Relationships between lumbar lordosis correction and the change in global tilt (GT) in adult spinal deformity.

PURPOSE: This study aimed to explore the relationships between lumbar lordosis (LL) correction and improvement of postoperative global sagittal alignment and to establish corresponding linear regressions to predict the change in global tilt (GT) based on the corrected LL following adult spinal deformity (ASD) surgery. METHODS: A total of 240 ASD patients who underwent lumbar correction were enrolled in this multicentre study. The following sagittal parameters were measured pre- and postoperatively: thoracic kyphosis (TK), LL, upper and lower LL (ULL and LLL), pelvic tilt (PT), sagittal vertical axis (SVA) and GT. The correlations among the changes in GT (△GT), SVA (△SVA), PT (△PT), TK (△TK), LL (△LL), ULL (△ULL) and LLL (△LLL) were assessed, and linear regressions were conducted to predict △GT, △SVA, △PT and △TK from △LL, △ULL and △LLL. RESULTS: △LL was statistically correlated with △GT (r = 0.798, P < 0.001), △SVA (r = 0.678, P < 0.001), △PT (r = 0.662, P < 0.001) and △TK (r = - 0.545, P < 0.001), and the outcomes of the linear regressions are: △GT = 3.18 + 0.69 × â–³LL (R2 = 0.636), △SVA = 4.78 + 2.57 × â–³LL (R2 = 0.459), △PT = 2.57 + 0.34 × â–³LL (R2 = 0.439), △TK = 7.06-0.43 × â–³LL (R2 = 0.297). In addition, △LLL had more correlations with △GT, △SVA and △PT, while △ULL had more correlations with △TK. CONCLUSION: Surgical correction of LL could contribute to the restoration of global sagittal morphology following ASD surgery. These models were established to predict the changes in sagittal parameters, in particular △GT, determined by △LL, which has not been previously done and may help to customize a more precise correction plan for ASD patients.

Predicting thoracic kyphosis morphology and the thoracolumbar inflection point determined by individual lumbar lordosis in asymptomatic adults.

PURPOSE: The aims of this study were to explore the correlations between thoracic kyphosis (TK) and lumbar lordosis (LL) parameters and to build corresponding linear regressions to predict TK morphology and the thoracolumbar inflection point (IP) determined by individual LL parameters in asymptomatic adults. METHODS: A total of 280 adult healthy volunteers were recruited, and full-spine X-rays were performed for each subject in a standing posture. The following sagittal parameters were measured: cumulative TK, LL, proximal LL (PLL), the apices of TK (TKA) and LL (LLA), the IP and the distance from the plumb line of the thoracic apex (TAPL) and the lumbar apex (LAPL) to the gravity line. The correlations between TK and LL parameters were analyzed, and the corresponding linear regressions were conducted. RESULTS: Extensive variations existed in TK alignment, including angular and morphological parameters. In addition, there were statistical correlations of all cumulative TK angles with LL (r values from - 0.173 to - 0.708) and PLL (r values from - 0.206 to - 0.803), TKA and IP with LLA (rs = 0.359 and 0.582, respectively) and TAPL with LAPL (rs = 0.335). The common predictive formulas employed in ASD surgery could include T10-L1 = - 3.6-0.2*LL (R2 = 0.201), T4-L1 = 3.4-0.5*LL (R2 = 0.457), TKA = - 10.3 + 1.1*LLA (R2 = 0.180) and IP = - 12.7 + 1.6*LLA (R2 = 0.330). CONCLUSION: There were intimate associations between TK and LL parameters in asymptomatic adults. Moreover, predictive models for thoracic alignment, particularly cumulative TK, based on LL parameters were proposed, which could better delineate anatomical relationships, guide thoracic construction during adult spinal deformity surgery and may help preventing proximal junctional failure.