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Les muscles paravertébraux lombaires : de l’anatomie à l’étude en élastographie ultrasonore et par résonance magnétique, appliquées à la lombalgie chronique

Abstract : Knowledge about the anatomy and the mode of action of the lumbar paraspinal muscles is major importance for the management of low back pain. Surgical experience shows that the paraspinal muscles constitute a voluminous muscle mass without large tendons and enclosed in an inextensible fascia. In biomechanics, the maximum strength of a muscle is positively correlated to the cross-sectional area of tendons and the muscle belly. Therefore, there is a paradox between the presumed high strength of the voluminous muscle belly and the low strength of the tendons. Traditional biomechanical models seem inappropriate for describing the mode of action of the paraspinal muscles. According to the beam theory, increasing elasticity within the paraspinal compartment would allow the stabilization of the spine.The work has two broad objectives. The first objective was to assess the assumption that there is an inconsistency betwenn the cross-sectional area of the tendon and of the belly of the main paraspinal muscles, i.e. the multifidus, the longissius and the iliocostalis. The second objective was to establish elastography protocols with magnetic resonance imaging and ultrasonography for the exploration of the elasticity of the paraspinal muscles at rest and in several different postures. Results of the anatomical studies show that the tendon-to-muscle area ratios of the longissimis and the iliocostalis were extremely small, as well as cross-sectional area of the belly of the multifidus. That suggests that paraspinal muscles are not able to provide the dorsal extension of the spine during muscle contraction. Rather, they seem to stabilize the spine by providing it with a certain rigidity ensured by a substantial muscle volume contained in an inextensible compartment. Through elastography, we have shown that the elasticity of the paraspinal muscles was the lowest at rest, in decubitus. Elasticity was not influenced by passive flexion or extension of the spine, nor by the stretching of the thoracolumbar fascia. Elasticity increased during sitting, standing, bending forward and bending backward the compared to decubitus. The biomechanical behaviour of the longissimus, the iliocostalis and multifidus differed according to the postures. This work confirms that there are significant changes in elasticity during standing postures. Low back pain is associated with stiffness changes of the spine and of the paraspinal muscles that have been observed through clinical examination. In the future, elastography could allow exploring low back pain.
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Submitted on : Monday, December 9, 2019 - 1:26:11 PM
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  • HAL Id : tel-02400067, version 1

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Maud Crézé. Les muscles paravertébraux lombaires : de l’anatomie à l’étude en élastographie ultrasonore et par résonance magnétique, appliquées à la lombalgie chronique. Anatomie, Histologie, Anatomopathologie [q-bio.TO]. Université Paris Saclay (COmUE), 2019. Français. ⟨NNT : 2019SACLS182⟩. ⟨tel-02400067⟩

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