Factors Related to Preoperative Coronal Malalignment in Degenerative Lumbar Scoliosis: An Analysis on Coronal Parameters.

Abstract

Objectives: Recently the effects of coronal malalignment (CM) in degenerative lumbar scoliosis (DLS) have been reported, however, there was few studies on the correlated parameters of coronal alignments at pre-operation. The aims of this current study were to investigate the associations of coronal parameters with scoliosis and coronal alignment, and to explore the relationships between the coronal pelvic tilt and coronal alignment in DLS.

Methods: One hundred and sixty-one DLS patients in our hospital from May 2016 to December 2020 were reviewed and documented. The coronal balance distance (CBD, the offset between the center of C7 and the plumb line drawn from the center of S1), major Cobb (MC), fractional Cobb (FC), L4 coronal tilt, L5 coronal tilt, coronal pelvic tilt, apical rotation, and the vertebras in major curve were measured and documented. CM was considered if the CBD ≥ 30mm. All of those participants were assigned into group A (CBD ≥ 30 mm) and group B (CBD < 30 mm). Comparisons of demographic and radiographic data were performed between groups A and B. Pearson correlation and further multiple regression with stepwise method analysis were used to investigate those coronal parameters correlated to MC and CBD, respectively.

Results: Thirty-one patients suffering from CM were assigned into group A, and the rest of 130 patients were assigned to group B accordingly. Then the incidence of CM was about 19.3% (31/161). Patients in group A had less vertebras in the main curve (P = 0.009), however, the apical rotation (P < 0.001) and the L4 coronal tilt (P = 0.007) were much larger. Although the MC (P = 0.426) and FC (P = 0.06) had no difference between the two groups, the match between MC and FC was much smaller (p = 0.021) in group A. The coronal pelvic tilt correlated significantly with FC (r = 0.552, p < 0.001), but mildly with MC (r = -0.366, p < 0.001), L4 coronal tilt (r = 0.348, p < 0.001), and L5 coronal tilt (r = 0.351, p < 0.001), respectively. The CBD correlated strongly with L4 coronal tilt (r = -0.471, p < 0.001) and L5 coronal tilt (r = -0.468, p < 0.001), respectively, but mildly with FC (r = -0.255, p = 0.016). Further multiple regression analysis revealed that only L4 coronal tilt was the independent factor for MC (r²  = 0.549, p < 0.001) and CBD (r²  = 0.221, p < 0.001), respectively.

Conclusions: The prevalence of CM in DLS patients is about 19% at pre-operation. With similar major Cobb, the less the vertebras in the major curve, the larger the CBD. L4 coronal tilt may correlate significantly to scoliosis and CBD. Coronal pelvic tilt may be just one of the compensations for the scoliosis deformity but effects CBD directly.