3D reconstruction of ribcage geometry from biplanar radiographs using a statistical parametric model approach

Rib cage 3D reconstruction is an important prerequisite for thoracic spine modelling, particularly for studies of the deformed thorax in adolescent idiopathic scoliosis. This study proposes a new method for rib cage 3D reconstruction from biplanar radiographs, using a statistical parametric model approach. Simplified parametric models were defined at the hierarchical levels of rib cage surface, rib midline and rib surface, and applied on a database of 86 trunks. The resulting parameter database served to statistical models learning which were used to quickly provide a first estimate of the reconstruction from identifications on both radiographs. This solution was then refined by manual adjustments in order to improve the matching between model and image. Accuracy was assessed by comparison with 29 rib cages from CT scans in terms of geometrical parameter differences and in terms of line-to-line error distance between the rib midlines. Intra and inter-observer reproducibility were determined regarding 20 scoliotic patients. The first estimate (mean reconstruction time of 2’30) was sufficient to extract the main rib cage global parameters with a 95% confidence interval lower than 7%, 8%, 2% and 4° for rib cage volume, antero-posterior and lateral maximal diameters and maximal rib hump, respectively. The mean error distance was 5.4 mm (max 35mm) down to 3.6 mm (max 24 mm) after the manual adjustment step (+3’30). The proposed method will improve developments of rib cage finite element modeling and evaluation of clinical outcomes.This work was funded by Paris Tech BiomecAM chair on subject specific muscular skeletal modeling, and we express our acknowledgments to the chair founders: Cotrel foundation, Société générale, Protéor Company and COVEA consortium. We extend your acknowledgements to Alina Badina for medical imaging data, Alexandre Journé for his advices, and Thomas Joubert for his technical support

MRI of acute osteomyelitis in long bones of children: pathophysiology study.

INTRODUCTION: The classic pathophysiology of acute osteomyelitis in children described by Trueta has a metaphyseal infection as the starting point. This hypothesis was recently brought into question by Labbé's study, which suggested a periosteal origin. Thus, we wanted to study this disease's pathophysiology through early MRI examinations and to look for prognostic factors based on abnormal findings. MATERIAL AND METHODS: This was a prospective, multicentre study that included cases of long bone osteomyelitis in children who underwent an MRI examination within 7days of the start of symptoms and within 24hours of the initiation of antibiotic therapy. We also collected clinical, laboratory and treatment-related data. RESULTS: Twenty patients were included, including one with a bifocal condition. The lower limb was involved in most cases (19/21). Staphylococcus aureus was found most frequently. Metaphyseal involvement was present in all cases. No isolated periosteal involvement was found in any of the cases. No prognostic factors were identified based on the various abnormal findings on MRI. CONCLUSION: Our study supports the metaphyseal origin of acute osteomyelitis in children. LEVEL OF EVIDENCE:II

EOS analysis of lower extremity segmental torsion in children and young adults

Introduction Lower limb torsion varies substantially among healthy children during growth. Values reported in the literature to date have been obtained using semi-quantitative clinical or 2D measurement methods. Quantitative 3D measurement would help determine the physiological range of lower limb torsion. Low-dose stereoradiography with 3D reconstruction provides a good alternative. Its use increases in pediatrics because of radiation minimization. Previous studies have shown accurate and reproducible results of lower limbs reconstruction in adults and children but the torsional parameters haven’t been measured yet. The present study reports the values of lower limb segmental torsion and its course during growth in a cohort of healthy children and young adults using the EOS low-dose biplanar X-ray. Hypothesis EOS 3D reconstruction is an accurate and reproducible method to measure the torsional parameters in children. Materials and methods Femoral torsion (FT) and tibial torsion (TT) were studied on 114 volunteers (228 lower limbs) from 6 to 30 years of age divided by age into 5 groups. The EOS™ acquisitions were obtained in subjects standing with their feet offset. Results Mean FT decreased during growth, passing from 21.6° to 18°, whereas mean TT increased from 26.8° to 34.7°. There was a statistically significant difference between the 2 extreme age groups, but no difference was found between any other age groups. The ICC for intra-observer reproducibility was 0.96 and 0.95 for FT and TT for the first operator, and 0.79 and 0.83 for the second operator respectively. The ICC for inter-observer reproducibility was 0.84 and 0.82 respectively. Discussion The course of lower limb segmental torsion observed was consistent with literature reports based upon clinical and 2D measurements. 3D reconstruction of EOS low-dose biplanar imaging appears to be a safe and reliable tool for lower limbs measurements, especially for investigating lower limb segmental torsion in children and adults

Titanium vs cobalt chromium: what is the best rod material to enhance adolescent idiopathic scoliosis correction with sublaminar bands?

PURPOSE: Cobalt chromium (CoCr) rods have recently gained popularity in adolescent idiopathic scoliosis (AIS) surgical treatment, replacing titanium (Ti) rods, with promising frontal correction rates in all-screw constructs. Posteromedial translation has been shown to emphasize thoracic sagittal correction, but the influence of rod material in this correction technique has never been investigated. The aim of this study was to compare the postoperative correction between Ti and CoCr rods for the treatment of thoracic AIS using posteromedial translation technique. METHODS: 70 patients operated for thoracic (Lenke 1 or 2) AIS, in 2 institutions, between 2010 and 2013, were included. All patients underwent posterior fusion with hybrid constructs using posteromedial translation technique. The only difference between groups in the surgical procedure was the rod material (Ti or CoCr rods). Radiological measurements were compared preoperatively, postoperatively and at last follow-up (minimum 2 years). RESULTS: Preoperatively, groups were similar in terms of coronal and sagittal parameters. Postoperatively, no significant difference was observed between Ti and CoCr regarding frontal corrections, even when the preoperative flexibility of the curves was taken into account (p = 0.13). CoCr rods allowed greater restoration of T4T12 thoracic kyphosis, which remained stable over time (p = 0.01). Most common postoperative complication was proximal junctional kyphosis (n = 4). However, no significant difference was found between groups regarding postoperative complications rate. CONCLUSION: CoCr and Ti rods both provide significant and stable frontal correction in AIS treated with posteromedial translation technique using hybrid constructs. However, CoCr might be considered to emphasize sagittal correction in hypokyphotic patients

Correction of hypokyphosis in thoracic adolescent idiopathic scoliosis using sublaminar bands: a 3D multicenter study

INTRODUCTION: The comparison of implants and correction methods remain controversial in AIS. Excellent frontal and axial correction rates have been reported with all-screw constructs, but at the expense of sagittal alignment, which has a tendency to flatten postoperatively. Posteromedial translation using hybrid constructs seems to preserve and improve thoracic kyphosis (TK), but no series exist to date with a significant number of hypokyphotic patients. In addition, the measures of TK in 2D are often wrong in severe AIS due to axial rotation. The goals of this study were therefore to analyze the 3D radiological outcomes of a group of hypokyphotic AIS patients operated with sublaminar bands. METHODS: 35 consecutive AIS hypokyphotic patients (T4T12 <15°) operated in three centers were included, with a minimum 2-year follow-up. The surgical technique was similar in all centers, associating lumbar pedicle screws and thoracic sublaminar bands. Posteromedial translation was the main correction technique, and no patient underwent prior anterior release. 3D spinal reconstructions were performed preoperatively, postoperatively and at the latest follow-up by an independent observer using SterEOS (EOS imaging, Paris, France), and 2D and 3D measurements were compared. In addition, a new 3D parameter [sagittal shift of the apical vertebra (SSAV)], reflecting the translation of the apical vertebra of the main curve in the patient sagittal plane, was described and reported. RESULTS: The age of the cohort was 16 years and the number of sublaminar bands used for correction averaged 6 (±1.5). T1T12 and T4T12 sagittal Cobb angles appeared to be overestimated on 2D postoperatively (3°, p = 0.002 and 4°, p < 0.001, respectively). Hence, only 3D measurements were kept for the quantitative analysis of the postoperative correction. T4T12 TK significantly increased after surgery (average 8° ± 7°, p < 0.001), but 11 patients (31.4%) remained hypokyphotic. Seven out of the eight patients (87.5%) who presented a thoracic lordosis (i.e., T4T12 <0°) preoperatively were corrected after surgery (mean gain 16° ± 4°). A posterior shift (positive SSAV) of the apical vertebra was reported in 24 patients (68.6%). In this subgroup, the mean SSAV was +2 cm (±1). Good correlation was found between the SSAV and the postoperative change in 3D T4T12 kyphosis (r = 0.62). CONCLUSION: Measures in 2D tend to overestimate sagittal alignment and are not sufficient to evaluate postoperative correction. SSAV is a new 3D parameter reflecting the TK change that needs to be further investigated and used in the future. This series confirms that sublaminar bands should be considered in hypokyphotic patients, since thoracic sagittal alignment was restored in 68.6% of the cases

Evaluation of a patient-specific finite element model to simulate conservative treatment in adolescent idiopathic scoliosis

Study design: Retrospective validation study Objectives: To propose a method to evaluate, from a clinical standpoint, the ability of a finite element model (FEM) of the trunk to simulate orthotic correction of spinal deformity, and to apply it to validate a previously described FEM Summary of background data: Several FEMs of the scoliotic spine have been described in the literature. These models can prove useful in understanding the mechanisms of scoliosis progression and in optimizing its treatment, but their validation has often been lacking or incomplete. Methods: Three-dimensional geometries of ten patients before and during conservative treatment were reconstructed from bi-planar radiographs. The effect of bracing was simulated by modeling displacements induced by the brace pads. Simulated clinical indices (Cobb angle, T1-T12 and T4-T12 kyphosis, L1-L5 lordosis, apical vertebral rotation, torsion, rib hump) and vertebral orientations and positions were compared to those measured in the patients’ three-dimensional geometries. Results: Errors in clinical indices were of the same order of magnitude as the uncertainties due to 3D reconstruction; for instance, Cobb angle was simulated with a root mean square error of 5.7° and rib hump error was 6.4°. Vertebral orientation was simulated with a root mean square error of 4.8° and vertebral position with an error of 2.5 mm. Conclusions: The methodology proposed here allowed in-depth evaluation of subject-specific simulations, confirming that FEMs of the trunk have the potential to accurately simulate brace action. These promising results provide a basis for ongoing 3D model development, toward the design of more efficient orthoses.The authors are grateful to the ParisTech BiomecAM chair program on subject-specific musculoskeletal modelling for funding (with the support of Proteor, ParisTech and Yves Cotrel Foundations) and to EOS imaging for logistic support in data collection

Selective versus hyperselective posterior fusions in Lenke 5 adolescent idiopathic scoliosis: comparison of radiological and clinical outcomes

PURPOSE: Recent literature has reported that the ]progression risk of Lenke 5 adolescent idiopathic scoliosis (AIS) during adulthood had been underestimated. Surgery is, therefore, proposed more to young patients with progressive curves. However, choice of the approach and fusion levels remains controversial. The aim of this study was to analyze the influence of the length of posterior fusion on clinical and radiological outcomes in Lenke 5 AIS. METHODS: All Lenke 5 AIS operated between 2008 and 2012 were included with a minimum 2-year follow-up. Patients were divided into two groups according to the length of fusion. In the first group (selective), the upper instrumented level (UIV) was the upper end vertebra of the main structural curve and distally the fusion was extended to the stable and neutral vertebra, according to Lenke's classification. In the second group (hyperselective), shorter fusions were performed and the number of levels fused depended on the location of the apex of the curve (at maximum, 2 levels above and below, according to Hall's criteria). Apart from the fusion level selection, the surgical procedure was similar in both groups. Radiological outcomes and SRS-22 scores were reported. RESULTS: 78 patients were included (35 selective and 43 hyperselective). The number of levels fused was significantly higher in the first group (7.8 ± 3 vs 4.3 ± 0.6). None of the patients was fused to L4 in selective group. No correlation was found between length of fusion and complication rate. Eight patients had adding-on phenomenon among which 6 (75%) had initially undergone hyperselective fusions and had significantly higher postoperative lower instrumented vertebra (LIV) tilt. In the adding-on group, LIV was located above the last touching vertebra (LTV) in 62.5% of the cases and above the stable vertebra (SV) in 87.5%. Patients in the selective group reported a significantly lower score in the SRS function domain. CONCLUSION: Coronal alignment was restored in both groups. Hyperselective posterior fusions can be considered in Lenke 5 AIS, preserving one or two mobile segments, with similar clinical and radiological outcomes. However, selection of the LIV according to SV and LTV need to be accurately analyzed in order to avoid adding-on during follow-up

Analyse tridimensionnelle de la correction des scolioses idiopathiques de l'adolescent par translation postéromédiale

Idiopathic scoliosis is a tridimensional trunk deformity, affecting both the spine and the rib cage. Low dose EOS stereoradiography is designed to assess the patient specific 3D geometry of the skeleton in standing position. The goal of this work is to improve the quantitative analysis of postoperative results in a routine clinical use, and to integrate the rib cage morphological analysis. Tools, methods and necessary proocols were first developed and validated to allow such an evaluation. In particular, the reliability of 3D measurements in severe scoliosis and instrumented spine were assessed. The modelization method was then applied to a series of adolescents operated for thoracic idiopathic scoliosis using posteromedial translation. The first part of the analysis focused on the instrumented spine, and included a new reference axis to estimate patients' global balance. The second part of the work aimed to describe the postoperative change of the sagittal cervical alignement. Significant improvement was found, correlated with thoracic kyphosis restoration. Finally, biplanar stereoradiography allowed a descriptive analysis of the endo and exothoracic morphology in a cohort of 80 adolescents with idiopathic scoliosis. Correlations between quantitative spinal and thoracic parameters and pulmonary function tests were investigated. The method was used in order to characterize the postoperative thoracic changes. This study confirms the interest of having in routine clinical use a 3D evaluation of the spine and the rib cage in the quantitative analysis of idiopathic scoliosis postoperative results.La scoliose idiopathique est une déformation tridimensionnelle du tronc, affectant le rachis et la cage thoracique. La stéréoradiographie basse dose EOS permet une analyse personnalisée en 3D de la géométrie du squelette en position debout. L'objectif de cette thèse est d'améliorer l'évaluation quantitative en routine clinique des résultats chirurgicaux, et d'y intégrer l'étude de la morphologie de la cage thoracique. Dans un premier temps, les outils, méthodes et protocoles nécessaires à une telle évaluation ont été mis en place et validés. En particulier, l'incertitude des reconstructions des déformations sévères et des rachis instrumentés a été quantifiée pour la première fois. La méthode a ensuite été appliquée à une série d'adolescents opérés de scoliose thoracique idiopathique par translation postéromédiale. La première partie de l'analyse quantitative a porté sur le rachis instrumenté, en incluant un nouvel axe de référence pour apprécier l'équilibre. Les résultats ont permis d'évaluer la correction obtenue dans le plan axial par cette méthode. La seconde partie de l'étude a porté sur les modifications postopératoires observées au niveau du rachis cervical. Une amélioration de l'alignement sagittal de ce segment non instrumenté, corrélée à la restauration de la cyphose thoracique, a été mise en évidence. La stéréoradiographie a enfin permis de faire une analyse descriptive de la morphologie endo et exothoracique d'un groupe de 80 adolescents suivis pour scoliose thoracique idiopathique, et d'étudier les corrélations entre paramètres quantitatifs thoraciques et rachidiens et épreuves fonctionnelles respiratoires. La méthode de modélisation du thorax a finalement été appliquée pour caractériser les modifications postopératoires. Ces travaux ont ainsi confirmé l'intérêt de l'analyse 3D du rachis et du thorax dans l'évaluation en routine clinique des résultats chirurgicaux de scolioses idiopathiques

Epiphysiodèses des membres inférieurs pour inégalité de longueur (évaluation de la technique par vissage percutané en croix)

PARIS7-Xavier Bichat (751182101) / SudocSudocFranceF