Biomechanical effects of spinal orthoses on the trunk during a sit-to-stand-to-sit task

Spinal orthoses can be used to limit active range of motion in different directions and to support trunk extension; however, their effect on movement and muscle activity remains uncertain.

This study explored the effects of two semi-rigid spinal orthoses on trunk kinematics and muscle activity compared to no brace (NB).

A pre-clinical, feasibility study.

Markerless motion capture and surface electromyography was collected from 20 healthy participants each performing 5 repetitions of a sit-to-stand-to-sit task under three conditions: NB, Brace A (Medi Spinomed®, Bayreuth, Germany), and Brace B (DonJoy® Osteostrap, Enovis, UK). Repeated measures analysis of variance was used to evaluate trunk kinematics and muscle activity between conditions.

During sit-to-stand, average muscle activity of the dominant latissimus dorsi was significantly reduced in Brace A compared to NB (MD = 0.13, p = 0.019), but there were no differences between Brace A and Brace B (MD = -0.08, p = 0.097). During both standing and sitting, participants were significantly more flexed forward in Brace A compared to NB (MD = 1.65-2.23, p < 0.015) and Brace B (MD = 1.46-1.55, p = 0.040). During stand-to-sit, peak extension angular velocity significantly increased in Brace A and Brace B compared to NB (MD = 5.74, p = 0.011, MD = 6.68, p = 0.046, respectively). Central tendencies for perceived comfort were "comfortable" for both braces, and perceived ease of task performance was "very easy" for Brace A and "easy" for Brace B, with brace preference split equally.

Active range of motion was not limited using either brace; however, these did assist movement into extension, which may offer a clinical benefit, with small changes also seen in latissimus dorsi muscle activity. Further work including clinical populations is warranted using intervention periods that reflects clinical practice.