The effect of standing vs. variants of the seated position on lumbar intersegmental angulation and spacing: a radiographic study of 20 asymptomatic subjects

Abstract

Background: Pain while sitting is the primary complaint of many patients with lumbar spinal ailments, including those with discogenic low back pain and lumbar disc herniations. There has been little basic research on the different mechanical stresses that different sitting positions place on the spine. To demonstrate the effect of different sitting positions on lumbar intersegmental relationships. Methods: Twenty healthy male volunteer subjects were recruited. Lateral X-rays of the lower lumbar spine were taken in four positions: (I) relaxed lateral standing; (II) "standard" sitting position; (III) sitting on a "kneeling" chair; and (IV) unsupported sitting on a stool. Anterior and posterior disc height, disc space angulation, L1-S1 angulation and interspinous distance were measured. Results: The L1-S1 lordotic angle in the standing position (48.8°±14.7°) was found to be statistically significantly greater than the angle measured with any of the sitting positions: the kneeling chair (34.0°±17.7°); hardback chair (28.6°±14.3°); and the stool (16.6°±15.6°). Total average disc height (arithmetic sum of average disc heights L2-S1) in the lumbar spine varied with position: standing (40.5±7.75 mm); hardback chair (38.5±6.9 mm); kneeling chair (38.4±7.9 mm); stool (36.9±7.1 mm). The mean interspinous distance over all the lumbar levels was significantly greater in each of the three seated positions than in the standing position: standing 6.8±4.5 mm; 11.6°±7.5° for the kneeling chair; 12.9±5.8 mm for the hardback chair; 16.9±7.0 mm for the stool. Conclusions: If segmental flexion and segmental loading are the important biomechanical correlates of pain on sitting, such patients should be most comfortable in a kneeling chair, which most closely approximates the standing position. These basic findings will allow better assessment of different seating positions from an ergonomic perspective, and hopefully lead to improvements in chair design.

The sitting vs standing spine

“…Posterior disc heights were increased by approximately 10% in L1-L2. The difference in disc height in other lumbar segments did not change significantly between natural sitting, sitting on a kneeling chair, sitting on a vertical angled chair, sitting on a hard- back chair, sitting on a chair with anterior support, sitting on stool, and cross leged sitting [19] . An overview of the alterations in spinal alignment between standing and sitting is provided in Fig.…”

“…All the studies, apart from Moon et al 2018 [16] evaluated subjects on a common natural sitting position comparing it with conventional standing lateral and/or sagittal radiographies. Few studies included more seated position variants in their analysis; namely erect sitting [17], floor sitting [16,18], sitting on a kneeling chair, sitting on a chair with back support, sitting on 90° angled chair, sitting on chair with anterior support, sitting on stool, sitting cross-legged [19], kneel sitting [16],…”

“…2018 [16] evaluated subjects on a common natural sitting position comparing it with conventional standing lateral and/or sagittal radiographies. Few studies included more seated position variants in their analysis; namely erect sitting [17] , floor sitting [16 , 18] , sitting on a kneeling chair, sitting on a chair with back support, sitting on 90° angled chair, sitting on chair with anterior support, sitting on stool, sitting cross-legged [19] , kneel sitting [16] , anteflexed sitting [20] , upright sitting [20 , 21] , seated flexion [21 , 22] , seated right and left axial rotation [21] , reclined and forward inclined sitting [23] . An overview of the included studies' and subjects' characteristics is presented in Table 1 .…”

“…The limited evidence about sitting radiographs and relevant planning in spinal surgery has multiple and interconnected causes. First and foremost, the lack of sufficient knowledge about mechanical stresses imposed to the spine during sitting and their potential impact on vertebrae, IVDs, spinal joints and ligaments hinders the development of sitting imaging techniques [19] . Further, erect radiographs have technical advantages over radiographs acquired in sitting position.…”

Effects of Resistance Footrest on Spine Posture in Visual Display Terminal Workers

“…In addition, a standing position can elicit the greatest segmental extension [39]. In a standing position, shortening of the hip flexors (iliopsoas, tensor fascia latae, rectus femoris) causes the pelvis to tilt forward, increasing the lumbar lordotic angle.…”