A novel quantitative grading system for implant fixation in revision total knee arthroplasty.

Aims: Obtaining solid implant fixation is crucial in revision total knee arthroplasty (rTKA) to avoid aseptic loosening, a major reason for re-revision. This study aims to validate a novel grading system that quantifies implant fixation across three anatomical zones (epiphysis, metaphysis, diaphysis). Methods: Based on pre-, intra-, and postoperative assessments, the novel grading system allocates a quantitative score (0, 0.5, or 1 point) for the quality of fixation achieved in each anatomical zone. The criteria used by the algorithm to assign the score include the bone quality, the size of the bone defect, and the type of fixation used. A consecutive cohort of 245 patients undergoing rTKA from 2012 to 2018 were evaluated using the current novel scoring system and followed prospectively. In addition, 100 first-time revision cases were assessed radiologically from the original cohort and graded by three observers to evaluate the intra- and inter-rater reliability of the novel radiological grading system. Results: At a mean follow-up of 90 months (64 to 130), only two out of 245 cases failed due to aseptic loosening. Intraoperative grading yielded mean scores of 1.87 (95% confidence interval (CI) 1.82 to 1.92) for the femur and 1.96 (95% CI 1.92 to 2.0) for the tibia. Only 3.7% of femoral and 1.7% of tibial reconstructions fell below the 1.5-point threshold, which included the two cases of aseptic loosening. Interobserver reliability for postoperative radiological grading was 0.97 for the femur and 0.85 for the tibia. Conclusion: A minimum score of 1.5 points for each skeletal segment appears to be a reasonable cut-off to define sufficient fixation in rTKA. There were no revisions for aseptic loosening at mid-term follow-up when this fixation threshold was achieved or exceeded. When assessing first-time revisions, this novel grading system has shown excellent intra- and interobserver reliability.

Interplay of Quantum Confinement and Strain Effects in Type I to Type II Transition in GeSi Core-Shell Nanocrystals.

The electronic properties of hydrogenated, spherical SiGe and GeSi core-shell nanocrystals, with a diameter ranging from 1.8 to 4.0 nm, are studied within density functional theory. Effects induced by quantum confinement and strain on the near-band-edge state localization, as well as the band-offset properties between Si and Ge regions, are investigated in detail. On the one hand, we prove that SiGe core-shell nanocrystals always show a type II band-offset alignment, with the HOMO mainly localized on the Ge shell region and the LUMO mainly localized on the Si core region. On the other hand, our results point out that a type II offset cannot be observed in small (diameter less than 3 nm) GeSi core-shell nanocrystals. In these systems, quantum confinement and strain drive the near-band-edge states to be mainly localized on Ge atoms, i.e., in the core region. In larger GeSi core-shell nanocrystals, instead, the formation of a type II offset can be engineered by playing with both core and shell thickness. The factors which determine the band-offset character at the Ge/Si interface are discussed in detail.

Restoration of pre-operative joint line orientation and alignment does not affect KSS and KOOS 1 year after total knee arthroplasty.

PURPOSE: The objectives of this study were to examine the relation between clinical outcomes 1 year postoperatively, in a cohort of mechanically aligned total knee arthroplasties (TKA), and (1) the degrees of alignment change of the tibial, femoral and the hip-knee-ankle (HKA) angle; (2) the change of phenotype; (3) the postoperative knee joint line orientation to the floor. METHODS: Pre-operative and postoperative long-leg X-rays of 90 patients were used to determine the coronal alignment. The absolute difference between the pre-operative and postoperative measurements was determined and the outcomes were categorized in whether or not a change in phenotype had occurred. Finally, the orientation of the knee joint line relative to the floor (tibial joint line angle-TJLA) was measured. Clinical outcomes were determined with the KOOS and KSS at 1-year follow-up. RESULTS: The clinical outcomes (1) did not correlate with the absolute difference of the alignment measured; (2) did not show a difference between patients with or without a change in phenotype; and (3) were higher (KOOS ADL, Sport and QoL) in patients with a medial open TJLA. CONCLUSION: This study showed no correlation between clinical outcomes and joint line restoration of the femur, tibia or HKA in patients after TKA. Leaving the prosthesis with some degrees of under correction on the coronal plane maintaining the phenotype, was not associated to better clinical results compared to TKA overcorrection. Nevertheless, the results showed that patients with a medial open TJLA had better clinical outcomes than patients with a lateral open TJLA. LEVEL OF EVIDENCE: III.

Surface chemistry effects on work function, ionization potential and electronic affinity of Si(100), Ge(100) surfaces and SiGe heterostructures.

We combine density functional theory and many body perturbation theory to investigate the electronic properties of Si(100) and Ge(100) surfaces terminated with halogen atoms (-I, -Br, -Cl, -F) and other chemical functionalizations (-H, -OH, -CH3) addressing the absolute values of their work function, electronic affinity and ionization potential. Our results point out that electronic properties of functionalized surfaces strongly depend on the chemisorbed species and much less on the surface crystal orientation. The presence of halogens at the surface always leads to an increment of the work function, ionization potential and electronic affinity with respect to fully hydrogenated surfaces. On the contrary, the presence of polar -OH and -CH3 groups at the surface leads to a reduction of the aforementioned quantities with respect to the H-terminated system. Starting from the work functions calculated for the Si and Ge passivated surfaces, we apply a simple model to estimate the properties of functionalized SiGe surfaces. The possibility of modulating the work function by changing the chemisorbed species and composition is predicted. The effects induced by different terminations on the band energy line-up profile of SiGe surfaces are then analyzed. Interestingly, our calculations predict a type-II band offset for the H-terminated systems and a type-I band offset for the other cases.

Ab initio studies of the optoelectronic structure of undoped and doped silicon nanocrystals and nanowires: the role of size, passivation, symmetry and phase.

Silicon nanocrystals and nanowires have been extensively studied because of their novel properties and their applications in electronic, optoelectronic, photovoltaic, thermoelectric and biological devices. Here we discuss results from ab initio calculations for undoped and doped Si nanocrystals and nanowires, showing how theory can aid and improve comprehension of the structural, electronic and optical properties of these systems.

Quantifying the resolution of spatial and temporal representation in children with 22q11.2 deletion syndrome.

OBJECTIVES: Our ability to generate mental representation of magnitude from sensory information affects how we perceive and experience the world. Reduced resolution of the mental representations formed from sensory inputs may generate impairment in the proximal and distal information processes that utilize these representations. Impairment of spatial and temporal information processing likely underpins the non-verbal cognitive impairments observed in 22q11.2 deletion syndrome (22q11DS). The present study builds on prior research by seeking to quantify the resolution of spatial and temporal representation in children with 22q11DS, sex chromosome aneuploidy (SCA), and a typically developing (TD) control group. PARTICIPANTS AND METHODS: Children (22q11DS = 70, SCA = 49, TD = 46) responded to visual or auditory stimuli with varying difference ratios. The participant's task was to identify which of two sequentially presented stimuli was of larger magnitude in terms of, size, duration, or auditory frequency. Detection threshold was calculated as the minimum difference ratio between the "standard" and the "target" stimuli required to achieve 75% accuracy in detecting that the two stimuli were different. RESULTS: Children with 22q11DS required larger magnitude difference between spatial stimuli for accurate identification compared with both the SCA and TD groups (% difference from standard: 22q11DS = 14; SCA = 8; TD: 7; F = 8.42, p < 0.001). Temporal detection threshold was also higher for the 22q11DS group to both visual (% difference from standard: 22q11DS = 14; SCA = 8; TD = 7; F = 8.33, p < 0.001) and auditory (% difference from standard: 22q11DS = 23; SCA = 12; TD: 8; F = 8.99, p < 0.001) stimuli compared with both the SCA and TD groups, while the SCA and TD groups displayed equivalent performance on these measures (p's > 0.05). Pitch detection threshold did not differ among the groups (p's > 0.05). CONCLUSIONS: The observation of higher detection thresholds to spatial and temporal stimuli indicates further evidence for reduced resolution in both spatial and temporal magnitude representation in 22q11DS, that does not extend to frequency magnitude representation (pitch detection), and which is not explained by generalized cognitive impairment alone. These findings generate further support for the hypothesis that spatiotemporal hypergranularity of mental representations contributes to the non-verbal cognitive impairment seen in 22q11DS.

Does navigated patellar resurfacing in total knee arthroplasty result in proper bone cut, motion and clinical outcomes?

BACKGROUND: In total knee arthroplasty with patellar resurfacing, patellar bone preparation, component positioning and motion assessments are still not navigated. Only femoral/tibial component positioning is supported by computer-assistance. The aim of this study was to verify, in-vivo, whether knee surgical navigation extended to patellar resurfacing, by original instrumentation and procedures for patellar-based tracking, could achieve accurate patella preparation in terms of original thickness restoration, bone cut orientation, and normal knee motion. METHODS: An additional navigation system for patellar data acquisition was used together with a standard navigation system for total knee arthroplasty in 20 patients. This supported the surgeon for patellar resurfacing via measurement of removed bone thickness, three-dimensional patellar cut orientations, and patello-femoral motion. Radiological and clinical examinations at 6 and 24-month follow-up were also performed. FINDINGS: The medio-lateral patellar-bone cut orientation was respectively 0.5° (standard deviation: 3.0°) and 1.4° (1.7°) lateral tilt, as measured via navigation and post-operatively on the Merchant x-ray view. The cranio-caudal orientation was 3.8° (7.2°) of flexion. The thickness variation between patellar pre- and post-implantation was 0.2 (1.3) mm. Immediately after implantation, patello-femoral as well as tibio-femoral kinematics was within the normality. Good radiological and clinical examinations at 6 and 24-month follow-up were also observed. INTERPRETATION: For the first time, the effect of patellar navigation for its resurfacing was assessed in-vivo during surgery, with very good results for thickness restoration, proper cut orientation, and normal knee motion. These results support the introduction of patella-related navigation-based surgical procedures for computer-assisted total knee arthroplasty.

Preferential Positioning, Stability, and Segregation of Dopants in Hexagonal Si Nanowires.

We studied the physics of common p- and n-type dopants in hexagonal-diamond Si, a Si polymorph that can be synthesized in nanowire geometry without the need of extreme pressure conditions, by means of first-principles electronic structure calculations and compared our results with those for the well-known case of cubic-diamond nanowires. We showed that (i) as observed in recent experiments, at larger diameters (beyond the quantum confinement regime) p-type dopants prefer the hexagonal-diamond phase with respect to the cubic one as a consequence of the stronger degree of three-fold coordination of the former, while n-type dopants are at a first approximation indifferent to the polytype of the host lattice; (ii) in ultrathin nanowires, because of the lower symmetry with respect to bulk systems and the greater freedom of structural relaxation, the order is reversed and both types of dopant slightly favor substitution at cubic lattice sites; (iii) the difference in formation energies leads, particularly in thicker nanowires, to larger concentration differences in different polytypes, which can be relevant for cubic-hexagonal homojunctions; (iv) ultrasmall diameters exhibit, regardless of the crystal phase, a pronounced surface segregation tendency for p-type dopants. Overall these findings shed light on the role of crystal phase in the doping mechanism at the nanoscale and could have a great potential in view of the recent experimental works on group IV nanowires polytypes.

Conventional versus computer-assisted surgery in total knee arthroplasty: comparison at ten years follow-up.

PURPOSE: Computer-assisted systems (CAS) for total knee arthroplasty (TKA) were expected to result in more accurate prosthesis implantation, better patient outcomes, and longer implant survival when compared to conventional instrumentation (CI). The aim of this study was to compare two groups of patients operated using CAS or CI at ten years follow-up. METHODS: One hundred twenty TKA patients, 60 using CAS and 60 using CI, were contacted after a decade for follow-up. Eligible patients received radiological examination to assess the lower-limb mechanical axis. They were also clinically assessed using the Knee Injury and Osteoarthritis Outcome Score (KOOS) and the Knee Society Score for Knee (KSS-K) and Function (KSS-F) Scoring. Kaplan-Meier survival analysis was performed to assess revisions, not for post-traumatic reasons. RESULTS: In CAS and CI groups, the lower-limb mechanical axis was 1.7° ± 2.4° and 1.5° ± 2.8°, respectively; corresponding KOOS values were 82.3 ± 14.3 and 78.6 ± 14.4; KSS-K values were 85.9 ± 11.1 and 85.0 ± 9.7; KSS-F values were 82.2 ± 19.3 and 83.8 ± 18. For these assessments, the differences between the two groups were not statistically significant (p > 0.05). Two CAS (3.8%) and three CI patients (5.7%) were revised. The Kaplan-Meier analysis showed no significant differences between the two groups. CONCLUSIONS: No significant differences were found at long-term follow-up in terms of radiographical-clinical outcomes and of implant survival between TKA operated using CAS or CI.

Crystalline, Phononic, and Electronic Properties of Heterostructured Polytypic Ge Nanowires by Raman Spectroscopy.

Semiconducting nanowires (NWs) offer the unprecedented opportunity to host different crystal phases in a nanostructure, which enables the formation of polytypic heterostructures where the material composition is unchanged. This characteristic boosts the potential of polytypic heterostructured NWs for optoelectronic and phononic applications. In this work, we investigate cubic Ge NWs where small (∼20 nm) hexagonal domains are formed due to a strain-induced phase transformation. By combining a nondestructive optical technique (Raman spectroscopy) with density-functional theory (DFT) calculations, we assess the phonon properties of hexagonal Ge, determine the crystal phase variations along the NW axis, and, quite remarkably, reconstruct the relative orientation of the two polytypes. Moreover, we provide information on the electronic band alignment of the heterostructure at points of the Brillouin zone different from the one (Γ) where the direct band gap recombination in hexagonal Ge takes place. We demonstrate the versatility of Raman spectroscopy and show that it can be used to determine the main crystalline, phononic, and electronic properties of the most challenging type of heterostructure (a polytypic, nanoscale heterostructure with constant material composition). The general procedure that we establish can be applied to several types of heterostructures.

High performance of α-defensin lateral flow assay (Synovasure) in the diagnosis of chronic knee prosthetic infections.

PURPOSE: This prospective study was undertaken to evaluate the diagnostic accuracy of the Synovasure™ α-defensin lateral flow assay to detect or exclude infection and to compare it to the sensitivity and specificity of other diagnostic criteria according to the International Consensus Group on Periprosthetic Joint Infection (PJI). METHODS: All patients who have undergone revision total knee arthroplasty (TKA) from September 2015 to July 2016 were included: 16 chronic (more than 3 months after performing arthroplasty) infections and 35 aseptic joints were identified. The diagnostic performance of single test was assessed by receiver operating characteristic (ROC) curve analyses. The sensitivity and specificity were calculated for each of the cut-off values and the area under the curve (AUC) was also calculated. RESULTS: The median synovial fluid (SF) leukocyte count, as well as the neutrophil percentage, was significantly higher in patients with PJI than in those with aseptic failure (p < 0.001). The sensitivity of α-defensin was 87.5% (95%; CI 74.6-94.7), the specificity was 97.1% (95% CI 86.9-99.7), the positive predictive value 93.3% (95% CI 81.8-98.1), and negative predictive value was 94.4% (95% CI 83.2-98.6). The results in terms of sensitivity and negative predictive value were greater than those of the other tests (cultures, synovial cell count, erythrocyte sedimentation rate, and C-reactive protein). The diagnostic accuracy of α-defensin, with an area under the curve of 0.92, was found to be higher than all the minor criteria for PJI. CONCLUSIONS: In this study, the α-defensin lateral flow test was found to have the highest performance of all tests studied to identify PJI. Synovasure™ holds the potential to be included in the daily clinical practice. LEVEL OF EVIDENCE: Level I diagnostic study.

Tailoring Strain and Morphology of Core-Shell SiGe Nanowires by Low-Temperature Ge Condensation.

Selective oxidation of the silicon element of silicon germanium (SiGe) alloys during thermal oxidation is a very important and technologically relevant mechanism used to fabricate a variety of microelectronic devices. We develop here a simple integrative approach involving vapor-liquid-solid (VLS) growth followed by selective oxidation steps to the construction of core-shell nanowires and higher-level ordered systems with scalable configurations. We examine the selective oxidation/condensation process under nonequilibrium conditions that gives rise to spontaneous formation of core-shell structures by germanium condensation. We contrast this strategy that uses reaction-diffusion-segregation mechanisms to produce coherently strained structures with highly configurable geometry and abrupt interfaces with growth-based processes which lead to low strained systems with nonuniform composition, three-dimensional morphology, and broad core-shell interface. We specially focus on SiGe core-shell nanowires and demonstrate that they can have up to 70% Ge-rich shell and 2% homogeneous strain with core diameter as small as 14 nm. Key elements of the building process associated with this approach are identified with regard to existing theoretical models. Moreover, starting from results of ab initio calculations, we discuss the electronic structure of these novel nanostructures as well as their wide potential for advanced device applications.

Crystal Phase Effects in Si Nanowire Polytypes and Their Homojunctions.

Recent experimental investigations have confirmed the possibility to synthesize and exploit polytypism in group IV nanowires. Driven by this promising evidence, we use first-principles methods based on density functional theory and many-body perturbation theory to investigate the electronic and optical properties of hexagonal-diamond and cubic-diamond Si NWs as well as their homojunctions. We show that hexagonal-diamond NWs are characterized by a more pronounced quantum confinement effect than cubic-diamond NWs. Furthermore, they absorb more light in the visible region with respect to cubic-diamond ones and, for most of the studied diameters, they are direct band gap materials. The study of the homojunctions reveals that the diameter has a crucial effect on the band alignment at the interface. In particular, at small diameters the band-offset is type-I whereas at experimentally relevant sizes the offset turns up to be of type-II. These findings highlight intriguing possibilities to modulate electron and hole separations as well as electronic and optical properties by simply modifying the crystal phase and the size of the junction.

Laparoscopic treatment of adrenal masses in children: Report of two cases and review of literature.

Laparoscopic adrenalectomy has become a common alternative to open surgery for the resection of adrenal lesions in adults: The advantages are to provide better exposure of the adrenal gland, diminish soft tissue dissection, decrease morbidity and postoperative pain; however, reporting on the laparoscopic adrenalectomy in paediatric patients has been limited. We present two cases of laparoscopic adrenalectomy performed at our institution in two children, for left adrenal neuroblastoma in a first patient with opsomyoclonus syndrome, and for a right incidentaloma in the second case. According to recent literature, our experience has demonstrated that the laparoscopic adrenalectomy is a feasible procedure in children with small, well-circumscribed adrenal masses: It can be used a safety to treat suspected benign and malignant adrenal masses in children, with minimal morbidity and short hospital stay. The lateral trans-peritoneal approach offers optimal visualisation and good outcomes in terms of minimal discomfort, rapid recovery and excellent cosmesis. However, in the paediatric field, the number of patients is limited, making the learning curve longer.

Shell-Thickness Controlled Semiconductor-Metal Transition in Si-SiC Core-Shell Nanowires.

We study Si-SiC core-shell nanowires by means of electronic structure first-principles calculations. We show that the strain induced by the growth of a lattice-mismatched SiC shell can drive a semiconductor-metal transition, which in the case of ultrathin Si cores is already observed for shells of more than one monolayer. Core-shell nanowires with thicker cores, however, remain semiconducting even when four SiC monolayers are grown, paving the way to versatile, biocompatible nanowire-based sensors.

NMDA blockade inhibits experience-dependent modification of anterior thalamic head direction cells.

Head Direction (HD) cells of the rodent Papez circuit are thought to reflect the spatial orientation of the animal. Because NMDA transmission is important for spatial behavior, we sought to determine the effects of NMDA blockade on the basic directional signal carried by HD cells and on experience-dependent modification of this system. In Experiment 1, HD cells were recorded from the anterior dorsal thalamus in female Long-Evans rats while they foraged in a familiar enclosure following administration of the NMDA antagonist CPP or saline. While the drug produced a significant decrease in peak firing rates, it failed to affect the overall directional specificity and landmark control of HD cells. Experiment 2 took place over 2 days and assessed whether the NMDA antagonist would interfere with the stabilization of the HD network in a novel environment. On Day 1 the animal was administered CPP or saline and placed in a novel enclosure to allow the stabilization of the HD signal relative to the new environmental landmarks. On Day 2 the animal was returned to the formerly novel enclosure to determine if the enclosure specific direction-dependent activity established on Day 1 was maintained. In contrast to HD cells from control animals, cells from animals receiving CPP during the initial exposure to the novel enclosure did not maintain the same direction-dependent activity relative to the enclosure in the subsequent drug-free exposure. These findings demonstrate that plasticity in the HD system is dependent on NMDA transmission similar to many other forms of spatial learning.

Coherent ultrafast charge transfer in an organic photovoltaic blend.

Blends of conjugated polymers and fullerene derivatives are prototype systems for organic photovoltaic devices. The primary charge-generation mechanism involves a light-induced ultrafast electron transfer from the light-absorbing and electron-donating polymer to the fullerene electron acceptor. Here, we elucidate the initial quantum dynamics of this process. Experimentally, we observed coherent vibrational motion of the fullerene moiety after impulsive optical excitation of the polymer donor. Comparison with first-principle theoretical simulations evidences coherent electron transfer between donor and acceptor and oscillations of the transferred charge with a 25-femtosecond period matching that of the observed vibrational modes. Our results show that coherent vibronic coupling between electronic and nuclear degrees of freedom is of key importance in triggering charge delocalization and transfer in a noncovalently bound reference system.

First-pass perfusion of non-small-cell lung cancer (NSCLC) with 64-detector-row CT: a study of technique repeatability and intra- and interobserver variability.

PURPOSE: This study was done to prospectively assess the repeatability and intra- and interobserver variability of first-pass perfusion with 64-detector-row computed tomography (CT) in non-small-cell lung cancer (NSCLC) with a maximum diameter of up to 8 cm. MATERIALS AND METHODS: Twelve patients with NSCLC underwent 64-detector-row first-pass CT perfusion (CTP) of the whole tumour. Two different techniques were used according to lesion size (cine mode; sequential mode). After 24 h, each study was repeated to assess repeatability. Lesion blood volume (BV), blood flow (BF), mean transit time (MTT) and peak enhancement intensity (PEI) were automatically calculated by two chest radiologists in two different reading sessions. Intra- and interobserver variability was also assessed. RESULTS: The first-pass CTP technique was repeatable and precise with within-subject coefficient of variation (WCV) of 9.3, 16.4, 11.2 and 14.9 %, respectively, for BV, BF, MTT and PEI. High intra- and interobserver agreement was demonstrated for each perfusion parameter, with Cronbach's α coefficients and intraclass correlation coefficients ranging from 0.99 to 1. Precision of measurements was slightly better for intraobserver analysis with WCV ranging between 1.05 and 3.03 %. CONCLUSIONS: Non-small-cell lung cancer first-pass perfusion performed with 64-detector-row CT showed good repeatability and high intra- and interobserver agreement for all perfusion parameters and may be considered a reliable and robust tool for assessing tumour vascularisation.

Carbon nanotube electrodes in organic transistors.

The scope of this Minireview is to provide an overview of the recent progress on carbon nanotube electrodes applied to organic thin film transistors. After an introduction on the general aspects of the charge injection processes at various electrode-semiconductor interfaces, we discuss the great potential of carbon nanotube electrodes for organic thin film transistors and the recent achievements in the field.