Although lumbar orthoses (LO) are commonly used for many years in the conservative treatment of low back pain, postural and mechanical effects are, to our knowledge, partly unexplored. Methodological difficulties are the main cause with, in the first place, the difficulty to assess the LO effects inside the trunk with a non-invasive and not expensive method adapted for current medical practice. This Ph.D work attempts to address these difficulties through the development of a specific methodology. The mechanical effect was studied by a non-invasive estimation of the intradiscal pressure through a finite element modeling controlled by radiographs. The first results showed the possibility of a mean reduction from 15 to 22% of the intradiscal pressure while wearing an LO which is able to change the spinal posture. The different works on postural balance allowed us to define a methodology for a suitable LO assessment in standing and then sitting postures. The first results in patients with subacute low back pain showed a more efficient postural control (reduction of active stiffness of the trunk) while wearing the most stiffer LO. In the future, this easy-to-implement assessment could be helpful to more accurately target the appropriate LO for a given patient in order to improve his / her clinical status
