Anatomy of the aortic segmental arteries-the fundamentals of preventing spinal cord ischemia in aortic aneurysm repair

Abstract

Objective: Spinal cord ischemia due to damage or occlusion of the orifices of aortic segmental arteries (ASA) is a serious complication of open and endovascular aortic repair. Our study aims to provide detailed descriptions of the proximal course of the ASAs and metric information on their origins.

Materials and methods: Initially, 200 randomly selected, embalmed cadavers of human body donors were anatomically dissected and systematically examined. On macroscopic inspection, 47 showed severe pathologies and were excluded. Of the remaining 153, 73 were males and 80 females.

Results: In total, 69.9% of the aortae showed 26-28 ASA orifices. In 59.5% the most proximal ASA, at least unilaterally, was the third posterior intercostal artery, which originated from the descending aorta at approximately 10% of its length. In 56.2%, the left and right ASAs had a common origin in at least one body segment. This mainly affected the abdominal aorta and L4 in particular (54.2%). The ASAs of lumber segments 1-3 originated strictly segmentally. In contrast, in 80.4%, at least one posterior intercostal artery originated from a cranially or caudally located ipsilateral ASA. Such an arrangement was seen along the entire thoracic aorta. Further descriptions of variants and metric data on ASA orifices are presented.

Conclusion: Our large-scale study presents a detailed topographic map of ASAs. It underscores the value of preoperative CT councils and provides crucial information for interpreting the results. Furthermore, it aids in planning and conducting safe aortic intervention and assists in deciding on single- or two-staged stent graft procedures.

Keywords: ASA; CT; aorta; aortic aneurysm; aortic segmental arteries; prevention.

Figure 1

Measured distances. Schematic drawing of the aorta. Posterior wall (pink) of the descending aorta with orifices of the ASA exposed. (A) Length of the descending aorta, measured along its centerline (yellow) between the level of the distal edge of the orifice of the LSA and the aorta bifurcation. (B) Distances between the distal edge of the orifice of the LSA and the ASA orifices. Note the angle of 90° with the centerline. (C) Distances between the right and left ASA orifices (green double-headed arrow).

Figure 2

Orifices of the ASA. (A) Number of ASA orifices per aorta. Asterisk indicates aortae with strictly segmentally and symmetrically originating T3-L4 ASAs. (B,C) Aorta with removed anterior wall. Endoluminal view. ASA orifices labeled with headpins. Note that there are 28 ASA orifices in (B) and 23 in (C). RAR, right renal artery; ARA, accessory renal artery. Scale bar, 1 cm.

Figure 3

Proximal courses of ASAs. Double-headed arrow indicates cranial (Cra.) and caudal (Cau.). A yellow asterisk indicates the aorta. (A) Situs after anatomic exposure of ASAs. (B–G) ASA (black asterisk) supplying two (C,D,F,G) and three (B,E) posterior intercostal arteries (PIA, black arrowhead). White arrowheads indicate PIAs originating from the supreme intercostal artery. Note that PIA3 transits are dorsal to the ribs in (E) and (F). (H–K) Common origin (red arrow) of the right and left segmental arteries. LAR, left renal artery; MSA, median sacral artery; MS, manubrium of sternum. Scale bar, 1 cm.

Figure 4

Metric characterization of the positions of the orifices of the ASA. (A) Schematic endoluminal view of the descending aorta. (B,C) Distance between the level of the origin of the LSA and the level of ASA orifices in mm. (B) Ratio of these distances and length of descending aorta in percentages. (C,D) Transversal distance between left and right ASAs of the same segment. Graphs provide means and standard deviations. Confidence level = 95%. PIA, posterior intercostal artery; SCA, subcostal artery; LA, lumbar artery.