Cell reorientation on a cyclically strained substrate

Cyclic strain avoidance, the phenomenon of cell and cytoskeleton alignment perpendicular to the direction of cyclic strain of the underlying 2D substrate, is an important characteristic of the adherent cell organization. This alignment has typically been attributed to the stress-fiber reorganization although observations clearly show that stress-fiber reorganization under cyclic loading is closely coupled to cell morphology and reorientation of the cells. Here, we develop a statistical mechanics framework that couples the cytoskeletal stress-fiber organization with cell morphology under imposed cyclic straining and make quantitative comparisons with observations. The framework accurately predicts that cyclic strain avoidance stems primarily from cell reorientation away from the cyclic straining rather than cytoskeletal reorganization within the cell. The reorientation of the cell is a consequence of the cell lowering its free energy by largely avoiding the imposed cyclic straining. Furthermore, we investigate the kinetics of the cyclic strain avoidance mechanism and demonstrate that it emerges primarily due to the rigid body rotation of the cell rather than via a trajectory involving cell straining. Our results provide clear physical insights into the coupled dynamics of cell morphology and stress-fibers, which ultimately leads to cellular organization in cyclically strained tissues.

Combined stent-retriever and aspiration intra-arterial thrombectomy performance for fragmentable blood clots: A proof-of-concept computational study

Mechanical thrombectomy (MT) treatment of acute ischemic stroke (AIS) patients typically involves use of stent retrievers or aspiration catheters alone or in combination. For in silico trials of AIS patients, it is crucial to incorporate the possibility of thrombus fragmentation during the intervention. This study focuses on two aspects of the thrombectomy simulation: i) Thrombus fragmentation on the basis of a failure model calibrated with experimental tests on clot analogs; ii) the combined stent-retriever and aspiration catheter MT procedure is modeled by adding both the proximal balloon guide catheter and the distal access catheter. The adopted failure criterion is based on maximum principal stress threshold value. If elements of the thrombus exceed this criterion during the retrieval simulation, then they are deleted from the calculation. Comparison with in-vitro tests indicates that the simulation correctly reproduces the procedures predicting thrombus fragmentation in the case of red blood cells rich thrombi, whereas non-fragmentation is predicted for fibrin-rich thrombi. Modeling of balloon guide catheter prevents clot fragments' embolization to further distal territories during MT procedure.

A new constitutive model for permanent deformation of blood clots with application to simulation of aspiration thrombectomy

As a first line option in the treatment of acute ischemic stroke (AIS), direct aspiration is a fast and effective technique with promising outcomes. In silico models are widely used for design and preclinical assessment of new developed devices and therapeutic methods. Accurate modelling of the mechanical behaviour of blood clot is a key factor in the design and simulation of aspiration devices. In this study we develop a new constitutive model which incorporates the unrecoverable plastic deformation of clots. The model is developed based on the deformation-induced microstructural changes in fibrin network, including the formation and dissociation of the cross-links between fibrin fibres. The model is calibrated using previously reported experimentally measured permanent clot deformation following uniaxial stretching. The calibrated plasticity model is then used to simulate aspiration thrombectomy. Results reveal that inclusion of permanent plastic deformation results in ∼ 15 % increase in clot aspiration length at an applied aspiration pressure of 100 mmHg. The constitutive law developed in this study provides a basis for improved design and evaluation of novel aspiration catheters leading to increased first-pass revascularization rate.

Impact of the Internal Carotid Artery Morphology on in silico Stent-Retriever Thrombectomy Outcome

The aim of this work is to propose a methodology for identifying relationships between morphological features of the cerebral vasculature and the outcome of in silico simulations of thrombectomy, the mechanical treatment for acute ischemic stroke. Fourteen patient-specific cerebral vasculature segmentations were collected and used for geometric characterization of the intracranial arteries mostly affected by large vessel occlusions, i.e., internal carotid artery (ICA), middle cerebral artery (MCA) and anterior cerebral artery (ACA). First, a set of global parameters was created, including the geometrical information commonly provided in the clinical context, namely the total length, the average diameter and the tortuosity (length over head-tail distance) of the intracranial ICA. Then, a more exhaustive geometrical analysis was performed to collect a set of local parameters. A total of 27 parameters was measured from each patient-specific vascular configuration. Fourteen virtual thrombectomy simulations were performed with a blood clot with the same length and composition placed in the middle of the MCA. The model of TREVO ProVue stent-retriever was used for all the simulations. Results from simulations produced five unsuccessful outcomes, i.e., the clot was not removed from the vessels. The geometric parameters of the successful and unsuccessful simulations were compared to find relations between the vascular geometry and the outcome. None of the global parameters alone or combined proved able to discriminate between positive and negative outcome, while a combination of local parameters allowed to correctly identify the successful from the unsuccessful simulations. Although these results are limited by the number of patients considered, this study indicates a promising methodology to relate patient-specific geometry to virtual thrombectomy outcome, which might eventually guide decision making in the treatment of acute ischemic stroke.

The first virtual patient-specific thrombectomy procedure

Treatment of acute ischemic stroke has been recently improved with the introduction of endovascular mechanical thrombectomy, a minimally invasive procedure able to remove a clot using aspiration devices and/or stent-retrievers. Despite the promising and encouraging results, improvements to the procedure and to the stent design are the focus of the recent efforts. Computational studies can pave the road to these improvements, providing their ability to describe and accurately reproduce a real procedure. A patient with ischemic stroke due to intracranial large vessel occlusion was selected and after the creation of the cerebral vasculature from computed tomography images and a histologic analysis to determine the clot composition, the entire thrombectomy procedure was virtually replicated. As in the real situation, the computational replica showed that two attempts were necessary to remove the clot, as a result of the position of the stent retriever with respect to the clot. Furthermore, the results indicated that clot fragmentation did not occur as the deformations were mainly in a compressive state without the possibility for clot cracks to propagate. The accurate representation of the procedure can be used as an important step for operative optimization planning and future improvements of stent designs.

Blood clot fracture properties are dependent on red blood cell and fibrin content

Thrombus fragmentation during endovascular stroke treatment, such as mechanical thrombectomy, leads to downstream emboli, resulting in poor clinical outcomes. Clinical studies suggest that fragmentation risk is dependent on clot composition. This current study presents the first experimental characterization of the composition-dependent fracture properties of blood clots, in addition to the development of a predictive model for blood clot fragmentation. A bespoke experimental test-rig and compact tension specimen fabrication has been developed to measure fracture toughness of thrombus material. Fracture tests are performed on three physiologically relevant clot compositions: a high-fibrin clot made from a 5% haematocrit (H) blood mixture, a medium-fibrin clot made form a 20% H blood mixture, a low-fibrin clot made from a 40% H blood mixture. Fracture toughness is observed to significantly increase with increasing fibrin content, i.e. red blood cell-rich clots are more prone to tear during loading compared to the fibrin-rich clots. Results also reveal that the mechanical behaviour of clot analogues is significantly different in compression and tension. Finite element cohesive zone modelling of clot fracture experiments show that fibrin fibres become highly aligned in the direction perpendicular to crack propagation, providing a significant toughening mechanism. The results presented in this study provide the first characterization of the composition-dependent fracture behaviour of blood clots and are of key importance for development of next-generation thrombectomy devices and clinical strategies. STATEMENT OF SIGNIFICANCE: This study provides a characterisation of the composition-dependent fracture toughness of blood clots. This entails the development of novel experimental techniques for fabrication and testing of blood clot compact tension fracture specimens. The study also develops cohesive zone models of fracture initiation and propagation in blood clots. Results reveal that the fracture resistance of fibrin-rich clots is significantly higher than red blood cell rich clots. Simulations also reveal that stretching and realignment of the fibrin network should be included in blood clot material models in order to accurately replicate compression-tension asymmetry and fibrin enhanced fracture toughness. The results of this study have potentially important clinical implications in terms of clot fracture risk and secondary embolization during mechanical thrombectomy procedures.

Image-derived modeling of nucleus strain amplification associated with chromatin heterogeneity

Beyond the critical role of cell nuclei in gene expression and DNA replication, they also have a significant influence on cell mechanosensation and migration. Nuclear stiffness can impact force transmission and, furthermore, act as a physical barrier to translocation across tight spaces. As such, it is of wide interest to accurately characterize nucleus mechanical behavior. In this study, we present a computational investigation of the in situ deformation of a heterogeneous chondrocyte nucleus. A methodology is developed to accurately reconstruct a three-dimensional finite-element model of a cell nucleus from confocal microscopy. By incorporating the reconstructed nucleus into a chondrocyte model embedded in pericellular and extracellular matrix, we explore the relationship between spatially heterogeneous nuclear DNA content, shear stiffness, and resultant shear strain. We simulate an externally applied extracellular matrix shear deformation and compute intranuclear strain distributions, which are directly compared with corresponding experimentally measured distributions. Simulations suggest that the mechanical behavior of the nucleus is highly heterogeneous, with a nonlinear relationship between experimentally measured grayscale values and corresponding local shear moduli (μn). Three distinct phases are identified within the nucleus: a low-stiffness mRNA-rich interchromatin phase (0.17 kPa ≤ μn ≤ 0.63 kPa), an intermediate-stiffness euchromatin phase (1.48 kPa ≤ μn ≤ 2.7 kPa), and a high-stiffness heterochromatin phase (3.58 kPa ≤ μn ≤ 4.0 kPa). Our simulations also indicate that disruption of the nuclear envelope associated with lamin A/C depletion significantly increases nuclear strain in regions of low DNA concentration. We further investigate a phenotypic shift of chondrocytes to fibroblast-like cells, a signature for osteoarthritic cartilage, by increasing the contractility of the actin cytoskeleton to a level associated with fibroblasts. Peak nucleus strains increase by 35% compared to control, with the nucleus becoming more ellipsoidal. Our findings may have broad implications for current understanding of how local DNA concentrations and associated strain amplification can impact cell mechanotransduction and drive cell behavior in development, migration, and tumorigenesis.

Development of a test method to investigate mode II fracture and dissection of arteries

The current study presents the development and implementation of a bespoke experimental technique to generate and characterise mode II crack initiation and propagation in arterial tissue. The current study begins with a demonstration that lap-shear testing of arterial tissue results in mixed mode fracture, rather than mode II. We perform a detailed computational design of a bespoke experimental method (which we refer to as a shear fracture ring test (SFRT)) to robustly and repeatably generate mode II crack initiation and propagation in arteries. This method is based on generating a localised region of high shear adjacent to a cylindrical loading bar. Placement of a radial notch in this region of high shear stress is predicted to result in a kinking of the crack during a mode II initiation and propagation of the crack over a long distance in the circumferential (c)-direction along the circumferential-axial (c-a) plane. Fabrication and experimental implementation of the SFRT on excised ovine aorta specimens confirms that the bespoke test method results in pure mode II initiation and propagation. We demonstrate that the mode II fracture strength along the c-a plane is eight times higher than the corresponding mode I strength determined from a standard peel test. We also calibrate the mode II fracture energy based on our measurement of crack propagation rates. The mechanisms of fracture uncovered in the current study, along with our quantification of mode II fracture properties have significant implications for current understanding of the biomechanical conditions underlying aortic dissection.

Applicability assessment of a stent-retriever thrombectomy finite-element model

An acute ischaemic stroke appears when a blood clot blocks the blood flow in a cerebral artery. Intra-arterial thrombectomy, a mini-invasive procedure based on stent technology, is a mechanical available treatment to extract the clot and restore the blood circulation. After stent deployment, the clot, trapped in the stent struts, is pulled along with the stent towards a receiving catheter. Recent clinical trials have confirmed the effectiveness and safety of mechanical thrombectomy. However, the procedure requires further investigation. The aim of this study is the development of a numerical finite-element-based model of the thrombectomy procedure. In vitro thrombectomy tests are performed in different vessel geometries and one simulation for each test is carried out to verify the accuracy and reliability of the proposed numerical model. The results of the simulations confirm the efficacy of the model to replicate all the experimental setups. Clot stress and strain fields from the numerical analysis, which vary depending on the geometric features of the vessel, could be used to evaluate the possible fragmentation of the clot during the procedure. The proposed in vitro/in silico comparison aims at assessing the applicability of the numerical model and at providing validation evidence for the specific in vivo thrombectomy outcomes prediction.

A thermodynamic transient cross-bridge model for prediction of contractility and remodelling of the ventricle

Cardiac hypertrophy is an adaption of the heart to a change in cardiovascular loading conditions. The current understanding is that progression may be stress or strain driven, but the multi-scale nature of the cellular remodelling processes have yet to be uncovered. In this study, we develop a model of the contractile left ventricle, with the active cell tension described by a thermodynamically motivated cross-bridge cycling model. Simulation of the transient recruitment of myosin results in correct patterns of ventricular pressure predicted over a cardiac cycle. We investigate how changes in tissue loading and associated deviations in transient force generation can drive restructuring of cellular myofibrils in the heart wall. Our thermodynamic framework predicts in-series sarcomere addition (eccentric remodelling) in response to volume overload, and sarcomere addition in parallel (concentric remodelling) in response to valve and signalling disfunction. This framework provides a significant advance in the current understanding of the fundamental sub-sarcomere level biomechanisms underlying cardiac remodelling. Simulations reveal that pathological tissue loading conditions can significantly alter actin-myosin cross-bridge cycling over the course of the cardiac cycle. The resultant variation in sarcomere stress pushes an imbalance between the internal free energy of the myofibril and that of unbound contractile proteins, initiating remodelling. The link between cross-bridge thermodynamics and myofibril remodelling proposed in this study may significantly advance current understanding of cardiac disease onset.

Development of an in vitro model of calcified cerebral emboli in acute ischemic stroke for mechanical thrombectomy evaluation

: ​ BACKGROUND: Calcified cerebral emboli (CCEs) are a rare cause of acute ischemic stroke (AIS) and are frequently associated with poor outcomes. The presence of dense calcified material enables reliable identification of CCEs using non-contrast CT. However, recanalization rates with the available mechanical thrombectomy (MT) devices remain low. OBJECTIVE: To recreate a large vessel occlusion involving a CCE using an in vitro silicone model of the intracranial vessels and to demonstrate the feasability of this model to test different endovascular strategies to recanalize an occlusion of the M1 segment of the middle cerebral artery (MCA). : ​ METHODS: An in vitro model was developed to evaluate different endovascular treatment approaches using contemporary devices in the M1 segment of the MCA. The in vitro model consisted of a CCE analog placed in a silicone neurovascular model. Development of an appropriate CCE analog was based on characterization of human calcified tissues that represent likely sources of CCEs. Feasibility of the model was demonstrated in a small number of MT devices using four common procedural techniques. : ​ RESULTS: CCE analogs were developed with similar mechanical behavior to that of ex vivo calcified material. The in vitro model was evaluated with various MT techniques and devices to show feasibility of the model. In this limited evaluation, the most successful retrieval approach was performed with a stent retriever combined with local aspiration through a distal access catheter, and importantly, with flow arrest and dual aspiration using a balloon guide catheter. : ​ CONCLUSION: Characterization of calcified tissues, which are likely sources of CCEs, has shown that CCEs are considerably stiffer than thrombus. This highlights the need for a different in vitro AIS model for CCEs than those used for thromboemboli. Consequentially, an in vitro AIS model representative of a CCE occlusion in the M1 segment of the MCA has been developed.

Finite element investigation into the use of carbon fibre reinforced PEEK laminated composites for distal radius fracture fixation implants

Carbon fibre reinforced PEEK (CF/PEEK) laminates provide mechanical advantages over homogenous metal osteo-synthesis implants, e.g. radiolucency, fatigue strength and strength to weight ratio. Implants can be designed with custom anisotropic material properties, thus enabling the engineer to tailor the overall stiffness of the implant to the specific loading conditions it will experience in vivo. In the current study a multi-scale computational investigation of idealised distal radius fracture fixation plate (DRP) is conducted. Physiological loading conditions are applied to macro-scale finite element models of DRPs. The mechanical response is compared for several CF/PEEK laminate layups to examine the effect of ply layup design. The importance of ply orientation in laminated DRPs is highlighted. A high number of 0° plies near the outer surfaces results in a greater bending strength while the addition of 45° plies increases the torsional strength of the laminates. Intra-laminar transverse tensile failure is predicted as the primary mode of failure. A micro-mechanical analysis of the CF/PEEK microstructure uncovers the precise mechanism under-lying intra-laminar transverse tensile crack to be debonding of the PEEK matrix from carbon fibres. Plastic strains in the matrix material are not sufficiently high to result in ductile failure of the matrix. The findings of this study demonstrate the significant challenge in the design and optimisation of fibre reinforced laminated composites for orthopaedic applications, highlighting the importance of multi-scale modelling for identification of failure mechanisms.

Transient active force generation and stress fibre remodelling in cells under cyclic loading

The active cytoskeleton is known to play an important mechanistic role in cellular structure, spreading, and contractility. Contractility is actively generated by stress fibres (SF), which continuously remodel in response to physiological dynamic loading conditions. The influence of actin-myosin cross-bridge cycling on SF remodelling under dynamic loading conditions has not previously been uncovered. In this study, a novel SF cross-bridge cycling model is developed to predict transient active force generation in cells subjected to dynamic loading. Rates of formation of cross-bridges within SFs are governed by the chemical potentials of attached and unattached myosin heads. This transient cross-bridge cycling model is coupled with a thermodynamically motivated framework for SF remodelling to analyse the influence of transient force generation on cytoskeletal evolution. A 1D implementation of the model is shown to correctly predict complex patterns of active cell force generation under a range of dynamic loading conditions, as reported in previous experimental studies.

Bladder management experiences among people living with neurologic disease: A systematic review and meta-synthesis of qualitative research

AIM

To systematically review the qualitative literature on neurogenic bladder management to better understand the relevant psychosocial issues.

METHODS

We used two reviewers to systematically review EMBASE, CINAHL, and PsycINFO for qualitative studies that included a neurogenic bladder patient population and were relevant to bladder management. We used a meta-ethnography technique to summarize and synthesize the data.

RESULTS

We found 13 studies that were relevant. When choosing a bladder management technique (three studies), there were two major themes (bladder management decision makers, and characteristics and risks) that impacted the process. For studies evaluating life with a urinary catheter (five about intermittent catheters, and five about indwelling catheters), relevant themes could be arranged into three consecutive periods: First, a changed life (the initial stage of selecting and using a catheter: coping, teaching and technical challenges, and control and independence). Second, learning to live with a catheter (the practical skill and knowledge that goes into using a catheter: knowledge, adjustments, and normalization). Third, a new life (the acceptance and integration of a catheter into a person's life: problems and benefits, unpredictability, travel and social activities, intimacy and relationships, and dealing with negative emotions). Themes were generally consistent across studies. Conclusions Several important themes were identified from the existing qualitative literature; these can provide insight into how neurogenic bladder patients select a bladder management method, and how physicians can optimize their counseling and the long-term management of these patients.

Successful Use of an Inflatable Penile Prosthesis for the Treatment of Distal Deficiency of the Tunica Albuginea and Cavernous Tissue

Introduction

Congenital hypoplasia of the distal half of the tunica albuginea has not been previously described.

Aim

To review a patient presenting with erectile dysfunction secondary to congenital penile hypoplasia.

Methods

History, physical exam and penile Doppler ultrasound of the patient, followed by a discussed of treatment options and definitive management.

Results

Successful operative treatment of our patient with insertion of an inflatable penile prosthesis.

Conclusion

We present a case of congenital hypoplasia of the distal tunica albuginea and a successful treatment strategy. We highlight the need for further study of penile embryology.

Punjani N, McGarry P, Brock G. Successful Use of an Inflatable Penile Prosthesis for the Treatment of Distal Deficiency of the Tunica Albuginea and Cavernous Tissue. Sex Med 2018;6:356–359.

Compressibility and Anisotropy of the Ventricular Myocardium: Experimental Analysis and Microstructural Modeling

While the anisotropic behavior of the complex composite myocardial tissue has been well characterized in recent years, the compressibility of the tissue has not been rigorously investigated to date. In the first part of this study, we present experimental evidence that passive-excised porcine myocardium exhibits volume change. Under tensile loading of a cylindrical specimen, a volume change of 4.1±1.95% is observed at a peak stretch of 1.3. Confined compression experiments also demonstrate significant volume change in the tissue (loading applied up to a volumetric strain of 10%). In order to simulate the multiaxial passive behavior of the myocardium, a nonlinear volumetric hyperelastic component is combined with the well-established Holzapfel–Ogden anisotropic hyperelastic component for myocardium fibers. This framework is shown to describe the experimentally observed behavior of porcine and human tissues under shear and biaxial loading conditions. In the second part of the study, a representative volumetric element (RVE) of myocardium tissue is constructed to parse the contribution of the tissue vasculature to observed volume change under confined compression loading. Simulations of the myocardium microstructure suggest that the vasculature cannot fully account for the experimentally measured volume change. Additionally, the RVE is subjected to six modes of shear loading to investigate the influence of microscale fiber alignment and dispersion on tissue-scale mechanical behavior.

Do Urodynamic Findings Other Than Outlet Obstruction Influence the Decision to Perform a Transurethral Resection of Prostate?

OBJECTIVE

To determine if urodynamic findings other than high-pressure voiding influence the decision to perform a transurethral resection of prostate (TURP).

METHODS

Four clinical scenarios were created featuring a healthy 65-year-old man. An electronic survey was distributed to members of the International Continence Society and the Society for Urodynamics, Female Pelvic Medicine and Urogenital Reconstruction.

RESULTS

Eighty-six urologists responded (median age was 45-54 years, 62% described their practice as academic). Scenario 1: an incidental residual urine >1 L with detrusor underactivity. The majority (76%) would offer a TURP; however, the estimated chance that the residual volume would improve was only 57%. Scenario 2: retention with detrusor overactivity but no voluntary voiding contraction. The majority (72%) would offer a TURP; however, the average chance quoted that he would void was only 48%. Scenario 3: catheter-dependent retention and an underactive detrusor. The majority (89%) would offer a TURP; however, the average chance quoted that he would void was only 53%. Scenario 4: a man with only frequency and urgency, but urodynamic bladder outlet obstruction. The majority (90%) would offer him a TURP; however, the average chance that his frequency and urgency would improve was only 64%, and the average estimated postoperative risk of urgency incontinence was 33%. Willingness to offer TURP did not correlate with physician characteristics.

CONCLUSION

Urodynamic findings other than bladder outlet obstruction were associated with modest perceived outcomes after TURP; however, despite this, urologists are still willing to offer this intervention.

Free energy analysis of cell spreading

In this study we present a steady-state adaptation of the thermodynamically motivated stress fiber (SF) model of Vigliotti et al. (2015). We implement this steady-state formulation in a non-local finite element setting where we also consider global conservation of the total number of cytoskeletal proteins within the cell, global conservation of the number of binding integrins on the cell membrane, and adhesion limiting ligand density on the substrate surface. We present a number of simulations of cell spreading in which we consider a limited subset of the possible deformed spread-states assumed by the cell in order to examine the hypothesis that free energy minimization drives the process of cell spreading. Simulations suggest that cell spreading can be viewed as a competition between (i) decreasing cytoskeletal free energy due to strain induced assembly of cytoskeletal proteins into contractile SFs, and (ii) increasing elastic free energy due to stretching of the mechanically passive components of the cell. The computed minimum free energy spread area is shown to be lower for a cell on a compliant substrate than on a rigid substrate. Furthermore, a low substrate ligand density is found to limit cell spreading. The predicted dependence of cell spread area on substrate stiffness and ligand density is in agreement with the experiments of Engler et al. (2003). We also simulate the experiments of Théry et al. (2006), whereby initially circular cells deform and adhere to "V-shaped" and "Y-shaped" ligand patches. Analysis of a number of different spread states reveals that deformed configurations with the lowest free energy exhibit a SF distribution that corresponds to experimental observations, i.e. a high concentration of highly aligned SFs occurs along free edges, with lower SF concentrations in the interior of the cell. In summary, the results of this study suggest that cell spreading is driven by free energy minimization based on a competition between decreasing cytoskeletal free energy and increasing passive elastic free energy.

Is varicocelectomy beneficial in men previously deemed subfertile but with normal semen parameters based on the new guidelines? A retrospective study

OBJECTIVE

To determine whether using the 2010 World Health Organization (WHO) semen parameter reference values to select varicocelectomy candidates may exclude infertile men who can potentially benefit from this treatment. With the application of the 2010 WHO semen parameter thresholds, some men previously considered to have abnormal semen parameters would now be considered normozoospermic.

METHODS

We conducted a retrospective review of infertile men with varicocele and identified those with abnormal semen parameters according to WHO 1992 or 1999 standards but normozoospermic by WHO 2010 standards. We compared outcomes (semen parameters and spontaneous pregnancy) of couples undergoing varicocelectomy with those choosing observation.

RESULTS

We identified 445 infertile men with varicocele and abnormal semen parameters by WHO 1992 or 1999 standards. Fifty-six of 445 men (13%) were normozoospermic by WHO 2010. Thirty-two of 56 (57%) of these normozoospermic men elected to have varicocelectomy, and 24 of 56 men (43%) choosing observation. In these normozoospermic men (by WHO 2010), varicocelectomy was associated with a significant increase in sperm concentration (50 ± 35 × 10(6)/mL [postsurgery] vs. 32 ± 23 × 10(6)/mL [presurgery]; P = .003). Although not statistically significant, the clinical pregnancy rate was higher in the varicocelectomy group compared with the observation group (52% vs. 38%; P = .37).

CONCLUSION

Varicocelectomy may be beneficial in those men with clinical varicocele and abnormal semen parameters by WHO 1992 or 1999 standards but now normozoospermic by WHO 2010 standards. Applying the 2010 WHO semen parameter reference values into practice may result in missed opportunities to correct treatable causes of male infertility.

Effect of calcium triphosphate cement on proximal humeral fracture osteosynthesis: a finite element analysis

PURPOSE. To measure the effect of void-filling calcium triphosphate cement on the loads at the implant-bone interface of a proximal humeral fracture osteosynthesis using a finite element analysis. METHODS. Finite element models of a 3-part proximal humeral fracture fixed with a plate with and without calcium triphosphate cement augmentation were generated from a quantitative computed tomography dataset of an intact proximal humerus. Material properties were assigned to bone fragments using published expressions relating Young's modulus to local Hounsfield number. Boundary conditions were then applied to the model to replicate the physiological loads. The effect of void-filling calcium triphosphate cement was analysed. RESULTS. When the void was filled with calcium triphosphate cement, the pressure gradient of the bone surrounding the screws in the medial fracture fragment decreased 97% from up to 21.41 to 0.66 MPa. Peak pressure of the fracture planes decreased 95% from 6.10 to 0.30 MPa and occurred along the medial aspect. The mean stress in the screw locking mechanisms decreased 78% from 71.23 to 15.92 MPa. The angled proximal metaphyseal screw had the highest stress. CONCLUSION. Augmentation with calcium triphosphate cement improves initial stability and reduces stress on the implant-bone interface.

Analysis of the mechanical behavior of a titanium scaffold with a repeating unit-cell substructure

Titanium scaffolds with controlled microarchitecture have been developed for load bearing orthopedic applications. The controlled microarchitecture refers to a repeating array of unit-cells, composed of sintered titanium powder, which make up the scaffold structure. The objective of this current research was to characterize the mechanical performance of three scaffolds with increasing porosity, using finite element analysis (FEA) and to compare the results with experimental data. Scaffolds were scanned using microcomputed tomography and FEA models were generated from the resulting computer models. Macroscale and unit-cell models of the scaffolds were created. The material properties of the sintered titanium powders were first evaluated in mechanical tests and the data used in the FEA. The macroscale and unit-cell FEA models proved to be a good predictor of Young's modulus and yield strength. Although macroscale models showed similar failure patterns and an expected trend in UCS, strain at UCS did not compare well with experimental data. Since a rapid prototyping method was used to create the scaffolds, the original CAD geometries of the scaffold were also evaluated using FEA but they did not reflect the mechanical properties of the physical scaffolds. This indicates that at present, determining the actual geometry of the scaffold through computed tomography imaging is important. Finally, a fatigue analysis was performed on the scaffold to simulate the loading conditions it would experience as a spinal interbody fusion device.

4-Chloro-3-fluoro-2-methyl-aniline-pyrrolidine-2,5-dione (1/1)

Chlorination of 3-fluoro-2-methyl­aniline with N-chloro­succinimide gave one major regioisomer whose structure was determined by X-ray crystallography. The product was found to have cocrystallized with succinimide, giving the title compound, C₇H₇ClFN·C₄H₅NO₂. The crystal structure is stabilized by N—H⋯O hydrogen-bonding and π–π stacking inter­actions with a centroid–centroid distance of 3.4501 (8) Å.

New variant Creutzfeldt-Jakob disease: psychiatric features

BACKGROUND

An apparently new variant of Creutzfeldt-Jakob disease (CJD), new variant CJD (nvCJD), was identified in the UK in 1996. There have now been 21 cases of nvCJD in the UK and one in France. Psychiatric symptoms are prominent in the initial presentation in these cases.

METHODS

Cases of nvCJD are identified mainly by direct referral from neurologists and neuropathologists. Detailed clinical information was obtained by review of case notes and interviewing patients' relatives. We report the psychiatric features of the first 14 cases on nvCJD in the UK. Psychiatric notes were examined in all 13 of these cases who were seen by a psychiatrist.

RESULTS

Eight cases were women. All 14 cases had early psychiatric features and in nine, the first symptom was psychiatric. 13 cases were seen by a psychiatrist and the majority were diagnosed as suffering from depression or depression secondary to organic disease. Two cases suffered from first-rank symptoms suggestive of psychotic illness and transient delusions and auditory or visual hallucinations occurred in the majority. All cases were referred to a neurologist as the illness evolved and neurological signs developed.

INTERPRETATION

Psychiatric symptoms are a consistent early clinical feature in nvCJD. Analysis of the psychiatric symptoms does not suggest specific features that readily allow distinction from more common psychiatric disorders, although the occurrence of associated persistent sensory symptoms may raise the possibility of this diagnosis. Neurological signs, including ataxia, involuntary movements and cognitive impairment developed in all cases and the evolution of increasing neurological deficits is likely to remain critical to the clinical diagnosis of nvCJD.

A two-year clinical evaluation of TPH for restoration of Class II carious lesions in permanent teeth

To evaluate the clinical suitability of a barium silicate-filled composite (TPH) for restoration of posterior teeth, 50 Class II restorations were restored in 36 patients. Restorations included 22 molars and 32 premolars. Cavity preparations were protected with calcium hydroxide or a resin-modified glass ionomer cement, or both. Enamel was etched for 30 seconds with 37 percent H3PO4. All dentin surfaces were treated with a dentin bonding system that was placed, cured, and restored in 2 microns increments. The restorations were finished using diamond burs, polishing points, and paste. Evaluation periods were at zero (50 restorations), 6 months (35 restorations), 1 year (31 restorations), and 2 years (29 restorations), using the USPHS System and M-L indirect scale. At zero time, 50 restorations were scored "a" in all categories by using two independent evaluators. After 6 months, 35 restorations were graded with one "a" in postoperative sensitivity. After 1 year, 31 restorations were evaluated with one additional "b" for marginal integrity. After 2 years, 2 additional "b" for marginal integrity and 1 "b" for surface staining were noted. No "c" was observed in any categories throughout this study. Wear analysis revealed, on average, 2 microns of wear after 6 months, 7.8 microns of wear after one year, and 10.3 microns of wear after 2 years.

Delicate longitudinal nuclear grooves in childhood ependymomas

Nuclei of ependymal tumor cells have a pattern of delicate uniform, linear, longitudinal, excentric grooves or clefts, usually single, involving the nuclear membrane and extending at least half the nuclear diameter, producing a notched mitten-shaped nuclear outline, forming a pattern not seen in other neural tumors. Histologically, 13 of 14 childhood ependymal tumors had nuclear clefts. Using these clefts with other histologic criteria, ependymal tumors were identified at the time of surgery 11 of 11 times, with no false-positive results. Cytologically, eight of 10 ependymal and seven of 32 other brain tumors had clefts. These seven other tumors had either additional nonuniform convolutions or folds (n = 5) or had only rare clefts (n = 2). This uniform pattern of nuclear clefts may help identify poorly differentiated ependymal tumors on permanent sections and may help recognize ependymal tumors at surgery, guiding the surgeons' resection.

A cluster classification for histologic diagnoses of CNS tumors in an epidemiologic study

This paper introduces a method which was utilized to sort multiple pathologic diagnoses pertaining to brain tumors into clusters of equivalent diagnostic terms for an epidemiological study of brain cancer. The method enabled the medical record abstractors to ascertain cases for the study. It enabled the reviewing pathologist to identify differences between original and reviewed diagnoses. It identified the large range of classification systems of brain tumors used by practicing pathologists as a factor contributing to confusion of data if slide reviews are not incorporated into epidemiological studies, and demonstrated how the use of a cluster classification alleviates this problem.

Cerebral atherosclerosis in New Orleans. Comparisons of lesions by age, sex, and race

We compared mean extent of atherosclerotic lesions in carotid and intracranial arteries at autopsy among age, sex, and race subgroups in New Orleans. Most comparisons were made within similar broad cause-to-death categories after excluding deaths due to diseases associated with increased amount of atherosclerosis. Use of this basal group of cases reduces the effect of selection bias due to cause of death in this autopsy population. Fatty streaks were present in the carotid arteries of almost all cases even in the youngest age group (10 to 14 years) and were more extensive in blacks than in whites. Raised atherosclerotic lesions increased with age in the carotid arteries of blacks from age group 15 to 24 years and in whites from age group 25 to 34 years; black men and white men had about the same amount of raised lesions, whereas black women consistently had more than white women. In the intracranial arteries, fatty streaks and fibrous plaques began from age 15 to 24 years; blacks had more raised lesions than whites, particularly in the oldest age group, 65 to 69 years. These findings and mortality data suggest that in the 1960s and early 1970s black men and women were more susceptible to cerebral atherosclerosis and cerebrovascular diseases than white men and women.

A case of primary amebic meningoencephalitis. Light and electron microscopy, and immunohistologic studies

A 56-year-old alcoholic developed primary meningoencephalitis and died 3 weeks later. Autopsy revealed multiple areas of necrosis and acute and granulomatous inflammation in the brain and pancreas. Trophozoites and cysts were discovered in the brain and trophozoites alone in the pancreas. Morphologic studies revealed some parasitic features described as characteristic for Naegleria, but clinical, histological and immunohistological features favored in Acanthamoeba infection. This study calls for caution in the use of pure morphological criteria for the differential diagnosis of Naegleria and Acanthamoeba in humans. Cultural characteristics, immunohistology and serologic tests are probably more reliable for differentiating these parasites.