Oral Posters: Thoraco-lumbar Degenerative
Presented by: A. Patwardhan - View Audio/Video Presentation (Members Only)
A. Patwardhan(1,2), F. Jabbour(3), R. Havey(1,2), S. Khayatzadeh(2), J.-C. Le Huec(3), E. Cohen(2), L. Lomasney(1), A. Faundez(4), L. Voronov(1,2)
(1) Loyola University Chicago, Orthopaedic Surgery and Rehabilitation, Maywood, IL, United States
(2) Edward Hines Jr. VA Hospital, Hines, IL, United States
(3) Bordeaux University Hospital, Bordeaux, France
(4) Hopital La Tour, Meyrin, Switzerland
Introduction: Studies of standing lumbopelvic alignment 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 spinal alignment even though adults spend increasingly larger amount of time sitting. Since the lower lumbar spine is the most prevalent site of spinal fusions for painful degenerative conditions in adults, we asked: how do sitting postures alter the lower lumbar spine alignment?
Methods: Eleven asymptomatic volunteer subjects (10M/1F, 39±12 years) consented to participate in the study, which was approved by the local institutional review board. Each subject was positioned inside an EOS X-ray 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 into a full-length mirror mounted in front of the subjects while a full-length lateral radiograph was taken for each posture. Lumbo-pelvic alignment parameters were compared between the three postures using paired t-tests (P1 vs P2 vs P3).
Results: 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). L3-L4 behaved as a transitional segment, behaving similar to the lower two lumbar levels from P1 to P2, and similar to upper lumbar levels from P2 to P3. Figure shows a subject who typifies the average alignment parameters of the cohort. The yellow overlay demonstrates spinal alignment (without other compensation) if the L4-S1 segment were fused in lordotic alignment corresponding to standing erect posture (P1). Because the L4-S1 alignment cannot change after fusion, the L4 superior endplate along with the rest of the cephalad segments are posteriorly tilted in the erect seated posture. The mismatch between the postfusion and normal seated alignment is further exacerbated in the slumped posture.
Conclusions: 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 should not be considered as the gold standard for surgical reconstruction since it may put the proximal segments at risk of developing postfusion breakdown. This is in line with our clinical observation of thoracolumbar junctional kyphosis in patients who have a hypercorrection of proximal lordosis in short fusions. Further exploration is warranted using a prospective study on patients with short fusions and taking into account compensation capabilities of individuals with different lumbar curve types.