Download The prevalence of ponticulus posticus among patients

Journal of Medicine, Radiology, Pathology & Surgery (2016), 3, 1–4
ORIGINAL ARTICLE
The prevalence of ponticulus posticus among patients
visiting JSS dental college - A radiographic study
Karthikeya Patil, Mahima V. Guledgud, Athira Joshy, Poornima Chandran, Bharathi Penumatsa
Department of Oral Medicine and Radiology, JSS Dental College and Hospital, JSS University, Mysuru, Karnataka, India
Keywords:
Atlas, arcuate foramen, cervical vertebrae,
ponticulus posticus
Correspondence:
Dr. Mahima V. Guledgud,
Department of Oral Medicine and Radiology,
JSS Dental College and Hospital, JSS
University, Mysuru, Karnataka, India.
E-mail: [email protected]
Received: 14 october 16;
Accepted: 28 November 16
Abstract
Objective: The objective of this study was to estimate the prevalence of ponticulus
posticus among patients visiting JSS Dental College.
Methods: The occurrence of ponticulus posticus and its forms were assessed in 435
lateral cephalograms (LCs) by 2 independent examiners. Data obtained were subjected
to statistical analysis using Chi-square and κ analysis.
Results: The prevalence of ponticulus posticus among patients visiting JSS Dental
College was found to be 31.8%, with no significant gender predilection.
Conclusion: Ponticulus posticus has been found to be a common anomaly in the
population of Mysuru. Due to its clinical significance during surgical intervention
and the association with headaches and migraines, patients must be educated on the
consequences of its presence. It must also be recorded as a finding in the LC taken.
doi: 10.15713/ins.jmrps.72
Introduction
Atlas is the first cervical vertebra. Historically, named after
a Greek myth, Atlas had to carry the weight of the sky on his
shoulders for eternity. Similarly, even the atlas bears the weight
of the entire head. It is a ring-shaped structure which comprises
two lateral masses, transverse process as well as anterior and
posterior arches. The two lateral masses consist of superior and
inferior articular facets. The superior articular facet forms the
atlanto-occipital joint whereas the inferior articular facet forms a
lateral atlanto-axial plane joint. The anterior arch forms anterior
2/5th while the posterior arch forms 3/5th of the circumference
of the atlantal ring. The superior surface of posterior arch
consists of a groove through which the vertebral artery passes.
A bridge of ossification named “ponticulus posticus” is seen
on the vertebral groove which extends from the lateral mass to
posterior arch of atlas. In Latin, ponticulus posticus means little
bridge.[1]
Ponticulus posticus is defined as an abnormal small bony
bridge which is formed between the posterior portion of the
superior articular process and the posterolateral part of the
superior margin of the posterior arch of the atlas. It is also
known as atlantal posterior foramen, sagittal foramen, a variant
of Kimmerle’s anomaly, arcuate foramen, canalis vertebralis,
upper retro-articular foramen, retro-articular vertebral artery
ring, retro-articular canal, and retrocondilar vertebral artery
ring. However, ponticulus posticus is the most accepted
terminology.[2]
Also called as the arcuate foramen, it is a bony arch on the
atlas vertebra. It converts from a groove on the upper surface
of the arcus posterior Atlantis to this foramen. It comprises
significant anatomic structures, such as the vertebral artery and
the suboccipital nerve. It is also attached to the atlanto-occipital
membrane, which is linked to the dura. Hence, any compression
to the vertebral artery or suboccipital nerve might cause
symptoms such as migraine, vertigo, diplopia, shoulder pain,
and neck pain. It has been reported that it could cause severe
complications such as stroke and even death during insertion
of C1 lateral mass screws due to the compression of vertebral
artery.[3]
With this background in mind, this study has been designed
to estimate the prevalence of ponticulus posticus among patients
visiting JSS Dental College.
Materials and Methods
This study was conducted in the Department of Oral Medicine
and Radiology, JSS Dental College and Hospital, Mysuru. The
archived lateral cephalograms (LCs) were recovered from the
Journal of Medicine, Radiology, Pathology & Surgery ● Vol. 3:6 ● Nov-Dec 20161
Patil, et al.
Prevalence of ponticulus posticus
department using simple random sampling technique. Totally
435 LCs satisfying the inclusion criteria were selected and
appraised by two blinded independent examiners for the existence
of ponticulus posticus and its variants, i.e., complete and partial.
Inclusion criteria
• LCs with optimum image quality.
• LCs with adequate visibility of atlas which is not obscured or
superimposed by the surrounding anatomical structures.
Exclusion criteria
• LCs where there is evidence of any anomaly or pathology.
• LCs with positioning and exposure errors.
A complete ponticulus posticus [Figure 1a] is one continuous
bridge that extends from the posterior aspect of the lateral mass
to the anterior aspect of the posterior tubercle whereas a partial
ponticulus posticus [Figure 1b] is one that does not extend fully
from the posterior lateral mass to the posterior tubercle.[4]
The selected radiographs were viewed using an X-ray viewer
and a magnifying lens. The radiographs were then divided into
3 groups as follows: Group 1 - absence of ponticulus posticus,
Group 2 - presence of partial ponticulus posticus, and Group 3
- presence of complete ponticulus posticus.
The prevalence was calculated by including only those
radiographs which the examiners agreed upon, pertaining to the
presence and absence of ponticulus posticus. The reliability of
the two examiners was assessed using k analysis.
Results
The interexaminer agreement was 0.61. Among the 435
radiographs, 83 radiographs were excluded from the analysis as
there was disagreement between the two examiners regarding
the presence and absence of ponticulus posticus. Out of the
remaining 352 radiographs, 240 (68.1%) did not show any form
of ponticulus posticus whereas its various forms were noted in
112 (31.8%) radiographs. The complete form of ponticulus
posticus was noted in 14 (4%) radiographs while the partial form
was noted in 98 (27.8%) radiographs [Table 1].
Among the 112 radiographs, 54 (48.2%) were males and
58 (51.7%) were females. No gender predilection was noted
[Tables 2 and 3].
Discussion
Considered as an important anomaly of the atlas, ponticulus
posticus is a bony arch that converts the groove into the foramen.
This foramen is called the arcuate foramen which comprises
vertebral artery and suboccipital nerve. According to various
surgeons, the screw must be inserted in the dorsal aspect of
the posterior arch instead at the base of the lateral mass, or at
the junction of the posterior arch and the lateral mass. A broad
dorsal arch of the atlas is the finest manifestation for this
2
a
b
Figure 1: (a) (left) - Lateral cephalogram showing complete form
of ponticulus posticus, (b) (right) - Lateral cephalogram showing
partial form of ponticulus posticus
Table 1: The cross‑tabulation of examiners 1 and 2 regarding the
presence and absence of ponticulus posticus
01
Absent
02
CP
Total
PP
Absent
Count
240
2
58
300
Percentage within 02 (%)
92.7
10.5
36.9
69.0
1
14
1
16
0.4
73.7
0.6
3.7
Count
18
3
98
119
Percentage within 02 (%)
6.9
15.8
62.4
27.4
259
19
157
435
100.0
100.0
100.0
100.0
CP
Count
Percentage within 02 (%)
PP
Total
Count
Percentage within 02 (%)
CP: Complete ponticulus posticus, PP: Partial ponticulus posticus,
01: Examiner 1, 02: Examiner 2
modified screw trajectory. However, in patients with ponticulus
posticus, it can be misconstrued for a broad dorsal arch which
can cause compression of the vertebral artery, stroke, or even
death by thrombosis, embolism, or arterial dissection. Hence,
we conducted this radiographic study to aid the surgeons in the
lateral mass screw fixation.[4]
According to our study, the prevalence was about 31.8%
which was less compared to the study conducted by Kuhta et al.
where the prevalence was 45.9%.[2] The difference in prevalence
could be because of the geographic or ethnic variations among
the populations.
In our study, the prevalence of partial form of ponticulus
posticus (27.8%) was found to be more than the complete form
(14%). It was similar to the study conducted by Cederberg
Journal of Medicine, Radiology, Pathology & Surgery ● Vol. 3:6 ● Nov-Dec 2016
Patil, et al.
Prevalence of ponticulus posticus
Table 2: The cross‑tabulation of examiners 1 and 2 regarding the
presence and absence of ponticulus posticus in males
01
Absent
02
CP
Total
PP
Absent
Count
100
1
23
124
Percentage within 02 (%)
91.7
10.0
32.9
65.6
1
7
0
8
0.9
70.0
0.0
4.2
8
2
47
57
7.3
20.0
67.1
30.2
109
10
70
189
100.0
100.0
100.0
100.0
CP
Count
Percentage within 02 (%)
PP
Count
Percentage within 02 (%)
Total
Count
Percentage within 02 (%)
CP: Complete ponticulus posticus, PP: Partial ponticulus posticus,
01: Examiner 1, 02: Examiner 2
Conclusion
Table 3: The cross‑tabulation of examiners 1 and 2 regarding the
presence and absence of ponticulus posticus in females
01
Absent
02
CP
PP
Total
Count
140
1
35
176
Percentage within 02 (%)
93.3
11.1
40.2
71.5
0
7
1
8
0.0
77.8
1.1
3.3
Absent
CP
Count
Percentage within 02 (%)
PP
Count
10
1
51
62
Percentage within 02 (%)
6.7
11.1
58.6
25.2
150
9
87
246
100.0
100.0
100.0
100.0
Total
Count
Percentage within 02 (%)
Kendrick GA and Biggs NL who reported a case, wherein two
females presented with the partial form of ponticulus posticus,
and over a time of 1-2 years, it was converted into a complete
form.[4]
Various studies have found an association of ponticulus
posticus with migraine without aura.[8] It was suggested that, due
to the attachment of ponticulus posticus to the atlanto-occipital
membrane and dura mater, pressure exerted on the dura results
in a type of headache seen in migraine.
Innumerable studies put forth that, due to the presence of
ponticulus posticus, occlusion of the vertebral artery occurs and
shows symptoms such as headache, vertigo, and diplopia from
vertebrobasilar insufficiency.[9] In 1972, a similar yet significant
study described by Eriksen reports two such cases of thrombosis
of the vertebrobasilar arterial system in the absence of identifiable
arterial disease, but in the presence of ponticulus posticus.[10]
Further research should be conducted on other populations
with larger sample size to compare age, racial, and genetic
predisposition for Ponticulus posticus.
CP: Complete ponticulus posticus, PP: Partial ponticulus posticus,
01: Examiner 1, 02: Examiner 2
et al. where the prevalence of partial form was about 27% and
complete form was about 11%.[5]
Numerous studies have been conducted to explain the
mechanism of ponticulus posticus formation. Among the
suggested etiologies are genetics, ossification by age, or
external mechanical factors.[6] A study conducted by Paraskevas
suggested that the incidence of complete form of ponticulus
posticus was more in laborers as compared to non-laborers.
However, we did not take the occupation into consideration.[7]
He also hypothesized that the partial form of ponticulus
posticus is precursor of the complete form. It was supported by
Ponticulus ponticus has been established to be a common
anomaly among patients visiting dental colleges. Due to its
clinical significance during surgical intervention and the
association with headaches and migraines, patients must be
educated on the consequences of its presence. It must also be
recorded as a finding in the LCs taken.
References
1. Rajani S. Is variant anatomy of atlas clinically important? A
review. Basic Sci Med 2014;3:1-7.
2. Kuhta P, Hart J, Orndorff L, Reizer B, Rush P. The prevalence of
posticus ponticus: Retrospective analysis of radiographs from a
chiropractic health center. J Chiropr Med 2010;9(1):162-5.
3. Bayrakdar IS, Miloglu O, Altun O, Gumussoy I, Durna D,
Yilmaz AB. Cone beam computed tomography imaging of
ponticulus posticus: Prevalence, characteristics, and a review
of the literature. Oral Surg Oral Med Oral Pathol Oral Radiol
2014;118:e210-9.
4. Akhtar JM, Fatima N, Ritu, Kumar V. A morphological study
of ponticuli of the human atlas vertebrae and its clinical
significance. Int J Anat Res 2015;3:1597-02.
5. Cederberg RA, Benson BW, Nunn M, English JD. Arcuate
foramen: Prevalence by age, gender and degree of calcification.
Clin Orthod Res 2000;3:162-7.
6. Schilling J, Schilling A, Suazo GI. Ponticulus posticus on the
posterior arch of atlas, prevalence analysis in asymptomatic
patients. Int J Morphol 2010;28:317-22.
7. Paraskevas G, Papaziogas B, Tsonidis C, Kapetanos G. Gross
morphology of the bridges over the vertebral artery groove on
the atlas. Surg Radiol Anat 2005;27:129-36.
8.Wight S, Osborne N, Breen AC. Incidence of ponticulus
posterior of the atlas in migraine and cervicogenic headache.
J Manipulative Physiol Ther 1999;22:15-20.
Journal of Medicine, Radiology, Pathology & Surgery ● Vol. 3:6 ● Nov-Dec 20163
Patil, et al.
9. Lamberty BG, Zivanovic S. The retro-articular vertebral artery ring
of the atlas and its significance. Acta Anat (Basel) 1973;85:113-22.
10.Sharma V, Chaudhary D, Mitra R. Prevalence of ponticulus
posticus in Indian orthodontic patients. Dentomaxillofac Radiol
2010;39:277-83.
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Prevalence of ponticulus posticus
How to cite this article: Patil K, Guledgud MV, Joshy A,
Chandran P, Penumatsa B. The prevalence of ponticulus
posticus among patients visiting JSS dental college - A
radiographic study. J Med Radiol Pathol Surg 2016;3:1-4.
Journal of Medicine, Radiology, Pathology & Surgery ● Vol. 3:6 ● Nov-Dec 2016