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Morphological Study of the Foramen Transversarium of the Atlas Vertebra among Egyptian Population and Its Clinical Significance

Authors:
Research Article
Volume 4 Issue 4- March 2018
DOI: 10.19080/APBIJ.2018.04.555642
Anatomy Physiol Biochem Int J
Copyright © All rights are reserved by Joseph N Aziz
Morphological Study of the Foramen
Transversarium of the Atlas Vertebra among
Egyptian Population and Its Clinical Significance
Joseph N Aziz* and Michel Morgan
Department of Anatomy, Cairo University, Egypt
Submission: February 20, 2018; Published: March 15, 2018
*Corresponding author: Joseph N Aziz, Department of Anatomy, Faculty of Medicine, Cairo University, Egypt, Email:
Abstract
Background: Foramina transversaria are characteristic bony features of the cervical vertebra, they are located on the transverse process
of cervical vertebrae. These foramina are of anatomical importance as they provide bony passages for several anatomical structures namely
vertebral artery, vertebral vein and sympathetic nerves. They have known to exhibit variations with regard to size, shape and may even
absent, incomplete or duplicated.
Objective: This study aim to investigate the morphology and variations of foramina transversaria of the human atlas vertebrae and to
point out the clinical importance of these variations.
Material and methods: 135 atlas vertebrae of Egyptian origin were studied. They were available in the dissecting room of the anatomy
department, Faculty of Medicine, Cairo University. Each vertebra was studied morphologically for the presence of various shapes of foramen
transversarium, presence or absences of any morphological anomaly like accessory foramen or incomplete foramen.
Results: Four shapes were noted. Type 1 (rounded) was predominant 54.1%, type 2 (oval) less prominent 29.6%, type 3 (irregular)
10.4% and type 4 (quadrangular) 5.8%. Double foramina were founded in 23 vertebras, incomplete foramina in 9 vertebras and accessory
incomplete foramina were seen in 12 vertebras.
Conclusion: The morphological knowledge of this type of variation is clinically important because the course of the vertebral artery
may be distorted in such condition. It may be compressed leading to some neurological symptoms or even hearing disturbances. Also, the
knowledge of this type of variation is important for the neurosurgeon during posterior surgical approaches of cervical spine. It is also useful
for radiologist during CT and MRI scan.
Keywords: Atlas vertebra; Cervical vertebra; Morphometry; Transverse process; Transverse foramina
Anatomy Physiol Biochem Int J 4(4): APBIJ. MS. ID. 555642 (2018) 00163
Introduction
The atlas is a ring of bone and consists of a pair of lateral
masses connected by a short anterior arch and a long posterior
arch. The transverse processes projects laterally from the lateral
masses and longer than that of other cervical vertebrae except
the seventh [1]. Marking the transverse processes, the foramen
transversaria (FT) which are located on the transverse process
and are cardinal features of cervical vertebrae [2]. FT transmits
the vertebral vascular bundle (vertebral artery, and veins)
and the sympathetic plexus which accompanies the vessels.
Derangements of these structures in their course because of
narrowing or deformation of the foramina, or osteophytes
impinging on them, have been extensively investigated by many
authors. The importance of such disturbances to these vital
vessels and nerves is obvious. Embryologically, FT is the result
of the special formation of the cervical transverse processes.
It is formed by a vestigial costal element fused to the body
and the originally true transverse process of the vertebra; the
vertebral vessels and nervous plexus are caught between the
bony parts. The FT is closed laterally by the “costotransverse
bar”, a plate of bone interconnecting the rib element to the
original transverse process (Figure 1). Generally, any variations
in the FT may affect the vital structure i.e. vertebral artery
      
knowledge of these variations is important for surgeons and
radiologist for interpreting CT and MRI scans [3]. From the
surgical point of view, study of the FT is of great value to the
neurosurgeons for posterior approaches of cervical spines [4].
These foramina exhibit variations in their shape, size, number
and even presence or absence. Morphometry and anomalous
variations are important to the neurosurgeons in determining
Anatomy Physiology & biochemistry international journal
00164 How to cite this article: Joseph N Aziz, Michel Morgan. Morphological Study of the Foramen Transversarium of the Atlas Vertebra among Egyptian
Population and Its Clinical Signicance. Anatomy Physiol Biochem Int J: 2018; 4(4): 555642. DOI: 10.19080/APBIJ.2018.04.555642.
the etiology, side predilection and vascular variations in the
atlanto-occipital region [5].
Figure 1: Schematic cervical vertebra: shows the foramen
transversaria with the various structures passing through it.
Shaded portion of transverse process represents rib component.
There is correlation between the atlas morphology with
head and neck posture [6]. Thus, the presence of other bony
variations, as well as the prevalence of neck syndromes and
injuries necessitates the study of the atlas transverse foramina.
     
for the posterior approaches of cervical spine [7]. From the
clinical point of view, occipital neuralgia is usually unilateral and
has a characteristic shock like pain lasting for a short duration
          
dermatome of the nerve root at the lower occipital region of scalp
and upper neck. Compression of the nerve root by an abnormal
course of vertebral artery has been reported in the literature.
Bony abnormalities at the craniovertebral junction can cause
occipital headache due to abnormal course of vertebral artery
and joint instability [8,9].
Aim of the Study
This study aims to investigate the morphology and variations
of foramina transversaria of the human atlas vertebrae and to
point out the clinical importance of these variations.
Materials and Methods
Dried 135 atlas vertebrae of Egyptian origin and of adult
size and unknown sex were obtained from the Dissecting room
of dental students, department of Anatomy, Cairo University,
Faculty of Medicine, for the present study. Broken or incomplete
atlases were excluded from the study. The vertebrae were
examined for the presence or absence of foramina, double
foramina and incomplete foramina. The side and shapes of the

into four categories using the criteria by Taitz et al. [10].
According to the shape and direction of the main diameter, the
  
studied as seen in an A-P direction where the anterior arch
facing the examiner).
Results
Figure 2: Pie chart showing predominance of rounded FT
compared with other shape.
Figure 3: Superior view of Atlas vertebrae showing unilateral
double FT (arrow) on the root of the transverse process
Figure 4: Superior view of Atlas vertebrae showing bilateral
double FT (arrows) located on the posterior arch.
The whole 135 dried vertebrae, used for this study, were
examined for the presence or absence of foremen transversaria
and the presence of accessory or incomplete foramen. The
following results were recorded: Double foramina were observed
in 23 vertebrae (17.7%) 7 on the left and 13 on the right and 3 on
00165
Anatomy Physiology & biochemistry international journal
How to cite this article: Joseph N Aziz, Michel Morgan. Morphological Study of the Foramen Transversarium of the Atlas Vertebra among Egyptian
Population and Its Clinical Signicance. Anatomy Physiol Biochem Int J: 2018; 4(4): 555642. DOI: 10.19080/APBIJ.2018.04.555642.
both sides. The accessary foramina were present on the posterior
root of the transverse process in 10 cases while in 13 cases the
foramina were observed at the posterior arch (Figure 3-5). Some
accessory foramina were too small. Incomplete foramina were
observed in 9 vertebrae (6.9%), 4 on right 3 on left 2 bilateral
(Figure 6). Also, in 6 vertebrae (4.6%) incomplete accessory
foramina were observed with different shape semicircular,
hemi circular and U shape in Figure 7 with 2 on the left 3 on
right 1 bilateral (Table 1). Study of the shape of the foramina
transversaria based on the anteroposterior and mediolateral
measurements showed four different shapes; type 1 (rounded)
was predominant 54.1%, type 2 (oval) less prominent 29.6%,
type 3 (irregular) 10.4% and type 4 (quadrangular) 5.8%.
Figure 5: superior view of Atlas vertebrae showing bilateral
incomplete FT (arrows) indicating absence of costal element of
both transverse process of atlas vertebra..
Figure 6: Superior view of Atlas vertebrae showing bilateral
double FT(arrows) located on the posterior arch.
Table 1: Percentage of occurrence of complete, incomplete, doubled
and absent foramen transversaria of atlas vertebrae.
Foramen
Transversarium Number
Total Number
Studied
bilaterally
Percentage
Complete 126 252 93%
Incomplete 911 7%
Double foramina 23 26 17.70%
Incomplete
accessory 6 7 4.60%
Absent 0260 0%
Figure 7: Superior view of Atlas vertebrae showing incomplete accessory FT (arrows) with different shape (7A) semicircular (7B) hemi circular
(7C) U shape.
Discussion
As one of the three bony components of the cranio-vertebral
       
mainly because of importance of its grooves and foramina in the
region of posterior and lateral margin [5]. Transverse foramen
of atlas has been studied in terms of shape, morphometry
and presence or absence in Kenyans [6]. In the current study,
the shapes of the foramen transversarium were categorized
into four different categories, rounded 54.1%, oval 29.6%,
irregular 10.4% and quadrangular 5.8%. In atlas vertebrae, true
transverse process is represented by a thick posterior bar in
intrauterine life, which fuses eventually with thin anterior bar
developed in third – fourth year of life from ventrolateral aspect
of articular pillar and thus completes the formation of FT. Hence
in atlas, the foramen transversarium is formed by fusion of
Anatomy Physiology & biochemistry international journal
00166 How to cite this article: Joseph N Aziz, Michel Morgan. Morphological Study of the Foramen Transversarium of the Atlas Vertebra among Egyptian
Population and Its Clinical Signicance. Anatomy Physiol Biochem Int J: 2018; 4(4): 555642. DOI: 10.19080/APBIJ.2018.04.555642.
anterior and posterior bars as they pass around the position of
vertebral artery at the age of 3-4 years [7]. The variable shape of
foramen transversarium as observed in the current study were
categorized on the basis of their plane and maximal medio lateral
dimension in coronal plane [8]. The variable shapes of foramina
have been known to have a correlation with the tortuosity and
size of vertebral artery, which is inturn dependent subsequent
on loading forces and stresses in the neck [9].
It has been observed that in some cases the accessory FT was
too small compared with the original FT. Thus smaller foramen
was explained by absence of vertebral artery or a variation where
the artery runs along the transverse process without entering
the foramen [6]. The current study found double foramina in
23 vertebrae (17.6%). Several authors have reported double or

the atlas. These variations are possibly linked with duplication of
the vertebral artery. However, occurrence of multiple transverse

as one foramina may be occupied by veins and nerves. The cause
  
atlas was attributed to fusion of two costal elements with the
transverse process [11]. Moreover, these variations may be
attributable to possible genetic differences and also carrying
heavy loads on the head, which has been associated with various
bony bridges on the atlas vertebrae [8].
In this study, incomplete transverse foramina were also found
in 9 vertebrae (11%), it could be explained on the base of erosion
of bones as the age advances. However, the age of the bones was

changes in most of these studies. Also, incomplete accessory
transverse foramina were also found in 6 vertebrae (4.6%),
most of them mainly located at the posterior root. However,
            
information about age related changes in most of these studies.
It is reported that tortuosity of the vertebral artery may cause
bony erosion, or impede complete formation of the transverse
foramen [12,13] Developmental changes could account for the
anomaly observed. Other explanations of incomplete foramina
are tensions and stress applied to bones by the running vessels
through foramina with relatively free movements of the cervical
spine [14]. Furthermore, the natural tortuosity of vertebral
artery may cause bony destruction which could be minimal
leading to bony bridge or sever [15]. Accordingly, the shape of
incomplete foramina in the current study is semicircular, hemi
circular and U shape (Table 2).
Table 2: Showing prevalence of double transverse foramina in di󰀨erent study populations.
Author Year Prevalence of double
foramina Study sample Population
Taitz et al. [10] 1978 7% 480 Indian
Nagar et al. [5] 1999 8.60% 1388 Roman
Das et al [11] 2005 1.50% 132 Indian
Kaya et al [12] 2011 22.70% 262 Jewish
Karau PB, Oduia P [8] 2012 3.90% 102 Kenyans
Rekha BS [13] 2013 6.54% 153 Indian
Present study 2017 17.70% 135 Egyptian
From the current study, it could be suggested that variations
of the foramina can be useful for estimating changes or variations
of vessels this runs concurrently with previous literature [13].
The occurrence of incomplete transverse foramina in atlas
should be noted by radiologist, as these can be confused with
other anomalies [6]. On the other hand, some authors have
noticed that the vertebral artery covers about two thirds of the
minimal diameter and more than half of maximal diameter of
the transverse foramen [11]. Moreover, it has been suggested
that the preponderance of osteophytes on lateral margins of
FT could lead to narrowing of mediolateral diameter leading
to compression of vertebral artery and its dissection [13].
Hence it can be assumed that oval shape FT oval 29.6% with
anteroposterior diameter greater than mediolateral diameter
had minimal risk of vertebral artery compression syndrome.
Also, it is well known that any narrowing of FT may result in
formation of atheromatous plaques in vertebral artery which


Conclusion
The study has revealed existence of many variations in the
transverse foramina of atlas among Egyptian. The data provided
in the present study is helpful in interpretation of radiographic
features of atlanto-occipital region, as well as surgical access.
Also, this suggests that defects in the FT of the atlas vertebrae
may be included in the cervicovertebral junction anomaly, when
anomalous can cause occipital headache. So that, neurosurgeons
should be aware of such variations while operating at the level


On the other hand, radiologists must also be aware of this fact
in order to correctly interpret the radiograph or CT scan or MRI
image of the cranio-vertebral region.
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Anatomy Physiology & biochemistry international journal
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Population and Its Clinical Signicance. Anatomy Physiol Biochem Int J: 2018; 4(4): 555642. DOI: 10.19080/APBIJ.2018.04.555642.
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DOI:
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... Also, FT of atlas possesses lots of clinical importance, so morphometric & morphological variability will be a great help for the surgeons performing various treatment modalities. [12,13] Spinal cord compression especially in the cervical region may lead to full blown neurological signs & symptoms due to unusual bony or soft tissue components. [14] So, not only FT but also vertebral foramen of atlas also plays a major role as a bony factor for the pathogenesis of various neurological consequences. ...
... In our observation, accessory foramina were seen in 9 % of atlas among 55 total vertebrae which was similar to study done by Nagar et al. [30] & Srobar et al. [13] . But very high incidence of accessory FT was observed in studies done by Kaya et al. [4] , Aziz et al. [12] ., Rao BS et al. [31] among different population group. The frequency of accessory FT was very high among Egyptian [12] & Jeweish [4] population. ...
... But very high incidence of accessory FT was observed in studies done by Kaya et al. [4] , Aziz et al. [12] ., Rao BS et al. [31] among different population group. The frequency of accessory FT was very high among Egyptian [12] & Jeweish [4] population. Very low incidence was observed among Das et al. study in 2005. ...
... The double opening of the transverse foramen of the C7 vertebra appears in literature as an inheritable non-metric feature (Katzenberg and Saunders 2007: 536). The fusion of the foramen could be congenital and may have caused alterations in blood circulation and nerve damage (Cai et al. 2018;Goray et al. 2005;Aziz and Morgan 2018). The narrowing of the original path for the vessels and nerves could cause problems with blood circulation (thrombosis, emboli, reflex spasm) and partial paralysis. ...
... It was possible to trace this in an older individual from Misti with improper leg formation (Socha et al. 2020) and in the case of Ampato #3. The malformation of the path for the vertebral artery and vein and the sympathetic nerve plexus could cause some serious medical issues (Cai et al. 2018;Goray et al. 2005;Aziz and Morgan 2018;Sultana et al. 2015). However, bone lesions alone are not enough to determine the health of an individual. ...
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One of the most important rituals in the Inca Empire was the capacocha. It required the most prestigious sacrificial offering of male and female children and young women who were characterized by their beauty and purity. The aim of this paper is to present the results of a bio-anthropological analysis of the remains of five individuals sacrificed on the summits of Ampato and Pichu Pichu during this ritual. Various methods (bone analysis and radiography) were applied in the investigation due to the diverse states of preservation of the remains. Four individuals were in the same age category: 6-7 years old. The individual Pichu Pichu #2 was sacrificed at age 3.5 years, which makes him the youngest capacocha sacrifice currently known. Results show proper development of the victims' bodies, the presence of stress markers related to the early childhood period, and, in the case of the Ampato boy, malformation of the cervical vertebrae. The studies of the Pichu Pichu and Ampato sacrifices confirm their widespread origins, privileged position, and high social status. They show that the victims were well-nourished and had proper body growth compared to juveniles from the lower social strata in different cemeteries in the region.
... The atlas vertebra differs in structure from other cervical vertebrae and variations of this vertebrae are common. In the past, various studies has been conducted by many authors on the variations in size, shape, absence, incomplete [2][3][4][5] or duplicated foramen transversarium [6][7][8]. ...
... Such variations in the foramen transversarium may cause compression of vertebral artery during manipulation of cervical spine surgery, excessive exercise of the neck, physiotherapy and this may result in vertebro-basilar ischemia which may lead to common symptoms like migrane, vertigo, diplopia, shoulder pain, neck pain and sometime cerebrovascular incidents [8]. Hence, the knowledge of variation of foramen transversarium of atlas vertebrae is important for physicians, surgeons, orthopedicians, neurologists and physiotherapists [5]. ...
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Introduction: Foramen transversarium are the characteristic bony feature of the cervical vertebrae. They are located on the transverse process of cervical vertebrae through which second part of vertebral artery passes along with vertebral venous and sympathetic plexus. Their variations are common with regard to size, shape, incomplete, duplicated and may even absent. Material & Methods: Two hundred foramen transversarium of one hundred atlas vertebrae were examined for morphological variations. Results: Out of hundred atlas vertebrae examined, foramen transversarium was present in all. Absence of costal element was noticed in four atlas vertebrae. Four atlas vertebrae showed incomplete bilateral foramen transversarium while four showed unilateral duplicated foramen transversarium. Conclusion: The increasing incidence of neck injuries and related syndromes necessitates the study of bony variations of the atlas vertebra and its foramen transversarium. The second part of vertebral artery is prone to be damaged during neck surgeries and posterior cervical injuries due to incomplete formation of the foramen transversarium, hence the knowledge of such variations is important for surgeons, otorhinolaryngologists, neurologists, orthopedicians, radiologists and physicians.
... The ITF www.acbjournal.org https://doi.org/10.5115/acb.23.281 is described as a gap in the antero-lateral forming a groove for the vertebral vessels found in around 7% of individuals [16]. It was identified on the right side of the subject in the present study (Fig. 2). ...
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In this report, atlantooccipital assimilation (AS), anterior arch defect (AAD), and posterior arch defect (PAD) of the atlas, and several variations around the craniocervical junction were identified on computed tomography (CT) of a patient of unknown sex and age. Coronal and sagittal CT scans showed AS and bilateral fusion of the atlas and the base of occipital bone. Axial CT scan at the atlas revealed PAD type B on the left side and midline AAD. Morphometric measurements indicated a potential ventral spinal cord compression. In addition, mid-sagittal CT revealed the presence of fossa navicularis magna and incomplete formation of the transverse foramen on the right side. This study reports an extremely rare AS associated with AAD, PAD, and other variations of the clivus and the atlas. To our knowledge, no similar case has been reported in the literature.
... was also observed on the left side. This result corroborates the previous finding by Aziz and Morgan [25] that documented a 10% frequency for the irregular type of FT. ...
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ARTICLE INFO Keywords Foramen transversarium Cervical vertebrae Morphometric Sex Age ABSTRACT Foramen transversarium (FT) is a distinguishing characteristic of cervical vertebrae based on the vertebral vessels and sympathetic nerve it transmits. This study aimed to analyze the morphometric parameters and variations of FT of the typical cervical vertebrae with regards to sex, age, and laterality within the KwaZulu-Natal (KZN) population , South Africa. One hundred and thirty dried human typical cervical vertebrae of the KZN population of known sex and age without any degeneration were sourced from the Discipline of Clinical Anatomy, University of KwaZulu-Natal (UKZN). The osteometry analyses were performed using Markus Bader (MB) Ruler and subjected to RStudio statistical analysis. Rounded (43.85%) or ellipsoid transversely (23.85%) shapes FTs were predominant in males and on the right side (46.16%). Morphometric indices were higher in males on the right side in age groups 20 to under 60 years. An unusually high prevalence of double foramen (36.92%) was present in about one-third of the specimen with a higher percentage in males and bilateral in about 10%. This study has provided a good basis on morphometric analysis and variations of FT with regards to specific sex, age group, and laterality.
... Taitz et al. and Aziz [22] observed the different shape of the accessory foramen transversarium such as round, oval, irregular, and quadrangular. They also reported that among the shapes, round-shaped foramen were the most common one (Taitz et al. -54.8% and Aziz et al. ...
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The aim of this study is to reveal the incidence and morphometric features of the accessory foramen transversarium in the population in eastern Turkey. In the study, a total of 125 cervical vertebrae of unknown gender and age, located in the Anatomy Department of Ataturk, Erzincan Binali Yıldırım and Kafkas University Medical Faculties, were used and accessory foramen transversarium was detected in 22 (17.6 %) of these cervical vertebrae. In this study, the area, vertical and horizontal diameters of the accessory foramen transversarium were measured for the first time. It was determined that the accessory foramen transversarium with the largest area was in C3-C6 (6.8 mm2) and the smallest area was in C7 (1.06 mm2). It was determined that the largest vertical diameter was C7 (2.38 mm), the smallest one was C3-C6 (0.91 mm), the largest horizontal diameter (3.66 mm), and the smallest (1.6 mm) were C3-C6. In addition, accessory foramen transversariums were typified. One foramen arcuate was also detected during the examinations. As a result, osteometric measurements of the accessory foramen transversarium were revealed. We think that these data will be an important reference in head and neck surgery, in the clinical approach of a. vertebralis, and in the evaluations of radiologists in the neck region.
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Introduction: The facet joints are the only synovial joint of spine and undergo osteoarthritic changes referred to as facet joint arthrosis (FJA). The arthrosis is akin to arthritic changes in any other synovial joint of the body and may manifest as back pain or may remain asymptomatic throughout life. The causes for pain manifestation in FJA are manifold but there is paucity of literature in defining reasons to remain asymptomatic even with a deranged pathology at the joint. Thus the aim of the study was to assess the prevalence of asymptomatic FJA and define its relation with respect to age, gender and vertebral level on CT evaluation and discuss the pertinent anatomy around each spinal motion segment which prevents manifestation of pain. Material & Methods: A total of 100 asymptomatic subjects were selected on basis of a low back pain questionnaire within age range of 20-70 years, reporting to radiology department for CT abdomen. The individuals were categorized as per the following age groups; 20-35yrs as young; 36-50 as middle and 51-70 as old age groups. All five lumbar vertebral levels with their facet joints were analysed for evidences of degenerative grades and their severity, in total selected subjects. The images obtained were further assessed on image analysis software for distribution as per the age-groups, gender and prevalence with respect to vertebral level. Results: A total of 136 (27.2%) levels in 43(43%) spines were found to have FJA. The highest prevalence (43.3%) of asymptomatic FJA was observed in the middle age group with involvement of multiple spinal motion segments and with grade 4 severity. Conclusion: Prevalence of severe grades of asymptomatic FJA in middle age group suggests the possible role of certain muscle groups in maintaining an appropriate posture in spite of on-going degenerative processes.
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Karau P.B, and P. Odula (2013).Some anatomical and morphometric observations in the transverse foramina of the atlas among Kenyans. Anatomy J of Africa Vol. 2(1): 61 -66
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Four hundred and eighty foramina transversaria in dry cervical vertebrae of 36 spines and in a number of dissections were studied and classified according to size, shape, and direction of their main diameter. A coefficient of roundness was then elaborated. The variations of foramina appear to follow a pattern at various vertebral levels. The possible factors (in addition to the embryological ones) involved in causing these variations-for example, mechanical stress, size, course, and number of vertebral vessels-were analysed. The importance of the correct interpretation of the variations in the foramina transversaria in radiographic or computerised axial tomography is discussed. The contribution of the present study to the understanding and diagnosis of pathological conditions related to the vertebral artery and its sympathetic plexus is stressed.
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The posterolateral tunnel on the superior surface of the first cervical (atlas) vertebra is of normal occurrence in monkeys and other lower animals, but its presence in the form of a tunnel-like canal, for the passage of the third part of the vertebral artery over the posterior arch of the human atlas vertebra is not reported. The aim of the present study was to detect the presence of such a canal, in addition to other types of ponticuli (little bridges) reported by earlier investigators, in macerated atlas vertebrae and routine cadaveric dissections. The posterolateral tunnel was detected in 1.14%, and the posterior and lateral ponticuli in 6.57 and 2% of vertebrae. Probably the bony roof of the posterolateral tunnel serves the purpose of additional lateral extension for the attachment of the posterior atlanto-occipital membrane in quadrupeds, where the load of the head is supported by the extensor muscles of the neck, ligaments and posterior atlanto-occipital membrane. In man, where the weight of the head is borne by the vertical loading of the superior articular process of the atlas, the roof of the tunnel has disappeared.
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An evaluation of the vertebral artery groove of the atlas vertebra using dry bony vertebrae. To measure the dimension of the vertebral artery groove of the atlas and to define its relation to the posterior midline. Anatomic descriptions of the vertebral artery groove of the atlas exist, but very little quantitative data focused on this groove have been reported. Fifty dry atlas vertebrae were obtained for this study. Anatomic evaluation focused on the vertebral artery groove and its relation to the midline. A total of eight linear and two angular measurements were made bilaterally. The mean, range, and standard deviation were calculated for all of the specimens and for male and female specimens separately. Differences in dimensions of male and female specimens were found to be statistically significant in one linear and two angular parameters. The average depths of the medial and lateral entrances, lengths of the axis, and thicknesses of the vertebral artery groove for male and female specimens were 9 mm, 6 mm, 14 mm, and 4 mm, respectively. The average angle of the vertebral artery groove axis for both genders was 64 degrees lateral to the sagittal plane. The distances from the midline to the medial-most edge of the vertebral artery groove on the inner and outer cortexes for male and female specimens averaged 10 mm, with a minimum of 8 mm, and 18 mm, with a minimum of 12 mm, respectively. The results of this study suggest that dissection on the posterior aspect of the posterior ring should remain within 12 mm lateral to the midline, and dissection on the superior aspect of the posterior ring should remain within 8 mm of the midline.
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Six hundred and seventy-two atlas vertebrae of 6 population groups were examined for the presence of a posterior and/or lateral bridge. Of these, 174 (25.9%) presented with partial posterior bridge formation and 53 (7.9%) with a complete bridge. Twenty-six (3.8%) showed some form of lateral bridging. Although controversy exists as to the origin of atlas bridging, the findings of the present study show that aging could be a factor predisposing to complete bridge formation. The clinical significance of bridge formation is discussed with reference to their possible effect on normal vertebral artery function, particularly in rotation.
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Erosions, caused by a vertebral artery loop, of the pedicles and vertebral bodies in the area of C2-C6 were found in nine patients, in a total of 12 intervertebral spaces. Two of the cases in which the changes seen in plain radiographs were considered bilateral, were confirmed by angiography of the aortic arch. A tortuous vertebral artery sometimes produces symptoms provoked by nerve root compression. To keep this differential diagnosis in mind is at least equally important when a tumor enlarging the foramen is suspected.
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Anatomical texts allude to many variations in the foramen transversarium of the seventh cervical vertebra, including its absence, but absent foramen transversarium of the atlas vertebra has not been mentioned. This is the case report of an atlas vertebra, the transverse process of which did not exhibit this foramen on the left side. However, the groove for the vertebral artery was present bilaterally on the posterior arch. The possible factors responsible for this interesting variant are discussed.
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This study assessed numerous structural features of the second cervical vertebra (C2), describing the projection point of the pedicle on its posterior aspect. Evaluation of the specimens included quantitative description of 18 linear and four angular parameters, which then were correlated between male and female specimens. The point of projection of the C2 pedicle axis was described with an emphasis on a perspective relevant to a posterior approach. The literature regarding the anatomy of the axis focuses mainly on the dens. Very little research regarding the quantitative study of the C2 pedicle has been reported. Fifty dry C2 cervical vertebrae (30 male, 20 female) were obtained for anatomic measurements. Anatomic evaluation focused on the pedicle, vertebral body, dens, superior facet, and vertebral canal. All measurements were made using calipers and a standard rule linear measurements and a goniometer for angular measures. Based on the measurement of 50 specimens, including 18 linear and four angular parameters, the mean, range, and standard deviation were calculated for all of the specimens and for male and female separately. A significant difference was found to exist for 11 of 18 linear measurements and one of four angular parameters. The projection point of the pedicle axis on the posterior aspect of the lateral mass was described with an emphasis on a perspective relevant to a posterior surgical approach. The location of the projection point of the pedicle axis was found to be 5.4 +/- 1.2 mm inferior to the horizontal line, and 7.2 +/- 1.3 mm lateral to the vertical line. The pedicle axis was found to lie at 33 degrees in the medial direction and 20 degrees in the superior direction form the point of pedicle axis projection. When the techniques described here are used, the findings may be helpful in cases involving C2 when surgical intervention and instrumentation are desired.
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This study is based on direct quantitative caliper measurements of 88 isolated anatomic specimens of the C1 vertebra. The study was undertaken to establish the range and variability of the external dimensions of the atlas and to describe the cortical thicknesses and trabecular distribution of this unique vertebra. Before this study, Francis in 1952 reported the total anterior and posterior diameter of 285 atlas vertebrae. Liu et al reported detailed external dimensions and facet joint surface morphologies on a total of three C1 vertebrae. Measurements were made of overall dimensions, canal diameters, and the dimensions of the anterior and posterior arches of 88 dried human C1 vertebrae. Eight specimens were sectioned in the frontal plane, eight in the sagittal plane, and four in the coronal plane. The anatomy of these sections was documented by radiographic imaging. Cortical thicknesses on the sections were then obtained by direct measurement. The canal diameter ranged from 32 mm (SD 2 mm) in the sagittal plane, and 29 mm (SD 2 mm) in the lateral dimension. The mean thickness of the anterior ring was 6 mm (SD 1 mm) and posteriorly was 8 mm (SD 2 mm). Cortical bone was thinnest posteriorly. These measurements indicated remarkably constant dimensions for the ring itself, suggesting there may be significant functional restraints on the canal size of this unique vertebra. In contrast, a significant variability was noted in objective measurements of lateral mass height and sagittal plane widths of the entire bone.
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The associations between dimensions of the first cervical vertebra, atlas, and a representative set of craniofacial and postural variables were studied on cephalometric radiographs of a sample of 103 adult males aged 22-30 years, recorded in the natural head position (mirror position). Atlas morphology was expressed by nine variables, linear and angular craniofacial dimensions by 27 variables, and head and cervical posture by seven variables. A pattern of low but significant correlations was found. Although the correlations were low, the study confirmed that the dimensions of the atlas vertebra reflect associations between cranio-cervical posture and craniofacial morphology. Negative correlations were found between the height of the posterior arch of atlas and the inclination of the mandible and the maxilla to the anterior cranial base. Low positive correlations between the height of the anterior arch and vertical facial dimensions reflect the general co-ordination of the vertical growth of the face and the cervical column. Moreover, the pattern of correlations between the atlanto-cranial angle and facial morphology suggests that in changes of the cranio-cervical angle, atlas follows the cervical column.