mammferation . Id2 andlt V-SVZ . Id3 andic cells . The ID1ic cells . ID factntenance . By combntenance . Recentl in vivo .trans interaction) Dll ligands are able to inactivate Notch signaling within the same cell (cis interaction/inhibition)  . In the ibition) . Dll1 deproposed . Jagged1proposed . Jagged1he V-SVZ . Ablatioin vitro . Convershe V-SVZ . Similarogenesis .Lfng from NSCs leads to increased NSC proliferation, reduced numbers of amplifying neural progenitors and an increased tendency for astrocytic differentiation. Similar to Lfng, Dll1 deletion leads to an increase in mitotic NSCs and less amplifying neural progenitors. On the other hand, genetic deletion of Jagged1 causes NSCs to re-enter the cell cycle leading to an increase in amplifying neural progenitor production  are β3-N-acetylglucosaminyltransferases that modify O-fucose on epidermal growth factor-like (EGF) repeats in the NECD. Specific fringe modifications therefore can enhance Notch binding to Dll1 resulting in activation of Notch signaling whereas others inhibit Notch activation by Jagged1 . Recentloduction . In summIn this review, we present an overview of our current knowledge about how the Notch signaling controls adult neurogenesis, with emphasis given to the roles of the pathway in NSC activity. It is now widely accepted that Notch signaling plays a pivotal role on NSC maintenance and neurogenesis. Different Notch receptor paralogues are able to control either the quiescent or activated state of NSCs through Rbpj and transcriptional regulation of target genes. In addition to Notch receptors, several Notch ligands and downstream transcriptional effectors play key roles in NSC maintenance and neurogenesis. However, the precise molecular mechanism that differentially controls Notch signaling in NSCs remains elusive and needs further investigation. The pleiotropic functions of Notch signaling in adult neurogenesis could be attributed to the complex nature and regulation of the pathway. Differential ligand-mediated activation of Notch receptors might control the quiescent or activated NSC state and maintenance. Additionally, differential transcriptional responses downstream of the Notch receptors might control the activation state of NSCs. It is intriguing to speculate that different Notch receptors modulate distinct gene networks and/or overlapping gene networks with distinctive strengths and dynamics. Additionally, the architecture of the NSC niches certainly adds another level of complexity to the regulation of Notch signaling in NSCs. Notch signaling mediates cell-to-cell communication between neighboring cells, and niche cells control NSC behavior, it could be that the expression of Notch ligands and/or other Notch interactors within the niche affects NSC fate and maintenance. The identification of new upstream or downstream effectors of the Notch signaling pathway will pave the way to a better understanding of NSC biology and fate switch.There are still a number of important open questions about the role of Notch signaling in adult neurogenesis that need to be addressed in the future. Many of these unknowns are manifested in the fact that our current knowledge of Notch signaling cannot explain why cells in the same neurogenic niche express multiple Notch receptors which regulate either none compensated different processes or exert different functions.Although it is clear that different Notch receptors play different roles in regulating the activity and fate of NSCs, how this is achieved for receptors that interact with the same set of ligands and use the same DNA binding molecule (CSL protein) is still not known. For example, it still remains unclear whether Notch receptors (Notch1-3) compete with each other for ligands, downstream effector proteins or target genes in order to modulate the response of the cell to different Notch receptor signals. Additionally, it is not known whether different ligands can activate Notch receptors to induce different downstream effectors of the pathway within the same cell. Although Notch1 has been shown to be target of its own signal in some cells, it remains to be shown whether Notch receptors can cross regulate the expression of other Notch receptors at the transcriptional level in adult NSCs. Finally, the discrete or compensatory roles of the individual Notch ligands in the adult neurogenesis remain to be elucidated. In summary, there remains much to be learnt about the Notch signaling in the control of NSCs in the adult brain, and future findings may have important implications for other organs and even in diseases including cancer.AL and VT wrote and edited the manuscript and designed and generated the figures. All authors contributed to the article and approved the submitted version.This work was supported by the Swiss National Science Foundation (31003A_162609 and 31003A_182388 to VT).The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher.


Homogenates of brain tissue from the frontal cortex at autopsy in patients with amyotrophic lateral sclerosis (ALS) showed dramatically reduced levels of the enzyme thiamine pyrophosphatase (TPPase), the enzyme responsible for the conversion of thiamine pyrophosphate (TPP) to thiamine monophosphate (TMP). Additionally, free thiamine (vitamin B1) and TMP levels have been shown to be significantly reduced in the plasma and cerebral spinal fluid (CSF) of patients with ALS. These findings suggest that there is impaired thiamine metabolism in patients with ALS. Impaired thiamine metabolism decreases adenosine triphosphate (ATP) production and is a well-established cause of neurodegeneration. Decreased levels of TPPase, resulting in decreased levels of TMP in the cells of the frontal cortex, might account for the focal neurodegenerative changes observed in motor neurons in ALS. Benfotiamine, a safe, lipid-soluble, highly absorbable thiamine analogue, significantly raises free thiamine, TMP, and TPP levels in the blood. A case in which benfotiamine may have positively impacted the symptoms of a patient with ALS is presented. The use of benfotiamine in patients with ALS appears to be a promising therapeutic option. Considering the severity and the lack of satisfactory treatment options associated with this disease, more research on the effects of benfotiamine on the course of ALS is urgently needed. Adenosine triphosphate (ATP) is essential for the intracellular transfer of energy needed in metabolic processes responsible for the healthy functioning of neurons and all other cell types. The vast majority of cellular ATP is believed to be produced in the mitochondria through the process of oxidative phosphorylation. Oxidative phosphorylation requires the action of Krebs cycle enzymes. Diminished activities of multiple enzymes of the Krebs cycle have been noted following thiamine deficiency . ImpairmSeveral neurodegenerative diseases have been shown to be associated with impaired thiamine metabolism. Thiamine deficiency results in Wernicke encephalopathy (WE), whose manifestations include cognitive impairment and confabulation . ThiaminBettendorff et al.  found thCostantini et al.  reportedImpaired thiamine metabolism has been associated with Alzheimer’s disease (AD). Rao et al.  found thDiabetic polyneuropathy and alcoholic polyneuropathy, both neurodegenerative diseases of the peripheral nervous system, are associated with thiamine deficiency and have been shown to improve with the use of benfotiamine ,17.Amyotrophic lateral sclerosis (ALS) has been associated with impaired thiamine metabolism -20. As iA 69-year-old white male with a diagnosis of slow-progressing ALS of one year’s duration claimed to be in less pain and to have significantly less fatigue within four days of initiating a course of 300 mg of benfotiamine and 1 mg of methylcobalamin (BAM) twice a day by mouth. He also claimed a sense of improved cognition. His sense of greater muscular strength and improved cognition remained unchanged for approximately eight weeks of taking BAM daily. At the end of the eight-week course, he discontinued taking BAM and claimed that within four days his symptoms had regressed to where they had been prior to initiating BAM. The patient then resumed taking BAM and claimed that within two days he experienced a resumption of his sense of greater muscular strength and improved cognition.Thiamine, also known as free thiamine, is essential for all animal life and the proper functioning of all cell types. It is not created by the body and must be obtained from food. After thiamine is absorbed from the gut, it enters the bloodstream, where it is subsequently transported into neurons and all other cell types. Under normal circumstances, during its intracellular metabolism, thiamine is converted to its biologically active form, TPP, through the actions of the enzyme thiamine pyrophosphokinase (TPK). TPP is then converted to thiamine monophosphate (TMP) through the action of the enzyme thiamine pyrophosphatase (TPPase). TMP is then converted to free thiamine through the action of the enzyme thiamine monophosphatase (TMPase). As such, thiamine metabolism is, in part, cyclical in nature ,22. The Impaired thiamine metabolism in ALS Homogenates from the frontal cortex of deceased ALS patients showed significantly lower levels of TPPase than controls in research by Laforenza et al. . Poloni Probert et al.  showed tDecreased availability of TPPase within motor neurons in ALS would impair thiamine metabolism, causing reduced efficiency in Krebs cycle enzymes, decreased ATP production, and neurodegeneration. A possible cause of decreased TPPase levels is the well-documented phenomenon of fragmentation and atrophy of the Golgi apparatus observed in the motor neurons of patients with ALS . TPPase Benfotiamine and ALSAnalysis of the therapeutic effect of methylcobalamin on the symptoms of ALS would suggest that, although methylcobalamin at high doses may have some beneficial effect, the perceived rapid improvement in symptoms experienced by the patient described in this case presentation is from the actions of benfotiamine and not methylcobalamin .Benfotiamine has been shown to raise free thiamine, TMP, and TPP levels in the blood to a much greater degree than direct thiamine administration ,15. IncrThis would have the effect of restoring normal thiamine metabolism and increasing ATP production. Increased ATP levels in motor neurons could potentially counteract the neurodegenerative processes observed in ALS, possibly improving neuronal function and inhibiting disease progression.Impaired thiamine metabolism appears to be involved in several neurodegenerative diseases. The evidence suggests that this may be the case in ALS. In ALS, the neurons of the frontal cortex have been shown to have decreased levels of the enzyme TPPase. Decreased TPPase activity is consistent with decreased TMP levels in the CSF of patients with ALS. The disruption in healthy thiamine metabolism would likely cause decreased efficiency of Krebs cycle enzymes required for oxidative phosphorylation, leading to decreased ATP production. This, in turn, may potentially cause the focal neurodegeneration of these motor neurons. The mechanism by which TPPase levels are reduced in these cells may be due to the well-documented finding in ALS of golgi fragmentation and atrophy, or the reduction may be due to some other yet-to-be-determined process. In any event, the pathobiological effects of impaired thiamine metabolism may be countered by benfotiamine. Although the improvement noted by the patient in this case presentation may be due to a placebo effect, the rapid improvement experienced by the patient after initiating BAM therapy, the regression of symptoms experienced after he discontinued BAM, and his perceived rapid resumption of improvement after restarting BAM further support this hypothesis.Considering the well-established association between impaired thiamine metabolism and neurodegeneration, the evidence that impaired thiamine metabolism is associated with ALS, and the paucity of satisfactory options currently available for the treatment of ALS, further research on the potential therapeutic benefits of benfotiamine is urgently needed.


The widespread of infectious diseases and the advent of complex illnesses because of the human lifestyle led to considerable human pathogenesis and subsequent mortality, leaving a massive loss on the shoulder of human society . Even wiAdvanced Nanotechnological Detection and Drug Delivery Configurations” is established with the aid of five expert editors with expertise in different disciplines toward promoting the current knowledge of drug discovery and advanced detection approaches. The Research Topic was prosperous, and five articles, including four original research articles and one review paper, were published after a rigorous peer review process supported by expert reviewers in the field.This Research Topic entitled “Dhondt et al. unveiled the contribution of fluid therapy in developing augmented renal clearance (ARC) in piglet models. Their study focused on the fluid administration of renal function by employing a piglet animal model to quantify the effect of fluid administration on the pharmacokinetic effects of the renally excreted drugs. Their study suggested the key impact of fluid therapy on the key factors of the ARC that should be considered upon the administration of the renally excreted drugs.Summarizing the published original research articles in the Research Topic, Huang et al. summarized and evaluated 10 years of progression in the field of gene therapy, focusing on the usage of nanomedicine and the problems in their transition into active use. Their study suggested the potential impact of several technologies in the case of targeted drug delivery. Accordingly, the systematic evolution of ligands by exponential enrichment (SELEX) and aptamer systems were found to be potent drug delivery configurations. The smart gene editing through clustered regularly interspaced short palindromic repeats (CRISPR)-associated protein 9 (Cas9) is recognized as another method of target-oriented and specific disease treatment that showcased promising results in cancer therapy. The exosomes and their derivatives were also suggested as promising intelligent drug delivery systems for treating complex illnesses. This comprehensive study is a useful tool for decision-makers to put effort into the most practical strategies for specific and efficient disease treatment.Zhu et al. correlated the ion channel gene signatures with the prognosis, diagnosis, and individualized treatments in patients with clear cell renal cell carcinoma (ccRCC). For this case, they extracted the RNA profiles, clinical data of patients with ccRCC, and public databases to propose a proper diagnosis approach and timely treatment techniques upon monitoring the level of ion-channel-related genes, known as specific biomarkers toward monitoring the typical structure of the kidney. Xian and co-workers  as a potential treatment tool. Based on their review, the long-circulating lifetime, biocompatibility, low toxicity, and ease of scale-up made the PEGylated lipid-based configurations versatile delivery systems for nucleic acids. They also investigated the recent progress in the case of these exciting drug delivery systems and provided the challenges they encounter and possible strategies to address them.In a review study published in the Research Topic,


In this study, a new probe was designed to enable electrocardiography of a rotated heart during cardiac surgery when skin electrodes became non-functional. This probe adhered non-invasively to the epicardium and collected the ECG signal independently from the position of the heart. The study compared the accuracy of cardiac ischemia detection between classic skin and epicardial electrodes in an animal model.Using six pigs, an open chest model was devised with cardiac ischemia induction by coronary artery ligation in two non-physiologic heart positions. Both the accuracy and the time of detection of electrocardiographic symptoms of acute cardiac ischemia were compared between skin and epicardial methods of signal collection.Heart rotation to expose either the anterior or the posterior wall resulted in a distortion or loss of the ECG signal collected by skin electrodes after coronary artery ligation, standard skin ECG monitoring did not reveal any ischemia symptoms. Attachment of an epicardial probe on the anterior and posterior walls helped in the recovery of the normal ECG wave. After ligation of the coronary artery, the epicardial probes recorded cardiac ischemia within 40 s.This study highlighted the effectiveness of ECG monitoring with epicardial probes in a rotated heart. It can be concluded that epicardial probes can detect the presence of acute ischemia of a rotated heart when skin ECG monitoring becomes ineffective. Coronary artery bypass grafting (CABG) is the most common heart surgery performed worldwide. In nearly half of heart patients, CABG is being performed on a beating heart–off-pump. During this surgery, exposure of the target coronary arteries requires a change in the position of the heart; however, this maneuver often leads to a loss of contact between the heart and the adjacent chest structures. As a result, there is a loss of proper electric signal conduction from the heart to the electrocardiographic (ECG) electrodes applied on a patient's skin. Thus, the ECG signal during the performance of off-pump coronary artery bypass (OPCAB) is often lost or distorted, placing restrictions on the monitoring of cardiac ischemia during surgery. In light of the above, and with the objective of restoring optimal ECG monitoring during heart positioning, a new epicardial ECG electrode was designed in this study.Using an animal beating heart model, this study aimed to compare the two methods of ECG monitoring of a rotated heart: standard monitoring with signal collection by skin electrodes and a new method of monitoring with epicardial signal recording. The comparison included testing the accuracy and rapidity of myocardial ischemia detection and the safety of electrode use.The new epicardial probe was designed as a thin and elastic slice manufactured with screen printing technology  with a cIn the electrode head and tail, there was a conduction layer containing graphene, which was isolated all along the tail. The tip of the tail had a connective platform for wire attachment with a standard crocodile clip, and the distal ending of the wire had a standard ECG snap . The traDuring the chest opening procedure, skin electrodes showed normal ECG levels with no cardiac ischemia or any heart rhythm disturbances in all animals. In the first three animals, the heart was rotated to expose the LAD artery. During the rotation, the ECG skin signal was distorted in two animals  and was completely lost in one. Attachment of an epicardial probe resulted in the recovery of ECG presentation as lead V. The morphology of the epicardial ECG signal was typical for physiologic precordial leads showing no signs of ischemia . After LAD ligation, the skin ECG revealed either no change  or an ST segment elevation change of less than 0.1 mV (no ischemia). The epicardially collected ECG showed acute cardiac ischemia with ST segment elevation exceeding 1 mV (Pardee wave) in all three animals at a duration ranging between 15 and 30 s.In the remaining three animals, the experiment heart was rotated to expose the PDA. During the rotation, the ECG skin signal was lost in all animals. The epicardial probe was attached to the posterior wall, which resulted in the restoration of the ECG curve in lead V. Also, the morphology of the epicardial ECG signal in this position was typical for a physiologic precordial lead showing no signs of ischemia . Then, the PDA was ligated. No reaction was recorded in the ECG collected with skin electrodes, since the signal was already lost. The epicardial probe located on the posterior wall revealed ST segment elevations exceeding 1 mV (Pardee wave) in all three animals at a duration ranging between 30 and 40 s .At the end of the experiments, the probes were detached from the epicardium and no macroscopic changes in tissue, such as bleeding, hematoma formation, or tissue tears, were noticed. In addition, there was no debridement of the electrode left on the epicardial tissue, and all probes remained intact and functional until the completion of the study protocol.Intraoperative ECG monitoring during the performance of OPCAB has not been widely studied, and it has been shown that hemodynamic instability during OPCAB can be secondary to transient ischemia , 2. NeveThe introduction of the presented technology may result in several benefits for patients undergoing OPCAB. First, the provision of continuous information on cardiac ischemia during the performance of coronary anastomosis may reduce the pressure of time for surgeons. This may result in an anastomosis of high quality. Some data showed lower anastomosis quality in OPCAB when compared with the arrested heart technique .Second, epicardial ECG monitoring may support the decision-making process in the positioning of the heart for exposure of the target coronary arteries. An inappropriate position may result in ischemia induction before coronary artery ligation, hemodynamic collapse, and poor coronary bypass performance, leading to incomplete revascularization affecting long-term results .Third, immediate ischemia diagnosis provides immediate actions, such as intracoronary shunt placement, repositioning of the heart, arterial pressure management, or even conversion to an on-pump technique before hemodynamic collapse.p = 0.0001)  .Epicardial electrocardiography will help in OPCAB technique expansion, which is a less invasive method than the classic on-pump technique with the use of cardio-pulmonary bypass (heart-lung machine). It should be noted that both short- and long-term results of OPCAB are related to the number of procedures performed in patients ; the morThe new epicardial device designed in this study has several other applications in cardiac surgery and may also be used as a temporary external pacing wire, or for electrical mapping of the pulmonary veins while monitoring the entry and exit block after pulmonary vein isolation. Since the signal collected by the probe is strong and clear, it may support an intraoperative assessment of the vitality of the cardiac wall regions.The limitation of this study is its small sample size of an animal model, and future clinical studies will evaluate whether any benefits can be had from the introduction of epicardial ECG monitoring.In conclusion, this study highlighted the effectiveness of ECG monitoring with epicardial probes in a rotated heart. Epicardial probes can detect the presence of acute ischemia of a rotated heart when skin ECG monitoring becomes ineffective. Epicardial ECG monitoring can potentially replace standard skin ECG monitoring during the performance of beating heart surgery.


The altered posterior question-mark incision for decompressive hemicraniectomy (DHC) was proposed to reduce the risk of intraoperative injury of the superficial temporal artery (STA) and demonstrated a reduced rate of wound-healing disorders after cranioplasty. However, decompression size during DHC is essential and it remains unclear if the new incision type allows for an equally effective decompression. Therefore, this study evaluated the efficacy of the altered posterior question-mark incision for craniectomy size and decompression of the temporal base and assessed intraoperative complications compared to a modified standard reversed question-mark incision. The authors retrospectively identified 69 patients who underwent DHC from 2019 to 2022. Decompression and preservation of the STA was assessed on postoperative CT scans and CT or MR angiography. Forty-two patients underwent DHC with the standard reversed and 27 patients with the altered posterior question-mark incision. The distance of the margin of the craniectomy to the temporal base was 6.9 mm in the modified standard reversed and 7.2 mm in the altered posterior question-mark group (p = 0.77). There was no difference between the craniectomy sizes of 158.8 mm and 158.2 mm, respectively (p = 0.45), and there was no difference in the rate of accidental opening of the mastoid air cells. In both groups, no transverse/sigmoid sinus was injured. Twenty-four out of 42 patients in the modified standard and 22/27 patients in the altered posterior question-mark group had a postoperative angiography, and the STA was preserved in all cases in both groups. Twelve (29%) and 5 (19%) patients underwent revision due to wound-healing disorders after DHC, respectively (p = 0.34). There was no difference in duration of surgery. Thus, the altered posterior question-mark incision demonstrated technically equivalent and allows for an equally effective craniectomy size and decompression of the temporal base without increasing risks of intraoperative complications. Previously described reduction in wound-healing complications and cranioplasty failures needs to be confirmed in prospective studies to demonstrate the superiority of the altered posterior question-mark incision. However, this straightforward procedure still constitutes a particular challenging and, in some points, controversial surgery that exposes the patients to significant risks for various intraoperative and postoperative complications9. Many of the DHC-associated complications are related to the significant skin and bone flap compared to most standard supratentorial craniotomies. Wound-healing problems are one of the most frequently encountered complications after DHC and the main reason for the higher rate of wound-healing disorders is supposed to be due to injuring the superficial temporal artery (STA), which constitutes the main blood supply of the large myocutaneous flap10. This might happen, since the universally used standard reversed question-mark incision for DHC starts anterior to the tragus, where the STA runs superficially over the temporal root of the zygoma and is jeopardized during incision11. Injuring the STA during the skin incision predisposes the wound to ischemia and consecutive wound-healing disorders12. Therefore, the altered posterior question-mark incision starting behind the ear and posterior of the base of the mastoid process was proposed14. This incision type is supposed to preserve the STA and demonstrated a significantly reduced rate of infections and wound-healing disorders after cranioplasty11. However, it still remains unclear if this incision allows for the exact same size of the bone flap and for a sufficient exploration and decompression of the temporal base compared to the standard reversed question-mark incision. Further, it has been suggested that there is an increased risk of accidentally opening the mastoid air cells or injuring the transverse and sigmoid sinuses15. This might happen if the skin flap behind the ear is retracted too vigorously and if the craniotomy crosses below the superior nuchal line. Even the external auditory canal might be damaged16. Therefore, in this study, we compared the size of the craniectomy and the decompression of the temporal base using the altered posterior question-mark incision and our modified standard reversed question-mark incision. This modified reversed question-mark incision starts superior to the pinna to preserve the STA but allows for an adequate retraction of the scalp flap. We further analyzed intraoperative complications associated with the posterior approach and assessed the rate of infections and wound-healing disorders after DHC.Decompressive hemicraniectomy (DHC) is common practice for various life-threatening indicationsthe ethics committee of the Charité–Universitätsmedizin Berlin (EA1/012/22), who also confirmed waiver of informed patients consent based on the retrospective nature of our study. Data acquisition and presentation were made according to the STROBE  guidelines for reporting observational studies17. All methods were performed in accordance with the Declaration of Helsinki.This is a retrospective single center study performed at our tertiary medical center. Ethical approval was granted by We included all consecutive patients over the age of 18 years who underwent decompressive hemicraniectomy for a malignant hemispheric stroke, traumatic brain injury or intracerebral hemorrhage from 2019 to 2022. Patients that died before receiving the first postoperative CT were excluded. Demographic, clinical and radiographic patient data were retrospectively extracted from clinical records and documentation. They included patient-specific risk factors for wound-healing disorders .20. Before January 2021 we performed the standard reverse question-mark incision for DHC. However, we modified the incision and started the incision line superior to the pinna without extending down to the zygomatic arch. Starting superior and slightly anterior to the ear allows for an effective retraction of the scalp flap anteroinferiorly without jeopardizing the STA  treated via the modified standard reverse question-mark incision, (b) altered posterior question-mark incision . The following issues were addressed: Decompression of temporal base, exploration of and access to the temporal base, occipital decompression, control of bleedings, intraoperative localization of the ear as landmark for further steps, protection of the ear, size of craniectomy, feasibility of wound closure. The questionnaire was distributed after the surgeon performed the altered posterior question-mark incision for the first time.Statistical analyses were performed with GraphPad Prism 8.4.2. and SPSS version 25 (IBM Corp). Discrete data were presented as counts and percentage and compared by Chi-Square-Test. Continuous data were presented as mean and standard deviation (SD) and analyzed by Mann–Whitney-U-Test.A total of 69 patients with postoperative imaging after DHC were included. 42 patients underwent DHC using the modified standard reverse question-mark incision and 27 using the altered posterior question-mark incision. The mean age of the study population was 51 ± 12 years. Major underlying pathologies were malignant hemispheric stroke (62.3%) and severe traumatic brain injury (23.2%). The baseline characteristic of the study population is provided in Table Both groups showed similar outcomes concerning the extent of decompression Table . The disThere was no difference between the duration of surgery and the median lengths of stay in the ICU. Wound-healing disorders requiring revision surgery after DHC were similar in the modified standard reversed and altered posterior question-mark group p = 0.344). Further there was no difference between the groups concerning accidental openings of the mastoid cells. All accidental openings of airy cells listed as complications were air cells of the squamous segment of the temporal bone associated with the mastoid (Fig. 44. FurthPersonal experience with the altered posterior question-mark incision was assessed using a 4-point scale (Table The major finding of our study is that the altered posterior question-mark incision, which starts behind the ear at the mastoid notch, allows for an equally effective decompression of the temporal base and for the same size of the craniectomy. The rate of additional intraoperative complications appeared to be low. However, the STA could be equally preserved in both groups and there was no difference in the rate of postoperative wound-healing complications.10. The main reason for the increased risk is supposed to be due to the large skin and bone flap and the increased risk of injuring the STA during the widely used standard reversed question-mark incision, leading to reduced perfusion and ischemia of the large skin flap8. The recently proposed altered posterior question-mark incision starts behind the ear and posterior of the base of the mastoid process and is supposed to better preserve the STA during incision13. However, beginning behind the ear, it is unclear if this incision allows for the same size of bone flap as well as for a sufficient exploration and decompression of the temporal base compared to the standard reversed question-mark incision. With the standard reversed question-mark incision, the inferior line is usually extended below the level of the zygomatic arch and the scalp is then reflected along with the temporalis muscle anteroinferiorly19. This allows for a maximum retraction of the combined myocutaneous flap down to the cranial base, in order to explore and adequately remove the temporal bone. An adequate bony decompression over the lateral temporal lobe down to the middle cerebral fossa is essential for an optimized decompression of the brainstem. Previous studies demonstrated a correlation of the state of the mesencephalic cisterns with the distance of the lower border of the craniectomy to the temporal base21 and it is well established, that abnormal cisterns increase the risk of critically high ICP and worse outcome after severe brain injury23. A sufficient diameter of the craniectomy of at least 15 cm also demonstrated to reduce the risk of external brain herniation and improved survival and favorable functional outcome after DHC25. Using the altered posterior question-mark incision starting behind the ear, however, the skin flap might be hindered by the attachment of the external auditory canal, making it more difficult to sufficiently reflect the myocutaneous flap anterioinferiorly in order to reach the lesser wing of the sphenoid and the squamous segment of the temporal bone11. It might also be more difficult to extend the craniectomy to the frontal squamous bone in order to achieve the necessary diameter of the bone flap. Therefore, in this study we evaluated if the size of the removed bone flap and the decompression of the temporal base differs between our modified standard reversed and the altered posterior question-mark incision. The modified standard reversed question-mark incision that we used to perform at our institution, starts slightly before the ear and superior to the pinna but is not extended down to the zygomatic arch. This modified incision allows for an equally sufficient retraction of the myocutaneous flap compared with the standard incision starting at the zygomatic arch, but is supposed to avoid crossing the STA.Wound-healing disorders belong to the most frequently encountered complications after DHC and in the literature, the rate of wound failure varies between 3 and 40%26. The similar decompression of the temporal base in our study was also reflected in the state of the basal cisterns, which were mostly open in both groups. Further, there was no difference in size of the removed bone flap. Therefore, the altered posterior question-mark incision allows for the same size of craniectomy and for an equally effective decompression of the temporal base. But there are other risks suggested to be associate with the altered incision. If the incision is extended below the mastoid process, there is a risk of accidentally opening the mastoid air cells and/or the transverse/sigmoid sinus15. Veldeman et al. even described a case during which the external auditory canal was opened16. The additional risk of intraoperative complications using the posterior incision was low in our cohort and might be easily avoided if the craniotomy stays superior of the transverse sinus and if the scalp flap is not retracted too forcefully. Careful downward retraction of the myocutaneous flap also prevents injuring the ear. In most cases the mastoid notch and the nuchal line can be easily identified and used as landmarks for the localization of the sinuses and the transverse-sigmoid junction before craniotomy. In our study, we did not experience any injury of the ear and did not encounter a significant an increased rate of accidental opening of the mastoid air cells or the transvers/sigmoid sinus. However, our data suggest that there may be a higher risk for accidental openings of the mastoid air cells using the altered posterior question-mark incision. Therefore, the authors recommend institutions switching to the altered posterior question-mark incision to be aware of this potential specific pitfall. Most importantly, there was no difference between both groups´ rate of intraoperatively preserved and open STA on postoperative angiography imaging. This can be primarily attributed to the fact, that the modified standard reverse question mark incision in our study starts superior to the pinna without extension in front of the ear and down to the zygomatic arc, allowing for an equally effective preservation of the STA. However, the modified standard reversed question-mark incision might injure the parietal branch, which is more likely to be preserved with the altered posterior incision and might not be reliably identified on the postoperative angiographies.Intraoperatively, we did not experience more difficulty to reach the temporal base and to remove the temporal bone with a rongeur using the altered posterior question-mark incision. This was confirmed by means of postoperative CT scans which demonstrated an equally effective decompression of the temporal base with no difference in the distance of the lower margin of the decompression down to the floor of the middle cerebral fossa. The median distance between the lower border of the craniectomy and the temporal cranial base in both groups was equal and in accordance with results previously reported on the standard reversed question-mark incision with extension down to the zygomatic arch11. This suggests, that reduced scalp flap perfusion and the role of the incision type is more relevant after cranioplasty than it is right after DHC. Regarding the early postoperative phase after DHC, several other factors have been suggested to influence infection rate and wound-healing disorders. Recently, we demonstrated an increased rate of postoperative subgaleal CSF accumulations on the ipsilateral side after DHC, significantly impacting wound-healing disorders and the rate of surgical revisions. Subgaleal CSF accumulations cause additional tension to the wound and can be reduced using early postoperative lumbar CSF drainage27. In this study, only a few patients had a postoperative lumbar drainage in both groups, minimizing this bias. Nevertheless, the novel posterior question-mark incision allows for an equally effective decompression without increased risk of intraoperative complications and a previous study demonstrated a reduced rate of wound-healing complications after cranioplasty, we changed our clinical practice in DCH by using the novel posterior question-mark incision starting behind the ear. However, bigger studies are needed to confirm the benefit of the new incision type on postoperative wound-healing complications and to demonstrate the superiority of the altered posterior question-mark incision for DHC.Still, we did not find a significant reduction in infections or wound-healing disorders requiring revision surgery using the altered posterior question-mark incision. However, the present study was not designed to detect differences in postoperative wound-healing disorders and the data shows a trend towards an advantage of the altered posterior question-mark incision regarding wound healing. The results are also in accordance with the findings by Veldeman et al., who demonstrated a significantly reduced rate of infection and wound-healing disorders after cranioplasty but not after primary DHC28. Furthermore, the authors cannot exclude that the high rate of preserved STAs in our study with the altered posterior question-mark incision may be attributed to our expertise as a vascular neurosurgical center. The observed rate may potentially differ in other institutions.Due to the retrospective nature, our single-center study is subject to various well-known limitations. First, the small patient number and heterogenous population might fail to detect significant differences in the rate of intraoperative complications and postoperative wound-healing disorders. Further, long-term wound infections and healing complications might not have been reported due to the variably and missing active follow-up after cranioplasty. However, patients are seldom referred to another center if postoperative complications occur. Therefore, it is unlikely that we missed a relevant number of patients with postoperative complications or wound-healing disorders. At least, the follow-up period was too short to detect or report all aseptic bone resorptions after DHC as previous study demonstrated that aseptic bone resorption occurs after a median time of 15 months after primary DHCSufficient decompression substantially influences outcome after DHC and the altered posterior question-mark incision for DHC demonstrated to allow for an equally effective decompression of the temporal base, while the STA could be preserved in all cases. Further, the rate of intraoperative complications was low and therefore, the altered posterior question-mark incision demonstrates to be a safe and effective alternative to the standard reversed question-mark incision. However, previously described reduction in wound-healing complications and cranioplasty failures needs to be confirmed in prospective studies to demonstrate the superiority of the altered posterior question-mark incision.


These IRFs are, to the best of the authors’ knowledge, the first attempt to generate injury prediction tools based on PMHS data for the four knee ligaments. The study has summarized all the relevant literature on PHMS experimental tensile tests on the knee ligaments and utilized the available empirical data to create the IRFs. Future improvements require upcoming experiments to provide comparable testing and strain measurements. Furthermore, emphasis on a clear definition of failure and transparent reporting of each specimen-specific result is necessary.The purpose of this study was to develop injury risk functions (IRFs) for the anterior and posterior cruciate ligaments  and the medial and lateral collateral ligaments  in the knee joint. The IRFs were based on post-mortem human subjects (PMHSs). Available specimen-specific failure strains were supplemented with statistically generated failure strains  to accommodate for unprovided detailed experimental data in the literature. The virtual values were derived from the reported mean and standard deviation in the experimental studies. All virtual and specimen-specific values were thereafter categorized into groups of static and dynamic rates, respectively, and tested for the best fitting theoretical distribution to derive a ligament-specific IRF. A total of 10 IRFs were derived . ACL, MCL, and LCL received IRFs in both dynamic and static tensile rates, while a sufficient dataset was achieved only for dynamic rates of the PCL. The log-logistic and Weibull distributions had the best fit ( Knee ligament injuries are associated with both low-energy and high-energy trauma . TrafficAlthough not life-threatening, knee ligament injuries increase the risk of subsequent injuries such as arthritis, meniscus tear, and the need for a total knee replacement . They alThe four primary knee ligaments, ACL, PCL, and the medial and lateral collateral ligaments , are commonly associated with three different injury mechanisms: 1) mid-section failure is a rupture within the ligament itself, 2) ligament detachment occurs at the interface between the ligament and the bone, and 3) avulsion fractures occur when osseous fragments adjacent to the ligament insertion sites detach together with the ligament . These tThe risk of injury can be evaluated using numerical simulations. Finite-element human body models (HBMs), such as Total HUman Model for Safety (THUMS) and the Global Human Body Model Consortium (GHBMC), are expected to increasingly complement experiments with physical dummies. HBMs offer the opportunity to evaluate impact down to the tissue level and address occupant diversities to a greater extent than what is practically possible with physical dummies. Local injury risk functions (IRFs) are needed in the evaluation of knee ligament responses as they predict the risk of injury on a material level, allowing injury mechanisms to be accounted for. Existing human-based IRFs for the lower extremities have primarily been focusing on skeletal fractures , while IPresently, there are no IRFs for any of the four knee ligaments. As every ligament has a unique role in stabilizing the knee joint, it is essential to address the ligaments separately. Therefore, local IRFs of the knee ligaments are needed tools in order to understand the impact responses of each ligament, which would further enhance the potential of using HBM simulations to develop preventive measures. The objective of this study is to map the available literature for PHMS experimental tensile failure studies of the four primary knee ligaments: ACL, PCL, MCL, and LCL, and use the obtained literature data to create local IRFs.Cumulative injury risk functions were derived from specimen-specific failure strains in experimental studies conducted on post-mortem human subject (PMHS) ligaments as previously utilized for hip fracture risk functions by A literature search was performed for experimental studies conducting uniaxial failure tests on PMHS ligaments. The search was conducted iteratively between February 2019 and April 2023, mainly using Google Scholar. Some of the search words used included “ACL/PCL/MCL/LCL material properties,” “Failure strain,” “Tensile properties,” and “Knee joint” in various combinations. Most of the collected studies shown in The inclusion criteria of studies for the injury risk functions were as follows: 1) ligament failures (deformation at maximum load) presented in terms of strain values or elongation failures together with initial ligament lengths; 2) conducted on adult PMHS; and 3) primary sources of the experimental results, exclusively. The results stating bony fracture or avulsion as the failure mode were excluded as they do not represent an injury mechanism on the ligament tissue itself. Five articles provided specimen-specific failure strains . Wilson The injury risk functions were generated based on whether the experiments were conducted on bone–ligament–bone (BLB) specimens or on dissected LIGament samples (LIG), as the two specimen types differ in which of the failure mechanisms they employ.p ≤ 0.05) in the failure strains were found at a mutual cutoff level of 10%/s for all ligaments  %/s order of magnitude. The four groups were systematically tested among themselves for statistical significance in the strain rate using Student’s t-test. Significant differences  were assembled in one dataset to derive one injury risk function.The failure strains used for the generation of virtual values  were asse size N . Z is a virtual were randomly generated failure strains within the range of every p-values from the AD test, 2) the lowest root mean square error (RMSE) between the mean-ECDF and each distribution’s corresponding TCDF, and 3) visual observation of the plotted curves ,α is the scale parameter, and β is the shape parameter.where p < 0.001, respectively) and for LCL BLB (p = 0.002) at a significance level of 5%.Student’s t-test analysis confirmed a statistical difference between the datasets of the static and dynamic subgroups of ACL BLB and MCL LIG  and the large SD, which is also reflected on the RMSEs of about 8% and 10%, respectively. The ACL-dynamic-BLB IRF has a slower increase of risk than the other dynamic IRFs , as a reThere are a number of limitations in comparing the ligament tensile responses between different knee angles . The orientation of the two bundles of the ACL varies inside the knee joint, and loading the ligament in the longitudinal direction along both bundles can be considered challenging . Most teThe BLB IRFs of the dynamic ACL and PCL, and the static LCL, are positioned to the left, relative to their corresponding LIG IRFs, as a result of the BLB dataset having lower failure strains than the LIG dataset . Both thThe IRFs of the MCL are only based on dissected ligaments which are provided for both the dynamic group, as well as the static. While the BLB IRFs for the other three ligaments behave as expected, the MCL IRFs have a reversed and unexpected relation between the dynamic IRF and the static IRF. The dynamic IRFs for ACL, PCL, and LCL have lower strain failures and more rapid accelerations of the injury risks compared to the static rates , positioIn the literature, data used in studies have tended to assume homogeneity of the ligaments. This assumption was therefore adopted in the construction of the IRFs. The defined tensile rate in most articles refers to the applied actuator displacement rate and not to the resulting ligament strain rate. That is, the experiments assumed that the displacement rate of the attachment grips corresponds to the ligament’s actual strain rate. This assumption might be applicable for the dissected ligaments; however, it is not obvious for the BLB components. As these specimens are a complex mix of bone and ligament, an additional variety of failure modes are possible when the ligament attachments are included in the test setup. The flaw of such simplification can be exemplified with ligament failures occurring at one attachment site and rarely in both, suggesting an inhomogeneous strain field across a ligament during uniaxial loading . NeverthThe tensile recruitment of the knee ligaments is highly dependent on the position of the knee joint at the time of impact or injury. The cruciate ligaments are divided into two functional bundles with a varied orientation relative to each other within the knee joint. The ACL is divided into an anteromedial (AM) and posterolateral (PL) bundle, and PCL into an anterolateral (AL) and posteromedial (PM) bundle. The varied orientation of the bundles makes them load-bearing in different knee joint angles. The AM-ACL and AL-PCL bundles are tensed during a passive flexion of the knee joint, while PL-ACL and PM-PCL are kept relatively slacked. The reverse occurs during passive extension, where the posterior bundles of the ACL and PCL are tensed instead . SimilarSeveral studies have tested the various functional parts of the ligaments . Evaluations have focused on the biomechanical properties and the relative differences between the sub-ligaments to better understand their function , which hper se. Both muscle activation and passive structures in the knee joint influence the relative motion between the tibia and the fibula, and the relative position between the bones at the time of injury might also deviate between passively and actively induced motion. This, in turn, results in different loading conditions of the knee ligaments, affecting the failure strain outcome. It is suggested to evaluate the relative positions of the bones during active motions in 3D motion capture recording, to capture the relative position between the tibia and the femur in all degrees of freedom, and to apply similar loading conditions according to the injurious scenario. This has been previously conducted by Knee ligaments are rarely injured in isolation, but rather in combination with other adjacent soft tissues, such as the capsular ligaments and menisci, which also contribute to the passive restraint of the knee joint and therefore also influence the translational and rotational laxity of the knee joint after ligament injury . The difIt is generally accepted that the biomechanical properties of tissues are affected by specimen age; however, only a few studies have been conducted that examine the correlation between age and biomechanical properties of human knee ligaments. The IRFs developed in this study are, to the best of the authors’ knowledge, the first attempt at knee ligament injury risk functions based on PMHS. The comparison between the dynamic and static IRFs for the ACL, PCL, and LCL has an expected behavior where the dynamic IRFs are translated to the left of the static IRFs . As thisAnalyzing the injury risk of simulated knee ligament responses using HBMs, the boundary conditions will most often involve the ligament attached to the bones, making BLB IRFs the most relevant for traffic- and sport-related accident reconstructions. However, apart from providing IRFs, the current study highlights available data in the literature, and the IRFs of the LIG specimens are believed to be valuable while assessing the risk of failure for the isolated ligament. In addition, the two specimen types address a variety of failure modes and thus the generated IRFs of BLB and LIG should not be compared between the two specimen preparations. The dynamic IRFs are most suitable for use in the injury prediction of knee ligaments, as (low- and high-energy) accidents are not likely to cause injurious ligament loading in static rates. However, these IRFs are based on literature where most of the experiments used strain rates with magnitudes of 20%–100%/s, making them less suitable for potential injurious scenarios, which usually are caused by much higher impact rates on the ligaments. On the contrary, Although both collateral ligaments have a similar restraining function of the knee joint, enough literature has not been found to support that the structural properties in the MCL and LCL are similar in the dynamic rate. Hence, a dynamic BLB IRF representing the MCL is needed for injury prediction of higher loading rates.Assessing the injury risk against the developed IRFs herein should be conducted by using the crosshead strain of the whole ligament, as the IRF-based studies measured neither local strain rates nor local failure strains. Local failure strain datasets would facilitate more refined loading rate arrangements and thereby more advanced IRFs, as well as addressing covariates that most likely affect the material properties of ligaments, such as age and gender . To cond- Due to data limitation, the current study has not accounted for the variety of study methods and test processes used between studies in the filtering process in the generation of IRFs due to the small sample size of the dataset for all the ligaments. The preservation method of the samples, the clamping methodology of the ligaments, preconditioning of the ligaments, the initial tensile angle of the ligament, and testing sample dimensions are examples of factors that could influence the resulting tensile failure strain—and should, ideally, be standardized.- The IRFs were generated for failure at any location along the ligaments, and the failure regions  have not been distinguished.The current study methodology was formulated to utilize data in the available literature to generate knee ligament IRFs, due to the insufficient amount of details correlated to the resulting failure strains provided. IRFs are ideally developed based on PMHS specimen-specific data from studies with comparable testing and measuring methods and a clear definition of ligament failure. Most experiments used to generate these IRFs deviated in all these factors, thereby adding complexity in finding uniform arrangements of the dataset. Consequently, a number of limitations exists and are worth considering.The issue of incomplete data information is probably not unique for knee ligaments but is most likely also present for other tissue and body parts as well. The method of generating virtual failure strains from a mean and SD could, therefore, have potential as a valuable alternative method and should be prioritized to be validated. Furthermore, the provided IRFs need to be evaluated for their ability to predict injury, for example, by reconstructing known injurious and non-injurious scenarios using HBMs.This study provides a first attempt at injury risk functions based on PMHS data for the four primary knee ligaments. Eight IRFs were developed for the ACL, MCL, and LCL—both in static and in more dynamic loading rates. Two IRFs were generated for the PCL in dynamic loading rates, while data for the PCL in static rates were insufficient. Specimen-specific failure strains were infrequently presented in the PMHS literature. For future improvements of the knee ligament IRFs, several important factors are required from the literature and upcoming experiments: comparable testing and strain-measuring methods, a clear definition of failure, and a transparent reporting of both specimen-specific results  and specimen-specific characteristics .