Why Vertebral Shape Matters: New Research on Lumbar Lordosis and Chronic Low Back Pain

A clinical research brief for patients and referring clinicians at Symmetry Health Center

Lumbar lordosis—the natural inward curve of the low back—is not merely a postural habit. It is a structural feature of the spine that develops from both the shape of the vertebral bodies and the discs between them. A 2026 study published in the Journal of Clinical Medicine examined whether the bony geometry of the lumbar vertebrae predicts lordosis independently of pelvic morphology, and whether that relationship differs in people with chronic low back pain (CLBP).

The findings have direct relevance to how we evaluate and restore sagittal alignment at Symmetry Health Center. In patients with chronic low back pain, the usual relationship between pelvic shape and lumbar curve is often disrupted. The bony wedge geometry of the lumbar vertebrae, however, remains a meaningful predictor of lordosis.

What the investigators measured

Harrison and colleagues digitized standing full-spine lateral radiographs from 72 asymptomatic volunteers and 72 patients with chronic low back pain lasting more than three months. Using a validated quadrilateral vertebral-body model, they calculated the wedge angle of each lumbar vertebra from L1 through L5. Negative values indicate lordotic (posterior) wedging; positive values indicate kyphotic (anterior) wedging.

They then summed those five angles into a single composite measure: the total wedge index (TWI). A more negative TWI indicates greater net posterior taper of the lumbar column—the bony contribution to lordosis. This index was compared with pelvic morphology, measured as the posterior tangent pelvic incidence angle (PTPIA), and with lumbar lordosis measured by the posterior tangent (absolute rotation angle) method from L1 to L5.

Principal findings

In both groups, TWI was the strongest structural correlate of lumbar lordosis. Among asymptomatic volunteers, TWI correlated with lordosis at r = +0.531. Among patients with CLBP, the correlation remained robust at r = +0.478. In both cohorts the association was statistically significant.

Hierarchical regression clarified the clinical importance of that result. In volunteers, pelvic morphology alone explained approximately 18 percent of lordosis variance; adding TWI increased explained variance by 18.3 percentage points. In CLBP, pelvic morphology explained less than 2 percent of lordosis variance—consistent with prior work from the same group showing pelvic–lordosis decoupling in chronic pain. TWI alone explained 22.8 percent of lordosis variance in that group, an incremental gain of 21.0 percentage points over pelvic morphology.

Between-group differences were concentrated at the endpoints of the lordotic arc. L1 was less kyphotic-wedged in CLBP than in volunteers, and L5 was less lordotically wedged. Mid-lumbar levels (L2–L4) did not differ significantly. In CLBP, L1 and L5 also lost their individual correlations with global lordosis, while L2–L4 retained them. The authors interpret this as selective attenuation of the structural contribution of the cephalad and caudal anchors of the curve.

TWI also correlated with sacral tilt in both groups. It did not correlate with T4–hip-axis translation, indicating that vertebral-body geometry is a local lumbar structural variable rather than a driver of global sagittal translation.

Sex differences and interpretive caution

Males demonstrated greater L1 wedge angles than females (combined-sample Cohen’s d = 0.67). This finding appears, at first glance, to conflict with the well-established observation that females typically have greater standing lumbar lordosis. The authors reconcile the paradox through the disc–body partition of lordosis: females often achieve greater curve through larger disc wedging, particularly at L4–S1, whereas males may show a relatively greater bony contribution at proximal levels. Sex did not explain the between-group L1 difference after covariate adjustment.

Several limitations should be stated plainly. The design is cross-sectional and cannot establish cause. The volunteer sample was a convenience cohort from a chiropractic practice (mean age 28.3 years; 68 percent male) and is not a population-normative standard. The CLBP cohort was older (mean age 52.0 years). Age-adjusted analyses did not eliminate the primary group differences, but residual age-related degeneration cannot be excluded. Disc wedge angles were not measured, so TWI reflects only the bony component of lordosis. The observed mean TWI difference between groups (3.4°) did not exceed the estimated minimal detectable change of approximately 7.3°; the clinical value of TWI therefore lies in its predictive relationship with lordosis, not in a large mean group difference.

Why this matters for care at Symmetry Health Center

Chiropractic Biophysics (CBP®) evaluation at our Oakland and Alameda clinic is built on standing radiographic analysis of sagittal alignment. This study supports three principles that already guide that work.

Lordosis is a distributed structural property. A composite bony index across L1–L5 predicted curve better than any single level and better than pelvic morphology alone. Measuring and planning the entire lumbar column remains more informative than focusing on a single segment.
When the pelvic–lordosis pathway fails, vertebral geometry still matters. Many patients with chronic low back pain no longer show the expected coupling between pelvic incidence and lumbar curve. TWI remained predictive in that setting. Structural rehabilitation that addresses vertebral alignment and loading is therefore not rendered irrelevant by pelvic decoupling.
The endpoints of the curve deserve particular attention. Group differences and lost correlations clustered at L1 and L5. Clinical radiographs should be inspected for remodeling at the thoracolumbar and lumbosacral junctions, not only at the apex of the curve.

The authors note that TWI centiles may eventually serve as a radiographic outcome measure. They also caution that the published centiles come from a young, male-predominant convenience sample and should not be applied uncritically as treatment targets for older adults or women. At Symmetry Health Center we treat those values as research context, not as rigid norms. Individual goals remain based on the patient’s full radiographic, clinical, and functional presentation—including scoliosis, spondylolisthesis, osteoporotic kyphosis, and disc-related disorders when present.

Conservative CBP® protocols that aim to restore lumbar lordosis have been reviewed separately. This 2026 paper does not test those protocols. It does, however, strengthen the rationale for measuring bony lumbar geometry and for treating lordosis as a structural, not merely postural, target.

Study citation and research support

Harrison DE, Colloca CJ, Oakley PA, Harrison AD, Moustafa IM. Vertebral Body Wedge Geometry Predicts Lumbar Lordosis Beyond Pelvic Morphology in Chronic Low Back Pain. J. Clin. Med. 2026, 15, 6865. https://doi.org/10.3390/jcm15176865

This investigation was supported in part by CBP NonProfit, Inc. (Eagle, Idaho), the NCMIC Foundation, and the International Spine Research (INSPIRE) Foundation. CBP NonProfit funds and disseminates independent research on spinal alignment, radiographic reliability, and non-surgical sagittal rehabilitation. Additional information on the organization’s research program is available at CBPnonprofit.com.

Readers seeking the companion analyses on pelvic morphology and postural alignment in chronic low back pain are directed to the related papers cited by the authors (Harrison et al., Spine Open, 2026, accepted; Harrison et al., J. Clin. Med. 2024, 13, 2178).

A note for patients

If you have chronic low back pain, a standing full-spine radiograph can show more than “wear and tear.” It can show whether the bony architecture of your lumbar spine still supports a healthy lordosis, and whether the usual relationship between your pelvis and your low-back curve has been disrupted. Those findings help us decide whether structural rehabilitation—mirror-image exercise, traction, and CBP® corrective care—is an appropriate part of your plan, either alone or alongside scoliosis-specific methods such as ScoliBalance® when deformity is present.

This article is educational and does not constitute individualized medical advice. Evaluation and treatment decisions are made after examination at the clinic.

Symmetry Health Center / Bay Area Scoliosis Center
1708 Park Street, Suite 130, Alameda, California 94501
Serving Oakland, Alameda, and the East Bay · Evidence-informed CBP® and scoliosis care