Impact of femoroacetabular impingement and dysplasia of the hip on hip joint sphericity

BACKGROUND

This paper presents a parametric investigation into the effect of femoroacetabular impingement (FAI) and developmental dysplasia of the hip (DDH) on the sphericity of the femoral supra-equatorial region and acetabulum.

METHODS

Radiographic parameters from x-rays, sphericity calculations and visualisation and joint contact area and pressure from FE models of 10 DDH, FAI and normal hips were analysed and compared both within and between hip groups.

RESULTS

The sphericity of the acetabulum and femoral head of both the DDH and FAI groups was found to be less than that for normal hips but the variation in sphericity was greater (range 2.4% for normal hips, compared to 3.3% and 3.1% for the FAI and DDH groups respectively). For the DDH group, femoral head sphericity was found to correlate strongly with 2 of the radiographic parameters used to diagnose the condition, CE angle and Sharp angle. For FAI and DDH hips peak contact pressure primarily occurred in Ilizaliturri Zone 2 (anterior-superior region) in the acetabulum and femoral head which corresponded with increased aspherity in this region compared to the normal hip group. These findings correlate with loading and damage patterns reported in the literature. Additionally, our analysis identified a protrusion of bone in Ilizaliturri Zones 1 and 6 (anterior-inferior region) of the acetabulum of a subgroup of FAI hips, whose existence was confirmed using a full-scale hip model fabricated using a 3D printer, which we believe could result in cartilage damage.

CONCLUSION

We postulate that such protrusions could potentially explain residual symptoms and unaddressed structural deformity in patients who have undergone FAI surgery.

Performance evaluation of surgical techniques for treatment of scapholunate instability in a type II wrist

We investigated the performance of three tenodesis techniques, modified Brunelli, Corella, and scapholunate axis (SLAM) methods in repairing scapholunate interosseous ligament (SLIL) disruption for a type II wrist using finite element-based virtual surgery and compared the results with those of a previous investigation for a type I wrist. In addition, a comparison of the carpal mechanics of type I and type II wrists was undertaken in order to elucidate the difference between the two types. For the type II wrist, following simulated SLIL disruption, the Corella reconstruction technique provided a superior outcome, restoring dorsal gap, volar gap, and SL angle to within 3.5%, 7.1%, and 8.4%, respectively, of the intact wrist. Moreover, application of the ligament reconstruction techniques did not significantly alter the motion pattern of the type II and type I wrists. For the type I wrist, SLIL disruption resulted in no contact between scaphoid-lunate cartilage articulation, whereas for the type II wrist, some contact was maintained. We conclude that the Corella ligamentous reconstruction technique is best able to restore SL gap, angle, and stability following SL ligament injury for both type II and type I wrists and is able to do so without altering wrist kinematics. Our findings also support the view that type I wrists exhibit row behaviour and type II wrists column behaviour. In addition, our analysis suggests that the extra articulation between the lunate and hamate in a type II wrist may help improve stability following SL ligament injury.

Effect of Femoral Head Size, Subject Weight, and Activity Level on Acetabular Cement Mantle Stress Following Total Hip Arthroplasty

In cases where cemented components are used in total hip arthroplasty, damage, or disruption of the cement mantle can lead to aseptic loosening and joint failure. Currently, the relationship between subject activity level, obesity, and prosthetic femoral head size and the risk of aseptic loosening of the acetabular component in cemented total hip arthroplasty is not well understood. This study aims to provide an insight into this. Finite element models, validated with experimental data, were developed to investigate stresses in the acetabular cement mantle and pelvic bone resulting from the use of three prosthetic femoral head sizes, during a variety of daily activities and one high impact activity (stumbling) for a range of subject body weights. We found that stresses in the superior quadrants of the cortical bone-cement interface increased with prosthetic head size, patient weight, and activity level. In stumbling, average von Mises stresses (22.4 MPa) exceeded the bone cement yield strength for an obese subject (143 kg) indicating that the cement mantle would fail. Our results support the view that obesity and activity level are potential risk factors for aseptic loosening of the acetabular component and provide insight into the increased risk of joint failure associated with larger prosthetic femoral heads. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 37:1771-1783, 2019.

Cement interface and bone stress in total hip arthroplasty: Relationship to head size

The use of larger prosthetic femoral heads in total hip arthroplasty (THA) has increased considerably in recent years in response to the need to improve joint stability and reduce risk of dislocation. However, data suggests larger femoral heads are associated with higher joint failure rates. For cemented implants, ensuring the continued integrity of the cement mantle is key to long term fixation. This paper describes an investigation into the effect of variation in femoral head size on stresses in the acetabular cement mantle and pelvic bone. Three commonly used femoral head sizes: 28, 32, and 36 mm diameter were investigated. The study was undertaken using a finite element model validated using surface strains obtained from Digital Image Correlation (DIC) during experimentation on a composite hemipelvis implanted with a cemented all-polyethylene acetabular cup. Following validation, the models were used to investigate stresses in the pelvic bone and acetabular cement mantle resulting from two loading scenarios; an average weight subject (700 N) and an overweight subject (1,000 N) undertaking a single leg stand. We found that the highest peak stresses occurred in the anterosuperior and posterosuperior regions of the bone-cement interface, in the line of action of the load, where debonding usually initiates. Stress on the cortical bone-cement interface increased with femoral head diameter by up to 9% whilst stresses in the trabecular bone remained relatively invariant. Our findings may help to explain higher joint failure rates associated with larger femoral heads. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:2966-2977, 2018.

CTCF genetic alterations in endometrial carcinoma are pro-tumorigenic

CTCF is a haploinsufficient tumour suppressor gene with diverse normal functions in genome structure and gene regulation. However the mechanism by which CTCF haploinsufficiency contributes to cancer development is not well understood. CTCF is frequently mutated in endometrial cancer. Here we show that most CTCF mutations effectively result in CTCF haploinsufficiency through nonsense-mediated decay of mutant transcripts, or loss-of-function missense mutation. Conversely, we identified a recurrent CTCF mutation K365T, which alters a DNA binding residue, and acts as a gain-of-function mutation enhancing cell survival. CTCF genetic deletion occurs predominantly in poor prognosis serous subtype tumours, and this genetic deletion is associated with poor overall survival. In addition, we have shown that CTCF haploinsufficiency also occurs in poor prognosis endometrial clear cell carcinomas and has some association with endometrial cancer relapse and metastasis. Using shRNA targeting CTCF to recapitulate CTCF haploinsufficiency, we have identified a novel role for CTCF in the regulation of cellular polarity of endometrial glandular epithelium. Overall, we have identified two novel pro-tumorigenic roles (promoting cell survival and altering cell polarity) for genetic alterations of CTCF in endometrial cancer.

Observation of hohlraum-wall motion with spectrally selective x-ray imaging at the National Ignition Facility

The high fuel capsule compression required for indirect drive inertial confinement fusion requires careful control of the X-ray drive symmetry throughout the laser pulse. When the outer cone beams strike the hohlraum wall, the plasma ablated off the hohlraum wall expands into the hohlraum and can alter both the outer and inner cone beam propagations and hence the X-ray drive symmetry especially at the final stage of the drive pulse. To quantitatively understand the wall motion, we developed a new experimental technique which visualizes the expansion and stagnation of the hohlraum wall plasma. Details of the experiment and the technique of spectrally selective x-ray imaging are discussed.

Two-color spatial and temporal temperature measurements using a streaked soft x-ray imager

A dual-channel streaked soft x-ray imager has been designed and used on high energy-density physics experiments at the National Ignition Facility. This streaked imager creates two images of the same x-ray source using two slit apertures and a single shallow angle reflection from a nickel mirror. Thin filters are used to create narrow band pass images at 510 eV and 360 eV. When measuring a Planckian spectrum, the brightness ratio of the two images can be translated into a color-temperature, provided that the spectral sensitivity of the two images is well known. To reduce uncertainty and remove spectral features in the streak camera photocathode from this photon energy range, a thin 100 nm CsI on 50 nm Al streak camera photocathode was implemented. Provided that the spectral shape is well-known, then uncertainties on the spectral sensitivity limits the accuracy of the temperature measurement to approximately 4.5% at 100 eV.

ASCT2/SLC1A5 controls glutamine uptake and tumour growth in triple-negative basal-like breast cancer

Alanine, serine, cysteine-preferring transporter 2 (ASCT2; SLC1A5) mediates uptake of glutamine, a conditionally essential amino acid in rapidly proliferating tumour cells. Uptake of glutamine and subsequent glutaminolysis is critical for activation of the mTORC1 nutrient-sensing pathway, which regulates cell growth and protein translation in cancer cells. This is of particular interest in breast cancer, as glutamine dependence is increased in high-risk breast cancer subtypes. Pharmacological inhibitors of ASCT2-mediated transport significantly reduced glutamine uptake in human breast cancer cell lines, leading to the suppression of mTORC1 signalling, cell growth and cell cycle progression. Notably, these effects were subtype-dependent, with ASCT2 transport critical only for triple-negative (TN) basal-like breast cancer cell growth compared with minimal effects in luminal breast cancer cells. Both stable and inducible shRNA-mediated ASCT2 knockdown confirmed that inhibiting ASCT2 function was sufficient to prevent cellular proliferation and induce rapid cell death in TN basal-like breast cancer cells, but not in luminal cells. Using a bioluminescent orthotopic xenograft mouse model, ASCT2 expression was then shown to be necessary for both successful engraftment and growth of HCC1806 TN breast cancer cells in vivo. Lower tumoral expression of ASCT2 conferred a significant survival advantage in xenografted mice. These responses remained intact in primary breast cancers, where gene expression analysis showed high expression of ASCT2 and glutamine metabolism-related genes, including GLUL and GLS, in a cohort of 90 TN breast cancer patients, as well as correlations with the transcriptional regulators, MYC and ATF4. This study provides preclinical evidence for the feasibility of novel therapies exploiting ASCT2 transporter activity in breast cancer, particularly in the high-risk basal-like subgroup of TN breast cancer where there is not only high expression of ASCT2, but also a marked reliance on its activity for sustained cellular proliferation.

A new streaked soft x-ray imager for the National Ignition Facility

A new streaked soft x-ray imager has been designed for use on high energy-density (HED) physics experiments at the National Ignition Facility based at the Lawrence Livermore National Laboratory. This streaked imager uses a slit aperture, single shallow angle reflection from a nickel mirror, and soft x-ray filtering to, when coupled to one of the NIF's x-ray streak cameras, record a 4× magnification, one-dimensional image of an x-ray source with a spatial resolution of less than 90 μm. The energy band pass produced depends upon the filter material used; for the first qualification shots, vanadium and silver-on-titanium filters were used to gate on photon energy ranges of approximately 300-510 eV and 200-400 eV, respectively. A two-channel version of the snout is available for x-ray sources up to 1 mm and a single-channel is available for larger sources up to 3 mm. Both the one and two-channel variants have been qualified on quartz wire and HED physics target shots.

A magnetic particle time-of-flight (MagPTOF) diagnostic for measurements of shock- and compression-bang time at the NIF (invited)

A magnetic particle time-of-flight (MagPTOF) diagnostic has been designed to measure shock- and compression-bang time using D(3)He-fusion protons and DD-fusion neutrons, respectively, at the National Ignition Facility (NIF). This capability, in combination with shock-burn weighted areal density measurements, will significantly constrain the modeling of the implosion dynamics. This design is an upgrade to the existing particle time-of-flight (pTOF) diagnostic, which records bang times using DD or DT neutrons with an accuracy better than ±70 ps [H. G. Rinderknecht et al., Rev. Sci. Instrum. 83, 10D902 (2012)]. The inclusion of a deflecting magnet will increase D(3)He-proton signal-to-background by a factor of 1000, allowing for the first time simultaneous measurements of shock- and compression-bang times in D(3)He-filled surrogate implosions at the NIF.

Changes in the stress in the femoral head neck junction after osteochondroplasty for hip impingement: a finite element study

The surgical treatment of femoroacetabular impingement (FAI) often involves femoral osteochondroplasty. One risk of this procedure is fracture of the femoral neck. We developed a finite element (FE) model to investigate the relationship between depth of resection and femoral neck stress. CT data were used to obtain the geometry of a typical cam-type hip, and a 3D FE model was constructed to predict stress in the head-neck after resection surgery. The model accounted for the forces acting on the head and abductor muscular forces. Bone resection was performed virtually to incremental resection depths. The stresses were calculated for five resection depths and for five different activities (i) standing on one leg (static case); (ii) two-to-one-to-two leg standing; (iii) normal walking; (iv) walking down stairs; and (v) a knee bend. In general, both the average Von Mises stresses and the area of bone that yielded significantly increased at a resection depth of ≥10 mm. The knee bend and walking down stairs demonstrated the highest stresses. The FE model predicts that fracture is likely to occur in the resection area first following removal of a third (10 mm) or more of the diameter of the femoral neck. We suggest that when surgeons perform osteochondroplasty for hip impingement, the depth of resection should be limited to 10 mm.

Loss of solute carriers in T cell-mediated rejection in mouse and human kidneys: an active epithelial injury-repair response

T cell-mediated rejection of kidney allografts causes epithelial deterioration, manifested by tubulitis, but the mechanism remains unclear. We hypothesized that interstitial inflammation triggers a stereotyped epithelial response similar to that triggered by other types of injury such as ischemia-reperfusion. We identified solute carrier transcripts with decreased expression in mouse allografts, and compared their behavior in T cell-mediated rejection to native kidneys with ischemic acute tubular necrosis (ATN). Average loss of solute carrier expression was similar in ATN (77%) and T cell-mediated rejection (75%) with high correlation of individual transcripts. Immunostaining of SLC6A19 confirmed loss of proteins. Analysis of human kidney transplant biopsies confirmed that T cell-mediated rejection and ATN showed similar loss of solute carrier mRNAs. The loss of solute carrier expression was weakly correlated with interstitial inflammation, but kidneys with ATN showed decreased solute carriers despite minimal inflammation. Loss of renal function correlated better with decreased solute carrier expression than with histologic lesions (r = 0.396, p < 0.001). Thus the loss of epithelial transcripts in rejection is not a unique consequence of T cell-mediated rejection but an active injury-repair response of epithelium, triggered by rejection but also by other injury mechanisms.

Hyperdigraph-theoretic analysis of the EGFR signaling network: initial steps leading to GTP:Ras complex formation

We construct an algebraic-combinatorial model of the SOS compartment of the EGFR biochemical network. A Petri net is used to construct an initial representation of the biochemical decision making network, which in turn defines a hyperdigraph. We observe that the linear algebraic structure of each hyperdigraph admits a canonical set of algebraic-combinatorial invariants that correspond to the information flow conservation laws governing a molecular kinetic reaction network. The linear algebraic structure of the hyperdigraph and its sets of invariants can be generalized to define a discrete algebraic-geometric structure, which is referred to as an oriented matroid. Oriented matroids define a polyhedral optimization geometry that is used to determine optimal subpaths that span the nullspace of a set of kinetic chemical reaction equations. Sets of constrained submodular path optimizations on the hyperdigraph are objectively obtained as a spanning tree of minimum cycle paths. This complete set of subcircuits is used to identify the network pinch points and invariant flow subpaths. We demonstrate that this family of minimal circuits also characteristically identifies additional significant biochemical reaction pattern features. We use the SOS Compartment A of the EGFR biochemical pathway to develop and demonstrate the application of our algebraic-combinatorial mathematical modeling methodology.

A computational model for the identification of biochemical pathways in the krebs cycle

We have applied an algorithmic methodology which provably decomposes any complex network into a complete family of principal subcircuits to study the minimal circuits that describe the Krebs cycle. Every operational behavior that the network is capable of exhibiting can be represented by some combination of these principal subcircuits and this computational decomposition is linearly efficient. We have developed a computational model that can be applied to biochemical reaction systems which accurately renders pathways of such reactions via directed hypergraphs (Petri nets). We have applied the model to the citric acid cycle (Krebs cycle). The Krebs cycle, which oxidizes the acetyl group of acetyl CoA to CO(2) and reduces NAD and FAD to NADH and FADH(2), is a complex interacting set of nine subreaction networks. The Krebs cycle was selected because of its familiarity to the biological community and because it exhibits enough complexity to be interesting in order to introduce this novel analytic approach. This study validates the algorithmic methodology for the identification of significant biochemical signaling subcircuits, based solely upon the mathematical model and not upon prior biological knowledge. The utility of the algebraic-combinatorial model for identifying the complete set of biochemical subcircuits as a data set is demonstrated for this important metabolic process.

An algebraic-combinatorial model for the identification and mapping of biochemical pathways

We develop the mathematical machinery for the construction of an algebraic-combinatorial model using Petri nets to construct an oriented matroid representation of biochemical pathways. For demonstration purposes, we use a model metabolic pathway example from the literature to derive a general biochemical reaction network model. The biomolecular networks define a connectivity matrix that identifies a linear representation of a Petri net. The sub-circuits that span a reaction network are subject to flux conservation laws. The conservation laws correspond to algebraic-combinatorial dual invariants, that are called S- (state) and T- (transition) invariants. Each invariant has an associated minimum support. We show that every minimum support of a Petri net invariant defines a unique signed sub-circuit representation. We prove that the family of signed sub-circuits has an implicit order that defines an oriented matroid. The oriented matroid is then used to identify the feasible sub-circuit pathways that span the biochemical network as the positive cycles in a hyper-digraph.

Indirect laser-induced fluorescence detection of explosive compounds using capillary electrochromatography and micellar electrokinetic chromatography

Mixtures of nitroaromatic and nitramine explosive compounds and their degradation products were analyzed using electrokinetically driven separations with both indirect laser-induced fluorescence (IDLIF) and UV absorption detection. Complete separations of the 14-component mixture (EPA 8330) were achieved using both capillary electrochromatography (CEC) and micellar electrokinetic chromatography (MEKC). IDLIF detection was performed using an epifluorescence system with excitation provided by a 635 nm diode laser and micromolar concentrations of the dye Cy-5 as the visualizing agent. While the sensitivity of the two detection methods was similar for the nitroaromatic compounds, the nitramines could only be detected using UV absorption due to their low fluorescence quenching efficiency of Cy-5. The detection sensitivity using IDLIF was limited by low frequency oscillations in the fluorescence background. The oscillations increased with higher electric field strength and were attributed to thermal fluctuations caused by Joule heating. Due to the more conductive running buffer and higher separation currents used in MEKC, sensitive IDLIF detection could only be achieved using low (approximately 100 V/cm) field strengths, resulting in long analysis times. CEC separations, which are typically run with low conductivity mobile phases to avoid bubble formation, are less sensitive to this effect. In CEC separations with IDLIF detection a stable fluorescence background using Cy-5 could be established using only a nonporous stationary phase. In capillaries packed with porous silica particles, anomalous migration behavior was observed with charged dye molecules and a stable fluorescence background could not be established under electrokinetic flow. This is the first demonstration of IDLIF in packed channel CEC.

On-chip chiral and achiral separation of amphetamine and related compounds labeled with 4-fluoro-7-nitrobenzofurazane

Amphetamine and analogous compounds have been labeled with 4-fluoro-7-nitrobenzofurazane and analyzed on a microfabricated chip. Separation of norephedrine, ephedrine, cathinone, pseudoephedrine, methcathinone, amphetamine and methamphetamine is demonstrated using micellar electrokinetic capillary chromatography (MEKC) and laser-induced fluorescence (LIF) detection. Chiral separations of individual drugs were studied using neutral and negatively charged cyclodextrins (CDs) with and without the addition of an organic modifier and/or sodium dodecyl sulfate (SDS). The best results were obtained using a highly sulfated gamma-CD (HS-gamm-CD) in combination with a low concentration of SDS. To obtain complete separation of a mixture of (+/-)-norephedrine, (+/-)ephedrine, (+/-)-pseudoephedrine, (+/-)-methcathinone, (+/-)-amphetamine and (+/-)-methamphetamine it was necessary to add a small amount (1.5 mM) of SDS to the separation buffer. Optimized chiral separation was achieved within 7 min using an S-folded separation channel, a separation voltage of 8 kV and a buffer consisting of 50 mM phosphate (pH 7.35), 10 mM HS-gamma-CD and 1.5 mM SDS.

Separation of related opiate compounds using capillary electrochromatography

Capillary electrophoretic separations have been investigated for six controlled narcotic analgesic compounds having related structures. Owing to the similar charge-to-mass ratios of these compounds, capillary zone electrophoresis failed to provide a satisfactory separation, whereas a baseline-resolved separation was achieved in 10 min using micellar electrokinetic chromatography. Column efficiencies of 40,000-150,000 plates/m were obtained with a 50 cm long, 50 microm inner diameter (ID) capillary using 50 mM sodium dodecyl sulfate (SDS) in a 50 mM borate solution containing 12% isopropanol. In contrast, separation of this mixture by capillary electrochromatography proved to be significantly superior. The capillary was 15 cm long, with an ID of 75 microm, and was packed with 1.5 microm nonporous octadecyl silica (ODS) particles. The mobile phase consisted of 80% 10 mM tris(hydroxymethyl)aminomethane (Tris) and 20% acetonitrile, and contained 5 mM SDS. A complete separation was obtained in 2.5 min with an efficiency of 250,000-500,000 plates/m.

Profiling of impurities in illicit methamphetamine by high-performance liquid chromatography and capillary electrochromatography

High performance liquid chromatography (HPLC) with photodiode array (PDA) UV and fluorescence (FL) detection, and capillary electrochromatography (CEC) with laser-induced fluorescence (LIF) detection were investigated for the analysis of acidic extracts derived from illicit methamphetamine. These compounds include major impurities from the hydriodic acid/red phosphorous reduction method, i.e., 1,3-dimethyl-2-phenylnaphthalene and 1-benzyl-3-methylnaphthalene, and other trace-level, structurally related impurities. For certain of these solutes, HPLC with conventional FL detection gave at least a 60x increase in sensitivity over UV detection. In addition, other highly fluorescent impurities were detected in methamphetamine produced via four other synthetic routes. The use of a rapid scanning FL detector (with acquisition of "on the fly" excitation or emission) provided structural information and gave "optimum" excitation and emission detection wavelengths. CEC with LIF detection using UV laser excitation provided greatly improved chromatography over HPLC, with good detection limits in the low ng/ml range. Both methodologies provide good run-to-run repeatability, and have the capability to distinguish between samples.

Design of a phase-locked multimode SAW oscillator

A 60-100 MHz multimode SAW (surface acoustic wave) oscillator with comb spacing Deltaf=10 MHz used a low-loss SPUDT (single-phase unidirectional transducer) comb filter in conjunction with two varactor-based control elements and two feedback loops, for mode selection and stability enhancement over long dwell times. The end aim is to reduce close-in phase noise over that of the unlocked oscillator, corresponding to improved intermediate-term time-domain stability. Frequency deviation was less than 20 Hz over two hours in each of the five comb modes.

Prolonged and functional survival with the asplenia syndrome

Asplenia syndrome is a rare congenital complex of splenic agenesis, cardiac malformation, and malposition of the abdominal viscera. Prolonged functional survival is very uncommon, with death usually caused by severe infection or congestive heart failure. A 21-year-old man with typical asplenia syndrome who is currently asymptomatic and in his third year of college is described.

Food preferences of the dusky grasshopper, Encoptolophus sordidus costalis (Scudder) (Orthoptera: Acrididae)

Crop analyses of 578 grasshoppers showed that the dusky grasshopper, Encoptolophus sordidus costalis, is primarily a grass-feeding species. All grasses are not selected randomly. About 80% of the diet consisted of Agropyron smithii, A. dasystachyum, and Carex eleocharis. The latter was eaten at a rate that was more than twice as great as that expected if feeding were proportional to the relative abundance of plant species on the study site. Therefore, this sedge is a specific preferred food plant, especially for the three early instars. Forbs were ingested very sparingly in nature (1% of diet) but 11 out of 22 species were fed upon when offered singly to starved adult grasshoppers. Non-adherence to a strictly grass diet under stress conditions is indicative of great flexibility and explains the widespread distribution of this species throughout central North America.