Original Article |
Corresponding author: Evangelos Nastoulis ( nastevang@yahoo.gr ) © 2024 Evangelos Nastoulis, Gregory Tsoucalas, Valeria Karakasi, Pavlos Pavlidis, Aliki Fiska.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Nastoulis E, Tsoucalas G, Karakasi V, Pavlidis P, Fiska A (2024) Complete dorsal wall agenesis of the sacral canal in a Greek population: an osteological study. Folia Medica 66(3): 386-394. https://doi.org/10.3897/folmed.66.e118790
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Introduction: The failure of closure of the dorsal wall of the sacral canal (SC) has been known since the eve of modern osteology, appearing in prehistoric times. Variants include partial or complete absence of the dorsal wall of the SC. SC presents a pathway for minimally invasive therapeutic and diagnostic procedures for spinal diseases and for ensuring analgesia and anesthesia in operations, including labor and genitourinary surgery.
Aim: Our objective is to verify the incidence of complete agenesis of the SC dorsal wall in Greek population.
Material and methods: We collected 155 adult dry sacra of known sex from the Third Cemetery of Athens for the study of the dorsal wall of the sacrum. Damaged or variated sacra were excluded. We also performed an exhaustive review of the relevant literature and compared our results with those of international studies.
Results: Complete dorsal wall agenesis of the sacral canal was found in three cases (1.93%), two men (1.29%) and one woman (0.64%). Our review examines its incidence in other populations and explores the possibility of regional or racial correlation.
Conclusion: Knowing the complete dorsal wall agenesis of the sacral canal by medical professionals is crucial for avoiding complications in spinal surgery, anesthetics and obstetrics, as well as in the differential diagnosis of neurological and urological diseases.
complete agenesis, Greek, sacrum, sacral variations, sacral canal, spina bifida
The sacral canal (SC) is the peripheral part of the vertebral canal, extending from the level of S1 vertebra to the sacral hiatus. Since the spinal cord terminates at approximately L2, SC encloses the cauda equina, including the filum terminale and the spinal meninges. The dura and arachnoid mater typically terminate at the level of S2, but variations include the lower border of S1 foramen in adults and the S3 in children. At the end point, they fuse into one layer, while the pia mater progresses to the coccyx as filum terminale. The sacral canal also contains epidural fat, which becomes denser with age, as well as the valveless sacral epidural vein plexus. This usually ends at S4, though it may extend throughout the canal.[
Numerous divergences occur in the SC dorsal wall including complete agenesis (total sacral spina bifida).[
Most cases of spina bifida are of multifactorial origin, influenced by both genetic and environmental factors. Increased risk of spina bifida presents with high pregnancy weight, antiepileptic drugs (valproic acid), folic acid antagonists, maternal diabetes, maternal smoking, hyperthermia, and fever during pregnancy.[
We conducted a descriptive osteological study aiming to estimate the incidence of complete dorsal wall agenesis in Hellenic population.
We studied 155 dry adult sacra of Hellenic (Caucasian) origin and known sex, retrieved by permission from the authorities of the Third Cemetery of Athens, Greece. Only intact bones were included in the study; sacra with any sign of fracture or variation, e.g. features of sacralization or lumbarization, were excluded. We took photographs of the bones using a digital camera (Nikon DSLR D5300) and saved them in JPEG format. We additionally performed a review of the relevant literature, to compare our findings with the recorded incidence of dorsal wall agenesis of the sacral canal in diverse populations.
Complete agenesis of the dorsal wall was identified in 3 cases of the 155 sacra (1.93%). Two bones belonged to male (1.29%) (Figs
SBO appeared in humans during the prehistoric period, evident in skeletal remains.[
Dorsal agenesis of the sacrum (DAS) has been studied in different countries such as the United States of America, Turkey, Japan, Nigeria, Thailand, India, and others. This is the first time the occurrence of complete agenesis of the SC dorsal wall is investigated in the Hellenic population. Our aim was to find the incidence of DAS, compare it with the results from other regions and find possible correlations or deviations (Table
The incidence of DAS in the literature ranges from 0.43% (Thailand) to 5% (Bangladesh). In our review, the mean incidence out of 35 studies from 1944 to 2023 was approximately 1.97% (Table
The incidence of DAS in our study was 1.93%, just below average and closest to Senoglou (Turkey) and Patel, Kiran and Shinde (India) findings (Fig.
Case 3: complete dorsal wall agenesis of sacral canal with unilateral coccyx sacralization (female).
Incidence of complete dorsal wall agenesis of the sacral canal in different population groups
No | First author | Ethnicity/ Race | Total sample of dry adult sacra | Complete dorsal wall agenesis | |
No | (%) | ||||
1 | Trotter M[ |
USA | 553 | 10 | 1.8 |
2 | Kumar et al.[ |
India | 202 | 3 | 1.49 |
3 | Sekiguchi et al.[ |
Japan | 92 | 1 | 1 |
4 | Nagar SK[ |
India | 263 | 4 | 1.5 |
5 | Senoglou et al.[ |
Turkey | 96 | 2 | 2.08 |
6 | Patel et al.[ |
India | 150 | 4 | 2 |
7 | Kiran et al.[ |
India | 50 | 1 | 2 |
8 | Patil et al.[ |
India | 103 | 3 | 2.91 |
9 | Singh R[ |
India | 140 | 2 | 1.4 |
10 | Seema et al.[ |
India | 159 | 5 | 3.14 |
11 | Suwanlikhid et al.[ |
Thailand | 235 | 1 | 0.43 |
12 | Shewale et al.[ |
India | 204 | 2 | 0.98 |
13 | Kubavat et al.[ |
India | 302 | 5 | 1.65 |
14 | Ukoha et al.[ |
Nigeria | 83 | 1 | 1.2 |
15 | Nasr et al.[ |
Egypt | 150 | 4 | 2.66 |
16 | Kamal et al.[ |
Bangladesh | 172 | 1 | 0.6 |
17 | Nagendrappa RB[ |
India | 100 | 3 | 3 |
18 | Shinde V[ |
India | 100 | 1 | 1 |
19 | Mishra et al.[ |
India | 93 | 4 | 4.3 |
20 | Chhabra N[ |
India | 32 | 1 | 3.12 |
21 | Malarvani et al.[ |
Nepal | 100 | 3 | 3 |
22 | Akhtar et al.[ |
India | 116 | 3 | 2.58 |
23 | Saha D[ |
India | 125 | 2 | 1.6 |
24 | Shinde et al.[ |
India | 300 | 4 | 1.33 |
25 | Dhuria et al.[ |
India | 88 | 3 | 3.4 |
26 | Aragao et al.[ |
Brazil | 45 | 2 | 4.44 |
27 | Bagoji et al.[ |
India | 138 | 4 | 2.89 |
28 | Pandey M[ |
India | 86 | 2 | 2.33 |
29 | Poudel et al.[ |
India | 70 | 3 | 4.28 |
30 | Yonkuc et al.[ |
Turkey | 110 | 4 | 3.63 |
31 | Punja et al.[ |
India | 50 | 1 | 2 |
32 | Abera et al.[ |
Ethiopia | 61 | 1 | 1.63 |
33 | Naznin et al.[ |
Bangladesh | 60 | 3 | 5 |
34 | Chandan et al.[ |
India | 276 | 3 | 1.08 |
35 | Present study | Greece | 155 | 3 | 1.93 |
TOTAL | 5059 | 99 |
In theory, since the spinal cord terminates at around L2, spina bifida shouldn’t cause any serious medical problems. However, there is evidence that it can affect various systems with serious consequences on medical procedures. The detailed knowledge of sacral anatomical divergences is of paramount significance for several medical specialists (orthopaedic surgeons, neurosurgeons, neurologists, urologists, anesthesiologists, obstetricians, radiologists).
The association between SSBO and low back pain is obscure, but obviously the compression of the spinal nerves’ roots that pass through the exposed sacral canal can be related to atypical low back pain (LBP).[
Caudal epidural block has been extensively used for the diagnosis and treatment of lumbar spinal disorders, for the management of chronic back pain and for the analgesia and anesthesia in labor and genitourinary surgery. For optimal access into the sacral epidural space, the apex of sacral hiatus and the sacral cornua are used as anatomical landmarks.[
SSBO, especially total SSBO, is suggested to be linked to a variety of functional disorders of the lower urinary tract. In 1985, Galloway and Tainsh found an increased number of spina bifida occulta cases in a small group of adults with lower urinary tract problems.[
Our sample size was rather small for safe and reliable documentation of the incidence of DAS in the Hellenic population and its relation to male sex. We suggest that further research should include greater numbers of Hellenic bone specimens. Sex as a possible etiologic or causative factor should be equally investigated.
The dorsal wall of the sacrum presents with an abundance of anatomical divergences. The inter-population incidence of complete agenesis of the sacral canal’s posterior wall ranges from 0.43% to 5% in the international literature. We found its incidence in the Hellenic population to be 1.93%.
The authors suggest that the future studies in different populations must mention the sex of the specimen, to determine it as a factor. More clinical studies on complete dorsal wall agenesis of the sacral canal are needed to establish pathophysiologic and genetic mechanisms. Awareness of anatomical variations is the key to successful results in the clinical setting; the complete agenesis of the SC dorsal wall (total spina bifida occulta) is not an exception to this rule.
The authors gratefully acknowledge for their invaluable support the authorities of Third Cemetery of Athens and especially Mr. Alexandros Korkodinos.
This review is part of doctoral dissertation. It was approved by the Research and Ethics Committee of Democritus University of Thrace, Faculty of Medicine.
None.