The Spinal Curvature of Three Different Sitting Positions Analysed in an Open MRI Scanner

Sitting is the most frequently performed posture of everyday life. Biomechanical interactions with office chairs have therefore a long-term effect on our musculoskeletal system and ultimately on our health and wellbeing. This paper highlights the kinematic effect of office chairs on the spinal column and its single segments. Novel chair concepts with multiple degrees of freedom provide enhanced spinal mobility. The angular changes of the spinal column in the sagittal plane in three different sitting positions (forward inclined, reclined, and upright) for six healthy subjects (aged 23 to 45 years) were determined using an open magnetic resonance imaging (MRI) scanner. An MRI-compatible and commercially available office chair was adapted for use in the scanner. The midpoint coordinates of the vertebral bodies, the wedge angles of the intervertebral discs, and the lumbar lordotic angle were analysed. The mean lordotic angles were 16.0±8.5∘ (mean ± standard deviation) in a forward inclined position, 24.7±8.3∘ in an upright position, and 28.7±8.1∘ in a reclined position. All segments from T10-T11 to L5-S1 were involved in movement during positional changes, whereas the range of motion in the lower lumbar segments was increased in comparison to the upper segments

Scatter diagram of the lumbar (a) and thoracic curvature angle (b) in the upright (circle), flexed (triangle) and extended positions (star).

<p>The x-axis represents the values calculated from the markers, and the y-axis from the vertebral bodies. The crosses show the open MRI's measurement uncertainty of the curvature angles calculated from the markers (x-axis) and calculated from the vertebral bodies (y-axis).</p

Literature summary of the soft tissue artefact of different body locations.

<p>Literature summary of the soft tissue artefact of different body locations.</p

Range of lumbar (a/b) and thoracic (c/d) curvature angle of the subjects, calculated using the vertebral bodies (black) and the skin markers (hatched).

<p>The range was defined from the upright to the flexed (a/c) and to the extended positions (c/d).</p

Acrylic glass plate with five MRI visible markers (paintballs: M1, M2, M3, M4, MC, with distances of M1–M2 = 180 mm, M2–M3 = 70 mm) and two lamb vertebrae, shown in the forward tilted position (45°).

<p>Acrylic glass plate with five MRI visible markers (paintballs: M1, M2, M3, M4, MC, with distances of M1–M2 = 180 mm, M2–M3 = 70 mm) and two lamb vertebrae, shown in the forward tilted position (45°).</p