Search

Low back pain represents a major economic and societal challenge due to its high prevalence. Lumbar orthoses are one of the recommended treatments. Even if previous results showed their clinical effects, the detailed mode of action is still poorly known, making the device design difficult. A renewed instrumentation and experimental protocol should bring better insight into the lumbar brace–trunk mechanical interaction. This instrumentation should give detailed information on the basic physical or geometrical parameters: the pressure applied on the trunk, the body shape and the strain in the belt. The principal objective of this study was to propose and validate a new measurement protocol, based on pressure mapping systems and full-field shape and strain measurement. The feasibility of the protocol was tested along with its validity and repeatability. The influence of various parameters, which could cause changes in the measurements, was tested with six different belt configurations on one subject. Measurements were also performed to study the impact of posture on pressure and strain. Both pressure and strain appeared to be asymmetric from left to right. The pressure applied by the lumbar belt on the back varies with breathing and with posture. This study showed that full-field measurements were necessary to render the high variability of pressure or strain around the trunk, under recommendations of their use to guarantee a satisfying repeatability. [ABSTRACT FROM AUTHOR]

Objective Although it is only a part of their therapeutic effect, the mechanical effect of compression or contention medical devices (CCMD) is always claimed by the manufacturers. However, the mechanism between the pressure application zone and the targeted organ is complex. It involves a purely passive mechanical effect and mechanisms related to the tonic postural system. Various strategies can be implemented to show the effectiveness of a mechanical action; among them, biomechanical modeling is a able to consider complex mechanical effects before any clinical trial. Objectives This work aims to describe the contributions of a biomechanical modeling in understanding the action of CCMD using as an illustration the lumbar belt treatment of chronic and sub-chronic back pain. Material and methods Three successive models are described: a finite elements model of the intervertebral discs, coupled with a low intensity X-ray imaging, a finite elements model of the entire trunk, including the spine but also the soft tissue of the abdomen and finally a purely analytical model based on external measurements of the trunk shape. Results These three models correspond to different questioning: the first shows that the use of lumbar belts changes the pressure in the back of intervertebral discs and therefore pain. The second allows kriging the most important parameters on posture – trunk shape, belt properties – from the others – abdominal tissues. Finally, the third model specifies the mechanical efficiency of a given lumbar belt on a specific patient. Discussion/Conclusion Each of the three proposed models answers to a specific question and cannot substitute for the other. The finite elements model used in the first two models is tedious to implement due to the geometry, obtained by segmentation of medical images, and calculation time can be high. However, this is a rich method, accurately describing the studied mechanical system and leading to detailed results. The analytical approach used in the third model requires more approximation, but its lower calculation time allows deployment in research and development units and clinics. [ABSTRACT FROM AUTHOR]