Coronal T1 Pelvic Tilt, a Novel Predictive Index for Global Coronal Alignment in Adult Spinal Deformity

A retrospective radiographic study.

The aim of this study was to examine the association between global coronal alignment (GCA) and L4/L5 coronal tilt, and to verify the validity of our new index for evaluating GCA.

The mechanism of coronal imbalance is still unknown. The ability to level coronal tilts of L4 and L5 has been reported to impact the ability to achieve coronal balance, but the relationship between GCA and coronal tilt of L4 or L5 is unclear. On the contrary, although C7 migration is widely used for evaluating GCA, it has inherent defects as distance parameter. We focused on a novel global coronal angular parameter for evaluating the association of GCA with coronal tilt of L4 or L5.

A total of 146 patients with adult spinal deformity were involved. The coronal measurements included C7 migration, fractional curve, L4 coronal tilt, L5 coronal tilt, major Cobb angle, and our novel global coronal parameter-coronal T1 pelvic tilt angle (CTPT, defined as the angle between a vertical line and the line connecting the middle point of S1 endplate to T1 centroid). We then determined the relationship between CTPT, C7 migration, and other coronal parameters.

C7 migration had significant correlation with L4 coronal tilt, L5 coronal tilt or fractional curve, but not with major Cobb angle. CTPT resembled C7 migration regarding its relationships with L4 coronal tilt, fractional curve, L5 coronal tilt and major Cobb angle. Regression analysis showed CTPT strongly associated with C7 migration (R = 0.985), CTPT = 0.02+0.14* C7 migration and neither L4 coronal tilt nor L5 coronal tilt was an independent predictor of GCA.

CTPT could be a practical index for evaluating GCA. Neither L4 coronal tilt nor L5 coronal tilt was an independent predictor of GCA.

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