Synchronization of Neurophysiological and Biomechanical Data in a Real-Time Virtual Gait Analysis System (GRAIL): A Proof-of-Principle Study.

The investigation of gait and its neuronal correlates under more ecologically valid conditions as well as real-time feedback visualization is becoming increasingly important in neuro-motor rehabilitation research. The Gait Real-time Analysis Interactive Lab (GRAIL) offers advanced opportunities for gait and gait-related research by creating more naturalistic yet controlled environments through immersive virtual reality. Investigating the neuronal aspects of gait requires parallel recording of brain activity, such as through mobile electroencephalography (EEG) and/or mobile functional near-infrared spectroscopy (fNIRS), which must be synchronized with the kinetic and /or kinematic data recorded while walking. This proof-of-concept study outlines the required setup by use of the lab streaming layer (LSL) ecosystem for real-time, simultaneous data collection of two independently operating multi-channel EEG and fNIRS measurement devices and gait kinetics. In this context, a customized approach using a photodiode to synchronize the systems is described. This study demonstrates the achievable temporal accuracy of synchronous data acquisition of neurophysiological and kinematic and kinetic data collection in the GRAIL. By using event-related cerebral hemodynamic activity and visually evoked potentials during a start-to-go task and a checkerboard test, we were able to confirm that our measurement system can replicate known physiological phenomena with latencies in the millisecond range and relate neurophysiological and kinetic data to each other with sufficient accuracy.

Developing a Biomechanical Testing Setup of the Pelvis-Part II: Experimental Testing.

Biomechanical testbench emulating the physiological loading of the pelvis is crucial in developing reconstructive implants for fragility fractures of the pelvis. Additionally, it will help understand the influence of the common daily loading on the pelvic ring. However, most reported experimental studies were mainly comparative with simplified loading and boundary conditions. In Part I of our study, we described the concept of the computational experiment design to design and construct a biomechanical testbench emulating the gait movement of the pelvis. The 57 muscles and joints' contact forces were reduced to four force actuators and one support, producing a similar stress distribution. The experimental setup is explained in this paper and some experimental results are presented. In addition, a series of repeatability and reproducibility tests were conducted to assess the test stand capabilities of replicating the gait physiological loading. The calculated stresses and the experimentally recorded strains showed that the pelvic ring response to the loading always follows the loaded leg side during the gait cycle. Furthermore, the experimental results of the pelvis displacement and strain at selected locations match the numerical ones. The developed test stand and the concept of computational experiment design behind it provide guidelines on how to design biomechanical testing equipment with physiological relevance.

Developing a Biomechanical Testing Setup of the Pelvis-Part I: Computational Design of Experiments.

Biomechanics of the human pelvis and the associated implants are still a medical and engineering debated topic. Today, no biomechanical testing setup is dedicated to pelvis testing and associated reconstructive implants with accepted clinical relevance. This paper uses the computational experiment design procedure to numerically design a biomechanical test stand that emulates the pelvis physiological gait loading. The numerically designed test stand reduces the 57 muscles and joints' contact forces iteratively to only four force actuators. Two hip joints' contact forces and two equivalent muscle forces with a maximum magnitude of 2.3 kN are applied in a bilateral reciprocating action. The stress distribution of the numerical model of the developed test stand is very similar to that of the numerical model of the pelvis with all 57 muscles and joint forces. For instance, at the right arcuate line, the state of stress is identical. However, at the location of superior rami, there is a deviation ranging from 2% to 20% between the two models. The boundary conditions and the nature of loading adopted in this study are more realistic regarding the clinical relevance than state-of-the-art. The numerically developed biomechanical testing setup of the pelvis in this numerical study (Part I) was found to be valid for the experimental testing of the pelvis. The construct of the testing setup and the experimental testing of an intact pelvis under gait loading are discussed in detail in Part II: Experimental Testing.

A finite element model of the lower limb during stance phase of gait cycle including the muscle forces.

BACKGROUND: Results of finite element (FE) analyses can give insight into musculoskeletal diseases if physiological boundary conditions, which include the muscle forces during specific activities of daily life, are considered in the FE modelling. So far, many simplifications of the boundary conditions are currently made. This study presents an approach for FE modelling of the lower limb for which muscle forces were included. METHODS: The stance phase of normal gait was simulated. Muscle forces were calculated using a musculoskeletal rigid body (RB) model of the human body, and were subsequently applied to a FE model of the lower limb. It was shown that the inertial forces are negligible during the stance phase of normal gait. The contact surfaces between the parts within the knee were modelled as bonded. Weak springs were attached to the distal tibia for numerical reasons. RESULTS: Hip joint reaction forces from the RB model and those from the FE model were similar in magnitude with relative differences less than 16%. The forces of the weak spring were negligible compared to the applied muscle forces. The maximal strain was 0.23% in the proximal region of the femoral diaphysis and 1.7% in the contact zone between the tibia and the fibula. CONCLUSIONS: The presented approach based on FE modelling by including muscle forces from inverse dynamic analysis of musculoskeletal RB model can be used to perform analyses of the lower limb with very realistic boundary conditions. In the present form, this model can be used to better understand the loading, stresses and strains of bones in the knee area and hence to analyse osteotomy fixation devices.

Molecular diversity through RNA editing: a balancing act.

RNA editing by adenosine deamination fuels the generation of RNA and protein diversity in eukaryotes, particularly in higher organisms. This includes the recoding of translated exons, widespread editing of retrotransposon-derived repeat elements and sequence modification of microRNA (miRNA) transcripts. Such changes can bring about specific amino acid substitutions, alternative splicing and changes in gene expression levels. Although the overall prevalence of adenosine-to-inosine (A-to-I) editing and its specific functional impact on many of the affected genes is not yet known, the importance of balancing RNA modification levels across time and space is becoming increasingly evident. In particular, transcriptome instabilities in the form of too much or too little RNA editing activity, or misguided editing, manifest in several human disease phenotypes and can disrupt that balance.

Experimental and numerical assessment of two reconstructive techniques for the fragility fractures of the pelvis type Ia.

Anterior pelvic ring fractures are common in geriatric patients. The Supraacetabular External Fixator (SEF) is a relatively simple and effective surgical procedure. On the other hand, there is the option of a Subcutaneous Iliopubic Plate (SIP) osteosynthesis. Only limited comparative biomechanical data of these two devices are available. Therefore, this biomechanical study's objective was to compare the stabilizing effect of the SEF versus the SIP in a model of Fragility Fractures of the Pelvis (FFP) type Ia. A test stand for pelvic biomechanics testing that emulates the gait loading cycle with physiological relevance was used. The osteotomy on the right pelvic ring was stabilized either with the SEF or the SIP. Strain gauges were used to measure strain in the pelvic ring. The osteotomy's spatial interfragmentary displacement (SID) was monitored using a 3D digital image correlation system. The SEF stabilization reduced the SID by approximately 10%, whereas the locking SIP could reduce displacement by about 62%. Additionally, the SIP reduced the stress/strain levels by 67% in the posterior pelvic ring. We could demonstrate that the SIP is superior to SEF in treating FFP type Ia as it significantly reduced the osteotomy's SID and the strain in the posterior pelvic ring.

Influence of individual characteristics on static rotational knee laxity using the Rotameter.

PURPOSE: The purpose of this study was to evaluate the influence of individual characteristics on rotational knee laxity in healthy participants. Our second aim was to verify whether the contralateral knee of patients with a non-contact ACL injury presents greater rotational knee laxity than a healthy control group. METHODS: Sixty healthy participants and 23 patients having sustained a non-contact ACL injury were tested with a new Rotameter prototype applying torques up to 10 Nm. Multiple linear regressions were performed to investigate the influence of gender, age, height and body mass on rotational knee laxity and to establish normative references for a set of variables related to rotational knee laxity. Multiple analyses of covariance were performed to compare the contralateral knee of ACL-injured patients and healthy participants. RESULTS: Being a women was associated with a significantly (P < 0.05) higher rotational knee laxity, and increased body mass was related to lower laxity results. In the multiple analyses of covariance, gender and body mass were also frequently associated with rotational knee laxity. When controlling for these variables, there were no differences in measurements between the contralateral leg of patients and healthy participants. CONCLUSION: In the present setting, gender and body mass significantly influenced rotational knee laxity. Furthermore, based on these preliminary results, patients with non-contact ACL injuries do not seem to have excessive rotational knee laxity. LEVEL OF EVIDENCE: Retrospective comparative study, Level III.

The role of the bilateral subcutaneous plate in the minimal invasive stabilization of fragility fractures of the pelvis.

Introduction: Anterior pelvic ring fractures are common in geriatric patients. Current treatment algorithms recommend osteosynthesis if no pain free mobilisation is possible. For this a multitude of surgical techniques have been described. Among these the Supraacetabular External Fixator (SEF) is regarded a simple and effective surgical procedure. However, this technique is associated with significant drawbacks.Alternatively, there is the option of an internal fixator or a formal plate osteosynthesis. It is the objective of this case report to present the Subcutaneous Iliopubic Plate (SIP) in a fragility fracture of the anterior and posterior pelvic ring. Case report: An 83-year-old female patient sustained a fracture of the anterior pelvic ring, the lateral sacrum and the medial femoral neck. After initially refusing any surgery, the patient agreed to have the endoprosthesis implanted first, and then secondarily to dorsoventral osteosynthesis of the pelvis. Dorsally a transiliosacral screw osteosynthesis was performed. Anteriorly a bilateral subcutaneous iliopubic plate-osteosynthesis was chosen, a plate position that is anterior to the aponeurosis. Conclusions: The subcutaneous plate has proven to be a quick and uncomplicated surgical procedure that is significantly better tolerated by patients than external stabilization.

RNA editing: a driving force for adaptive evolution?

Genetic variability is considered a key to the evolvability of species. The conversion of an adenosine (A) to inosine (I) in primary RNA transcripts can result in an amino acid change in the encoded protein, a change in secondary structure of the RNA, creation or destruction of a splice consensus site, or otherwise alter RNA fate. Substantial transcriptome and proteome variability is generated by A-to-I RNA editing through site-selective post-transcriptional recoding of single nucleotides. We posit that this epigenetic source of phenotypic variation is an unrecognized mechanism of adaptive evolution. The genetic variation introduced through editing occurs at low evolutionary cost since predominant production of the wild-type protein is retained. This property even allows exploration of sequence space that is inaccessible through mutation, leading to increased phenotypic plasticity and provides an evolutionary advantage for acclimatization as well as long-term adaptation. Furthermore, continuous probing for novel RNA editing sites throughout the transcriptome is an intrinsic property of the editing machinery and represents the molecular basis for increased adaptability. We propose that higher organisms have therefore evolved to systems with increasing RNA editing activity and, as a result, to more complex systems.

Identification of a selective nuclear import signal in adenosine deaminases acting on RNA.

The adenosine deaminases acting on RNA (ADARs) comprise a family of RNA editing enzymes that selectively modify single codons within RNA primary transcripts with often profound impact on protein function. Little is known about the mechanisms that regulate nuclear RNA editing activity. Editing levels show cell-type specific and developmental modulation that does not strictly coincide with observed expression levels of ADARs. Here, we provide evidence for a molecular mechanism that might control nuclear import of specific ADARs and, in turn, nuclear RNA editing. We identify an in vivo ADAR3 interaction partner, importin alpha 1 (KPNA2) that specifically recognizes an arginine-rich ADAR3 sequence motif and show that it acts as a functional nuclear localization sequence. Furthermore, whereas KPNA2, but not KPNA1 or KNPA3, recognizes the ADAR3 NLS, we observe the converse binding specificity with ADAR2. Interestingly, alternative splicing of ADAR2 pre-mRNA introduces an ADAR3-like NLS that alters the interaction profile with the importins. Thus, in vivo RNA editing might be regulated, in part, through controlled subcellular localization of ADARs, which in turn is governed by the coordinated local expression of importin alpha proteins and ADAR protein variants.

Field monitoring data on a residential exhaust air heat pump system (air-to-air heat pump).

This data article presents the raw data used in the article "Experimental and analytical evaluation of exhaust air heat pumps in ventilation-based heating systems" [1]. The data set contains measurement results of a field monitoring on a residential exhaust air heat pump system (air-to-air heat pump) in Germany. This data could be used to investigate the dynamic behavior and performance of the exhaust air heat pump systems. The data set contains air temperature and humidity of all four sides of the heat pump unit. Moreover, the electrical consumption of the unit and the dynamic pressure difference on the exhaust side (as indication of the air volume rate) could be also found in the data set.

Screening of human SNP database identifies recoding sites of A-to-I RNA editing.

Single nucleotide polymorphisms (SNPs) are DNA sequence variations that can affect the expression or function of genes. As a result, they may lead to phenotypic differences between individuals, such as susceptibility to disease, response to medications, and disease progression. Millions of SNPs have been mapped within the human genome providing a rich resource for genetic variation studies. Adenosine-to-inosine RNA editing also leads to the production of RNA and protein sequence variants, but it acts on the level of primary gene transcripts. Sequence variations due to RNA editing may be misannotated as SNPs when relying solely on expressed sequence data instead of genomic material. In this study, we screened the human SNP database for potential cases of A-to-I RNA editing that cause amino acid changes in the encoded protein. Our search strategy applies five molecular features to score candidate sites. It identifies all previously known cases of editing present in the SNP database and successfully uncovers novel, bona fide targets of adenosine deamination editing. Our approach sets the stage for effective and comprehensive genome-wide screens for A-to-I editing targets.

A mammalian reporter system for fast and quantitative detection of intracellular A-to-I RNA editing levels.

An important molecular mechanism to create protein diversity from a limited set of genes is A-to-I RNA editing. RNA editing converts single adenosines into inosines in pre-mRNA. These single base conversions can have a wide variety of consequences. Editing can lead to codon changes and, consequently, altered protein function. Moreover, editing can alter splice sites and influences miRNA biogenesis and target recognition. The two enzymes responsible for editing in mammals are adenosine deaminase acting on RNA (ADAR) 1 and 2. However, it is currently largely unknown how the activity of these enzymes is regulated in vivo. Editing activity does not always correlate with ADAR expression levels, suggesting posttranscriptional or posttranslational mechanisms for controlling activity. To investigate how editing is regulated in mammalian cells, we have developed a straightforward quantitative reporter system to detect editing levels. By employing luciferase activity as a readout, we could easily detect different levels of editing in a cellular context. In addition, increased levels of ADAR2 correlated with increased levels of luciferase activity. This reporter system therefore sets the stage for the effective screening of cDNA libraries or small molecules for strong modulators of intracellular editing to ultimately elucidate how A-to-I editing is regulated in vivo.

Influence of pubic symphysis stiffness on pelvic load distribution during single leg stance.

This study focuses on the influence of the softening and stiffening of pubic symphysis on the load distribution within the bones of the pelvic ring under the physiological loadings of the single leg stance. Muscle forces and joint reaction forces were first determined by inverse dynamics and applied to a linear finite element model of the pelvis. With normal pubic symphysis stiffness, high Von Mises stresses are located on the anterior surface to the sacrum around the sacroiliac joint and on the superior ramus, both on the side of the weight-bearing leg. Softening of the pubic symphysis redirects the load backward, decreases the stresses at the anterior pelvis, and increases them at the posterior pelvis. A stiffening of the pubic symphysis redirects the load forward, increases the load on the posterior pelvis, and decreases them at the anterior pelvis. This investigation highlights the significance of the pubic symphysis on the load distribution of the pelvis and in maintaining the integrity of the structures. Its role should not be neglected when analyzing the pelvis.

Mechanical strength of a new plate compared to six previously tested opening wedge high tibial osteotomy implants.

BACKGROUND: This study aimed to assess the mechanical static and fatigue strength provided by the FlexitSystem plate in medial opening wedge high tibial osteotomies (MOWHTO), and to compare it to six previously tested implants: the TomoFix small stature, the TomoFix standard, the ContourLock, the iBalance, the second generation PEEKPower and the size 2 Activmotion. Thus, this will provide surgeons with data that will help in the choice of the most appropriate implant for MOWHTO. METHODS: Six fourth-generation tibial bone composites underwent a MOWHTO and each was fixed using six FlexitSystem plates, according to standard techniques. The same testing procedure that has already been previously defined, used and published, was used to investigate the static and dynamic strength of the prepared bone-implant constructs. The test consisted of static loading and cyclical loading for fatigue testing. RESULTS: During static testing, the group constituted by the FlexitSystem showed a fracture load higher than the physiological loading of slow walking (3.7 kN > 2.4 kN). Although this fracture load was relatively small compared to the average values for the other Implants from our previous studies, except for the TomoFix small stature and the Contour Lock. During fatigue testing, FlexitSystem group showed the smallest stiffness and higher lifespan than the TomoFix and the PEEKPower groups. CONCLUSIONS: The FlexitSystem plate showed sufficient strength for static loading, and average fatigue strength compared to the previously tested implants. Full body dynamic loading of the tibia after MOWHTO with the investigated implants should be avoided for at least 3 weeks. Implants with a wider T-shaped proximal end, positioned onto the antero-medial side of the tibia head, or inserted in the osteotomy opening in a closed-wedge construction, provided higher mechanical strength than implants with small a T-shaped proximal end, centred onto the medial side of the tibia head.

Graft materials provide greater static strength to medial opening wedge high tibial osteotomy than when no graft is included.

BACKGROUND: The purpose of this study was to compare the stability of medial opening-wedge high tibial osteotomy (MOWHTO) with and without different graft materials. Good clinical and radiological outcomes have been demonstrated when either using or not using graft materials during MOWHTO. Variations in the biomechanical properties of different graft types, regarding the stability they provide a MOWHTO, have not been previously investigated. METHODS: A 10 mm biplanar MOWHTO was performed on 15 artificial sawbone tibiae, which were fixed using the Activmotion 2 plate. Five bones had OSferion60 wedges (synthetic group), five had allograft bone wedges (allograft group), and five had no wedges (control group) inserted into the osteotomy gap. Static compression was applied axially to each specimen until failure of the osteotomy. Ultimate load, horizontal and vertical displacements were measured and used to calculate construct stiffness and valgus malrotation of the tibial head. RESULTS: The synthetic group failed at 6.3 kN, followed by the allograft group (6 kN), and the control group (4.5 kN). The most valgus malrotation of the tibial head was observed in the allograft group (2.6°). The synthetic group showed the highest stiffness at the medial side of the tibial head (9.54 kN·mm- 1), but the lowest stiffness at the lateral side (1.59 kN·mm-1). The allograft group showed high stiffness on the medial side of the tibial head (7.54 kN·mm- 1) as well as the highest stiffness on the lateral side (2.18 kN·mm- 1). CONCLUSIONS: The use of graft materials in MOWHTO results in superior material properties compared to the use of no graft. The static strength of MOWHTO is highest when synthetic grafts are inserted into the osteotomy gap. Allograft wedges provide higher mechanical strength to a MOWHTO than when no graft used. In comparison to the synthetic grafts, allograft wedges result in the stiffness of the osteotomy being more similar at the medial and lateral cortices.

The biomechanical effects of allograft wedges used for large corrections during medial opening wedge high tibial osteotomy.

The inclusion of an allograft wedge during medial opening wedge high tibial osteotomy has been shown to lead to satisfactory time-to-union in larger corrections (>10°). Such large corrections are associated with greater incidences of intraoperative hinge fracture and reduced construct stability. The purpose of this study was to investigate the biomechanical stability that an allograft wedge brings to an osteotomy. Ten medium-size fourth generation artificial sawbone tibiae underwent 12 mm biplanar medial opening wedge high tibial osteotomy with a standard Tomofix plate. Five tibiae had an allograft wedge inserted into the osteotomy gap prior to plate fixation (allograft group). The gap in the remaining tibiae was left unfilled (control group). Each group underwent static compression testing and cyclical fatigue testing until failure of the osteotomy. Peak force, valgus malrotation, number of cycles, displacement and stiffness around the tibial head were analysed. Intraoperative hinge fractures occurred in all specimens. Under static compression, the allograft group withstood higher peak forces (6.01 kN) compared with the control group (5.12 kN). Valgus malrotation was lower, and stiffness was higher, in the allograft group. During cyclical fatigue testing, results within the allograft group were more consistent than within the control group. This may indicate more predictable results in large osteotomies with an allograft. Tibial osteotomies with allograft wedges appear beneficial for larger corrections, and in cases of intraoperative hinge fracture, due to the added construct stability they provide, and the consistency of results compared with tibial osteotomies without a graft.

Altered editing in cyclic nucleotide phosphodiesterase 8A1 gene transcripts of systemic lupus erythematosus T lymphocytes.

The aetiopathogenesis of the abnormal immune response in systemic lupus erythematosus (SLE) remains incompletely understood. We and other investigators demonstrated altered expression of adenosine deaminase that act on RNA (ADAR) genes in SLE patients. Based on this information, we hypothesize that the altered expression and function of ADAR enzymes is a mechanism for the immunopathogenesis of SLE. ADARs edit gene transcripts through site-specific conversion of adenosine to inosine by hydrolytic deamination at C6 of the adenosine. Thirteen SLE subjects and eight healthy controls were studied. We assessed the role of ADAR enzymes in editing of PDE8A1 gene transcripts of normal and SLE T cells. These studies demonstrated the occurrence of ADAR-catalysed altered and site-selective editing profile of specific sites in the PDE8A1 gene transcripts of normal and SLE T cells. Two hot spots for A to I editing were observed in the PDE8A1 transcripts of normal and SLE T cells. A fundamental finding of this study is A to I hypo-editing followed by up-regulation of PDE8A1 transcripts in SLE T cells. These results are confirmed by analysing PDE8A1 transcripts of normal T cells activated with type I interferon-alpha. It is proposed that, the altered expression of ADAR enzymes tilt the balance of editing machinery and alter editing in SLE transcriptome. Such altered editing may contribute to the modulation of gene regulation and ultimately, immune functions in SLE and play an important role in the initiation and propagation of SLE pathogenesis.

Molecular characterization of the injury-induced aromatase transcript in the adult zebra finch brain.

In the zebra finch (Taeniopygia guttata), the aromatase gene is transcribed from one of two promoters resulting in two transcripts constitutively expressed in brain or ovary. These transcripts differ only in Exon 1 which lies in the 5' un-translated region (UTR). An inducible form of aromatase is expressed following brain injury in glia. Towards characterizing this transcript, we (a) examined the up-regulation of amplicons within the aromatase transcript using quantitative PCR (qPCR), (b) performed 5' and 3' rapid amplification of cDNA ends (RACE) on injured brain RNA and (c) sequenced the injury-induced aromatase transcript. qPCR suggested that inducible aromatase may contain a novel 3'UTR. However, neither 3' nor 5' RACE revealed novel UTRs in the injured telencephalon. We then sequenced aromatase from injured entopallium, a region that lacks detectable constitutive aromatase. Inducible aromatase was identical in sequence to the known neural aromatase transcript. These data suggest that injury-induced aromatase differs from ovarian, but is indistinguishable from neuronal aromatase. We suggest that an injury-specific signal in glia may modulate aromatase transcription. Alternatively, injury-induced aromatase transcription may be silenced under constitutive conditions. To the best of our knowledge, this is the first report that documents the sequence of inducible aromatase in any vertebrate.