SAM

Non-invasive assessment of human multifidus muscle stiffness using ultrasound shear wave elastography: A feasibility study

MOREAU, Baptiste — Fri, 01 Jan 2016 00:00:00 GMT

Non-invasive assessment of human multifidus muscle stiffness using ultrasound shear wave elastography: A feasibility study MOREAU, Baptiste; GAD, Hisham; SANDOZ, Baptiste; SKALLI, Wafa; LAPORTE, Sébastien; VERGARI, Claudio INTRODUCTION: There is a lack of numeric data for the mechanical characterization of spine muscles, especially in vivo data. The multifidus muscle is a major muscle for the stabilization of the spine and may be involved in the pathogenesis of chronic low back pain (LBP). Supersonic shear wave elastography (SWE) has not yet been used on back muscles. The purpose of this prospective study is to assess the feasibility of ultrasound SWE to measure the elastic modulus of lumbar multifidus muscle in a passive stretching posture and at rest with a repeatable and reproducible method. METHOD: A total of 10 asymptotic subjects (aged 25.5±2.2 years) participated, 4 females and 6 males. Three operators performed 6 measurements for each of the 2 postures on the right multifidus muscle at vertebral levels L2-L3 and L4-L5. Repeatability and reproducibility have been assessed according to ISO 5725 standard. RESULTS: Intra-class correlation coefficients (ICC) for intra- and inter observer reliability were rated as both excellent [ICC=0.99 and ICC=0.95, respectively]. Reproducibility was 11% at L2-L3 level and 19% at L4-L5. In the passive stretching posture, shear modulus was significantly higher than at rest (u<0.05). DISCUSSION: This preliminary work enabled to validate the feasibility of measuring the shear modulus of the multifidus muscle with SWE. This kind of measurement could be easily introduces into clinical routine like for the medical follow-up of chronic LBP or scoliosis treatments.

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

AUBERT, Benjamin — Wed, 01 Jan 2014 00:00:00 GMT

3D reconstruction of ribcage geometry from biplanar radiographs using a statistical parametric model approach AUBERT, Benjamin; ILHARREBORDE, Brice; COURVOISIER, Aurélien; SKALLI, Wafa; VERGARI, Claudio 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.

Quasi-automatic early detection of progressive idiopathic scoliosis from biplanar radiography: a preliminary validation

COURTOIS, Isabelle — Tue, 01 Jan 2019 00:00:00 GMT

Quasi-automatic early detection of progressive idiopathic scoliosis from biplanar radiography: a preliminary validation COURTOIS, Isabelle; EBERMEYER, Eric; ABELIN-GENEVOIS, Kariman; KIM, Youngwoo; LANGLAIS, Tristan; VIALLE, Raphaël; ASSI, Ayman; GHANEM, Ismat; DUBOUSSET, Jean; SKALLI, Wafa; GAJNY, Laurent; VERGARI, Claudio Purpose To validate the predictive power and reliability of a novel quasi-automatic method to calculate the severity index of adolescent idiopathic scoliosis (AIS). Methods Fifty-five AIS patients were prospectively included (Age: 10-15, Cobb: 16° ± 4°). Patients underwent low-dose biplanar x-rays and a novel fast method for 3D reconstruction of the spine was performed. They were followed until skeletal maturity (stable patients) or brace prescription (progressive patients). The severity index was calculated at the first exam, based on 3D parameters of the scoliotic curve, and it was compared with the patient’s final outcome (progressive or stable). Three operators have repeated the 3D reconstruction twice for a subset of 30 patients to assess reproducibility (through Cohen’s kappa and intraclass correlation coefficient). Results 85% of the patients were correctly classified as stable or progressive by the severity index, with a sensitivity of 92% and specificity of 74%. Substantial intra-operator agreement and good inter-operator agreement were observed, with 80% of the progressive patients correctly detected at the first exam. The novel severity index assessment took less than 4 minutes of operator time. Conclusions The fast and semi-automatic method for 3D reconstruction developed in this work allowed for a fast and reliable calculation of the severity index. The method is fast and user friendly. Once extensively validated, this severity index could allow very early initiation of conservative treatment for progressive patients, thus increasing treatment efficacy and therefore reducing the need for corrective surgery.

Quasi-automatic 3D reconstruction of the full spine from low-dose biplanar X-rays based on statistical inferences and image analysis

EBRAHIMI, Shahin — Mon, 01 Jan 2018 00:00:00 GMT

Quasi-automatic 3D reconstruction of the full spine from low-dose biplanar X-rays based on statistical inferences and image analysis EBRAHIMI, Shahin; SKALLI, Wafa; ANGELINI, Elsa D.; GAJNY, Laurent; VERGARI, Claudio Purpose: To design a quasi-automated three-dimensional reconstruction method of the spine from biplanar X-rays as the daily used method in clinical routine is based on manual adjustments of a trained operator and the reconstruction time is more than 10 minutes per patient. Methods: The proposed method of 3D reconstruction of the spine (C3-L5) relies first on a new manual input strategy designed to fit clinicians’ skills. Then, a parametric model of the spine is computed using statistical inferences, image analysis techniques and fast manual rigid registration. Results: An agreement study with the clinically used method on a cohort of 57 adolescent scoliotic subjects has shown that both methods have similar performance on vertebral body position and axial rotation (null bias in both cases and standard deviation of signed differences of 1mm and 3.5° around respectively). In average, the solution could be computed in less than 5 minutes of operator time, even for severe scoliosis. Conclusions: The proposed method allows fast and accurate 3D reconstruction of the spine for wide clinical applications and represents a significant step toward full automatization of 3D reconstruction of the spine. Moreover, it is to the best of our knowledge the first method including also the cervical spine.

Evaluation of a Patient-Specific Finite-Element Model to Simulate Conservative Treatment in Adolescent Idiopathic Scoliosis

RIBES, Gwenael — Thu, 01 Jan 2015 00:00:00 GMT

Evaluation of a Patient-Specific Finite-Element Model to Simulate Conservative Treatment in Adolescent Idiopathic Scoliosis RIBES, Gwenael; AUBERT, Benjamin; ADAM, Clayton; MILADI, Lotfi; ABELIN-GENEVOIS, Kariman; SKALLI, Wafa; ROUCH, Philippe; VERGARI, Claudio 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 (3D) geometries of 10 patients before and during conservative treatment were reconstructed from biplanar radiographs. The effect of bracing was simulated by modeling displacements induced by the brace pads. Simulated clinical indices (Cobb angle, T1eT12 and T4eT12 kyphosis, L1eL5 lordosis, apical vertebral rotation, torsion, rib hump) and vertebral orientations and positions were compared to those measured in the patients’ 3D 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 5.6 . 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.

Feasibility of sub-dermal soft tissue deformation assessment using B-mode ultrasound for pressure ulcer prevention

DORIDAM, Jennifer — Mon, 01 Jan 2018 00:00:00 GMT

Feasibility of sub-dermal soft tissue deformation assessment using B-mode ultrasound for pressure ulcer prevention DORIDAM, Jennifer; MACRON, Aurélien; VERNEY, A.; ROHAN, Pierre-Yves; PILLET, Helene; VERGARI, Claudio Pressure Ulcer (PU) prevention remains a main public health issue. The physio-pathology of this injury is not fully understood, and a satisfactory therapy is currently not available. Recently, several works suggested that mechanical strains are responsible of deformation-induced damage involved in the initiation of Deep Tissue Injury (DTI). A better assessment of the internal behavior could allow to enhance the modeling of the transmission of loads into the different structures composing the buttock. A few studies focused on the experimental in vivo buttock deformation quantification using Magnetic Resonance Imaging (MRI), but its use has important drawbacks. In clinical practice, ultrasound imaging is an accessible, low cost, and real-time technic to study the soft tissue. The objective of the present work was to show the feasibility of using B-mode ultrasound imaging for the quantification of localised soft-tissue strains of buttock tissues during sitting. An original protocol was designed, and the intra-operator reliability of the method was assessed. Digital Image Correlation was used to compute the displacement field of the soft tissue of the buttock during a full realistic loading while sitting. Reference data of the strains in the frontal and sagittal planes under the ischium were reported for a population of 7 healthy subjects. The average of shear strains over the region of interest in the fat layer reached levels up to 117% higher than the damage thresholds previously quantified for the muscular tissue in rats. In addition, the observation of the muscles displacements seems to confirm previous results which already reported the absence of muscular tissue under the ischium in the seated position, questioning the assumption commonly made in Finite Element modeling that deep tissue injury initiates in the muscle underlying the bone.

Stand-to-Sit Kinematics of the Pelvis Is Not Always as Expected: Hip and Spine Pathologies Can Have an Impact

KIM, Youngwoo — Tue, 01 Jan 2019 00:00:00 GMT

Stand-to-Sit Kinematics of the Pelvis Is Not Always as Expected: Hip and Spine Pathologies Can Have an Impact KIM, Youngwoo; GIRINON, François; LAZENNEC, Jean-Yves; SKALLI, Wafa; VERGARI, Claudio Introduction; Stand to sit pelvis kinematics is commonly considered as a rotation around the bicoxofemoral axis. However, abnormal kinematics could occur for patients with musculoskeletal disorders affecting the hip-spine complex. The aim of this study is to perform a quantitative analysis of the stand to sit pelvis kinematics using 3D reconstruction from bi-planar x-rays. Material & Methods; Thirty volunteers as a control group (C), 30 patients with hip pathology (Hip) and 30 patients with spine pathology (Spine) were evaluated. All subjects underwent standing and sitting full-body bi-planar x-rays. 3D reconstruction was performed in each configuration and then translated such as the middle of the line joining the center of each acetabulum corresponds to the origin. Rigid registration quantified the finite helical axis (FHA) describing the transition between standing and sitting with two specific parameters. The orientation angle (OA) is the signed 3D angle between FHA and bicoxofemoral axis and the rotation angle (RA) represents the signed angle around FHA. Results; Mean OA was -1.8° for C group, 0.3° for Hip group and -2.4° for Spine group. There was no significant difference in mean OA between groups. However, variability was higher for Spine group with a standard deviation of 16.4° compared to 10.8° in C group and 12.3° in Hip group. Mean RA in C group was 18.1° (SD 9.1°). There was significant difference in RA between Hip and Spine groups (21.1° SD 8.0°) and 16.4° (SD 10.8°), respectively) (p=0.04). Conclusion; Hip and spine pathologies affect stand to sit pelvic kinematics.

Biplanar stereoradiography predicts pulmonary function tests in adolescent idiopathic scoliosis: a cross-sectional study

BOULOUSSA, Houssam — Tue, 01 Jan 2019 00:00:00 GMT

Biplanar stereoradiography predicts pulmonary function tests in adolescent idiopathic scoliosis: a cross-sectional study BOULOUSSA, Houssam; HAEN, Thomas-Xavier; SKALLI, Wafa; VIALLE, Raphaël; VERGARI, Claudio Purpose Various spinal and rib cage parameters measured from complex examinations were found to be correlated with preoperative pulmonary function tests (PFT). The aim was to investigate the relationship between preoperative rib cage parameters and PFT using biplanar stereoradiography in patients with severe adolescent idiopathic scoliosis. Methods Fifty-four patients, 45 girls and nine boys, aged 13.8 ± 1.2 years, with Lenke 1 or 2 thoracic scoliosis (> 50°) requiring surgical correction were prospectively included. All patients underwent preoperative PFT and low-dose biplanar X-rays. The following data were collected: forced vital capacity (FVC), forced expiratory volume in 1 s (FEV1), FEV1/FVC ratio, residual volume, slow vital capacity (SVC), total lung capacity (TLC), rib cage volume (RCV), maximum rib hump, maximum width, mean thoracic index, spinal penetration index, apical vertebral rotation, main curve Cobb angle (MCCA), T4–T12 kyphosis. The primary outcome was the relationship between rib cage parameters and PFT. The secondary outcome was the relationship between rib cage parameters and spine parameters. Data were analyzed using Spearman’s rank test. A multivariable regression analysis was performed to compare PFTs and structural parameters. Significance was set at α = 0.05. Results The mean MCCA was 68.7° ± 16.7°. RCV was highly correlated with all pulmonary capacities: TLC (r = 0.76, p < 0.0001), SVC (r = 0.78, p < 0.0001) and FVC (r = 0.77, p < 0.0001). RCV had a low correlation with FEV1/FVC (r = − 0.34, p = 0.014). SPI was not correlated with any pulmonary parameters. Conclusion Rib cage volume measured by biplanar stereoradiography may represent a prediction tool for PFTs.

A reduced micro-dose protocol for 3D reconstruction of the spine in children with scoliosis: results of a phantom-based and clinically validated study using stereo-radiography

PEDERSEN, Peter H. — Tue, 01 Jan 2019 00:00:00 GMT

A reduced micro-dose protocol for 3D reconstruction of the spine in children with scoliosis: results of a phantom-based and clinically validated study using stereo-radiography PEDERSEN, Peter H.; ALZAKRI, Abdulmajeed; VIALLE, Raphaël; SKALLI, Wafa; VERGARI, Claudio Purpose The aim of this study was to validate the reproducibility of 3D reconstructions of the spine using a new reduced micro-dose protocol. Methods First, semi-quantitative image analysis was performed using an anthropomorphic child phantom undergoing low-dose biplanar radiography. This analysis was used to establish a “lowest dose” allowing for acceptable visibility of spinal landmarks. Subsequently a group of 18 scoliotic children, 12 years of age or younger, underwent full-spine biplanar radiography with both micro-dose and the newly-defined reduced micro-dose. An intra- and inter-observer reliability study of 3D reconstructions of the spine was performed according to the International Organization for Standardization (ISO)-5725 standard, with three operators. Results The reduced micro-dose setting corresponded to a theoretical reduction of radiation dose exposure of approximately 58%. In vivo results showed acceptable intra- and inter-observer reliability (for instance 3.8° uncertainty on Cobb angle), comparable to previous studies on 3D spine reconstruction reliability and reproducibility based on stereo-radiography. Conclusion A new reduced micro-dose protocol offered reliable 3D reconstructions of the spine in patients with mild scoliosis. However, the quality of 3D reconstructions from both reduced micro-dose and micro-dose was inferior to standard-dose protocol on most parameters. Standard–dose protocol remains the option of choice for most accurate assessment and 3D reconstruction of the spine. Still, this new protocol offers a preliminary screening option and a follow-up tool for children with mild scoliosis yielding extremely low radiation and could replace micro-dose protocol for these patients.

Global Sagittal Alignment and Proximal Junctional Kyphosis in Adolescent Idiopathic Scoliosis

ALZAKRI, Abdulmajeed — Tue, 01 Jan 2019 00:00:00 GMT

Global Sagittal Alignment and Proximal Junctional Kyphosis in Adolescent Idiopathic Scoliosis ALZAKRI, Abdulmajeed; VAN DEN ABBEELE, M.; GILLE, Olivier; SKALLI, Wafa; OBEID, Ibrahim; VERGARI, Claudio Study design: Case-Control Study Objectives: To analyse global sagittal alignment including the cranial center of mass (CCOM) and proximal junctional kyphosis (PJK) in Adolescent Idiopathic Scoliosis (AIS) patients treated with posterior instrumentation. Summary of background data: PJK plays an important role in the global sagittal alignment in AIS patients. Maintaining the head above the pelvis allows for a minimization of energy expense in ambulation and upright posture. Numerous studies have been performed to understand PJK phenomena in AIS patients. However, to our knowledge, no study performed on AIS patients included the head in the analysis of global sagittal alignment and PJK. Methods: This study included 85 AIS patients and 51 asymptomatic adolescents. Low-dose bi-planar X-rays were acquired for each subject preoperatively and at two years follow up. Two global sagittal alignment parameters were calculated, i.e. the angle between the vertical and the line joining the center of the bi-coxofemoral axis (HA) and either the most superior point of the dentiform apophysis of C2 (OD) or the cranial center of mass (CCOM). Results: Among normal adolescents, the average OD-HA and CCOM-HA angles were -2.3°±2° and -1.5°±1.8°, respectively. Among AIS patients the average OD-HA and CCOM-HA angles were respectively -2.3°±1.9° and -1.3°±1.8° preoperatively and -2.8°±1.7° and -1.9°±1.7° at the last follow up. 13% of the patients developed PJK postoperatively. Case-by-case analysis showed that adjusting the thoracic kyphosis and the compensations required to maintain this constant could provide explanatory elements. Conclusions: OD-HA and CCOM-HA angles remain almost constant among normal group and patients, pre- and post-operatively, whether PJK or non-PJK. Five patients without PJK and only one patient with PJK produced abnormal values relative to the asymptomatic subjects. Therefore, PJK could be a compensation mechanism, which allows for CCOM-HA and, to a lesser extent, OD-HA to remain invariant. Level of Evidence: III