Different Angular Kyphosis Locations Have Different Relative Positions of Aorta to Spine in Patients with Pott's Deformity

Abstract

Background. The position of the aorta relative to the spine in kyphosis secondary to ankylosing spondylitis is little understood. The purpose of this study was to investigate the anatomic relationship between the aorta and the spine in patients with Pott's deformity and to compare it with the normal people.Methods. Seventy-six patients with Pott's deformity (Group TB) and seventy-two age- and sex-matched patients with a normal spine (group NC) were enrolled in this study. The relative position of aorta to the spine was evaluated from T4 to L4 on the computed tomographic angiography scans for controls and at the apex level for TB patient, and was classified into 4 kinds of degrees. Results. The left pedicle-aorta angle in group TB was significantly larger than that in group NC at the T6-L3 levels. Group TB exhibited significantly smaller left pedicle-aorta distance, pedicular line-aorta distance and vertebra/rib-aorta distance than those in group NC at the T5-T10 levels, but bigger at the L1-3 levels. Patients with grade 3 and 4 aorta had more segments involved compared with those with grade 1 aorta. Patients with grade 2, 3, and 4 aorta showed larger kyphotic angles than those with grade 1.Conclusions. Patients whose morbid segments involved only thoracic vertebrae presented with an “Ω” shaped aorta in sagittal plane, and 4 different kinds of degrees of aorta relative to the vertebra/rib in axial plane. Patients whose morbid segments covered lumbar vertebrae presented with an “M” shaped aorta in sagittal plane, and the aorta shifted further from apex vertebra but was located in close proximity to the vertebral body at levels above and below the osteotomy levels in axial plane.