|Beitragstitel||Variations of Lumbopelvic Alignment in Standing, Seated, and Slumped Postures in a Cohort of Asymptomatic Adults: Implications for lumbar fusion surgery|
Studies of spinopelvic alignment in the standing posture have formed the basis of recommendations regarding the ideal lumbar fusion alignment to avoid postoperative complications. Only a few studies have investigated the effect of various sitting postures on alignment of the lumbar spine even though adults spend an increasingly larger proportion of their waking hours sitting in a chair at the office or at home. We asked the question: how do sitting postures alter the alignment of the lower lumbar spine, which is the most prevalent site of spinal fusions for painful degenerative conditions in adults.
Eleven asymptomatic volunteer subjects (10M/1F, 39±12years) consented to participate in the study, which was approved by the local institutional review board. Each subject was positioned inside an EOS machine and instructed to assume the following postures: (i) standing erect (P1), (ii) sitting erect (P2), and (iii) sitting slumped (P3). Subjects were instructed to maintain horizontal gaze by looking straight ahead in a full-length mirror mounted in front of the subjects while a full-length lateral radiograph was taken for each posture. All alignment parameters were compared between the three postures using paired t-tests (P1 vs. P2 vs. P3).
As subjects transitioned from standing (P1) to sitting erect (P2), upper lumbar (L1-L3) lordosis did not change while L4-S1 lordosis significantly decreased, (28.8 to 17.4 degrees, p<0.001). Postural change from erect sitting to slumped sitting (P2 to P3) had the opposite effect: the L1-L3 segments underwent a significant alignment change, from 11.1 degrees of lordosis to 3.1 degrees of kyphosis (p<0.001); while L4-S1 lordosis did not significantly reduce (17.4 to 12.7 degrees lordosis, p=0.1). The L3-L4 segment behaved similar to the lower two lumbar levels for transition from P1 to P2, and similar to upper lumbar levels when transitioning from P2 to P3.
L4-S1 lordosis significantly decreased when transitioning from standing to sitting. If fusion across L4-S1 is indicated, our observations suggest the sagittal alignment of the lower lumbar spine in the standing posture may not be considered as the gold standard for surgical reconstruction since it may put the proximal segments at risk of developing postfusion breakdown. Further exploration is warranted using a prospective study on patients with short fusions and taking into account compensation possibilities of individuals.