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International audience; Osteosarcoma is a malignant bone tumor that preferentially arises in adolescents and young adults. Like many sarcomas with complex genomics, this type of tumors exhibits strong spatial heterogeneities in terms of micro-architecture or differentiated response to treatments due to localized effect of chemotherapy. Clinical images at a tissue scale such as histological and immunohistological sections, exhibit three phases: fluid, solid, cells populations. Therefore the tumor can be considered as a porous medium. The objective of this work was to develop a mechanical approach based on upscaling methods to study the interstitial flow within the tumor at the tissue scale. The statistical study of the micro-architecture of the media shows that the identification of characteristic lengths is complex and that a separation of spatial scales is not necessarily identified. We therefore chose a special sequential upscaling technique, named Grid-Block approach to solve this problem.

International audience; Like most sarcomas with complex genomics,or more generally bone tissues, osteosarcoma isa type of tumors exhibiting a strong spatialheterogeneity of the micro-environment. Thisheterogeneity makes the diagnostic complex andcan induce strong spatial variability in theresponse to treatments. New researchstrategies are consequently needed tounderstand the impact of spatial heterogeneity onthe diagnostic accuracy and on the treatmentefficiency, and more generally to understand thelinks between tissue scale bone matrix structuresand underlying biology occurring at the cell scale.The aim of this interdisciplinary work is to obtain the quantification of correlations between clinicaldata, heterogeneity of bone tissues and mechanobiological parameters. To this purpose, original numerical developments were initiated in our group to study the intratumoral and healthy bone tissue heterogeneity from histological and immunohistological sections. The code aimed at obtaining quantitative metrics of the cell population distribution, of the bone matrix micro-architecture (porosity) and of the transport properties (such as effective diffusivity). Because tissues exhibit naturally a complex spatial scales cascade, it can be modeled, at the tissue scale, as a three phases porous medium (fluid, solid, cell populations). Using methodologies related to porous media analysis, characteristic lengths were extracted and correlations of phenomena occurring cell and tissue scale examined. Further developments permitted the calculation of effective mechanical properties. The methodology used successive algorithms of machine learning for the histological image segmentation and a combination of iterative algorithms and filters for the correlation calculations. Results put forward the strength of this approach for the identification of new markers in the study of pathological bone tissues.

International audience; Overweight is a risk factor for osteoarthritis on the knees. Subchondral trabecular bone (SCTB) densification has been shown to be associated with cartilage degeneration. This study analyzed the microarchitectural changes in the SCTB of tibial plateaus to validate the hypothesis that the degree of remodeling is correlated with a patient's body weight. Twenty-one tibial plateaus were collected during total knee arthroplasty from 21 patients (15 women and 6 men). These patients had a mean age of 70.4 years (49-81), mean weight of 74.7 kg (57-93) and mean body mass index (BMI) of 28.4 kg/m2 (21.3-40.8). One cylindrical plug was harvested in the center of each tibial plateau (medial and lateral). Micro-CT parameters (7.4 μm resolution) were determined to describe the SCTB structure. On the medial plateau, there were significant correlations between BMI and bone volume fraction BV/TV (r = 0.595, p = 0.004), structure model index SMI (r = -0.704 p = 0.0002), trabecular space Tb.Sp (r = 0.600, p = 0.04) and trabecular number Tb.N (r = 0.549, p = 0.01). SCTB densification during osteoarthritis is associated with a reduction in its elastic modulus, which could increase cartilage stress, and accelerate cartilage loss. SCTB densification has been shown to precede cartilage degeneration. The correlation of SCTB microarchitecture and body weight may explain why knee osteoarthritis is more common in overweight or obese patients. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res.

International audience; OBJECTIVES/HYPOTHESIS: Adipose derived stromal cells (ASCs) are abundant and easy to prepare. Such cells may be useful for treating severe vocal disturbance caused by acute vocal fold scars. STUDY DESIGN: Prospective animal experiments with controls. METHODS: Twenty New-Zealand white rabbits were used in the present study. We evaluated vocal fold healing, with or without injection of autologous ASCs, after acute scarring. A defined lesion was created and the ASCs were immediately injected. Vocal fold regeneration was evaluated histomorphometrically and via viscoelastic analysis using an electrodynamic shaker. RESULTS: Six weeks after ASC injection, vocal folds exhibited significantly less inflammation than control folds (P < 0.005). In addition, hypertrophy of the lamina propria and fibrosis were significantly reduced upon ASC injection (P < 0.02). The decrease in viscoelastic parameters was less important in the ASC injected group compared to the noninjected group (P = 0.08). CONCLUSION: Injection of autologous ASCs improved vocal fold healing in our preclinical model. Further studies are needed, but this method may be useful in humans. LEVEL OF EVIDENCE: NA. Laryngoscope, 126:E278-E285, 2016.

We compared disc hydration properties of adolescent idiopathic scoliosis before and 5 years after spinal fusion with an age-matched control group. We conducted a prospective MRI follow-up of 23 patients. Disc and nucleus volumes were reconstructed on T2 weighted sequence. In the scoliotic group, vd and vn were lower than control group, hydration ratio (Vn/Vd) was lower. After surgery, subjacent discs rehydrated. AIS induces a loss of IVD hydration. Surgical correction can reverse homeostasis disturbances related to spinal deformity.

Dispositif de mesure de la rigidité des tissus orbitaires, caractérisé en ce qu'il comprend : - une poutre élastique (PE) ayant une extrémité libre (B), dite distale, et une extrémité opposée (A), dite proximale, encastrée dans une base (BP); - un système de fixation crânienne (BF), pour maintenir ladite base en contact avec le front (FP) d'un patient; - une interface mécanique d'appui (CO) s'étendant à partir de ladite poutre pour venir en contact avec un œil (OP) dudit patient; - au moins quatre jauges d'extensométrie (XI - X4) fixées sur au moins une face de la poutre; et - un module de traitement des signaux (MTS) configuré pour fournir une valeur de rigidité des tissus orbitaires (K) à partir des signaux générés par lesdites jauges d'extensométrie lorsqu'une force (Fl) est appliquée à ladite poutre provoquant sa flexion, de telle sorte que ladite interface mécanique d'appui exerce une pression sur ledit œil du patient. Utilisation d'un tel dispositif pour mesurer la rigidité des tissus orbitaires d'un patient.

International audience; There are no published studies describing the strength quadrupled gracilis tendon alone and quadrupled semitendinosus tendon alone in the configuration used for anterior cruciate ligament (ACL) reconstruction. The primary objective was to compare the mechanical properties of grafts used for ACL reconstruction during a tensile failure test. The secondary objective was to evaluate the effect of uniform suturing on graft strength. Fifteen pairs of knees were used. The mechanical properties of five types of ACL grafts were evaluated: patellar tendon (PT), sutured patellar tendon (sPT), both hamstring tendons (GST4), quadrupled semitendinosus (ST4), and quadrupled gracilis (G4). Validated methods were used to perform the tensile tests to failure and to record the results. Student's t-test was used to compare the various samples. The maximum load to failure was 630.8N (± 239.1) for the ST4, 473.5N (± 176.9) for the GST4, 413.3N (± 120.4) for the sPT, and 416.4N (± 187.7) for the G4 construct. Only the ST4 had a significantly higher failure load than the other grafts. The sPT had a higher failure load than the PT. The ST4 construct had the highest maximum load to failure of all the ACL graft types in the testing performed here. Uniform suturing of the grafts improved their ability to withstand tensile loading.

International audience; OBJECTIVES: The number of locking screws required per fragment during bridging osteosynthesis in the dog has not been determined. The purpose of this study was to assess the survival of two constructs, with either two or three screws per fragment, under cyclic torsion.METHODS: Ten-hole 3.5 mm stainless steel locking compression plates (LCP) were fixed 1 mm away from bone surrogates with a fracture gap of 47 mm using two bicortical locking screws (10 constructs) or three bicortical locking screws (10 constructs) per fragment, placed at the extremities of each LCP. Constructs were tested in cyclic torsion (range: 0 to +0.218 rad) until failure.RESULTS: The 3-screws constructs (29.65 ± 1.89 N.m/rad) were stiffer than the 2-screws constructs (23.73 ± 0.87 N.m/rad), and therefore, were subjected to a greater torque during cycling (6.05 ± 1.33 N.m and 4.88 ± 1.14 N.m respectively). The 3-screws constructs sustained a significantly greater number of cycles (20,700 ± 5,735 cycles) than the 2-screws constructs (15,600 ± 5,272 cycles). In most constructs, failure was due to screw damage at the junction of the shaft and head. The remaining constructs failed because of screw head unlocking, sometimes due to incomplete seating of the screw head prior to testing.CLINICAL SIGNIFICANCE: Omitting the third innermost locking screw during bridging osteosynthesis led to a reduction in fatigue life of 25% and construct stiffness by 20%. Fracture of the screws is believed to occur sequentially, starting with the innermost screw that initially shields the other screws.

International audience; Purpose: To analyse the biomechanical properties of the intervertebral disc after scoliosis surgery according to the underlying spino-pelvic organization.

Ideal surgical management of adolescent idiopathic scoliosis (AIS) aims for an optimal correction of the deformity while preserving mobility. An unbalanced rigid spine puts the mobile segment at higher risk of disk degeneration. The goal of our study is to clarify the long term outcome of AIS after spinal fusion.

La présente invention concerne le domaine de la chirurgie orthognathique. Plus précisément, elle concerne la réalisation de gouttières de positionnement utilisées pour repositionner les os des mâchoires du patient, après une opération par laquelle le praticien a découpé des fractions des maxillaires (mâchoire supérieure) et/ou de la mandibule (mâchoire inférieure).

La cicatrisation des fractures comminutives diaphysaires constitue une préoccupation majeure en orthopédie vétérinaire, vu leur incidence élevée, leur fort taux de complications et le défi thérapeutique que leur traitement constitue. L’un des implants les plus récents pour l’ostéosynthèse de pontage de telles fractures est la plaque de compression à verrouillage (LCP), utilisable avec des vis standard ou des vis verrouillées. Malgré les quelques études cliniques et biomécaniques comparant les plaques LCP avec vis verrouillées à d’autres types de plaque (DCP, LC-DCP), l’avantage réel des vis verrouillées demeure inconnu et non quantifié. Le but de cette étude est de comparer les propriétés mécaniques de montages par plaques LCP équipées de vis standard ou verrouillées, pontant un modèle de fracture comminutive diaphysaire.

In young scoliotic patients, the post-operative consequence of spine fusion upon the free lower lumbar spine is one of the major concerns of the surgical treatment. The remodeling of free-motion segment and the role of discs below thoraco-lumbar fusions remains unknown. However, disc hydration and mass exchange flow between disc and vertebral body should play a significant role in the mechano-biology of the vertebral segment. Magnetic resonance imaging is relevant to study intervertebral discs in young scoliotic patients since related to hydration and non-radiant.

Colloque avec actes et comité de lecture. Internationale.; International audience; L'objectif était de développer un modèle numérique prédictif de cicatrisation péri-prothétique en s'appuyant sur des analyses histomorphométriques d'implants canins stables et non cimentés. L'hypothèse centrale du travail de recherche a consisté à supposer que la mécanique des milieux poreux déformables associée aux concepts de migrations cellulaires (ostéoblastes) passives et actives et de diffusion de facteurs de croissance en interaction pouvait aider à la compréhension des phénomènes de cicatrisation péri-prothétique. Les corrélations numériques et histomorphométriques ont été très satisfaisantes compte tenu de la complexité des phénomènes mécano-biologiques. Le modèle a permis de prévoir les cicatrisations hétérogènes précédant généralement le descellement. Il offre la possibilité d'évaluer l'impact de paramètres cliniques tels que la concentration des facteurs de croissance ou les conditions de pose (alésage osseux) ainsi que la stabilité de l'implant par rapport à l'os hôte.