ePub ahead of print
C. Vergari, D. Chan, A. Clarke, J. Mansfield, J. R. Meakin, P. C. Winlove, ePub ahead of print. Bovine and degenerated human annulus fibrosus: a microstructural and micromechanical comparison. [PDF]
The complex structure of the annulus fibrosus is strongly related to its
mechanical properties. Recent work showed that it is possible to observe the relative
movement of fibre bundles in loaded cow tail annulus; the aim of this work was to
describe and quantify annulus fibrosus micromechanics in degenerated human disc,
and compare it with cow tail annulus, an animal model often used in the literature.
Second harmonic generation was used to image the collagen matrix in twenty strips of annulus fibrosus harvested from intervertebral disc of seven patients undergoing surgery. Samples were loaded to 6 % tensile strain in 1 % steps. Elastic modulus was calculated from loading curves, and micromechanical strains were calculated from the images using custom software. The same protocol was applied to twenty strips of annulus harvested from cow tail discs.
Significant morphological differences were found between human and cow tail samples, the most striking being the lack of collagen fibre crimp in the former. Fibres were also observed bending and running from one lamella to the other, forming a strong flexible interface. Interdigitation of fibre bundles was also present at this interface. Quantitative results show complex patterns of inter-bundle and inter-lamellar behaviour, with inter-bundle sliding being the main strain mechanism. Elastic modulus was similar between species, and it was not affected by the degree of degeneration.
This work gives an insight on the complex structure and mechanical function of the annulus fibrosus, which should be accounted for in disc numerical modelling
W. Skalli, C.Vergari, E. Ebermeyer, I. Courtois, X. Drevelle, R. Kohler, K. Abelin-Genevois, J. Dubousset, In press. Early Detection of Progressive Adolescent Idiopathic Scoliosis: A Severity Index. Spine.
Study Design. Early detection of progressive adolescent idiopathic scoliosis (AIS) was assessed based on 3D quantification of the deformity.
Objective. Based on 3D quantitative description of scoliosis curves, the aim is to assess a specific deformation pattern that could be an early detectable severity index for progressive AIS.
Summary of Background Data. Early detection of progressive scoliosis is important for adapted treatment to limit progression. However, progression risk assessment is mainly based on the follow up, waiting for signs of rapid progression that generally occur during the growth peak.
Methods. 65 mild scoliosis (16 boys, 49 girls, Cobb Angle between 10 and 20°) with a Risser between 0 and 2 were followed from their first exam until a decision was made by the clinician, either considering the spine as stable at the end of growth (26 patients) or planning to brace because of progression (39 patients). Calibrated bi-planar X-rays were performed and 3D reconstructions of the spine allowed to calculate six local parameters related to main curve deformity. For progressive curve 3D phenotype assessment, data were compared to those previously assessed for 30 severe scoliosis (Cobb Angle > 35°), 17 scoliosis before brace (Cobb Angle > 29°) and 53 spines of non-scoliosis subjects. A predictive discriminant analysis was performed to assess similarity of mild scoliosis curves either to those of scoliosis or non-scoliosis spines, yielding a severity index (S-index). S index value at first exam was compared to clinical outcome.
Results. At the first exam, 53 out of 65 predictions (82%) were in agreement with actual clinical outcome. 89 % of the curves that were predicted as progressive proved accurate
Conclusion. Although still requiring large scale validation, results are promising for early detection of progressive curves.
J. Rouissi, R. Arvieu, A. Dubory, C. Vergari, M. Bachy, R. Vialle, 2017. Intra and inter-observer reliability of determining degree of pelvic obliquity in neuromuscular scoliosis using the EOS-CHAIR® protocol. Child's Nervous System 33(2):337-341.
Scoliosis with pelvic obliquity (PO) could be investigated with the EOS-CHAIR protocol as the most common deformity especially in patients with trunk hypotonia and quadriplegia. However, the intra-observer and inter-observer reliability of various angles assessing PO was not investigated with this new imaging protocol.
Methods A retrospective cohort of 36 EOS frontal full-spine acquisitions made in sitting position was used. The sacroiliac pelvic obliquity angle, iliac crest pelvic obliquity angle, and ischiatic pelvic obliquity angle were assessed in an intra-observer and inter-observer study.
Results The use of the EOS-CHAIR protocol was implemented satisfactory with a high acceptance rate by all caregivers and patients and their families. Intra-observer and inter-observer reliability was excellent for the three tested angular measurements.
Discussion As for idiopathic scoliosis, we postulate the EOS system as being superior to standard radiographs to assess 3D spinal deformities in neuromuscular conditions. The EOS-CHAIR protocol improves preoperative comprehension of the lumbosacral junction anatomy in patients with poor standing or sitting postures. Our results show a very high reliability of three different angular measurements of the frontal pelvic obliquity in sitting position. Then it is possible to use one of these three angles as well as the others to assess frontal pelvic obliquity in neuromuscular patients. This frontal pelvic obliquity protocol in sitting position with the EOS-CHAIR is a validated measurement technique that needs to be used now to measure PO as a critical parameter of the global trunk balance in neuromuscular patients.
C.Vergari, I. Courtois, E. Ebermeyer, H. Bouloussa, R. Vialle, W. Skalli, 2016. Experimental validation of a patient-specific model of orthotic action in adolescent idiopathic scoliosis. European Spine Journal 25(10):3049-3055. [PDF]
Purpose: Personalized modeling of brace action have potential in improving brace efficacy in adolescent idiopathic scoliosis (AIS). Model validation and simulation uncertainty are rarely addressed, limiting the clinical implementation of personalized models. We hypothesized that a thorough validation of a personalized finite element model (FEM) of brace action would highlight potential means of improving the model.
Methods: 42 AIS patients were included retrospectively and prospectively. Personalized FEMs of pelvis, spine and ribcage were built from stereoradiographies. Brace action was simulated through soft cylindrical pads acting on the ribcage and through displacements applied to key vertebrae. Simulation root mean squared errors (RMSEs) were calculated by comparison with the actual brace action (quantified through clinical indices, vertebral positions and orientations) observed in in-brace stereoradiographies.
Results: Simulation RMSEs of Cobb angle and vertebral apical axial rotation was lower than measurement uncertainty in 79% of the patients. Pooling all patients and clinical indices, 87 % of the indices had lower RMSEs than the measurement uncertainty.
Conclusions: In-depth analysis suggests that personalization of spinal functional units mechanical properties could improve the simulation’s accuracy, but the model gave good results, thus justifying further research on its clinical application.
B.Moreau, C.Vergari, H.Gad, B.Sandoz, W. Skalli, S.Laporte, Accepted. Non-invasive assessment of human multifidus muscle stiffness using ultrasound shear wave elastography: A feasibility study. Journal of Engineering in Medicine 230(8):809-814. [PDF]
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.
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.
B. Aubert, C. Vergari, B. Ilharreborde, Courvoisier A., W. Skalli, In Press. 3D reconstruction of ribcage geometry from biplanar radiographs using a statistical parametric model approach. Computer Methods in Biomechanics and Biomedical Engineering: Imaging & Visualization 4(5): 281-295. [PDF]
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.
C.Vergari, J. Mansfield, J. R. Meakin, P. C. Winlove, 2016. Lamellar and fibre bundle mechanics of the annulus fibrosus in bovine intervertebral disc. Acta Biomaterialia 37, 14:20. [PDF]
The intervertebral disc is a multicomposite structure, with an outer fibrous ring, the annulus fibrosus, retaining a gel-like core, the nucleus pulposus. The disc presents complex mechanical behaviour, and it is of high importance for spine biomechanics. Advances in multiscale modelling and disc repair raised a need for new quantitative data on the finest details of annulus fibrosus mechanics. In this work we explored inter-lamella and inter-bundle behaviour of the outer annulus using micromechanical testing and second harmonic generation microscopy. Twenty-one intervertebral discs were dissected from cow tails; the nucleus and inner annulus were excised to leave a ring of outer annulus, which was tested in circumferential loading while imaging the tissue’s collagen fibres network with sub-micron resolution. Custom software was developed to determine local tissue strains through image analysis. Inter-bundle linear and shear strains were 5.5 and 2.8 times higher than intra-bundle strains. Bundles tended to remain parallel while rotating under loading, with large slipping between them. Inter-lamella linear strain was almost 3 times the intra-lamella one, but no slipping was observed at the junction between lamellae. This study confirms that outer annulus straining is mainly due to bundles slipping and rotating. Further development of disc multiscale modelling and repair techniques should take into account this modular behaviour of the lamella, rather than considering it as a homogeneous fibre-reinforced matrix.
C.Vergari, G. Dubois, R. Vialle, J.-L. Gennisson, M. Tanter, J. Dubousset, P. Rouch, W. Skalli, 2016. Lumbar annulus fibrosus biomechanical characterization in children by ultrasound shear wave elastography. European Radiology 26, 4:1213-1217. [PDF]
Objectives: Intervertebral disc (IVD) is key to spine biomechanics, and it is often involved in the cascade leading to spinal deformities such as idiopathic scoliosis, especially during the growth spurt. Recent progress in elastographic techniques allowed access to noninvasively measure cervical IVD in adults; the aim of this study was to determine the feasibility and reliability of shear wave elastography in healthy children lumbar IVD.
Methods: Elastographic measurements were performed in thirty-one healthy children (6 to 17 years old), in the annulus fibrosus and in the transverse plane of L5-S1 or L4-L5 IVD. Reliability was determined by 3 experienced operators repeating measurements.
Results: Average shear wave speed in IVD was 2.9 ± 0.5 m/s; no significant correlations were observed with sex, age or body morphology. Intra-operator repeatability was 5.0 % while inter-operator reproducibility was 6.2 %. Intraclass correlation coefficient was higher than 0.9 for each operator.
Conclusions: Feasibility and reliability of IVD shear wave elastography was demonstrated. The measurement protocol is compatible with the clinical routine, and the results show the potential to give an insight into spine deformity progression and early detection.
G.Dubois, W. Kheireddine, C.Vergari, D. Bonneau, P. Thoreux, P. Rouch, M. Tanter, J.L. Gennisson, W. Skalli, 2015. A reliable protocol for shearwave elastography of lower limb muscles at rest and during passive stretching. Ultrasound in Medicine & Biology (41), 9:2284-2291. [PDF]
Development of shear wave elastography gave access to non-invasive muscle stiffness assessment in vivo. The aim of the present study was to define a measurement protocol to be used in clinical routine for quantifying the shear modulus of lower limb muscles. Four positions were defined to evaluate shear modulus in 10 healthy subjects: parallel to the fibers, in the anterior and posterior aspects of the lower limb, at rest and during passive stretching. Reliability was first evaluated on two muscles by three operators; these measurements were repeated six times. Then, measurement reliability was compared in 11 muscles by two operators; these measurements were repeated three times. Reproducibility of shear modulus was 0.48 kPa and repeatability was 0.41 kPa, with all muscles pooled. Position did not significantly influence reliability. Shear wave elastography appeared to be an appropriate and reliable tool to evaluate the shear modulus of lower limb muscles with the proposed protocol.
C. Vergari, G. Ribes, B. Aubert, C. Adam, L. Miladi, B. Ilharreborde, K. Abelin-Genevois, P. Rouch, W. Skalli, 2015. Evaluation of a patient-specific finite element model to simulate conservative treatment in adolescent idiopathic scoliosis. Spine Deformity (3), 1:4-11. [PDF]
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.
C. Vergari, P.Rouch, G. Dubois, D. Bonneau,J. Dubousset, M. Tanter, J.L. Gennisson, W.Skalli, 2014. Non-invasive biomechanical characterization of intervertebral disc by shearwave ultrasound elastography: a feasibility study. European Radiology (24), 12:3210-3216 . [PDF]
Objectives: Although magnetic resonance is widely spread to qualitatively assess disc morphology, a simple method to reliably determine intervertebral disc status is still lacking. Shear wave elastography is a recent technique that allows quantitative evaluation of soft-tissues mechanical properties; the aim of this study was to preliminary assess the feasibility and reliability of cervical intervertebral disc mechanical characterization by elastography and to provide first reference values for asymptomatic subjects.
Methods: Elastographic measurements were performed to determine shear wave speed (SWS) in C6-C7 or C7-T1 disc of forty-seven subjects; repeatability and inter-operator reproducibility were assessed.
Results: Global average shear wave speed (SWS) was 3.0 ± 0.4 m/s; measurement repeatability and inter-user reproducibility were 7 and 10 %, respectively. SWS was correlated with both subject’s age (p = 1.3e-5) and body mass index (p = 0.008).
Conclusions: Shear wave elastography in intervertebral disc proved reliable and allowed stratification of subjects according to age and BMI. Applications could be relevant, for instance, in early detection of disc degeneration or in follow-up after trauma; these results open the way to larger cohort studies to define the place of this technique in routine intervertebral disc assessment.
C. Vergari, P.Rouch, G. Dubois, D. Bonneau,J. Dubousset, M. Tanter, J.L. Gennisson, W.Skalli, 2014. Intervertebral disc characterization by shear wave elastography: an in-vitro preliminary study. Journal of Engineering in Medicine (228), 6:607-615. [PDF]
Patient-specific numerical simulation of the spine is a useful tool both in clinic and research. While geometrical personalization of the spine is no more an issue, thanks to recent technological advances, non-invasive personalization of soft tissue’s mechanical properties remains a challenge. Ultrasound elastography is a relatively recent measurement technique allowing the evaluation of soft tissue’s elastic modulus through the measurement of shear wave speed (SWS). The aim of this study was to determine the feasibility of elastographic measurements in intervertebral disc (IVD). An in-vitro approach was chosen to test the hypothesis that SWS can be used to evaluate IVD mechanical properties and to assess measurement repeatability. Eleven oxtail IVDs were tested in compression to determine their stiffness and apparent elastic modulus at rest and at 400 N. Elastographic measurements were performed in these two conditions and compared to these mechanical parameters. The protocol was repeated six times to determine elastographic measurement repeatability. Average SWS over all samples was 5.3 ± 1.0 m/s, with a repeatability of 7 % at rest and 4.6 % at 400 N; stiffness and apparent elastic modulus were 266.3 ± 70.5 N/mm and 5.4 ± 1.1 MPa at rest, respectively, while at 400 N they were 781.0 ± 153.8 N/mm and 13.2 ± 2.4 MPa. Correlations were found between elastographic measurements and IVD mechanical properties; these preliminary results are promising for further in-vivo application.
N. Crevier-Denoix, S. Falala, L. Holden-Douilly, M. Camus, J. Martino, B. Ravary-Plumioën, C. Vergari, L. Desquilbet, J.-M. Denoix, H. Chateau, P. Pourcelot, 2013. Comparative kinematic analysis of the leading and trailing forelimbs of horses cantering on a turf and a synthetic surface. Equine Veterinary Journal (IF: 2.286) (45), S45: 54-61.
Reasons for performing study: The relationship between track surface properties and limb kinematics is poorly understood. Hoof orientation within the track surface has never been quantified under training conditions. Previously described kinematic and dynamic differences between leading and trailing forelimbs at the canter poorly correlate with epidemiological data regarding injuries.
Objectives: To compare joint kinematics and hoof orientation in the leading and trailing forelimbs of horses cantering on turf and on a synthetic surface.
Study design: Noninvasive experimental study.
Methods: The right forelimb of 5 horses was equipped with markers facing the main joints while markers and a dynamometric horseshoe were placed on the hoof. The horses were filmed with 2 high-speed cameras (1000 Hz) while cantering (30 km/h). Recordings were repeated at each lead and alternated on turf and on a synthetic surface. Joint angles and angles of the hoof and limb to the track were measured from the 2-dimensional coordinates of the markers.
Results: Elbow, carpus and fetlock were more maximally flexed during swing and had a larger range of motion throughout the stride in the leading forelimb. Maximal carpal extension during stance was also larger on this limb, which had a more toe-up orientation. Comparing surfaces, the limb was more oblique at landing, the range of motion of the hoof into the surface was larger, most kinematic events were delayed and fetlock and carpus extension velocities were smaller on the synthetic surface.
Conclusions: The differences between limbs were more prominent than those between surfaces and the more toe-up orientation on the hoof of the leading forelimb suggests a different loading of that limb's joints and tendons. Differences between limbs may be important in the interpretation of lead changes in lame horses. While the synthetic surface appears to be less strenuous for the joints in the forelimbs, it was associated with changes in timing of the kinematic events of the stride.
H. Chateau, M. Camus, L. Holden-Douilly, S. Falala, B. Ravary-Plumioën, C. Vergari, J. Lepley, J.M. Denoix, P. Pourcelot, N. Crevier-Denoix, 2013. Kinetics of the forelimb in horses circling on different ground surfaces at the trot. The Veterinary Journal (IF: 2.424) (198),S1:e20–e26.
Circling increases the expression of distal forelimb lameness in the horse, depending on rein, diameter and surface properties of the circle. However, there is limited information about the kinetics of horses trotting on circles. The aim of this study was to quantify ground reaction force (GRF) and moments in the inside and outside forelimb of horses trotting on circles and to compare the results obtained on different ground surfaces. The right front hoof of six horses was equipped with a dynamometric horseshoe, allowing the measurement of 3-dimensional GRF, moments and trajectory of the centre of pressure. The horses were lunged at slow trot (3 m/s) on right and left 4 m radius circles on asphalt and on a fibre sand surface. During circling, the inside forelimb produced a smaller peak vertical force and the stance phase was longer in comparison with the outside forelimb. Both right and left circling produced a substantial transversal force directed outwards. On a soft surface (sand fibre), the peak transversal force and moments around the longitudinal and vertical axes of the hoof were significantly decreased in comparison with a hard surface (asphalt). Sinking of the lateral or medial part of the hoof in a more compliant surface enables reallocation of part of the transversal force into a proximo-distal force, aligned with the limb axis, thus limiting extrasagittal stress on the joints.
N. Crevier-Denoix, B. Ravary-Plumioën, C. Vergari, M. Camus, L. Holden-Douilly, S. Falala, H. Jerbi, L. Desquilbet, H. Chateau, J.M. Denoix and P. Pourcelot, 2013. Comparison of superficial digital flexor tendon loading on asphalt and on sand in horses at the walk and trot. The Veterinary Journal (IF: 2.424) (198), S1: e130–e136.
The incidence of superficial digital flexor tendon (SDFT) injuries is one of the highest of all equine musculoskeletal conditions. Horses with SDFT injuries commonly show no improvement of lameness on soft ground, unlike those suffering from distal bone or joint lesions. The aim of this study was to compare the SDFT loading in five horses at the walk and trot on asphalt and sand using a non-invasive ultrasonic tendon force measurement device. Three horses were equipped with the ultrasonic device, whereas the other two horses were equipped with the ultrasonic device and a dynamometric horseshoe (DHS); the DHS was used to calibrate the measured values of tendon speed of sound (SOS) converted to tendon force, while a previously established ground reaction force pattern was used to calibrate SOS measurements for the other three horses. Although the horses tended to be slower on S, maximal tendon force was higher on sand than on asphalt at the trot (+6%); there was no significant difference between the two surfaces at the walk. The duration of tendon loading was longer on S (+5%) and the area under the tendon force–time curve was larger on S (+10%) at both walk and trot. SDFT loading is significantly affected by the ground surface and the observed increase in SDFT loading on sand compared with asphalt is consistent with clinical observations in horses with SDFT injuries.
N. Crevier-Denoix, P. Pourcelot, L. Holden-Douilly, M. Camus, S. Falala, B. Ravary-Plumioën, C. Vergari, L. Desquilbet and H. Chateau, 2013. Discrimination of two equine racing surfaces based on forelimb dynamic and hoof kinematic variables at the canter. The Veterinary Journal (IF: 2.424) (198): e124-e129.
The type and condition of sport surfaces affect performance and can also be a risk factor for injury. Combining the use a 3-dimensional dynamometric horseshoe (DHS), an accelerometer and high-speed cameras, variables reflecting hoof–ground interaction and maximal limb loading can be measured. The aim of the present study was to compare the effects of two racing surfaces, turf and all-weather waxed (AWW), on the forelimbs of five horses at the canter. Vertical hoof velocity before impact was higher on AWW. Maximal deceleration at impact (vertical impact shock) was not significantly different between the two surfaces, whereas the corresponding vertical force peak at impact measured by the DHS was higher on turf. Low frequency (0–200 Hz) vibration energy was also higher on turf; however high frequency (>400 Hz) vibration energy tended to be higher on AWW. The maximal longitudinal force during braking and the maximal vertical force at mid-stance were lower on AWW and their times of occurrence were delayed. AWW was also characterised by larger slip distances and sink distances, both during braking and at maximal sink. On a given surface, no systematic association was found between maximal vertical force at mid-stance and either sink distance or vertical impact shock. This study confirms the damping properties of AWW, which appear to be more efficient for low frequency events. Given the biomechanical changes induced by equestrian surfaces, combining dynamic and kinematic approaches is strongly recommended for a reliable assessment of hoof–ground interaction and maximal limb loading.
C. Vergari, B. Ravary-Plumioën, D. Evrard, P. Laugier, D. Mitton, P. Pourcelot and N. Crevier-Denoix, 2012. Axial Speed of Sound is Related to Tendon's Nonlinear Elasticity. Journal of Biomechanics (45), 2: 263-268. [pdf]
Axial speed of sound (SOS) measurements have been successfully applied to noninvasively evaluate tendon load, while preliminary studies showed that this technique also has a potential clinical interest in the follow up of tendon injuries. The ultrasound propagation theory predicts that the SOS is determined by the effective stiffness, mass density and Poisson’s ratio of the propagating medium. Tendon stiffness characterizes the tissue’s mechanical quality, but it is often measured in quasi-static condition and for entire tendon segments, so it might not be the same as the effective stiffness which determines the SOS. The objectives of the present study were to investigate the relationship between axial SOS and tendon’s nonlinear elasticity, measured in standard laboratory conditions, and to evaluate if tendon’s mass density and cross-sectional area (CSA) affect the SOS level.
Axial SOS was measured during in vitro cycling of 9 equine superficial digital tendons. Each tendon’s stiffness was characterized with a tangent modulus (the continuous derivative of the true stress / true strain curve) and an elastic modulus (the slope of this curve’s linear region).
Tendon’s SOS was found to linearly vary with the square root of the tangent modulus during loading; tendon’s SOS level was found correlated to the elastic modulus’s square root and inversely correlated to the tendon’s CSA, but it was not affected by tendon’s mass density. These results confirm that tendon’s tangent and elastic moduli, measured in laboratory conditions, are related to axial SOS and they represent one of its primary determinants.
C. Vergari, P. Pourcelot, B. Ravary-Plumioën, A.G. Dupays, J.M. Denoix , D. Mitton, Laugier P. and N. Crevier-Denoix, 2012. First Application of Axial Speed of Sound to Follow up Injured Equine Tendons. Ultrasound in Medicine & Biology (38), 1: 162-167. [pdf]
Ultrasonography is an established technique to follow up injured tendons, although the lesions’ echogenicity tends to become normal before the tendon is ready to sustain the stresses imposed by exercise. Normalized axial speed of sound (SOS) has been found to correlate with an injured tendon’s stiffness; therefore, the purpose of this study was to establish whether SOS would be a useful tool in tendon injury follow-up. Axial SOS was measured in 11 equine superficial digital flexor tendons during a 15 weeks follow-up period, and compared with an ultrasonographic grading system. SOS significantly decreased 2 weeks after the surgical induction of a core lesion, showing a minimum between 7 and 10 weeks; ultrasonographic grade showed a minimum at 3 weeks and increased thereafter. The ultrasonographic grading at 15 weeks was correlated to normalized SOS. These results suggest that axial SOS provides complementary information to ultrasonography that could be of clinical interest.
C. Vergari, P. Pourcelot, B. Ravary-Plumioën, A.G. Dupays, S. Jacquet, F. Audigié, J.M. Denoix, P. Laugier, D. Mitton, and N. Crevier-Denoix, 2012. Axial speed of sound for the monitoring of injured equine tendons: a preliminary study. Journal of Biomechanics (45), 1: 53-58. [pdf]
Equine superficial digital flexor tendons (SDFT) are often injured, and they represent an excellent model for human sport tendinopathies. While lesions can be precisely diagnosed by clinical evaluation and ultrasonography, a prognosis is often difficult to establish; the knowledge of the injured tendon's mechanical properties would help in anticipating the outcome. The objectives of the present study were to compare the axial speed of sound (SOS) measured in vivo in normal and injured tendons and to investigate their relationship with the tendons' mechanical parameters, in order to assess the potential of quantitative axial ultrasound to monitor the healing of the injured tendons.
SOS was measured in vivo in the right fore SDFTs of 12 horses during walk, before and 3.5 months after the surgical induction of a bilateral core lesion. The 12 horses were then euthanized, their SDFTs isolated and tested in tension to measure their elastic modulus and maximal load (and corresponding stress).
SOS significantly decreased from 2179.4±31.4 m/s in normal tendons to 2065.8±67.1 m/s 3.5 months after the surgical induction, and the tendons' elastic modulus (0.90±0.17 GPa) was found lower than what has been reported in normal tendons. While SOS was not correlated to tendon maximal load and corresponding stress, the SOS normalized on its value in normal tendons was correlated to the tendons' elastic modulus. These preliminary results confirm the potential of axial SOS in helping the functional assessment of injured tendon.
C. Vergari, P. Pourcelot, Holden, L., B. Ravary-Plumioën, Gerard, G., P. Laugier, D. Mitton, and N. Crevier-Denoix, 2011. True Stress and Poisson's Ratio of Tendons during Loading. Journal of Biomechanics, (44): 719-724. [pdf]
Excessive axial tension is very likely involved in the aetiology of tendon lesions, and the most appropriate indicator of tendon stress state is the true stress, the ratio of instantaneous load to instantaneous cross-sectional area (CSA). Difficulties to measure tendon CSA during tension often led to approximate true stress by assuming that CSA is constant during loading (i.e. by the engineering stress) or that tendon is incompressible, implying a Poisson's ratio of 0.5, although these hypotheses have never been tested. The objective of this study was to measure tendon CSA variation during quasi-static tensile loading, in order to assess the true stress to which the tendon is subjected and its Poisson's ratio. Eight equine superficial digital flexor tendons (SDFT, about 30 cm long) were tested in tension until failure while the CSA of each tendon was measured in its metacarpal part by means of a linear laser scanner. Axial elongation and load were synchronously recorded during the test. CSA was found to linearly decrease with strain, with a mean decrease at failure of −10.7±2.8% (mean±standard deviation). True stress at failure was 7.1–13.6% higher than engineering stress, while stress estimation under the hypothesis of incompressibility differed from true stress of −6.6 to 2.3%. Average Poisson's ratio was 0.55±0.12 and did not significantly vary with load. From these results on equine SDFT it was demonstrated that tendon in axial quasi-static tension can be considered, at first approximation, as an incompressible material.
C. Vergari, P. Pourcelot, Holden, L., B. Ravary-Plumioën,P. Laugier, D. Mitton, and N. Crevier-Denoix, 2010. A Linear Laser Scanner to Measure Cross-Sectional Shape and Area of Biological Specimens During Mechanical Testing. Journal of Biomechanical Engineering, (132), 10: 105001-105007.
Measure of the cross-sectional area (CSA) of biological specimens is a primary concern for many biomechanical tests. Different procedures are presented in literature but besides the fact that noncontact techniques are required during mechanical testing, most of these procedures lack accuracy or speed. Moreover, they often require a precise positioning of the specimen, which is not always feasible, and do not enable the measure of the same section during tension.
The objective of this study was to design a noncontact, fast, and accurate device capable of acquiring CSA of specimens mounted on a testing machine. A system based on the horizontal linear displacement of two charge-coupled device reflectance laser devices next to the specimen, one for each side, was chosen. The whole measuring block is mounted on a vertical linear guide to allow following the measured zone during sample tension (or compression).
The device was validated by measuring the CSA of metallic rods machined with geometrical shapes (circular, hexagonal, semicircular, and triangular) as well as an equine superficial digital flexor tendon (SDFT) in static condition. We also performed measurements during mechanical testing of three SDFTs, obtaining the CSA variations until tendon rupture.
The system was revealed to be very fast with acquisition times in the order of 0.1 s and interacquisition time of about 1.5 s. Measurements of the geometrical shapes yielded mean errors lower than 1.4 % (n=20 for each shape) while the tendon CSA at rest was 90.29±1.69 mm² (n=20). As for the tendons that underwent tension, a mean of 60 measures were performed for each test, which lasted about 2 min until rupture (at 20 mm/min), finding CSA variations linear with stress (R²>0.85).
The proposed device was revealed to be accurate and repeatable. It is easy to assemble and operate and capable of moving to follow a defined zone on the specimen during testing. The system does not need precise centering of the sample and can perform noncontact measures during mechanical testing; therefore, it can be used to measure variations of the specimen CSA during a tension (or compression) test in order to determine, for instance, the true stress and transverse deformations.
Communications at international meetings
C. Vergari, D. Chan, A. Clarke, J. Mansfield, J.R. Meakin, C. P. Winlove. Micromechanical effects of needle injury o annulus fibrosus.. 23rd Congress of the European Society of Biomechanics, July 2 - 5, 2017, Seville, Spain. [podium communication] [PDF]
C. Vergari, D. Chan, A. Clarke, J. Mansfield, J.R. Meakin, C. P. Winlove. Macro- and micromechanical properties of human and bovine annulus fibrosus. 23rd Congress of the European Society of Biomechanics, July 2 - 5, 2017, Seville, Spain. [podium communication]. [PDF]
Z. Chen, L. Robichon; C. Vergari, W.Skalli. Preliminary study of posture prediction in finite element model of adolescent idiopathic scoliosis. 23rd Congress of the European Society of Biomechanics, July 2 - 5, 2017, Seville, Spain. [podium communication].
S. Ghailane, H. Bouloussa, C. Vergari, S. Mazas, V. Challier, J-M. Vital, P. Coudert, O.Gille. Clinical Relevance of a New Classification System for Degenerative Spondylolisthesis of the Lumbar Spine. 24th International Meeting on Advanced Spine Techniques, July 12-15, 2017, Cape Town, South Africa. [PDF]
A. Macron, P-Y Rohan, C. Vergari, A. Verney, H. Pillet. Sub-dermal tissue deformation assessed using ultrasound: methodology for validating Finite Element Models for pressure ulcer prevention. EUROMECH Colloquium 595 : Biomechanics and computer assisted surgery meets medical reality, 29-31 August 2017, Villeneuve d’Ascq, France.
S. Ghilane, H. Bouloussa, C. Vergari, V.Challier, G. Yoshida, J.M. Vidal, O. Gille. New Classification for Degenerative Spondylolisthesis of the Lumbar Spine: a Reliability Study. 51st Annual Meeting of the Scoliosis Research Society. 21st – 24th September 2016, Prague, Czech Republic. [PDF]
J. Rouissi, R. Arvieu, R. Laurent, C. Vergari, M. Bachy, R. Vialle. Assessment of pelvic obliquity in neuromuscular scoliosis using the EOS-CHAIR protocol. British Scoliosis Society Annual Meeting. 13-14/10 2016, Middlesbrough, UK.
R. Pietton, H. Bouloussa, R. Laurent, C. Vergari, R.Vialle. Stereoradiographic reconstruc1on of the rib cage predicts pulmonary function for preoperaive assessment in adolescent idiopathic scoliosis. British Scoliosis Society Annual Meeting. 13-14/10 2016, Middlesbrough, UK.
S. Ghilane, V. Challier, H.Bouloussa, C. Vergari, G. Yoshida, J.-M Vital, O. Gille. Clinical Relevance of a New Classification for Degenerative Spondylolisthesis of the Lumbar Spine. 37th Congress of the International Society of Orthopaedic Surgery and Traumatology . 8th – 10th September 2016, Rome, Italy.
C. Vergari, J.C. Mansfield, J.R. Meakin, C.P. Winlove. An investigation on annulus fibrosus micromechanics with second harmonic generation microscopy. 22nd Congress of the European Society of Biomechanics (ESB). 10th – 13th July 2016, Lyon, France. [podium presentation]
H. Bouloussa, C. Vergari, R. Vialle, W. Skalli. Preoperative Rib Cage Measurement Reproducibility using 3D Stereoradiographic Reconstructions in Adolescent Idiopathic Scoliosis. 31st Annual Meeting of the North American Spine Society (NASS). 26th – 29th October 2016, Boston, MA, USA. [ePoster] [PDF]
S. Ghilane, H. Bouloussa, C. Vergari, V.Challier, G. Yoshida, J.M. Vidal, O. Gille. New Classification for Degenerative Spondylolisthesis of the Lumbar Spine: a Reliability Study. 51st Annual Meeting of the Scoliosis Research Society. 21st – 24th September 2016, Prague, Czech Republic. [podium presentation] [PDF]
C. Vergari, J.C. Mansfield, J.R. Meakin, C.P. Winlove. Quantifying intervertebral disc inter-lamellar and inter-bundle mechanics. Spineweek. 16th – 20th May 2016, Singapore. [special poster presentation] [PDF]
H.Bouloussa, R.Pietton, C. Vergari, W. Skalli, R. Vialle. Biplanar stereography predicts pulmonary function tests in adolescent idiopathic scoliosis. Spineweek. 16th – 20th May 2016, Singapore. [podium communication]
R.Pietton, H.Bouloussa, C. Vergari, W. Skalli, R. Vialle. Rib cage measurement reproducibility using biplanar stereographic 3D reconstructions in severe adolescent idiopathic scoliosis. Spineweek. 16th – 20th May 2016, Singapore. [podium communication]
H.Bouloussa, C. Vergari, R.Pietton, W. Skalli, R. Vialle. Comparison of the CTM Brace Against Nighttime Braces in Adolescent Idiopathic Scoliosis Using Biplanar Stereograpy and 3D Spinal Reconstructions. Spineweek. 16th – 20th May 2016, Singapore. [poster communication]
H.Bouloussa, R.Pietton, T.X. Haen, C. Vergari, W. Skalli, R. Vialle. Biplanar X-rays with Chest Volumetry Predict Preoperative Pulmonary Function in Adolescent Idiopathic Scoliosis. American Academy of Orthopaedic Surgeons Annual meeting. 1st – 5th March 2016, Orlando (FL), USA. [poster communication]
C. Vergari, I. Courtois, E. Ebermeyer, H. Bouloussa, R. Vialle, W. Skalli. Simulation of orthotic treatment in adolescent idiopathic scoliosis using a subject‑specific finite element model. 40th Congress of the Société de Biomécanique. 28th – 30th October 2015, Paris, France. [podium communication]
T.X. Haen, A. Roux, C. Labruyere, C. Vergari, P. Rouch, O. Gagey, M. Soubeyrand, S. Laporte. Shear wear elastography of the human Achilles tendon: a cadaveric study of factors influencing the repeatability. 40th Congress of the Société de Biomécanique. 28th – 30th October 2015, Paris, France. [podium communication]
C. Vergari, I. Courtois, E. Ebermeyer, H. Bouloussa, R. Vialle, W. Skalli. Extensive evaluation of brace simulation for adolescent idiopathic scoliosis using a subject-specific finite element model. Computer Methods in Biomechanics and Biomedical Engineering 2015. 1st-5th September, Montreal, Canada. [podium presentation]
C. Vergari, P. Coloma, W. Skalli. Acoustic Shear Modulus of Cervical Intervertebral Disc is Related to the Functional Unit’s Torsional Stiffness. 21st Congress of the European Society of Biomechanics. 5 - 8th July 2015, Prague, Czech Republic. [poster]
C. Vergari, J. Mazué, K. Abelin-Genevois, C. Adam, W. Skalli. Personalization of spine and trunk models for the simulation of brace action in spinal deformity: an inverse approach. World Congress of the International Society for Prosthetics and Orthotics (ISPO). 22-25th June 2015, Lyon, France [podium presentation]
D. Subit, B. Sandoz, J. Choisne, C. Amabile, C. Vergari, W. Skalli, S. Laporte. Age-induced variations in ribcage morphology from high-resolution X-ray images of volunteer subjects. 24th International Technical Conference on the Enhanced Safety of Vehicles , 8-11 June 2015, Gothenburg, Sweden.
H.Gad, C.Vergari, B.Moreau, B.Sandoz, W.Skalli, S.Laporte. Reference values of the elastic modulus of lumbar multifidus muscle using ultrasound shear wave elastography. 19th ArgoSpine Symposium, 29-30 January 2015, Paris, France. [poster]
C. Vergari, K.Abelin-Genevois, X. Drevelle, N. Champain, E. Ebermeyer, I. Courtois, J. Dubousset, W. Skalli. A preliminary validation of a severity index for early detection of progressive adolescent idiopathic scoliosis. 49th Annual Meeting of the Scoliosis Research Society, 10-13th September 2014, Anchorage, AK, USA. [podium presentation] [PDF]
C. Vergari, P. Rouch, G.Dubois, D.Bonneau, J.Dubousset, M. Tanter, J.L. Gennisson, W.Skalli. In-vivo Cervical Intervertebral Disc Characterization by Elastography. 39th Congress of the international francophone Société de Biomécanique, 27-29th August, Valenciennes (France).
C. Vergari, P.Rouch, D. Bonneau,G. Dubois, J. Dubousset, M. Tanter, J.L. Gennisson, W.Skalli. Shear wave elastography for cervical disc characterization: a feasibility study. 22nd annual meeting of the European Orthopaedic Research Society, 2-4th July 2014, Nantes, France. [podium presentation]
C. Vergari, G. Ribes, B. Aubert, C. Adam, L. Miladi, B. Ilharreborde, K. Abelin-Genevois, P. Rouch, W. Skalli. A Method for Validation of Finite Element Models in Scoliosis Bracing Simulation. 7th World Congress of Biomechanics, 6-11th July 2014, Boston, MA, USA. [poster]
H. Chateau, M. Camus, L. Holden-Douilly, J. Lepley, S. Falala, B. Ravary, C. Vergari, J.M. Denoix, P. Pourcelot and N. Crevier-Denoix. Kinetics of the Forelimb in Horses Trotting an Uphill and Downhill Slope. 9th International Conference on Equine Exercise Physiology, 15-20th June, 2014 Chester, UK.
G. Dubois, W. Kheireddine, C. Vergari, D. Bonneau, P. Thoreux, P. Rouch, M. Tanter, J. Gennisson, W. Skalli. A Reliable Protocol for Shearwave Elastography of Lower Limb Muscles at Rest and Stretched. 7th World Congress of Biomechanics, July 6-11 2014, Boston, MA, USA.
C. Vergari, P.Rouch, D. Bonneau,G. Dubois, J. Dubousset, M. Tanter, J.L. Gennisson, W.Skalli. In vivo mechanical characterization of cervical intervertebral disc by shear wave elastography: a preliminary study. 18th ArgoSpine Symposium, 30-31 January 2014, Paris, France. [podium presentation]
C. Vergari, P.Rouch, G. Dubois, J. Dubousset, D. Bonneau, M. Tanter, J.L. Gennisson, W.Skalli. Mesure élastographique du disque intervertébrale in vivo. 26ème Réunion Annuelle du GIEDA INTER RACHIS, 13-14th September 2013, Nice, France. [podium presentation]
B.Aubert, C.Vergari, B. Ilharreborde, W. Skalli. Reconstruction of the Rib Cage Geometric Properties from Biplanar Radiographs. 48th Annual Meeting of the Scoliosis Research Society, 18-21st September , Lyon, France.
C. Vergari, P.Rouch, G. Dubois, M. Tanter, J.L. Gennisson, W. Skalli. Intervertebral disc characterization by elastography: a preliminary study. 38th Congress of the Société de Biomécanique, 3-6th September 2013, Marseille, France. [poster]
C. Vergari, P.Rouch, G. Dubois, M. Tanter, J.L. Gennisson, W.Skalli . In vitro evaluation of intervertebral disc elastic modulus by elastography. 19th Congress of the European Society of Biomechanics, 25-28th August 2013, Patras, Greece. [podium presentation]
W. Skalli, A. Courvoisier, X. Drevelle, C. Vergari, P. Rouch and J. Dubousset. Advances in Subject Specific Modeling and Application to Scoliosis. Computer Methods in Biomechanics and Biomedical Engineering, 11th International Symposium, 3-6th Apris 2013, Salt Lake City, Utah (USA).
C. Vergari, P. Pourcelot, B. Ravary-Plumioën, M. Camus, L. Holden-Douilly, S. Falala, H. Chateau and N. Crevier-Denoix. Equine Superficial Digital Flexor Tendon Force And Axial Speed of Sound: A Calibration Method Under Clinical Conditions. XXXVII Congress of the Société de Biomécanique, 16-19th October 2012, Toulouse (France). [podium presentation]
C. Vergari, D. Pradon, B. Ravary-Plumiöen, P. Pourcelot and N. Crevier-Denoix. Achilles tendon force and axial speed of sound: a calibration method under clinical conditions. XXXVII Congress of the Société de Biomécanique, 16-19th October 2012, Toulouse (France).
B. Ravary-Plumiöen, P. Pourcelot, C. Vergari, L. Desquilbet, N. Crevier-Denoix. Effects of ground surface on the equine superficial digital flexor tendon loading at the walk and trot. XXXVII Congress of the Société de Biomécanique, 16-19th October 2012, Toulouse (France).
N. Crevier-Denoix, P. Pourcelot, M. Camus, L. Holden-Douilly, S. Falala, B. Ravary-Plumioën, D. Robin, J. Martino, C. Vergari, L. Desquilbet,J .M. Denoix and H. Chateau. Effets biomécaniques des pistes équestres: Impact sur la sécurité et la performance du cheval. 12ème Congrès de médecine et Chirurgie Equine, 11-13th December 2012, Génève, Switwerland.
N. Crevier-Denoix, P. Pourcelot, L. Holden-Douilly, M. Camus, S. Falala, B. Ravary-Plumioën, C. Vergari, L. Desquilbet and H. Chateau. Discrimination of two equine racing surfaces based on forelimb dynamic and kinematic variables at the canter. 7th International conference on Canine and Equine Locomotion, 25-28th June 2012, Strömsholm (Sweden).
H. Chateau, M. Camus, L. Holden-Douilly, S. Falala, B. Ravary-Plumioën, C. Vergari, J.M. Denoix, P. Pourcelot and N. Crevier-Denoix. Ground reaction force and moments around the hoof axes during circling on different ground surfaces at the trot. 7th International conference on Canine and Equine Locomotion, 25-28th June 2012, Strömsholm (Sweden).
N. Crevier-Denoix, B. Ravary-Plumioën, C. Vergari, M. Camus, L. Holden-Douilly, S. Falala, L. Desquilbet, H. Chateau, J.M. Denoix and P. Pourcelot. GComparison of superficial digital flexor tendon loading on asphalt and on deep sand in horses at the walk and trot. 7th International conference on Canine and Equine Locomotion, 25-28th June 2012, Strömsholm (Sweden).
C. Vergari, P. Pourcelot, B. Ravary-Plumioën, A.G. Dupays, S. Jacquet, J.M. Denoix, D. Mitton, P. Laugier, and N. Crevier-Denoix. First application of an axial speed of sound measurement technique in the monitoring of tendon healing. 36th Congress of the Société de Biomécanique, 31th August - 2nd September 2011, Besançon (France). Published in: Computer Methods in Biomechanics and Biomedical Engineering, (14), S1, 2011. [podium presentation]
C. Vergari, P. Pourcelot, B. Ravary-Plumioën, A.G. Dupays, S. Jacquet, F. Audigé, J.M. Denoix, D. Mitton, P. Laugier, and N. Crevier-Denoix. Axial speed of sound in injured tendons: a preliminary study. XXIIIrd Congress of the International society of Biomechanics, 3-7th July 2011, Bruxelles (Belgium) [pdf] [poster].
C. Vergari, P. Pourcelot, L. Holden, B. Ravary-Plumioën,P. Laugier, D. Mitton, and N. Crevier-Denoix. Measurement of cross-sectional area variations of five equine superficial digital flexor tendons during tension. 35th Congress of the Société de Biomécanique, 25-27th August 2010, Le Mans (France). Published in: Computer Methods in Biomechanics and Biomedical Engineering, (13), S1, September 2010. [podium presentation]
C. Vergari. Caractérisation des propriétés mécaniques du disque par élastrographie. 2ème Journée SB-SOFAMEA (Société de Biomécanique - Société Francophone d'Analyse du Mouvement chez l'Enfant et l'Adulte): "Modélisation du rachis: quoi de neuf en 2014? ". Ecole Nationale Supérieure des Arts et Métiers, Paris (France). 8th October 2014.
W. Skalli, C. Vergari, L. Venancio, P. Rouch, J. Choisne, C. Travert, J. Dubousset. Modélisation personnalisée de la colonne vertébrale, son intérêt pour le chirurgien. Académie Nationale de Chirurgie, 4th July 2014, Paris, France.
C.Vergari, P.Rouch, G.Dubois, J.Dubousset, D.Bonneau, M.Tanter, J.L.Gennisson, W.Skalli. Non-invasive characterization of intervertebral disc by shear wave elastography. Journées scientifiques de la Fondation Cotrel,20-21st November 2013, Paris, France.
Natonal meetings and other communications
Z. Cheng, C. Vergari, W. Skalli. Simulation en èléments finis de l’effet des corsets prenant en compte le rèalignement postural. 48éme rèunion du Groupe d'ètude de la scoliose, 10-11 March 2017, Strasbourg, France.
T. Langlais, C. Vergari, R. Pietton, W. Skalli, R. Vialle. Evaluation non invasive de l’altération du disque intervertébral lombaire dans les scolioses idiopathiques de l’adolescent : Résultats préliminaires. 48éme rèunion du Groupe d'ètude de la scoliose, 10-11 March 2017, Strasbourg, France.
A.Abdulmajeed, H. Bouloussa, S. Ghailane, C. Vergari, J.-M. Vital, G.Olivier. Is it Safe to Perform Lumbar Spine Surgery in Patients Older than 85 years old? A Retrospective Cohort of 54 Patients. Sociètè Française de Chirurgie Rachidienne, 1-3 June 2017, Lille, France.
C. Vergari, J.C. Mansfield, J.R. Meakin, P.C. Winlove. Lamellar and fibre bundle mechanics of the annulus fibrosus. Back2Back Meeting. 16th March 2016, Cardiff, United Kingdom.
T.X. Haen, A. Roux, C. Labruyere, C. Vergari, P. Rouch, O. Gagey, S. Laporte, M . Soubeyrand. Caractérisation Biomécanique Du Tendon D’Achille Par Elastographie Shear Waves : Validation Expérimentale. SOFCOT (Société Française de Chirurgie Orthopédique et Traumatologie) 9th – 12th November 2015, Paris, France.
H. Bouloussa, C. Vergari, R. Pietton,T.X. Haen, W.Skalli,R. Vialle. Prédiction des paramètres EFR par reconstructions 3D de radiographies biplanaires avec volumétrie de la cage thoracique dans la scoliose idiopathique de l’adolescent. SOFCOT (Société Française de Chirurgie Orthopédique et Traumatologie) 9th – 12th November 2015, Paris, France.
C. Vergari, J. Mansfield, J. Meakin, P.C. Winlove. Investigating the mechanism of needle injury to the disc. DISCs Meeting. 30th September 2015, London, United Kingdom. [podium communication]
P. Lallemant-Dudek, G. Dubois, C. Vergari, V. Forin, R. Vialle, W. Skalli. Étude de reproductibilité de l'élastographie musculaire par ultrasons chez l'enfant. Les journées de la Société Française d’Orthopédie Pédiatrique (SOFOP). 25-27th Mars 2015, Paris, France.
H. Bouloussa, Tx. Haen, C. Vergari, R. Pietton, W. Skalli, R. Vialle. Correlation du volume de la cage thoracique et des paramètres fonctionnels respiratoires chez les patients porteurs de scolioses idiopathiques : apport de l'imagerie EOS. Les journées de la Société Française d’Orthopédie Pédiatrique (SOFOP). 25-27th Mars 2015, Paris, France.
C. Vergari, G. Dubois, R. Vialle, M. Tanter, D. Bonneau, J. Dubousset, P. Rouch, W. Skalli. Elastographie du disque intervertébral lombaire chez l’enfant. 46ème congrès du Groupe d’Etude des Scolioses, 13-14th Mars, Paris, France.
K. Abelin Genevois, C. Vergari, E. Ebermeyer, I. Courtois, R. Kohler, J.P. Pracros, W. Skalli. Validation d’un indice de sévérité pour la détection précoce des scolioses idiopathiques de l’adolescent progressives. 89e Réunion annuelle de la SOFCOT, 9-12st November 2014, Paris, France. Published in: Revue de Chirurgie Orthopédique et Traumatologique (10), 7:S231.
W. Skalli, C. Vergari, B. Aubert, B. Ilharreborde, J. Dubousset. Advances in Biomechanics of scoliosis : ribcage modelling. Journées scientifiques de la Fondation Cotrel,20-21st November 2013, Paris, France
W. Skalli, C. Vergari, B. Aubert, A. Courvoisier, B. Ilharreborde, J. Dubousset. Clinical biomechanics of scoliosis. Pan Arab Spine Society et Moroccan Spine Society, 29th June 2013, Marrakech, Morocco.
C. Vergari. Axial Speed of Sound and Injured Tendon’s Mechanical Properties. Journée de l'Ecole Doctorale Normande de Biologie Integrative, Santé et Environnement, June 2011 [pdf].
C. Vergari, P. Pourcelot, B. Ravary-Plumioën, A.G. Dupays, S. Jacquet, F. Audigé, J.M. Denoix, Mitton, P. Laugier, and N. Crevier-Denoix. The Potential Of Axial Speed Of Sound In Monitoring Tendon Lesions. Journées d'Animation Scientifique du Département de Santé Animale, May 2011.
C. Vergari. Influence of Poisson's ratio on Ultrasound Speed in Tendon Journée des Doctorants, Ecole Nationale Vétérinaire d'Alfort, Maison-Alfort, France, 22nd October 2010.