Effects of pedicle subtraction osteotomy on aortic morphology and hemodynamics in ankylosing spondylitis with kyphosis: a finite element analysis study

Osteotomy can correct kyphosis, restore the spinal sequence, and restore the healthy appearance of a patient. However, the aorta is stretched during pedicle subtraction osteotomy (PSO), and some surgeons are concerned about aortic injury. We used finite element analysis to construct an aortic model to simulate hemodynamic changes during osteotomy. 16 patients with ankylosing spondylitis kyphosis who had undergone a two-level osteotomy at the L1 and L3 levels was included in this study. Aortic computed tomography angiography (CTA) was performed, and a 3D image model was constructed. The length, transverse diameter, and curvature of the aorta were used to evaluate morphological changes. Finite element analysis was used to analyze the changes in aortic fluid dynamics. Blood pressure, wall shear stress, and blood flow velocity were compared pre- and postoperatively. The overall length of the aorta before surgery was 424.3 ± 42.9 mm, and the overall length of the aorta after surgery was 436.2 ± 54.8 mm. The aortic curvature decreased from 0.27 ± 0.13 to 0.17 ± 0.09. The mean transverse diameter of the aorta did not change (19.3 ± 6.6 vs. 19.2 ± 7.4 mm, P > 0.05). The blood flow velocity (2.8 ± 1.1 vs. 1.5 ± 0.8 m/s, P < 0.05), blood pressure (6.6 ± 1.7 vs. 4.3 ± 1.2 Kpa, P < 0.05), and wall shear stress (47.6 ± 17.3 vs. 22.3 ± 8.6, P < 0.05) at the T10-L4 level decreased postoperatively. Changes in LL were significantly correlated with changes in ld, dc, blood flow velocity, blood pressure and wall shear stress (ld : r = 0.713, P < 0.001; dc: r = 0.626,P = 0.010; blood flow velocity: r= - 0.541, P = 0.041; blood pressure: r = - 0.601, P = 0.016; wall shear stress: r= - 0.594, P = 0.027). The aorta was stretched, and its curvature decreased. The mean transverse diameter of the aorta did not change. Blood flow velocity, blood pressure, and wall shear stress decreased after surgery. Our study provides hemodynamic support for the possible cardiovascular benefits of osteotomes.