Analysis of spino-pelvic sagittal alignment in Chinese young subjects in standing versus sitting positions

English Keywords:Spine  Pelvis  Sitting-standing position  Sagittal alignment

English Abstract:

  【Abstract】 Objectives: To analyze the spino-pelvic sagittal alignment of Chinese asymptomatic adults in standing versus sitting positions, based on the characteristics of asymptomatic adults′ sagittal alignment in standing, the variation in sitting position. Methods: This was a prospective radiological analysis by using full-spine standing and sitting lateral radiographs of Chinese volunteers. 145 volunteers(51 males, 94 females; mean age, 23.1±2.3 years) participated. Pelvic and spinal parameters were measured, including pelvic incidence(PI), pelvic tilt(PT), sacral slope(SS), lumbar lordosis(LL), thoracic kyphosis(TK), thoracic lordotic kyphosis(TLK), lordosis tilt(LT), sagittal vertical axis(SVA) and T1-pelvic angle(T1PA). By using Student′s t test, the angular parameters were compared between standing posture and sitting posture. By using Pearson′s correlation test according to different position, difference of relationship between spinal and pelvic parameters in standing versus sitting position were discussed. Results: Mean PI was 46.6°±9.1°. When moving from standing to sitting position, the spine lost nearly 24° of LL(49.6°±9.8° vs 25.2°±10.8°, P<0.001). The SVA also moved more anteriorly by 45mm(-20.7±20.8mm vs 24.5±29.5mm, P<0.001). Regarding changes from the standing to sitting position, average PT, LT, T1PA were greater(P<0.05), and TK, SS were decreased(P<0.05). In sitting position, the correlations of PI-SVA, LL-SVA, PI-T1PA, LL-T1PA were enhanced. Conclusions: In sitting position, the majority of changes occures in the lumbar spine and pelvis alignment. Sitting significantly straightens the spine with decreased TK, LL and SS. Lumbar alignment and SVA move anteriorly. Pelvis rotation and lumbar hypolordosis are the mechanisms of adjusting the trunk sagittal balance in sitting position. This variation in sitting position should be fully considered in terms of long-term effects of the sitting position in patients with lumbar and thoracic fusion.