The Role of Routine Preoperative Magnetic Resonance Imaging in Idiopathic Scoliosis: A Ten Years Review

Study DesignProspective study.PurposeTo determine the role of routine preoperative magnetic resonance imaging (MRI) to detect the incidence and risk factors for intraspinal anomalies in patients with idiopathic scoliosis.Overview of LiteratureThe incidence and risk factors for intraspinal anomalies in patients with idiopathic scoliosis are controversial, and the indications for preoperative MRI in these patients vary among centers.MethodsInformation on patients with idiopathic scoliosis who were surgical candidates over 10 years (age at presentation, sex, magnitude and apex of major curve, intraspinal anomalies detected by MRI, and neurological examination results) were recorded, the patients were grouped according to the intraspinal anomaly, and the data were analyzed.ResultsOf the 271 patients with idiopathic scoliosis, 27 had neuroaxial abnormalities (9.9%). Of these 27 patients, 14 (52%) underwent a neurosurgical procedure. Significant differences were observed in the frequency of early disease onset and male sex (p<0.05) between the group of patients with neuroaxial abnormalities on preoperative MRI and those who did not have a cord anomaly. No difference was detected in the magnitude or direction of the curve.ConclusionsNeuroaxial abnormalities in patients with idiopathic scoliosis and a normal neurological examination were highly frequent (9.9%). Missing these abnormalities before surgery could inflict catastrophic postoperative complications. The incidence of neuroaxial abnormalities was higher in male patients and in those with early onset disease. Thus, MRI is essential for all patients with idiopathic scoliosis who require medical intervention

Mesoscale Full Field Modeling of Stress Localization in Polycrystalline Materials Deforming by Both Slip and Twin

The aim of this PhD thesis is to incorporate deformation twinning in a fullield viscoplastic crystal plasticity model based on fast Fourier transform in an effort to gain insights into its role on strain localization. This work is motivated by current experimental evidences on the important role that dislocation reactions at the twin interface play on damage initiation in materials during plastic deformation. We began first by investigating the role of slip on stress localization. To this end, we simulated the effect of macroscopic deformation path, which dictates a macroscopic stress state, as well as pre-existing microstructure in typical ferritic steel, where plastic deformation is accommodated by slip mechanism. The results show that the width of localized strain rate regions near grain boundaries is a function of the deformation path, and there is a positive correlation between local Taylor factor and local stress field, which slightly depends on deformation path. For the incorporation of mechanical twinning in twinning-induced plasticity (TWIP) steel, we implemented predominant reorientation scheme (PTR) in vpFFT, which was implemented previously in the mean field VPSC. The comparison between experimental and simulation results indicates that twin volume fraction, final texture, and stress-strain curve were satisfactorily predicted. Despite that predominant twin reorientation scheme was not suitable to capture lamellar shape of twins in the microstructure, twin domains were predicted to form and grow at or close to grain boundary regions. Finally, we surveyed current literature, which aimed at capturing the characteristic lamellar morphology of twins. Literature review shows several unsuccessful crystal plasticity simulations in capturing twin nucleation and twin lamellar shape at measocale. These inabilities can be attributed to i) twin nucleation that is controlled by local atomistic configurations and stress fluctuations at the grain boundaries, and ii) the random or stochastic nature of twin nucleation, which has been proved by EBSD observation. Based on the EBSD observations, twin nucleation depends on both microstructural (e.g, grain size, dislocation density) and loading conditions ( e.g, stress, strain). Furthermore, the propensity, frequency, and morphology of deformation twins are different among grain with the same orientation and applied boundary conditions

Crystallographic analysis of intervariant boundaries in a lath martensite

In the current study, the crystallographic of intervariant boundary planes distribution in the lath martensite has been measured as a function of lattice misorientation and boundary plane orientation using five macroscopic parameters approach. The distribution revealed a relatively high anisotropy with a tendency for the lath interfaces to terminate on (110) planes. This results from the crystallographic constraints associated with the shear transformation rather than a low energy interface configuration. The lath martensite habit plane was determined to be mostly (110) or near (110). The relative populations of boundaries with [111] and [110] misorientations were greater than other high index misorientations, mostly characterised as (110) symmetric tilt and (110) twist boundary types, respectively

The Prevalence of Distal Junctional Kyphosis Following Posterior Instrumentation and Arthrodesis for Adolescent Idiopathic Scoliosis

Distal junctional kyphosis (DJK) is a radiographic finding in patients that undergo spinal instrumentation and fusion, since there is an abrupt transition between fixed and mobile spinal segments.The true incidence of DJK is variable in literature and seems that has a multifactorial etiology. A consecutive series of 130 patients (mean age 15.6 years) with Adolescent Idiopathic Scoliosis who underwent posterior spinal fusion and instrumentation were evaluated by analyzing coronal and sagittal angulation and balance measurements from standing radiographs obtained pre-operatively, within 6 weeks post-operation, at two years postoperative and at the latest follow-up. There was 35 male and 95 female. The mean time of follow-up was 36 months. The incidence of DJK at latest follow-up was 6.9% (9 patients). In DJK group ,distal junctional angle from pre-operative of -12.5 ̊ lordosis (-30 to 0) reached to -5.5 ̊ (P=0.015) at 6 weeks postoperation and to -1.4 ̊ (-20 to 12 ̊) (P=0.000) at 2 years follow-up,with mean of 12.1 ̊ kyphotic change (10-20 ̊). In non DJK group, distal junctional angle from pre-operative angle of -7.5 ̊ reached -8.1 ̊ at 2 years follow-up (P=0.43). The mean age of DJK group at surgery was 17 years and for non-DJK group was 15.4 years (P=0.022). Distal junctional kyphosis was less common in this study than previous reports and stabilized after two years. The magnitude of coronal cobb angles or multiplicity of coronal curves had no effect in developing DJK that may be prevented by incorporation of the first lordotic disc into the fusion construct

Proximal Junctional Kyphosis in Adolescent Idiopathic Scoliosis Following Segmental Posterior Spinal Instrumentation and Fusion; Minimum 2 Years Follow-Up

Background:To evaluate proximal junctional segment changes in Adolescent Idiopathic Scoliosis(AIS) the posterior spinal fusion and also instrumentation also and finding of probable risk factors, were all considered in this study.Methods: We retrospectively reviewed radiographs of 121 consecutive patients who underwent posterior spinal fusion for AIS from T3 or below, with a mean follow-   up of 32.8 months(range,24-83). All coronal and sagittal measurements including the proximal junctional kyphosis (PJK)angle recorded on standing anteroposterior and lateral radiographs preoperative, early postoperative and on follow-up radiographs.The data were analyzed using the Spss 10.0 software.Dependent(paired) samples student t-test was used for analysis between the groups Results: There was PJK angle above normal for the same junctional segment preoperatively in 13 patients (10.7%) and the incidence of the PJK postoperatively was   7.4% (9 patients, 7 female and 2 male), all detected until 2 years postoperation.The mean increase in the PJK angle from pre-operation until 6 weeks postoperation was 5.9° (range,0-13°)(P=0.02) and until 2 years post operation was 14.3° (range, 2- 16°)(p=0.000).The mean proximal junctional angle increased 1.6° until 2 years postoperation in non-PJK group(n=112).Conclusion: The prevalence of Proximal Junctional Kyphosis was low and a silent radiographic problem. In some cases is preventable with perfect pre-operative planning. There is no specific demographic or radiographic variables or instrumentation types associated with developing PJK

Dependence on mitochondrial respiration of malignant T cells reveals a new therapeutic target for angioimmunoblastic T-cell lymphoma

Abstract Cancer metabolic reprogramming has been recognized as one of the cancer hallmarks that promote cell proliferation, survival, as well as therapeutic resistance. Up-to-date regulation of metabolism in T-cell lymphoma is poorly understood. In particular, for human angioimmunoblastic T-cell lymphoma (AITL) the metabolic profile is not known. Metabolic intervention could help identify new treatment options for this cancer with very poor outcomes and no effective medication. Transcriptomic analysis of AITL tumor cells, identified that these cells use preferentially mitochondrial metabolism. By using our preclinical AITL mouse model, mimicking closely human AITL features, we confirmed that T follicular helper (Tfh) tumor cells exhibit a strong enrichment of mitochondrial metabolic signatures. Consistent with these results, disruption of mitochondrial metabolism using metformin or a mitochondrial complex I inhibitor such as IACS improved the survival of AITL lymphoma-bearing mice. Additionally, we confirmed a selective elimination of the malignant human AITL T cells in patient biopsies upon mitochondrial respiration inhibition. Moreover, we confirmed that diabetic patients suffering from T-cell lymphoma, treated with metformin survived longer as compared to patients receiving alternative treatments. Taking together, our findings suggest that targeting the mitochondrial metabolic pathway could be a clinically efficient approach to inhibit aggressive cancers such as peripheral T-cell lymphoma