Proximal ulna comminuted fractures: Fixation using a double-plating technique

SummaryIntroductionComminuted fractures of the proximal ulna are severe injuries often associated with bone and ligament injuries of the elbow joint (Monteggia lesion, radial head fractures, dislocation of the elbow). The treatment of these fractures is very demanding and the functional results often fairly mediocre due to associated injuries. Based on a single-center retrospective study, we report the results of the treatment of these fractures fixed using a double-plate technique. The aim was to evaluate the feasibility and reliability of this fixation mode and to compare it with other fractures series using a single plate fixation (in terms of bone union, elbow joint function, and complications stemming from the plates).Patients and methodsEighteen patients sustained a comminuted proximal ulna fracture between 2002 and 2006. The fractures were associated in five cases with a Monteggia type lesion, in two cases with elbow dislocation, and in four cases with a Mason 3 radial head fracture. Four patients had an open fracture. These comminuted ulna fractures included nine Mayo Clinic IIIB fractures. Bone fixation was performed with two third-cylinder tubular plates, one plate on each side of the proximal ulna. This allows more versatile solutions for screw insertion. Functional assessment (according to Broberg and Morrey) and radiological evaluation (bone healing) were provided at 6 months and at the longest follow-up by an independent surgeon.ResultsSixteen of 18 patients achieved bone union. No septic complications occurred and no hardware removal was required on patient request. In 67% of the cases, the Morrey score indicated excellent or good results with a mean score of 82.DiscussionThere are no reports in the literature on the technical point of fixation concerning complex fractures of the ulna. Two plates mean the possibility of twice the number of screw insertions for epiphyseal reconstruction . This fixation remains easy to perform and provides stable anatomic reconstruction of the ulna.Level of evidenceLevel IV. Retrospective study

Strong excitons in novel two-dimensional crystals: Silicane and germanane

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Quasiparticle interfacial level alignment of highly hybridized frontier levels: H2_2O on TiO2_2(110)

Knowledge of the frontier levels' alignment prior to photo-irradiation is necessary to achieve a complete quantitative description of H$_2$O photocatalysis on TiO$_2$(110). Although H$_2$O on rutile TiO$_2$(110) has been thoroughly studied both experimentally and theoretically, a quantitative value for the energy of the highest H$_2$O occupied levels is still lacking. For experiment, this is due to the H$_2$O levels being obscured by hybridization with TiO$_2$(110) levels in the difference spectra obtained via ultraviolet photoemission spectroscopy (UPS). For theory, this is due to inherent difficulties in properly describing many-body effects at the H$_2$O-TiO$_2$(110) interface. Using the projected density of states (DOS) from state-of-the-art quasiparticle (QP) $G_0W_0$, we disentangle the adsorbate and surface contributions to the complex UPS spectra of H$_2$O on TiO$_2$(110). We perform this separation as a function of H$_2$O coverage and dissociation on stoichiometric and reduced surfaces. Due to hybridization with the TiO$_2$(110) surface, the H$_2$O 3a$_1$ and 1b$_1$ levels are broadened into several peaks between 5 and 1 eV below the TiO$_2$(110) valence band maximum (VBM). These peaks have both intermolecular and interfacial bonding and antibonding character. We find the highest occupied levels of H$_2$O adsorbed intact and dissociated on stoichiometric TiO$_2$(110) are 1.1 and 0.9 eV below the VBM. We also find a similar energy of 1.1 eV for the highest occupied levels of H$_2$O when adsorbed dissociatively on a bridging O vacancy of the reduced surface. In both cases, these energies are significantly higher (by 0.6 to 2.6 eV) than those estimated from UPS difference spectra, which are inconclusive in this energy region. Finally, we apply self-consistent QP$GW$ (scQP$GW$1) to obtain the ionization potential of the H$_2$O-TiO$_2$(110) interface.Comment: 12 pages, 12 figures, 1 tabl

Élaboration et validation d'un modèle numérique reflétant le comportement mécanique du fémur sous chargement statique de compression

Pour tenter d'améliorer les techniques d'ostéosynthèse, afin de réduire les fractures du fémur, apparaît la nécessité de développer un modèle géométrique et numérique capable de caractériser le comportement mécanique du fémur humain. La présente étude propose des résultats expérimentaux issus de tests de compression sur fémurs frais équipés de jauges d'extensomètre. Le modèle géométrique est introduit dans un code de calculs par éléments finis pour représenter le champ des déformations à la surface de l'os. On montre la cohérence du modèle au plan qualitatif et des améliorations pouvant être apportées à ce modèle sont discutées

Three or four parts complex proximal humerus fractures: Hemiarthroplasty versus reverse prosthesis: A comparative study of 40 cases

SummaryIntroductionAs population ages, the number of fractures of the proximal humerus in still-active patients is increasing. For three- or four-parts displaced fractures in which replacement is indicated, hemiarthroplasty with tuberosity reattachment remains the reference treatment; this technique, however, can lead to catastrophic functional results due to nonunion or tuberosity migration. The present study compared short-term functional results for reverse prosthesis and hemiarthroplasty in complex fractures of the proximal humerus.HypothesisIn selected complex proximal humerus fractures, the reverse shoulder arthroplasties is a superior treatment option.Patients and methodsForty patients were treated by shoulder replacement for three- or four-part displaced fractures of the proximal humerus between 1996 and 2004. Twenty-one had a hemiarthroplasty and 19 were treated by reverse prosthesis. All patients of both groups were reviewed retrospectively by an independent observer. Joint amplitude and Constant score were measured; quality of life was assessed by DASH score. Standard X-ray assessment comprised frontal imaging in three rotation positions and Lamy's incidence.ResultsIn the hemiarthroplasty group, 17 patients, mean age 74 years (range: 49–95), were followed up for a mean 16.5 months (6–55). In the reverse prosthesis group, 16 patients, mean age 74 years (range: 58–84), were followed up for a mean 12.4 months (6–18). The reverse prosthesis group showed better results in terms of abduction (mean=91° versus 60°), anterior elevation (mean=97.5° versus 53.5°) and Constant score (mean=53 versus 39). Rotation was better in the hemiarthroplasty group (external rotation, 13.5° versus 9°; internal rotation, 54.6° versus 31°). DASH scores were identical in both groups. X-ray showed three abnormal tuberosity fixations in the hemiarthroplasty group and 15 glenoid notches in the reverse arthroplasty group.DiscussionIn three- or four-part displaced proximal humerus fracture, arthroplasty does not ensure recovery of pretrauma shoulder function. Management is therefore to be decided in terms of outcome predictability and rapid recovery of daily comfort for elderly patients. Hemiarthroplasty can provide good functional results, but depends on tuberosity union quality and this often necessitates a prolonged immobilization. Reverse prostheses provide reliable, rapid and predictable results in terms of abduction, anterior elevation and pain relief, but impaired rotation; this impacts quality of life and long-term implant durability (glenoid notching). Reverse prostheses should thus prove advantageous in the treatment of complex fractures of the proximal humerus if these two drawbacks can be resolved and at present seem indicated on condition that the patient is no younger than 70 years of age.Level of evidence: level IV; therapeutic study

Micro-indentation et couplage essais-calculs pour l’identification par méthode inverse du comportement mécanique non linéaire du cartilage fémoral humain

L’objectif principal de cette étude consiste à identifier différents modèles de comportement mécanique et les paramètres associés du cartilage coxo-fémoral dans le but de les utiliser dans des calculs prédictifs de type éléments finis. Les données expérimentales ont été obtenues à l’aide d’essais de micro-indentation instrumentés sur du cartilage fémoral non congelé prélevé et étudié dans la journée suite aux interventions chirurgicales de pose de prothèse de hanche totale ou intermédiaire. Un modèle éléments finis de ces essais a été couplé à une méthode inverse permettant d’identifier les paramètres matériau de trois modèles de comportement : élastique, hyperélastique et viscoélastique. Les résultats obtenus se corrèlent avec les résultats expérimentaux et sont en accord avec ceux de la littérature (cartilage congelé animal et humain). Les propriétés mécaniques du cartilage ont pu être correctement identifiées. Les meilleurs résultats ont été obtenus avec le modèle viscoélastique, néanmoins, il serait intéressant d’étendre notre étude en prenant en compte l’anisotropie et la structure multicouche du matériau

Excitons in two-dimensional sheets with honeycomb symmetry

In this paper, we present results concerning ab initio calculations of the optical properties of group IV two-dimensional sheets and compare them with the prediction of an analytical model for excitons in two dimensions, which we explicitly derive. This comparison helps to understand the physics at the basis of the strong many-body effects present in the optical spectra of this class of materials. Although it demonstrates the need of full ab initio calculations for an accurate description of the two-dimensional excitons, it validates, at the same time, this simple approach to estimate, through a density functional theory calculation of the two-dimensional electronic and optical properties, the binding energy and the radius of the excitons in this class of materials