Accepted Manuscript. Ultrasound in Medicine and Biologyy. The original publication is available at www.sciencedirect.com. DOI: doi:10.1016/j.ultrasmedbio.2015.04.020.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 quantify the shear modulus of lower limb muscles in order to be used in clinical routine. Four positions were defined to evaluate shear modulus, parallel to the fibers, in the anterior and posterior aspect of the lower limb, at rest and during passive stretching, of 10 healthy subjects. Reliability was first evaluated on 2 muscles by 3 operators, measurements were repeated 6 times. Then, reliability comparison of different muscle was evaluated on 11 muscles by 2 operators, measurements repeated 3 times. Reproducibility of shear modulus was 0.48 kPa and repeatability was 0.41 kPa, with all muscles pooled. The position did not significantly influence the reliability. SWE appeared as an appropriate and reliable tool to evaluate shear modulus of lower limb muscles with the proposed protocol.

Graphical abstract

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 to 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 quasistatic tension can be considered, at first approximation, as an incompressible material.

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is an open access repository that collects the work of Arts et Métiers ParisTech researchers and makes it freely available over the web where possible. This is an author-deposited version published in: https://sam.ensam.eu Handle ID AbstractRib 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.

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is an open access repository that collects the work of Arts et Métiers ParisTech researchers and makes it freely available over the web where possible. 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.

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