The differences in the sagittal alignment of patients who had short-segment lumbar fusion when moving from standing to sitting

English Keywords:Sagittal alignment  Sitting  Lumbar fusion

English Abstract:

  【Abstract】 Objectives: To explore how the sagittal alignment of spine after short-segment lumbar fusion changes from standing to sitting and compare this change with that of healthy people. Methods: The lateral whole spinal radiography in the standing and sitting positions of 58 patients (group A, 30 males, 28 females; mean age, 63.7±8.5 years) who underwent lumbar fusion surgery in Peking University Third Hospital was reviewed. And the group A was divided into the group with lumbosacral fusion (group A1, 26 subjects) and the group without lumbosacral fusion (group A2, 32 subjects). The control group contained 90 healthy elderly volunteers(group B, 39 males, 51 females; mean age, 53.2±5.7 years). The parameters including sagittal vertical axis(SVA), T1-pelvic angle(TPA), pelvic incidence(PI), sacral slope(SS), pelvic tilt(PT), lumbar lordosis(LL) and thoracic kyphosis(TK) were measured. The parameters in different position(group A) were compared by using paired t test and the differences in changes from standing to sitting between patients (group A, A1, A2)and the control group(group B) were compared by using independent t test. Results: When moving from standing to sitting in group A, SVA increased(19.7±33.1mm vs 37.9±27.4mm, P＜0.001), followed by decrease in LL(41.6°±13.6° vs 35.6°±14.3°, P＜0.001) and TK (30.5°±12.0° vs 28.0°±12.1°, P=0.006), and TPA increased(11.7°±6.2° vs 17.1°±8.0°, P＜0.001) with the increased in PT(15.1°±6.7° vs 19.4°±9.5°, P＜0.001) and SS(32.3°±8.7° vs 28.7°±9.9°, P＜0.001). Compared with the control group, the patients in group A showed smaller increase in TPA, SVA, PT and smaller decrease in LL, TK(P＜0.05), while the patients with lumbosacral fusion(group A1) presented significantly smaller increase in PT (2.1°±7.1° vs 6.1°±8.9°, P＜0.05). But the patients without lumbosacral fusion(group A2) showed similar PT(6.0°±6.6° vs 6.1°±8.9°, P＞0.05) compared to the control group. Conclusions: When moving from standing to sitting, the spine went forwards with a straighter curvature in lumbar and thoracic spine, followed by pelvic retroversion. However, the straightening in lumbar and thoracic curve, as well as increase in SVA was smaller in patients, and the lumbosacral fusion would limit the pelvic retroversion in the sitting position.