SAM

Biological and Biomechanical Evaluation of the Ligament Advanced Reinforcement System (LARS AC) in a Sheep Model of Anterior Cruciate Ligament Replacement: A 3-Month and 12-Month Study

VIATEAU, Véronique — Tue, 01 Jan 2013 00:00:00 GMT

Biological and Biomechanical Evaluation of the Ligament Advanced Reinforcement System (LARS AC) in a Sheep Model of Anterior Cruciate Ligament Replacement: A 3-Month and 12-Month Study VIATEAU, Véronique; MANASSERO, Mathieu; ANAGNOSTOU, Fani; MITTON, David; MIGONNEY, Véronique; GUÉRARD, Sandra PurposeThe purposes of this study were to assess tissue ingrowth within the Ligament Advanced Reinforcement System (LARS) artificial ligament (LARS AC; LARS, Arc sur Tille, France) and to study the biomechanical characteristics of the reconstructed knees in a sheep model of anterior cruciate ligament (ACL) replacement.MethodsTwenty-five female sheep underwent excision of the proximal third of the left ACL and intra-articular joint stabilization with a 44-strand polyethylene terephthalate ligament (mean ultimate tensile failure load, 2,500 N). Animals were killed either 3 or 12 months after surgery. Explanted knees were processed for histology (n = 10) or mechanical tests including tests of laxity and loading to failure in tension (n = 15).ResultsWell-vascularized tissue ingrowth within the artificial ligament was only observed in the portions of the ligament in contact with the host's tissues (native ligament and bone tunnels). Ligament wear was observed in 40% of explanted knees. The ultimate tensile failure loads of the operated knees at both time points were inferior to those of the contralateral, intact knees (144 ± 69 N at 3 months and 260 ± 126 N at 12 months versus 1,241 ± 270 N and 1,218 ± 189 N, respectively) (P < .01). In specimens with intact artificial ligaments, failure occurred by slippage from the bone tunnels in all specimens explanted 3 months postoperatively and in half of the specimens explanted 12 months postoperatively.ConclusionsThis study provides evidence that the LARS AC has a satisfactory biointegration but that it is not suitable for ACL replacement if uniform tissue ingrowth is contemplated. Despite good clinical performance up to 1 year after implantation, none of the reconstructions approached the mechanical performance of the normal ACL in the ovine model. Partial tearing of the artificial ligament, which led to a significant decrease in ultimate tensile strength, was observed in 40% of cases in the ovine model.Clinical RelevanceThe LARS is not a suitable scaffold for ACL replacement. Further animal studies are needed to evaluate its potential for augmentation of ligament repair.

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.

Monitoring trabecular bone microdamage using a dynamic acousto-elastic testing method

MORESCHI, Hélène — Sat, 01 Jan 2011 00:00:00 GMT

Monitoring trabecular bone microdamage using a dynamic acousto-elastic testing method MORESCHI, Hélène; CALLE, Samuel; MITTON, David; RENAUD, Guillaume; DEFONTAINE, Marielle; GUÉRARD, Sandra Dynamic acousto-elastic testing (DAET) is based on the coupling of a lowfrequency (LF) acoustic wave and high-frequency ultrasound (US) pulses (probing wave). It was developed to measure US viscoelastic and dissipative non-linearity in trabecular bone. It is well known that this complex biphasic medium contains microdamage, even when tissues are healthy. The purpose of the present study was to assess the sensitivity of DAET to monitor microdamage in human calcanei. Three protocols were therefore performed to investigate the regional heterogeneity of the calcaneus, the correlation between DAET measurements and microdamage revealed by histology, and DAET sensitivity to mechanically induced fatigue microdamage. The non-linear elastic parameter b was computed for all these protocols. The study demonstrated the presence of high viscoelastic and dissipative non-linearity only in the region of the calcaneus close to the anterior talocalcaneal articulation (region of high bone density). Protocols 1 and 2 also showed that most unsorted calcanei did not naturally exhibit high non-linearity, which is correlated with a low level of microcracks. Nevertheless, when microdamage was actually present, high levels of US non-linearity were always found, with characteristic non-linear signatures such as hysteresis and tension/compression asymmetry. Finally, protocol 3 demonstrated the high sensitivity of DAET measurement to fatigue-induced microdamage.

Variability of Child Rib Bone Hounsfield Units using in vivo Computed Tomography

SIDELKEIR, Zaki — Tue, 01 Jan 2013 00:00:00 GMT

Variability of Child Rib Bone Hounsfield Units using in vivo Computed Tomography SIDELKEIR, Zaki; BADINA, Alina; BERMOND, François; MITTON, David; SKALLI, Wafa; SANDOZ, Baptiste The variability assessment of the rib bone mechanical properties during the growth process is still missing. These properties could not be obtained in vivo on children. Relationships have been obtained between Hounsfield Units from computed tomography (CT) and mechanical properties (e.g. for the cortical bone on adults). As a first step for investigation of the mechanical properties of child ribs, the aim of this study was to determine the Hounsfield Units variation of child ribs from CT‐scan data, by rib level, along the rib and within the rib sections. Twenty‐seven right ribs of levels 4, 6 and 9 were processed from 11 thoracic CT scans of children without bone lesions aged between 1 and 10 years. A first set of 10 equidistributed cross‐sections normal to the rib midline were extracted. Sixteen equally distributed elements defined 4 areas into the cortical band: internal, external, caudal and cranial. Within the rib sections, Hounsfield Units were found significantly higher in internal and external areas than in caudal and cranial. In a further step using calibrated CT scans, it would be possible to derive the mechanical properties of in vivo child ribs using bone density correlation with Hounsfield Units.

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

Nonlinear ultrasound monitoring of fatigue microdamage accumulation in cortical bone

HAUPERT, Sylvain — Sat, 01 Jan 2011 00:00:00 GMT

Nonlinear ultrasound monitoring of fatigue microdamage accumulation in cortical bone HAUPERT, Sylvain; LAUGIER, Pascal; PEYRIN, Françoise; GUÉRARD, Sandra; MITTON, David Accumulation of bone micro-damage is suspected to lead to severe impairment of mechanical properties with an increase in skeletal fragility and fracture risk. The objective of the study was to evaluate the potential of Nonlinear Resonant Ultrasound Spectroscopy (NRUS) for measuring micro-damage accumulation in cortical bone using four-point bending cycling fatigue. Sixteen human cortical bone specimens were machined as parallelepiped beams. Damage progression was controlled by measuring the linear elastic beam theory modulus (E LEBT ), known to reflect microdamage accumulation. Before and between each damage step, the nonlinear ultrasonic elastic coefficient was measured by NRUS. At the end of each cycling fatigue, a subset of bone samples was measured by μCT at the European Synchrotron Radiation Facility. Results showing a progressive increase of nonlinear ultrasonic elastic coefficient along fatigue cycling suggest that NRUS measurements are sensitive to micro-damage accumulation. The results mentioned above were validated using synchrotron radiation μCT. The variation of elastic nonlinearity was found to be significantly correlated to the variation of number density of small microcracks which almost doubled in damaged regions

In vitro implant-bone interface pressure measurements for a cementless femoral implant. A preliminary study

COURVOISIER, Aurélien — Fri, 01 Jan 2016 00:00:00 GMT

In vitro implant-bone interface pressure measurements for a cementless femoral implant. A preliminary study COURVOISIER, Aurélien; BARBOUR, Valéry; SKALLI, Wafa; MITTON, David PURPOSE: Implants endurance as well as a good clinical tolerance depends on the recovery of a physiological stress distribution within bone after implantation. The purpose of the present work was to develop an alternative technique using Force Sensing Resistors (FSR) to gather in vitro pressure values at the implant-bone interface for a cementless implant. METHOD: Eight cementless femoral stems were instrumented with six calibrated FSR bonded on each facet and then implanted in eight cadaver femurs. Compression tests were performed until failure and FSR pressure values were recorded. RESULTS: The average failure load was 4241 N. The maximum contact pressure measured with the FSR averaged 1.965 MPa. CONCLUSION: FSR reached many of the requirements for an ideal implant-bone interfacial sensor. This experimentation provided in vitro quantitative data on contact pressure at the implant-bone interface, which could help understanding stress shielding phenomenon and developing relevant numerical model.

In Vivo Assessment of Elasticity of Child Rib Cortical Bone Using Quantitative Computed Tomography

ZHU, Y. — Sun, 01 Jan 2017 00:00:00 GMT

In Vivo Assessment of Elasticity of Child Rib Cortical Bone Using Quantitative Computed Tomography ZHU, Y.; BERMOND, François; PAYEN DE LA GARANDERIE, J.; PIALAT, J.-B.; SANDOZ, Baptiste; BRIZARD, D.; PRACROS, J.-P.; RONGIERAS, F.; SKALLI, Wafa; MITTON, David Elasticity of the child rib cortical bone is poorly known due to the difficulties in obtaining specimens to perform conventional tests. It was shown on the femoral cortical bone that elasticity is strongly correlated with density for both children and adults through a unique relationship. Thus, it is assumed that the relationships between the elasticity and density of adult rib cortical bones could be expanded to include that of children. This study estimated in vivo the elasticity of the child rib cortical bone using quantitative computed tomography (QCT). Twenty-eight children (from 1 to 18 y.o.) were considered. Calibrated QCT images were prescribed for various thoracic pathologies. The Hounsfield units were converted to bone mineral density (BMD). A relationship between the BMD and the elasticity of the rib cortical bone was applied to estimate the elasticity of children’s ribs in vivo. The estimated elasticity increases with growth (7.1 ± 2.5 GPa at 1 y.o. up to 11.6 ± 1.9 GPa at 18 y.o.). This data is in agreement with the few previous values obtained using direct measurements. This methodology paves the way for in vivo assessment of the elasticity of the child cortical bone based on calibrated QCT images.

Prediction of Hip Failure Load: In Vitro Study of 80 Femurs Using Three Imaging Methods and Finite Element Models-The European Fracture Study (EFFECT).

POTTECHER, Pierre — Fri, 01 Jan 2016 00:00:00 GMT

Prediction of Hip Failure Load: In Vitro Study of 80 Femurs Using Three Imaging Methods and Finite Element Models-The European Fracture Study (EFFECT). POTTECHER, Pierre; ENGELKE, Klaus; DUCHEMIN, Laure; MUSEYKO, Oleg; MOSER, Thomas; MITTON, David; VICAUT, Eric; ADAMS, Judith; SKALLI, Wafa; LAREDO, Jean-Denis; BOUSSON, Valérie Purpose To evaluate the performance of three imaging methods (radiography, dual-energy x-ray absorptiometry DXA, and quantitative computed tomography CT) and that of a numerical analysis with finite element modeling (FEM) in the prediction of failure load of the proximal femur and to identify the best densitometric or geometric predictors of hip failure load.

Short isthmic versus long trans-isthmic C2 screw: anatomical and biomechanical evaluation

LUCAS, François — Fri, 01 Jan 2016 00:00:00 GMT

Short isthmic versus long trans-isthmic C2 screw: anatomical and biomechanical evaluation LUCAS, François; MITTON, David; FRECHEDE, Bertrand; BARREY, Cédric INTRODUCTION: The Harms technique is now considered as the gold standard to stabilize C1-C2 cervical spine. It has been reported to decrease the risk of vertebral artery injury. However, the risk of vascular injury does not totally disappear, particularly due to the proximity of the trans-isthmic C2 screw with the foramen transversarium of C2. In order to decrease this risk of vertebral artery injury, it has been proposed to use a shorter screw which stops before the foramen transversarium. OBJECT: The main objective was to compare the pull-out strength of long trans-isthmic screw (LS) versus short isthmic screw (SS) C2 screw. An additional morphological study was also performed. METHOD: Thirteen fresh-frozen human cadaveric cervical spines were included in the study. Orientation, width and height of the isthmus of C2 were measured on CT scan. Then, 3.5-mm titanium screws were inserted in C2 isthmus according to the Harms technique. Each specimen received a LS and a SS. The side and the order of placement were determined with a randomization table. Pull-out strengths and stiffness were evaluated with a testing machine, and paired samples were compared using Wilcoxon signed-rank test and also the Kaplan-Meier method. RESULTS: The mean isthmus transversal orientation was 20° ± 6°. The mean width of C2 isthmus was less than 3.5 mm in 35 % of the cases. The mean pull-out strength for LS was 340 ± 85 versus 213 ± 104 N for SS (p = 0.004). The mean stiffness for the LS was 144 ± 40 and 97 ± 54 N/mm for the SS (p = 0.02). DISCUSSION: The pull-out strength of trans-isthmic C2 screws was significantly higher (60 % additional pull-out resistance) than SSs. Although associated with an inferior resistance, SSs may be used in case of narrow isthmus which contraindicates 3.5-mm screw insertion but does not represent the first option for C2 instrumentation. LEVEL OF EVIDENCE: Level V.