Anatomical Variations of The Fifth Lumbar Artery in A Sample Kenyan Population 

Ibsen Ongidi1, Thomas Amuti1, Joseph Mageto1, Nick Dennis1, Innocent Ouko1, Rebecca Murerwa1, Beda Olabu1,Julius Ogeng’o1

1Department of Human Anatomy,University of Nairobi, Nairobi, Kenya

 

Correspondence to: Thomas Amuti; tomamuti@gmail.com.

Received: 06 Jan 2021; Revised: 27 Feb 2021; Accepted: 06 March 2022; Available online: 26 Mar 2022

 

Abstract 

Background: The fifth lumbar arteries have a more variable presence and origin as compared to the first four arteries. Its anatomical variations may influence lower spine surgical and vascular interventions. Aim: Our objective was to determine the variations of the fifth lumbar artery in a cadaveric and contrast computed tomography (CT) study.  Materials and methods: This descriptive cross-sectional study combined data from 90 cadaveric and 120 post-contrast abdomino-pelvic computed tomography (CT) from Human Anatomy Department, University–of-Nairobi and Radiology Department, Kenyatta-National-Hospital.Cadavers were dissected to expose the arteries. Their prevalence, patterns and position of origin on the 5th vertebral bodies were determined. Data were analyzed using SPSS. Results: The artery was present in 26.7% of the cadaveric group, and 16.7% of the CT group. It was only noted in males in both the cadaveric and CT groups. It originated bilaterally as a common stem in 50% and as paired single branches in 50%. It originated at a mean distance of 9.03mm ± 7.23mm from the top of the L5 vertebra, maintaining a consistent relation to the upper third (90%) and the middle third (10%) of the body. Conclusions: The arteries were only noted in males and portrayed population specific variations.

 

Keywords: Fifth lumbar artery, lower back pain, endovascular surgery, aortography

 

Ann Afr Surg. 2022; 19(2): 100-107

DOI: http://dx.doi.org/10.4314/aas.v19i2.7

 

Funding: None

© 2022 Author. This work is licensed under the Creative Commons Attribution 4.0 International License. 

Introduction 

The lumbar arteries constitute the principal arterial supply to the lower back, with branches that extend to supply the anterior abdominal wall. Most studies describe them as four pairs, while a fifth lumbar artery may occasionally be present. While the first four lumbar arteries almost always arise bilaterally from the postero-lateral aspect of the aorta, the fifth lumbar arteries may arise either from the aorta, iliolumbar artery or the middle sacral artery (1-3).  The fifth lumbar arteries tend to be smaller in size and have a shorter course, supplying mainly the adjacent spine and at times perforators to the skin of the lower back and gluteal region (4, 5). Studies have reported variable prevalence of the fifth lumbar arteries (ranging from <1% to 38.6%), its pattern of origin either as a common stem or single stem, and level of origin in relation to the lumbar vertebra (4, 6, 7, 8). These variations may influence clinical symptoms of disease as well as surgical and vascular interventions in the lower back. Persons who present with fewer pairs of lumbar arteries or fifth lumbar arteries that have been narrowed due to atherosclerosis, are more likely to report lower back pain (9-11). Such factors reduce  

vascular supply to the back hence causing pain. Africans have been noted to have a high lifetime prevalence of lower back pain at 47% (95% CI 37;58) and point prevalence of 39% (95% CI 30;47); a value that is higher than the global prevalence (12). Insufficient arterial blood flow due to lumbar artery variations may be an underlying factor for these observations. 

Variations of the fifth lumbar artery may also influence endovascular and surgical procedures for abdominal aortic and lumbar artery aneurysms as well as spine pathology. Variable origin brings about difficulty in accessing these vessels during procedures such as embolization in treatment of vertebral body tumors or aortic stent graft placements emphasizing the need of its quantification (8, 12). When it is present, inadvertent injury to the fifth lumbar artery is likely occur during percutaneous vertebroplasty and other spine surgical interventions, especially due to its abnormal trajectory in relation to the spine compared to the other four lumbar arteries (8, 13, 14).

Owing to these important clinical applications, it is imperative to understand the anatomy of the fifth lumbar arteries. There is a paucity of data especially in the African setting, and thus, we report on the variant anatomy of the lumbar artery in the Kenyan setting.

Materials and methods 

We designed a descriptive cross-sectional study, which combined both cadaveric and computed tomography (CT) analysis of the 5th lumbar vessels. A total of 90 cadavers were obtained from the department of Human Anatomy and Chiromo Funeral Parlour of the University of Nairobi for the cadaveric study. A total of 120 post contrast abdominopelvic CT scans from patients were sought from the Kenyatta National Hospital Radiology Department for the CT study. The sample size was arrived at using the formula shown: where n is the sample size, SD is standard deviation of a variable from previous studies, and m is the margin of error.

In calculating the sample size, the variable chosen was the mean diameter of the artery. This objective was chosen out of the rest, even though it is not a current variable of interest