SAM

Intermediate strain rate behavior of cancellous bone: From the lower to the higher strain rate

PROT, Marianne — Wed, 01 Jan 2014 00:00:00 GMT

Intermediate strain rate behavior of cancellous bone: From the lower to the higher strain rate PROT, Marianne; CLOETE, Trevor John; SALETTI, Dominique; LAPORTE, Sébastien Not applicable

Quantitative geometric analysis of rib, costal cartilage and sternum from childhood to teenagehood

SANDOZ, Baptiste — Tue, 01 Jan 2013 00:00:00 GMT

Quantitative geometric analysis of rib, costal cartilage and sternum from childhood to teenagehood SANDOZ, Baptiste; BADINA, Alina; LAMBOT, Karene; MITTON, David; SKALLI, Wafa; LAPORTE, Sébastien Better understanding of the effects of growth on children’s bones and cartilage is necessary for clinical and biomechanical purposes. The aim of this study is to define the 3D geometry of children’s rib cages: including sternum, ribs and costal cartilage. Three-dimensional reconstructions of 960 ribs, 518 costal cartilages and 113 sternebrae were performed on thoracic CT-scans of 48 children, aged four months to 15 years. The geometry of the sternum was detailed and nine parameters were used to describe the ribs and rib cages. A "costal index" was defined as the ratio between cartilage length and whole rib length to evaluate the cartilage ratio for each rib level. For all children, the costal index decreased from rib level one to three and increased from level three to seven. For all levels, the cartilage accounted for 45 to 60% of the rib length, and was longer for the first years of life. The mean costal index decreased by 21% for subjects over three years old compared to those under three (p<10-4). The volume of the sternebrae was found to be highly age dependent. Such data could be useful to define the standard geometry of the paediatric thorax and help to detect clinical abnormalities.

Parametric finite element modeling of the thoracic spine. Geometry and mesh evaluations.

TOUBIANA MEYER, Rivka — Wed, 01 Jan 2014 00:00:00 GMT

Parametric finite element modeling of the thoracic spine. Geometry and mesh evaluations. TOUBIANA MEYER, Rivka; LAVILLE, Aurélien; BAUDU, Samuel; SANDOZ, Baptiste; SKALLI, Wafa; LAPORTE, Sébastien Introduction Vertebrae present a wide interindividual variability, with a shape strongly dependent on the vertebral level. Based on a previous validated “parametric and subject-specific modeling” (PSSM) method (Laville et al. 2009), the aim of this study is to develop and evaluate a parametric finite element model of the human thoracic spine. Materials and methods Both 3D reconstructions and geometric parameters of 12 spines were extracted from bi-planar X-rays (EOS system, EOS imaging©) of 6 men (mean: 29yo, 1.79m, 81kg) and 6 women (mean: 39.5yo, 1.61m, 54.6kg). In order to validate each vertebra modeling on Matlab, a thorough geometric and mesh analysis has been performed. The geometry of each generated model has been compared to the reconstructed geometry: the mean distance between the points of the reconstructed vertebra and the outer surface of the model was calculated. The mesh analysis consisted to calculate aspect ratios, parallel deviations, maximum corner angles, Jacobian ratios and warping factors and to know the warning ratio and error ratio for each vertebra. Results and discussion Automatic mesh generation was obtained from geometric parameters for the 12 subjects. The mean point-surface distance was 0.87mm (RMS=1.16mm), close to the one previously obtained on the cervical spine. On average, 2.16% of the elements resulted in a warning. Most warned elements were in the lower thoracic vertebrae because the geometry changes as these vertebrae are transitional ones. Indeed, for T1 to T9, 0.7% of elements were with warning and for T10 3.6% (less than 5%). The vertebrae T11 and T12 had more than 5% of elements with warning, respectively 5.3% and 10.6%. Conclusion Automated generation of parametric finite element models provides new possibilities for efficiently studying the influence of geometric parameters. Preliminary evaluations have been performed to validate the coherence of the model. In order to enhance the validation of the models, kinematic simulation will be performed, followed by a stress study. The parametric subject-specific modeling method has been applied to the thoracic spine, and paved the way for large-scale clinical studies or dynamic safety applications.

Motion analysis of the seated posture on auto automotive prototype seat

TOUBIANA MEYER, Rivka — Thu, 01 Jan 2015 00:00:00 GMT

Motion analysis of the seated posture on auto automotive prototype seat TOUBIANA MEYER, Rivka; BAUDU, Samuel; SANDOZ, Baptiste; LAPORTE, Sébastien 1. Introduction In automotive industry, by the past, postural comfort was generally predicted through pressure distribution [Mergl, 2005; Zenk, 2007]. Measuring the joint angles, for the automotive sitting comfort, becomes a new investigation field [Schmidt, 2014]. The aim of this study is to evaluate the reproducibility of sitting movement. 2. Methods Six asymptomatic volunteers (mean: 26yo, 1.74m, 69kg), without back pain, participated in this study. The volunteers sat on a normative prototype seat as Robbins et al (1983). The footrest was placed in order to have a thigh angle of 15°. Participants were asked to successively sit 20 times during 3 phases (for a total of 60). The 2 first phases took place in the same day (morning and afternoon) and the third phase took place in the coming month. Motion capture was made with an opto-electronic system Vicon at 100 Hz. The whole body was equipped with 29 retroreflective markers placed on specific anatomical landmarks and technical plates. Anatomical frames, segmental and articular kinematics of the lower limbs (hip), the pelvis and the trunk were computed according to Pillet et al (2010). Flexion/extension, lateral bending and axial rotation were calculated for trunk and pelvis. Lateral bending and axial rotation were used to confirm that the movement was plane. For the flexion-extension, the variation between the beginning and the end of the movement was measured. The reproducibility was evaluated by Mann-Whitney test. 3. Results Axial rotation and lateral bending can be considered as negligible. Indeed, the standard deviation (SD) is less than 2.5°. For the flexion/extension, the volunteers are repeatable during a phase. For the trunk, 3 volunteers are reproducible for the 3 phases. One volunteer is reproducible between the 2 first phases. And 2 volunteers are not reproducible. For the pelvis, only 2 volunteers are reproducible between 2 phases: phase 1 and phase 3 or phase 2 and phase 3. The others are not reproducible. 4. Discussion According to the variation of axial rotation and lateral bending, the movement is considered to be plane. As expected, the pelvic anteversion is observed during the movement. For the reproducibility study, the results show that volunteers do not sit in the same way for the 3 phases. These preliminary results quantified the movement during sitting. More volunteers currently increase the number of experimentations.

Transient Response of the Head Kinematics - Influence of a Disturbed Visual Flow

SANDOZ, Baptiste — Wed, 01 Jan 2014 00:00:00 GMT

Transient Response of the Head Kinematics - Influence of a Disturbed Visual Flow SANDOZ, Baptiste; PROVOST, Clément; LE COZ, Jean-Yves; LAPORTE, Sébastien Vision influences the controlled kinematics of human body. Previous studies have shown the influence of vision on head stabilization or whole posture. However, latencies between the stimuli and the head motion have never been quantified. The aim of this study is to quantify the influence of a perturbed vision on the head kinematics. Seven healthy volunteers without uncorrected vision (26.7±6.9 years old, 1 female, 2 right-handed/right-dominant eye, 5 right-handed/left-dominant eye) were studied. Visual stimuli were performed through an immersive personal 3D viewer (HMZ-T1, Sony), securely tied on the head. Motion analysis of the head and the torso were performed using the optoelectronic Vicon system (100Hz). Three markers were glued on the personal viewer, close to the nasion, left and right tragus, in order to create the head frame. Three markers were glued to create the torso frame (both acromia and C7). Two different 3D animated scenes were created on Blender and displayed at 24Hz. The first animation was a landscape with a ball rolling on the ground, and then the ball stopped before being virtually launched via a catapult toward the screen. Two velocities were programmed: 4.67 and 10.58 m.s-1. The second animation was a beach with sea and sky, where horizon tilted anticlockwise at 2 different constant rates: 0.24 deg.s-1 and 0.48 deg.s-1 with maximal amplitude of 8° and 16° respectively. The motion of the head relative to the torso was calculated for both scenes on seated and upright position, at the 2 different velocities, 2 times each, for a total of 16 random tests on each volunteer. For the launched ball animated scene, the reaction time seated was, as expected, shorter for the fast launches. For the beach animated scene, the head profiles followed most of the time the kinematic profile of the tilted animation, linearly or by steps, and not necessary until the end. Volunteers who were right-handed and right dominant eye tilted their head clockwise, at the inverse of the stimuli. Both experiments confirmed that visual stimulus could influence the kinematics of the head-neck system. In the ball animation, velocity of the stimulus does not seem to affect the amplitude of movement. In the beach animation, the head motions were variable, but performed at the same mean speed than the stimuli. Furthermore, the limited number of volunteer cannot conclude on the direction of rotation of the head, depending of the dominant hand and eye.

Subject-specific body segment parameters’ estimation using biplanar X-rays: a feasibility study

SANDOZ, Baptiste — Fri, 01 Jan 2010 00:00:00 GMT

Subject-specific body segment parameters’ estimation using biplanar X-rays: a feasibility study SANDOZ, Baptiste; SKALLI, Wafa; MITTON, David; LAPORTE, Sébastien In order to improve the reliability of children’s models, the aim of this study was to determine the subject-specific masses and 3D locations of the centres of mass (CoM) of body segments using biplanar X-rays. Previous methods, validated on upper leg segments, were applied to the whole body. Six children and six adults were studied. The low-dose X-ray system EOS was used to simultaneously get head-to-foot biplanar X-rays in the upright position. Specific methods were used to get 3D reconstructions of bones and body shape. The densities from the literature were used to define the masses. To assess the accuracy of the reconstructions, a force plate was used to compare the mass and the projection of the CoM. A mean distance of 4.5mm between the measured and the calculated projections of the CoM was found. The mean error between the estimated and the actual body mass was 2.6%. Such a method will be useful in obtaining the body segment parameters in children, hard to obtain using direct measurement techniques. Version éditeur : http://www.tandfonline.com/toc/gcmb20/13/6

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.

Quantification of the stress generated by theendoscopic movement in the brain parenchymaduring intra ventricular surgical procedure

FRANÇOIS, Pierre-Marc — Sun, 01 Jan 2017 00:00:00 GMT

Quantification of the stress generated by theendoscopic movement in the brain parenchymaduring intra ventricular surgical procedure FRANÇOIS, Pierre-Marc; SANDOZ, Baptiste; DECQ, Philippe; LAPORTE, Sébastien Endoscopy is increasingly used for intra ventricular surgeries such as hydrocephalus and tumor removal (Miwa et al. 2015 Miwa T, Hayashi N, Endo S, Ohira T. 2015. Neuroendoscopic biopsy and the treatment of tumor-associated hydrocephalus of the ventricular and paraventricular region in pediatric patients: a nationwide study in Japan. Neurosurg Rev.[Crossref], [PubMed], [Web of Science ®], , [Google Scholar]). Robotic based surgeries are more and more developed to control the trajectory and the movement of the endoscope and then to enhance the accuracy of surgical procedures and to reduce post-operative issues. The use of computer- aided robot is then well-suited to accurately reach ventricles cavities through the brain parenchyma and to minimize cerebral damage caused by the movement of the endoscope. On a mechanical point of view, moderate and severe traumatic brain injury (TBI) had a 50% risk to locally occur when Von Mises stress respectively exceeds 18 and 38 kPa (Willinger & Baumgartner 2003 Willinger R, Baumgartner D. 2003. Human head tolerance limits to specific injury mechanisms. Int J Crashworthiness.[Taylor & Francis Online], , [Google Scholar]). The purpose of this study was to assess the Von Mises stress generated in the brain by the endoscopic movement.

Intra cranial volume quantification from 3D reconstruction based on CT-scan data

FRANÇOIS, Pierre-Marc — Sun, 01 Jan 2017 00:00:00 GMT

Intra cranial volume quantification from 3D reconstruction based on CT-scan data FRANÇOIS, Pierre-Marc; SANDOZ, Baptiste; DECQ, Philippe; LAPORTE, Sébastien The evolution of some congenital diseases impacting the shape of the skull such as the Chiari malformation or Craniosynostosis condition can be quantify measuring the increasing of the intra cranial volume (ICV) (Gault et al. 1993). This volume could be calculated from ana-tomic measurements (Gordon 1966). Nevertheless, in case of important variations of shape, these techniques were not suitable to accurately assess ICV from measure-ments of global parameters. Some studies, using automatic segmentation combined with manual adjustments from MRI acquisition were used to assess the ICV (Reite et al. 2010). However, 3-4 hours were required for each patient to complete the process. Other studies used total auto-matic segmentation to calculate volume of the brain and the ICV (de Jong et al. 2017). But high quality of MRI was necessary to get accurate results.The purpose of this study was to develop a fast, efficient and reproducible procedure to calculate the ICV, based on 3D skull reconstruction obtained from scanner imaging.

Modelling of fascia lata rupture during tensile tests via the discrete element method

MUTH-SENG, Christophe — Sun, 01 Jan 2017 00:00:00 GMT

Modelling of fascia lata rupture during tensile tests via the discrete element method MUTH-SENG, Christophe; GRAS, Laure-Lise; ROUX, ANTHONY; LAPORTE, Sébastien The aim of this study is to reproduce numerically the macroscopic behaviour of the fascia lata submitted to a tensile test using DEM.