Magnetic-Domain-Wall-Induced Electrical Polarization in Rare-Earth Iron Garnet Systems: A First-Principles Study.

First-principles methods are employed to understand the existence of magnetic-domain-wall-induced electric polarization observed in rare-earth iron garnets. In contrast with previous beliefs, it is found that the occurrence of such polarization neither requires the local magnetic moments of the rare-earth ions nor noncollinear magnetism. It can rather be understood as originating from a magnetoelectric effect arising from ferromagnetic interactions between octahedral and tetrahedral Fe ions at the domain walls, and the mechanism behind is found to be a symmetric exchange-striction mechanism.

Simulating the Radio-Frequency Dielectric Response of Relaxor Ferroelectrics: Combination of Coarse-Grained Hamiltonians and Kinetic Monte Carlo Simulations.

The radio-frequency dielectric response of the lead-free Ba(Zr_{0.5}Ti_{0.5})O_{3} relaxor ferroelectric is simulated using a coarse-grained Hamiltonian. This concept, taken from real-space renormalization group theories, allows us to depict the collective behavior of correlated local modes gathered in blocks. Free-energy barriers for their thermally activated collective hopping are deduced from this ab initio-based approach, and used as input data for kinetic Monte Carlo simulations. The resulting numerical scheme allows us to simulate the dielectric response for external field frequencies ranging from kHz up to a few tens of MHz for the first time and to demonstrate, e.g., that local (electric or elastic) random fields lead to the dielectric relaxation in the radio-frequency range that has been observed in relaxors.

Descriptive epidemiology of mechanical hip pathology in adults under 50 years of age. Prospective series of 292 cases: Clinical and radiological aspects and physiopathological review.

Two hundred and ninety-two patients, aged between 16 and 50 years and presenting with mechanical hip pathology, were included in a prospective multicenter study. The descriptive study concerned the clinical examination and analysis of three X-ray views (AP pelvic, Lequesne false profile and lateral axial view). The series comprised 62% males, mean age 35 years, with 53% right side and 22% bilateral involvement. Initial trauma was reported in 19% of cases, and direct familial history of hip pathology in 20%. Seventy percent of the patients played sports, 30% were high-level athletes, and 17% played combat sports. The physical impingement sign was present in 18% to 65% of cases depending on the variant studied. On imaging (n=241), 62% of hips showed osteoarthritis, with 25% at the evolved stage. In the series, as a whole, there was a 35% rate of dysplasia, 63% of impingement and 5% of normal X-ray results. The radiologic impingement aspects were 58% cam-type, 19% pincer-type and 23% mixed. Twenty-two percent of dysplasia cases showed signs of associated impingement. Pain experienced exclusively in flexion/internal rotation/adduction on examination showed little sensitivity (20%) but considerable specificity (86%) for the main diagnosis of impingement. The links between impingement and dysplasia are discussed, and an integrative schema of all risk factors is put forward.

Can we improve radiological analysis of osseous lesions in chronic anterior shoulder instability?

Osseous lesions of the glenoid cavity and humeral head are predictive of recurrence after Bankart arthroscopic procedures. The objective of this study was to analyze, for each glenoid and humeral defect plain x-ray criteria of the Instability Severity Index Score (ISIS), two aspects: inter- and intraobserver reliability of their qualitative and quantitative assessment and correlations between positive criteria and their quantitative measurement. Thirty-one medical files were retained for evaluation of the glenoid and 26 for humeral notch assessment. The yes or no response for the ISIS criterion was completed by its quantitative measurement using the Griffiths and Sugaya CT methods for the glenoid and the P/R index calculation on plain x-rays with internal rotation for the Hill-Sachs lesion. Three observers provided two consecutive readings for each criterion. The analysis of the glenoid radiological criterion of the ISIS seems sufficiently reproducible for daily practice. When the evaluation is positive, bone loss is greater than 15%, without a maximum value established. In this study, the analysis of the ISIS humeral notch criterion was not reproducible. It can be improved using the P/R index and should be completed by CT imaging.

Imaging data in a prospective series of adult hip pain in under-50 year-olds.

Two hundred and ninety-two patients under the age of 50 years, presenting with mechanical hip pain, were included in a prospective multicenter study. In 241 cases, imaging assessment included AP standing pelvic X-ray and Lequesne's false profile (LFP) and/or lateral neck (Ducroquet, Dunn or variant) hip X-ray. Cross-sectional arthroscan and/or arthro-MRI images were available in 81 cases. Exploration looked for acetabular and femoral head/neck dysplasia liable to induce cam or pincer anterior femoroacetabular impingement (AFAI), respectively. Labral and chondral lesions arise secondarily to hip osteoarthritis (HOA) and/or AFAI. Two-thirds of patients showed HOA. Only 6% showed a strictly normal aspect on imaging. More than half (52%) of cases had cam AFAI, half of these involving an osteophytic neck, associated in more than 90% of cases with large multifocal bone spurs of the head, neck and acetabula. These cases were considered ambiguous, due to the uncertainty as to the congenital nature of the cervico-cephalic dysmorphy; if they are excluded, only 23% of the series involved cam AFAI. Crossover sign on AP standing pelvic X-ray is the best assessment criterion for acetabular retroversion, the most frequent form of acetabular dysplasia underlying pincer AFAI, and should be explored for. Secondary neck lesions were visible only on lateral neck view in 42% of cases: this view should be included in standard radiologic work-up in under-50 year-olds. The alpha angle can be measured on this type of lateral view and on axial arthroscan and arthro-MR images; more than half of the cases in which it was pathological involved an osteophytic neck and thus a pseudo-cam effect.

[Arthro-C-scan analysis of rotator cuff tears healing after arthroscopic repair: analysis of predictive factors in a consecutive series of 167 arthroscopic repairs]. / Etude par arthroscanner de la cicatrisation tendineuse après réparation arthroscopique de la coiffe des rotateurs: analyse des facteurs predictifs à propos d'une série consécutive de 167 réparations.

PURPOSE OF THE STUDY: Arthroscopic repair of rotator cuff tears is a well described technique with good clinical results. The purpose of this work was to use the arthro-CT-scan to evaluate tendon healing after arthroscopic repair and search for epidemiological, anatomic and technical factors predictive of tendon healing. MATERIAL AND METHOD: This prospective consecutive series included 167 non-randomized shoulders. All patients underwent a preoperative assessment using the crude Constant score and a standard x-ray protocol to evaluate cuff status. Cuff repairs were all performed arthroscopically. The crude Constant score was used to follow patients. A control arthroscan was obtained in 148 patients. RESULTS: Mean patient age was 59 years, 46% men and 77% dominant side. Mean duration of symptoms before repair was nine months. The tears resulted from trauma in 28%, including 9% occupational accidents. The preoperative mean crude Constant score was 52.4 (range 15-77). An isolated tear of the supraspinatus was observed in 68%. Frontal retraction of the supraspinatus was distal in 74%. In 29 cases, reduction was difficult. The quality of the tendon was considered normal in 56 cases and non-anatomic repair was necessary in six. At last follow-up (19 months on average) the mean crude Constant score was 80 (range 49-95). Arthro-CT-scan was performed to control healing in 148 patients and revealed anatomic healing in 69, defective healing in 27, and repeated tears in 52 shoulders. Factors predictive of healing were: tear less than six months old, sedentary occupational activity, non-dominant side, young patient, female gender, isolated small non-retracted tear of the supraspinatus, normal appearance of an easily reduced tendon, and good bone quality. DISCUSSION: Time from tear to repair was long in this series. Tendon and muscle changes occurring after the injury could explain in part the healing failures. CONCLUSION: But this study confirmed good functional and anatomic results given by arthroscopic repair of rotator cuff tears.

Accuracy of CT arthrography in the assessment of tears of the rotator cuff.

CT arthrography and arthroscopy were used to assess tears of the rotator cuff in 259 shoulders. Tear size was determined in the frontal and sagittal planes according to the classification of the French Arthroscopy Society. CT arthrography had a sensitivity of 99% and a specificity of 100% for the diagnosis of tears of supraspinatus. For infraspinatus these figures were 97.44% and 99.52%, respectively and, for subscapularis, 64.71% and 98.17%. For lesions of the long head of the biceps, the sensitivity was 45.76% and the specificity was 99.57%. Our study showed an excellent correlation between CT arthrography and arthroscopy when assessing the extent of a rotator cuff tear. CT arthrography should, therefore, be an indispensable part of pre-operative assessment. It allows determination of whether a tear is reparable (retraction of the tendon and fatty degeneration of the corresponding muscle) and whether this is possible by arthroscopy (degree of tendon retraction and extension to subscapularis).

Microscopic view of a two-dimensional lattice-Gas ising system within the grand canonical ensemble

A reversible 2D critical transition is observed on the GaAs(001) surface and modeled as a lattice-gas Ising system. Without depositing any material, 2D GaAs islands spontaneously form. The order parameter, four critical exponents, and coupling energies are measured from scanning tunneling microscope images of the microscopic domain structure and correlation functions as a function of temperature and pressure. Unprecedented insight into the domain structure of a 2D Ising system through the critical point and a complete Hamiltonian for modeling the GaAs(001) surface are presented.

Magnetic resonance appearance of monoclonal gammopathies of unknown significance and multiple myeloma. The GRI Study Group.

STUDY DESIGN: A prospective multicenter study. OBJECTIVES: To evaluate the use of magnetic resonance imaging, in the differentiation between monoclonal gammopathies of unknown significance and multiple myeloma. SUMMARY OF BACKGROUND DATA: Although multiple myeloma has been studied extensively with magnetic resonance imaging, to the authors' knowledge, no study has evaluated the clinical interest of magnetic resonance imaging in the differentiation between monoclonal gammopathies of unknown significance and multiple myeloma. METHODS: The magnetic resonance examinations of the thoracolumbar spine in 24 patients with newly diagnosed monoclonal gammopathies of unknown significance were compared with those performed in 44 patients with newly diagnosed nontreated multiple myeloma. RESULTS: All findings on magnetic resonance examination performed in patients with monoclonal gammopathies of unknown significance were normal, whereas findings on 38 (86%) of the 44 magnetic resonance examinations performed in patients with multiple myeloma were abnormal. CONCLUSION: Magnetic resonance imaging can be considered as an additional diagnostic tool in differentiating between monoclonal gammopathies of unknown significance and multiple myeloma, which may be helpful when routine criteria are not sufficient. An abnormal finding on magnetic resonance examination in a patient with monoclonal gammopathies of unknown significance should suggest the diagnosis of multiple myeloma after other causes of marrow signal abnormalities are excluded. Magnetic resonance imaging also may be proposed in the long-term follow-up of monoclonal gammopathies of unknown significance when a new biologic or clinical event suggests the diagnosis of malignant monoclonal gammopathy.

Clinical evaluation of Duraflo II heparin treated extracorporeal circulation circuits (2nd version). The European Working Group on heparin coated extracorporeal circulation circuits.

OBJECTIVES: To evaluate whether the application of heparin treated circuits for elective coronary artery surgery improves postoperative recovery, a European multicenter randomised clinical trial was carried out. METHODS: In 11 European heart centers, 805 low-risk patients underwent cardiopulmonary bypass (CPB) with either an untreated circuit (n = 407) or an identical but heparin treated circuit (n = 398, Duraflo II). RESULTS: Significant differences were found among participating centers with respect to patient characteristics, blood handling procedures and postoperative care. The use of heparin treated circuits revealed no overall changes in blood loss, blood use, time on ventilator, occurrence of adverse events, morbidity, mortality, and intensive care stay. These results did not change after adjustment for centers and (other) prognostic factors as analysed with logistic regression. In both groups no clinical or technical (patient or device related) side effects were reported. Because female gender and aortic cross clamp time appeared as prognostic factors in the logistic regression analysis, a subgroup analysis with these variables was performed. In a subpopulation of females (n = 99), those receiving heparin treated circuits needed less blood products, had a lower incidence of rhythm disturbances and were extubated earlier than controls. In another subgroup of patients with aortic cross clamp time exceeding 60 min (n = 197), the amount of patients requiring prolonged intensive care treatment (> 24 h) was significantly lower when they received heparin treated circuits versus controls. CONCLUSION: These findings suggest that improved recovery can be expected with heparin treated circuits in specific higher risk patient populations (e.g. females) and when prolonged aortic cross clamp time is anticipated. Further investigations are recommended to analyses the clinical benefit of heparin treated circuits in studies with patients in different well defined risk categories and under better standardised circumstances.

-Arthrography of the hip-. / Arthrographie de hanche.

Painful hip with normal X-rays (including false-lateral view of both hips) is the main indication for hip arthrography, searching for focal chondropathy. In the presence of moderate hip degenerative arthritis contrasting with increasing disability, a labrum lesion must be investigated. Such lesions are of two kinds, mainly degenerative (of the superior labrum) or post-traumatic (of the posterior labrum). Arthrography allows the diagnosis of cystic changes located in the acetabulum. It also allows the diagnosis and evaluation of the extent of synovial osteochondromatosis or villonodular synovitis. In three indications, computed tomographies must be added to plain arthrography: posterior labrum lesions, osteochondromatosis (looking for foreign bodies in the acetabular fossa) and cystic changes in the acetabulum (with density measurements). In all cases, a complete conventional radiological assessment must be available. Strict asepsis must be ensured. When osteochondromatosis is suspected, evaluation of articular capacity must be systematic.

Magnetic resonance imaging of the spine in plasma cell dyscrasias. A review.

This review of recent data on the techniques and results of spinal magnetic resonance imaging in plasma cell dyscrasias provides a basis for selecting those patients who are most likely to benefit from this investigation. Sagittal images should be obtained using T1-weighted spin-echo and T2-weighted gradient-echo sequences. Epiduritis is best detected on sagittal or axial images acquired after gadolinium injection using T1-weighted spin-echo or phase-opposed gradient-echo sequences. Among patients with symptomatic multiple myeloma, 80% have abnormal magnetic resonance images of the lower spine due to plasma cell infiltration and this proportion increases with the stage in the Durie and Salmon staging system. Bone marrow signal abnormalities can be focal, diffuse and homogeneous, or diffuse and variegated. Vertebral fractures due to spinal infiltration or osteoporosis are seen in 48% of cases and spinal canal narrowing with impingement of bone tumors or epiduritis on nervous structures in 20%. The response to chemotherapy as evaluated based on conventional criteria is fairly well correlated with changes in magnetic resonance imaging findings. Among asymptomatic multiple myeloma patients with normal roentgenograms, 50% have tumor-related abnormalities on magnetic resonance images of the lower spine, which are associated with an increased likelihood of rapid progression to symptomatic disease. Similarly, one third of patients with an apparently solitary plasmacytoma of bone have evidence of other plasma cell tumors on magnetic resonance images of the lower spine, and this finding is associated with persistence of monoclonal component production after irradiation therapy, which may be of adverse prognostic significance. Patients with monoclonal gammopathies of uncertain significance have no evidence of tumorous lesions on magnetic resonance images of the lower spine.

Monitoring thrombin generation with prothrombin fragment 1.2 assay during cardiopulmonary bypass surgery.

UNLABELLED: Despite high plasma levels of heparin during cardiopulmonary bypass surgery, activation of the coagulation system has been reported. We hypothesize that the coagulation system activity most appropriately could be assessed by molecular markers of thrombin generation. The aim of the present study was to describe the changes in thrombin generation during CPB, using prothrombin fragment F1 + 2 (F1.2) as an indicator and evaluate different blood sampling regimens for interpretation of the F1.2 measurements. Twenty patients, operated under extracorporeal circulation with coronary artery bypass grafting (CABG), comprised the study material. The heparin levels were maintained above 2.5 IU/ml throughout the bypass procedure and the functional AT-III level was kept above 0.5 U/ml. Despite of this anticipated inactivation of the coagulation system, the concentrations of F1.2 and FpA increased throughout CPB, particularly after release of the aortic crossclamp. F1.2 and FpA correlated significantly (R = 0.69). No statistically significant correlation was found between F1.2 formation rate and age, bodyweight, baseline ACT, ACT after 200 IU heparin/kg, average heparin concentration during CPB or average AT-III level during CPB. CONCLUSIONS: Thrombin formation seems to be a continuous process during CPB despite adequate heparinization. The pattern of thrombin generation can be assessed most appropriately in terms of F1.2 generation rate. Extraordinary high levels of F1.2 were seen after release of the aortic crossclamp, indicating that the periods before and after aortic crossclamping should be evaluated separately.

Acute vertebral collapse: CT findings in benign and malignant nontraumatic cases.

PURPOSE: The value of computed tomography (CT) for differentiating benign from malignant causes of nontraumatic acute vertebral collapse (AVC) (associated with pain of less than 3 months duration) was evaluated. MATERIALS AND METHODS: The CT findings of 34 benign (osteoporotic) and 32 malignant (metastatic or myelomatous) nontraumatic AVCs were compared. RESULTS: The following CT findings were significantly more frequent in benign AVCs: cortical fractures of the vertebral body without cortical bone destruction, retropulsion of a bone fragment of the posterior cortex of the vertebral body into the spinal canal, fracture lines within the cancellous bone of the vertebral body, an intravertebral vacuum phenomenon, and a thin diffuse paraspinal soft-tissue mass (PSTM). The following CT findings were significantly more frequent in malignant AVCs: destruction of the anterolateral or posterior cortical bone of the vertebral body, destruction of the cancellous bone of the vertebral body, destruction of a vertebral pedicle, a focal PSTM, and an epidural mass. CONCLUSION: CT can help distinguish benign from malignant causes of nontraumatic AVC.

[The labrum acetabulare]. / Le bourrelet cotyloïdien.

There are two types of labrum acetabulare lesions. The first, posterior in the labrum, must be evocated when hip pain occurs secondary after slight traumatisms. The second, much more frequent, superior in the labrum, is responsible for important hip pain contrasting with slight X-ray abnormalities of the pelvis, except for frequent acetabular dysplasia. Not only arthrography, but also coronal arthro-tomography and CT-arthrography are necessary for the diagnosis of labrum acetabulare lesions.

Current status of musculoskeletal interventional radiology.

This article details many of the latest developments in the field of musculoskeletal interventional radiology. Some of the topics included in this discussion are percutaneous biopsy of musculoskeletal lesions, automated percutaneous discectomy, facet joint arthrography, percutaneous vertebroplasty, and percutaneous drainage of abscesses.

[Value of magnetic resonance imaging in myeloma]. / Intérêt de l'imagerie par résonance magnétique dans le myélome.

Magnetic resonance imagery (MRI) of the spinal cord has become a standard method and its diagnostic and prognostic power in multiple myeloma has been widely demonstrated. Before treatment, MRI reveals two basic types of abnormalities yielding focal and diffuse signals. Focal lesions are seen as localized hyposignals on spin echo T1 sequences (SET1) and are enhanced by injection of gadolinium and changed to hypersignals in T2 weighted sequences. These images identify nodular tumoural masses. Diffuse lesions are seen most often as homogeneous SET1 images with an intensity similar to the vertebral body. This type of image is not specific of tumoural infiltration and can be benign in nature. The second type of diffuse signal is often called a "salt and pepper" image due to the juxtaposition of multiple hyposignals (suspected tumoural tissue) and hypersignals (fat tissue). We have observed this type of image in 27% of our series of multiple myelomas. The capacity of MRI to detect myelomas located in bone tissue is much greater than conventional radiography of the spine and is particularly sensitive to expansive tumoural lesions threatening the cord. MRI should always be performed as part of the initial work-up even in the absence of clinical signs. There is a good correlation between MRI of focal tumours and the biological response to treatment, although other biological markers may be more precise and easier to obtain. MRI can also be used to differentiate between benign monoclonal gammapathy and multiple myeloma, particularly in cases where there is a disagreement between the clinical and laboratory data. We have also studied MRI in solitary plasmacytomas of the spine.

[Topography of tumoral and pseudotumoral lesions of the proximal femur]. / Essai de cartographie des lésions tumorales et pseudo-tumorales de l'extrémité supérieure du fémur.

This study of the topographic distribution of tumoral and pseudotumoral lesions of the proximal femur shows that certain lesions have a preferential site, for example osteoid osteoma affects the internal cortex of the neck and diaphysis or the intertrochanteric zone; chondroblastoma occurs in zones of epiphyseal ossification of the head; fibrous dysplasia affects the femoral neck, while sparing the epiphyseal femoral head and trochanters. The island of osteosclerosis is situated, at least partially, in the support fan; so-called physiological cysts are situated on or above the midline of the neck and below the basicapital line. Osteolytic or mixed metastases preferentially involve Ward's triangle in the femoral neck and the intertrochanteric region. The sites of these lesions therefore appears to depend on the bony architecture which, in turn, is dependent on mechanical stresses. However, this purely morphological study fails to demonstrate whether mechanical stresses influence the development of these lesions.

[Radiological anatomy of the hip in adults]. / Radio-anatomie de la hanche de l'adulte.

The authors review the embryology of the hip joint with its pathological implications. The radioanatomy is presented in an elementary fashion, with the appearance of each component as seen on the various imaging techniques (conventional X-rays, CT scan, MRI). The authors also describe the views used in conventional radiology and the invasive techniques of arthrography and arthroscanning.