International Journal of Anatomy and Research

eISSN 2321-4287 · pISSN 2321-8967

Volume 14 · Issue 2 · Pages 9539–9545 · June 2026

Research Article

Positional and Morphometric Anatomy of the Thoracic Aorta of Melanoderms living in Togo: CT Angiographic Study of 53 cases

Ananivi Sogan1*, Solim Carolle Nabede², Pihou Gbande², Yaovi Edem James¹, H. Madzra Dzoka Kodjo¹, K. Okassate Sibabi-Akpo¹, Augustin Agoda-Koussema²

¹Laboratory of Human Anatomy, Faculty of Health Sciences/University of Lomé, Togo.
²Radiology Department, Teaching hospital Sylvanus Olympio of Lomé, Togo.

Corresponding author: Sogan Ananivi (MD, Surgeon, MSc, Assistant Professor in anatomy and organogenesis); E-mail: sopher2@hotmail.fr

Received: 21 March 2026 · Revision received: 08 April 2026 · Accepted: 01 May 2026 · Published: 05 June 2026

DOI: 10.16965/ijar.2026.145

ABSTRACT

Background/Aim

The nursing of surgical ailments of the thoracic aorta cannot be carried out without the knowledge of its anatomy. The advent of thoracic aortic surgery in Africa requires us to have local anatomical data on this artery. The aim of this work is to enrich the literature by studying the thoracic artery in melanoderms living in Togo.

Methods

We conducted a cross-sectional, retrospective, single-center, descriptive, and analytical study over six months (July to December 2024) at Nadouvi Lawson-Body Hospital in Lomé, Togo. CT angiographic images from 53 patients were selected and analyzed. The parameters studied were: the morphology of the thoracic aorta, the locations of its origin and termination, the location of the most anterior point of the ascending aorta, the highest point of the aortic arch and then the metric data.

Results

The morphology of the thoracic aorta (TA) was type C in 37.7% (n=20), type B in 32.1% (n=17), and type D in 22.6% (n=12). Morphology varied according to age. Its origin projected at Th8 in 37.7% (n=20) and at Th7 in 22.6% (n=12); its termination was located at Th12 in 58.5% (n=31) and at L1 in 18.9% (n=10). The most anterior point of the ascending aorta was located at the level of the 2EICD, 3PSCD, and 2PSCD in 24.5% (n=13), 22.6% (n=12), and 15.1% (n=8), respectively. The distance from this point to the anterior chest wall was 23.0 ± 9.4 mm and decreased with age. The highest point of the aortic arch projected at Th3 in 52.8% (n=28) and Th2 in 22.6% (n=12). The medium diameter of the TA at the origin and termination was 31.4 ± 4.7 mm and 21.9 ± 2.8 mm, respectively. An increase in the various diameters was noted with age.

Conclusion

This study outlines the anatomical bases of certain known clinical concepts and positional variations. These concepts are useful for avoiding interpretation errors in thoracic aortic imaging and also in surgical treatment. It would be desirable to compare these results with those of a study of the thoracic aorta on anatomical subjects later on.

Keywords: Thoracic Aorta; Anatomy; Melanoderm; CT Angiography; Lomé-Togo.

INTRODUCTION

The thoracic aorta (TA) is the portion of the aorta between the aortic orifice of the left ventricle and the aortic orifice of the thoraco-abdominal diaphragm. It is classically divided into three parts: the ascending aorta, the aortic arch, and the descending thoracic aorta [1]. It provides arterial blood supply to major organs such as the heart and the encephalon [2]. This shows the extent to which these pathologies, namely those defining acute aortic syndrome, can be life-threatening and rightly constitute extreme medical-surgical-radiological emergencies. The etiological diagnosis and optimal nursing of these pathologies require a good knowledge of the anatomy of the thoracic aorta and its dimensions [3].

The advent of complex surgery of the thoracic aorta in our African countries requires the researcher to study the possible anatomical particularities of this vessel in the melanoderm subject. The anatomical study of the thoracic aorta can be carried out either on anatomical subjects, or if not, by means of medical imaging: transthoracic echocardiogram (TTE) or trans-esophageal ultrasound, aortography, CT or thoracic CT angiography, positron emission tomography associated or not with CT, MRI [4]. In order to enrich the data in the literature on the anatomy of this artery, we are carrying out this study on the thoracic aorta of the melanoderm living in Togo.

METHODS

This was a cross-sectional, retrospective, single-center, descriptive, and analytical study carried out from July to December 2024, over six months, at Nadouvi Lawson-Body Hospital (a private hospital specialized in the management of cardiovascular disease) in Lomé, Togo.

Study Materials

These consisted of CT angiographic images of patients aged 18 and older from 2023. Were excluded from the study, non-contributory images (technical error, aorta not visualized in its entirety), images of subjects with a history of thoracic and/or thoracic aortic surgery, and images of pathological thoracic aorta (congenital or acquired). The scanographic examinations were performed using an Institum 64-barrette scanner, installed in 2020.

CT angiographic examination procedure

The CT angiographic examinations were performed under an appropriate field of vision (according to the patient's morphology) with full longitudinal coverage of the thoracic aorta. The tube rotation time was 0.42 seconds with a tube voltage of 100 to 120 kV and a table movement of 3 mm per rotation. An injection of iodinated contrast agent (Iohexo-M® 50 mg) (80 to 120 ml) was administered using a Seacrown dual-syringe automatic injector, through a venous access (with a flow rate of 2-3 ml/second) at the flexor of the elbow or the wrist. The ROI was positioned in the inferior vena cava and the pulmonary artery trunk, with automatic detection of enhancement in the aortic sinus to initiate acquisition. The period was often 4 seconds if the access was at the flexor of the elbow and 8 to 10 seconds if access was at the wrist. Images were acquired during blocked deep inspiration on native axial slices with 10 mm thicknesses. Sagittal and coronal reconstructions were then performed with 1.25 mm thicknesses in the mediastinal and parenchymal window.

Parameters Studied

They were represented by: the morphology of the thoracic aorta according to the classification (Figure 1) of Yoshiaki and others [5], the location of its origin, its termination, the location of the most anterior point of the ascending aorta and its distance from the anterior chest wall, the projection of the highest point of the aortic arch, the diameters at the origin and termination, the diameters of the ascending and descending aorta at the bifurcation of the pulmonary artery and the diameter at the level of the aortic arch (between brachiocephalic arterial trunk and left common carotid artery). The diameters were measured in a plane perpendicular to the axis of the vessel at the measurement point and in two directions, ventro-dorsal and transverse (Figures 2 and 3) and at each point the largest measured value was retained. The measurements were carried out manually by two specialists, an anatomist and a radiologist.

[picture]

Fig. 1: Classification of the morphology of the thoracic aorta according to Yoshiaki and others.

[picture]

Fig. 2: Measurement of the thoracic aorta diameter in the ventro-dorsal direction.

[picture]

Fig. 3: Measurement of the thoracic aorta diameter in the transverse direction.

Statistical Analyses

Data were entered using Epidata 3.1 software. Analyses were performed using Microsoft Excel 2019 and R 4.0.4 software in the RStudio 1.4 environment. Quantitative variables were described as averages +/- standard deviations with minimum and maximum values; Wilcoxon and Kruskal tests were used for comparisons. Qualitative variables were described in terms of numbers and percentages; and were compared using Chi-square or Fisher tests with a significance level of p < 0.05.

RESULTS

In accordance with the exclusion criteria, 53 images were retained (25 men, 28 women); the medium age of patients was 52.6 years ± 17.1, with a range of 24 to 86 years. The age group most represented was 60 and over, in 37.7% or 20 cases.

From a positional perspective, the origin of the thoracic aorta projected at Th8 in 37.7% (n=20) and at Th7 in 22.6% (n=12); origins were noted at Th5 and Th9 in 7.5% (n=4) and 3.8% (n=2), respectively. The termination was located at Th12 in 58.5% (n=31), at L1 in 18.9% (n=10), and at Th11 in 13.2% (n=7). The most anterior point of the ascending aorta was located at the level of 2EICD, 3PSCD and 2PSCD in 24.5% (n=13); 22.6% (n=12) and 15.1% (n=8) respectively. The distance from the most anterior point of the ascending aorta to the internal surface of the anterior chest wall was 23.0 ± 9.4 mm [5.7 and 39.7]. This distance decreased statistically with age with p = 0.003 (Table 1); it did not vary statistically with sex (p = 0.07). The highest point of the aortic arch projected at Th3 in 52.8% (n=28) and Th2 in 22.6% (n=12). The situation of this point varied neither to age (p = 0.4021) nor to sex (p = 0.5842).

Table 1: Distance from MAP to anterior chest wall according to the age.

Age Group | Average (mm) | SD (mm) | Min (mm) | Max (mm) | p-value
[18-40[ years (n=14) | 29.8 | 6.3 | 20.5 | 36.6 | 0.003
[40-60[ years (n=19) | 21.2 | 9.3 | 9.7 | 39.3 | -
60 years and over (n=20) | 19.9 | 9.3 | 5.7 | 39.7 | -

Legend: MAP = Most Anterior Point of ascending aorta; mm = millimeters.

Morphologically, type C thoracic aorta (Figure 4) was the most common in 37.7% (n=20), followed by type B (32.1%; n=17) and type D (22.6%; n=12). The morphology of the thoracic aorta varied according to age; in fact, types D and E were the prerogative of individuals over 40 years of age and types A and B were more common in those under 40 years of age (Table 2). There was no statistically significant morphological difference between the TA of women and men (p = 0.9132).

Table 2: Thoracic aorta morphology according to the age.

TA Morphology | [18-40[ n (%) | [40-60[ n (%) | 60 and over n (%) | Total n (%) | p-value
A | 1 (7.1) | 0 (0) | 0 (0) | 1 (1.9) | 7.2 × 10⁻⁵
B | 10 (71.4) | 6 (31.6) | 1 (5.0) | 17 (32.1) | -
C | 3 (21.4) | 10 (52.6) | 7 (35.0) | 20 (37.7) | -
D | 0 (0) | 3 (15.8) | 9 (45.0) | 12 (22.6) | -
E | 0 (0) | 0 (0) | 3 (15.0) | 3 (5.7) | -
Total | 14 (100) | 19 (100) | 20 (100) | 53 (100) | -

Legend: TA = Thoracic aorta.

[picture]

Fig. 4: Type C thoracic aorta, the most common morphology observed in this study.

The medium diameter of the TA at the origin and termination was 31.4 ± 4.7 mm [22.02; 47.47] and 21.9 ± 2.8 mm [16.7; 31.0] (Table 3) and we observe on the whole a decrease in the diameter from the origin to the end. Furthermore, we note an increase in the different diameters according to age with statistically significant differences (Table 4); which is not the case when considering the variations according to sex.

Table 3: Diameters of thoracic aorta at different points (mm).

Location | Average (mm) | SD (mm) | Min (mm) | Max (mm)
Origin | 31.4 | 4.7 | 22.02 | 47.47
Ascending aorta | 33.1 | 4.6 | 24.4 | 47.0
Aorta arch | 29.1 | 4.0 | 20.7 | 40.3
Descending Aorta | 25.0 | 3.5 | 19.0 | 35.9
Termination | 21.9 | 2.8 | 16.7 | 31.0

Table 4: Diameters (mm) of thoracic aorta at different points according to age.

Location | [18-40[ y Min | Avg | Max | SD | [40-60[ y Min | Avg | Max | SD | 60+ y Min | Avg | Max | SD | p-value
Origin | 22.0 | 28.9 | 33.6 | 3.4 | 27.2 | 31.8 | 43.3 | 3.5 | 25.8 | 32.8 | 47.5 | 5.8 | 0.069
Ascending aorta | 24.4 | 29.4 | 33.3 | 2.7 | 27.6 | 33.1 | 39.7 | 3.4 | 28.4 | 35.7 | 47.0 | 5.0 | 0.0003
Aorta arch | 20.7 | 25.8 | 28.1 | 2.6 | 24.1 | 29.6 | 37.5 | 3.5 | 26.2 | 31.0 | 40.3 | 3.9 | 3 × 10⁻⁵
Descending aorta | 19.0 | 23.0 | 29.8 | 3.0 | 20.8 | 24.8 | 28.5 | 2.2 | 20.7 | 26.6 | 35.9 | 4.0 | 0.007
Termination | 16.7 | 19.9 | 21.3 | 1.4 | 17.7 | 21.3 | 23.0 | 1.4 | 20.0 | 23.8 | 31.0 | 3.2 | 1.8 × 10⁻⁴

Table 5: Diameters (mm) of thoracic aorta at different points according to other studies.

Location | Garcier and others [1] | Aronberg and others [19] | Our study
Origin | - | - | 31.4
Ascending aorta | 32.8 | 36.0 | 33.1
Aorta arch | 29.3 | 26.3 | 29.1
Descending aorta | 24.3 | 24.8 | 25.0
Termination | - | - | 21.9

DISCUSSION

The unavailability of anatomical subjects in our academic contexts forces us to most often conduct our studies using modern imaging techniques. The study of the aorta can be performed using TTE because the results are comparable to those obtained by CT according to James and others [6,7]; but ultrasound is not yet the technique of choice for exploring the entire thoracic aorta [4]. MRI provides good resolution and is non-invasive, but its performance is time-consuming and costly. Among all imaging methods, CT remains the gold standard for exploring the aorta [7-9] by offering good spatial resolution in record time, and appears more accessible in developing country contexts.

The origin of the TA was located at Th8 in 37.7% of cases, consistent with modal anatomy manuals (typically occurring in ~30% of the population). Termination at Th12 occurred in 58.5% (and L1 in 18.9%). The location of the most anterior point of the ascending aorta around 2EICD, 3PSCD, and 2PSCD (totaling 62.2%) aligns with the clinical aortic auscultation focus at 2EICD, where the aorta lies closest (23.0 ± 9.4 mm) to the anterior chest wall. This is a critical surgical consideration for penetrating thoracic trauma.

Changes in morphology with age (types D and E in older cohorts) reflect vascular wall remodeling, circulatory dynamics, and continuous cardiac pulsations [5,10-12]. Aortic diameters progressively increased with age (p < 0.05 across segments), consistent with physiological dilation of ~0.9 mm/decade in men and ~0.7 mm/decade in women [18]. The metric values obtained in this Togolese melanoderm population closely match international reference standards reported by Garcier et al. and Aronberg et al. [1,19].

CONCLUSION

Considering the geometry and segmentation of the thoracic aorta and its continuous exposure to heartbeat and hemodynamics, surgical and clinical management requires mastery of its anatomy. This study provides positional variations, age-related morphometric standards, and anatomical reference values for melanoderms in Togo, useful for preventing diagnostic errors in imaging and complications in thoracic aortic surgery.

ABBREVIATIONS

Th

Thoracic vertebra

L1

First lumbar vertebra

2EICD

Second right intercostal space (2ème Espace Intercostal Droit)

3PSCD

Third right sternocostal breastplate / joint (3ème Plastron Sterno-Costal Droit)

2PSCD

Second right sternocostal breastplate / joint (2ème Plastron Sterno-Costal Droit)

TA

Thoracic Aorta

MAP

Most Anterior Point of ascending aorta

TTE

Transthoracic Echocardiogram

DECLARATIONS

Conflict of interest: None.

Author's contribution: All authors/co-authors equally contributed to the manuscript right from conception of the study plan to the final drafting for publication.

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