The balance control effects on sitting posture induced by lumbosacral orthosis wear vary depending on the level of stability

This study aimed to assess the differential impacts of lumbosacral orthosis (LO) wear in different sitting conditions through posturographic measurements. Twelve healthy subjects sat on a force platform with three variable stability levels (stable and on seesaws with a long and short radius, inferring slightly and highly unstable sitting, respectively) and three orthosis conditions (no LO, neutral LO, lordotic LO). Using fractional Brownian motion modelling of the centre of pressure (CoP) displacements, it appears that a stable sitting position did not highlight any particular differences between the LO models. With the lordotic LO, a slightly unstable sitting position decreased the mean time by 72% (p < 0.002) before postural corrective mechanisms took over. In contrast, in highly unstable sitting conditions, the lordotic LO induced larger CoP displacements (increasing variance by 162%, p < 0.038). Thus, depending on the amount of perturbation and the device design, wearing an LO may have a neutral, positive or negative impact on postural control in the sitting position.

► The lumbosacral orthoses (LO) can be tested through sitting postural tasks in human healthy subjects.
► Some of the LOs favour lumbar lordosis while others do not.
► Adding a seesaw under the buttocks should increase the pelvic motions.
► Results show that both sitting conditions and LO models interfere in the postural behaviours.
► A sitting position allowing reduced pelvic motions appear appropriate for testing LOs.