How Does Gravity Influence the Distribution of Lordosis in Patients With Sagittal Malalignment?

Abstract

Study Design Retrospective cohort study. Objective Compare the supine vs standing radiographs of patients with adult spinal deformity against ideals defined by healthy standing alignment. Methods 56 patients with primary sagittal ASD (SRS-Schwab Type N) and 119 asymptomatic volunteers were included. Standing alignment of asymptomatic volunteers was used to calculate PI-based formulas for normative age-adjusted standing PI–LL, L4–S1, and L1–L4. These formulas were applied to the supine and standing alignment of ASD cohort. Analyses were repeated on a cohort of 25 patients with at least 5 degrees of lumbar flexibility (difference between supine and standing lordosis). Results The asymptomatic cohort yielded the following PI-based formulas: PI–LL = −38.3 + .41*PI + .21*Age, L4–S1 = 45.3–.18*Age, L1–L4 = −3 + .48*PI). PI–LL improved with supine positioning (mean 8.9 ± 18.7°, P < .001), though not enough to correct to age-matched norms (mean offset 12.2 ± 16.9°). Compared with mean normative alignment at L1–L4 (22.1 ± 6.2°), L1–L4 was flatter on standing (7.2 ± 17.0°, P < .001) and supine imaging (8.5 ± 15.0°, P < .001). L4-S1 lordosis of subjects with L1-S1 flexibility >5° corrected on supine imaging (33.9 ± 11.1°, P = 1.000), but L1–L4 did not (23.0 ± 6.2° norm vs 2.2 ± 14.4° standing, P < .001; vs 7.3 ± 12.9° supine, P < .001). Conclusions When the effects of gravity are removed, the distal portion of the lumbar spine (i.e., below the apex of lordosis) corrects, suggesting that structural lumbar deformity is primarily proximal.

Impact of Supine versus Prone Positioning on Segmental Lumbar Lordosis in Patients Undergoing ALIF Followed by PSF: A Comparative Study

“…While interpreting these findings, it is crucial to note that segmental lumbar lordosis measurements in supine and prone positions may not directly compare to those calculated from pre-operative standing radiographs. For instance, in a retrospective cohort study of 56 patients with sagittal malalignment, Fourman et al found that supine positioning improved distal lumbar lordosis but did not fully correct to age-matched norms, particularly in the proximal lumbar spine, indicating that gravity significantly influences lordosis distribution in patients with sagittal malalignment [ 27 ]. Furthermore, in a retrospective study of 63 patients, Benditz et al noted that standing radiographs typically showed slightly higher lordosis values compared to supine Magnetic Resonance Images (MRIs), especially at L5/S1, indicating that MRI can estimate global lumbar lordosis, but single-level lordosis should ideally be determined using standing radiographs [ 28 ].…”

Clinical Faceoff: Hip Osteoarthritis in the Setting of Adult Spinal Deformity

“…Dr. Kim: Lumbar spine flexibility is key to evaluating adult spinal deformity [10,18,19] and predicting the usage for osteotomies to achieve the correct sagittal alignment during corrective surgery [12]. Flexibility of the lumbar spine can be identified using supine radiographs, in which the PI-LL mismatch will normalize compared with standing radiographs.…”