In-silico pre-clinical trials are made possible by a new simple and comprehensive lumbar belt mechanical model based on the Law of Laplace including support deformation and adhesion effects

Abstract

Lower back pain is a major public health problem. Despite claims that lumbar belts change spinal posture due to applied pressure on the trunk, no mechanical model has yet been published to prove this treatment. This paper describes a first model for belt design, based on the one hand on the mechanical properties of the fabrics and the belt geometry, and on the other hand on the trunk geometrical and mechanical description. The model provides the estimation of the pressure applied to the trunk, and a unique indicator of the belt mechanical efficiency is proposed: pressure is integrated into a bending moment characterizing the belt delordosing action on the spine. A first in-silico clinical study of belt efficiency for 15 patients with 2 different belts was conducted. Results are very dependent on the body shape: in the case of high BMI patients, the belt effect is significantly decreased, and can be even inverted, increasing the lordosis. The belt stiffness proportionally increases the pressure applied to the trunk, but the influence of the design itself on the bending moment is clearly outlined. Moreover, the belt/trunk interaction, modeled as sticking contact and the specific way patients lock their belts, dramatically modifies the belt action. Finally, even if further developments and tests are still necessary, the model presented in this paper seems suitable for in-silico pre-clinical trials on real body shapes at a design stage.

Feasibility of a Full-Field Measurements-Based Protocol for the Biomechanical Study of a Lumbar Belt: A Case Study

“…Considering the global body symmetry in the sagittal plane, this might indicate that the Laplace Law is not enough to describe the loading of a belt on the body. In [29], it is suggested that this left/right difference could be explained by the adhesion between the belt and the body, in conjunction with the locking system.…”

“…This mode of action is closely related to the pressure applied by the belt on the trunk, as shown, for example, in [12]. The Laplace Law is a simple way to describe the pressure generation of a compression textile on a body part [29]. It states:…”

An In-Silico Study on the Therapeutic Effect of Low Back Belts: Biomechanical Correlation between Belt Design and Patient Morphology

“…Since the patient closes the belt in a loosening phase, the stiffness is taken as the tangential slope of the strain/lineic force curve during unloading at 20% strain. This procedure is explained in more detail in Molimard et al [18].…”

“…Moreover, the quality of the belt geometrical representation was poor, considering that the choice of the belt is influential. Recently, a semi-analytical approach based on real trunk shape and a more detailed belt structure has been proposed [18]. This approach provided a first in-silico pre-clinical trial that clearly outlines the influence of morphology on belt response; it also shows that the belt structure could change the treatment efficiency.…”

Soft tissue material properties based on human abdominal in vivo macro-indenter measurements

“…Recent simulation models that include the biomechanical behavior of the abdomen or parts of it differ in their implementing methods, scope, and degree of detail, depending on the requirements of their intended use case (Anderson et al, 2007;Hicks et al, 2015). Possible use cases encompass, for example, studies on 1) the effect of individual braces in scoliosis treatment (Périé et al, 2004;Clin et al, 2010;Sattout et al, 2016), or of lumbar orthoses (Molimard et al, 2019;Bonnaire et al, 2020) on the lumbosacral spine, 2) injury prevention in crash testing (King, 2018;Untaroiu et al, 2018;Grébonval et al, 2021) and stiff structure impact (Lee and Yang, 2001;Haug et al, 2004;Snedeker et al, 2007) or vertical impact load (Cox, 2020) studies, or 3) the load removal of the spine by increasing the intra-abdominal pressure (El-Monajjed and Driscoll, 2020;Guo et al, 2021). Another use case is modelling the interaction of organs (Misra et al, 2008), or the abdominal wall with surgical instruments (Hernández et al, 2011); these models are used for virtual surgical planning or support of education (Leong et al, 2022).…”