Download Ponticulus posticus - not such a rare finding on lateral cervical spine

Ponticulus posticus - not such a rare finding on lateral
cervical spine radiographs
Poster No.:
C-0545
Congress:
ECR 2014
Type:
Scientific Exhibit
Authors:
A. M. Calin , M. Calin ; Cluj-Napoca/RO, Cluj Napoca/RO
Keywords:
Epidemiology, Education and training, Normal variants,
Education, Plain radiographic studies, Conventional radiography,
Musculoskeletal bone, Head and neck, Anatomy
DOI:
10.1594/ecr2014/C-0545
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Aims and objectives
The atlas stands as the first cervical vertebra, being articulated with the occipital bone
above and the axis vertebra below. It has the shape of a ring and 2 arches.
The anterior arch is short and articulates with the dens of the axis vertebra, while the
posterior arch bears a groove on its surface for the vertebral artery and the dorsal ramus
of the first cervical spine nerve.
The vertebra has 2 transverse processes, which form a foramen transversarium, crossed
by the vertebral artery and also 2 lateral masses, which articulate with the occipital
condyles and form an ellipsoid type of synovial joint.
Fig. 1: Atlas, first cervical vertebra - anatomy
References: www.wikipedia.org
After its exit from the transverse foramina, the vertebral artery passes over the posterior
arch of the atlas, forming a groove called the vertebral artery sulcus, which varies in size
and can sometimes be very deep, located on the posterolateral margin of the posterior
arch of the atlas.
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Fig. 3: Vertebral artery - lateral view
References: www.wikipedia.org
Inferiorly and posteriorly to the posterior arch of the atlas, the posterior occipital ligament
is attached. It is connected above with the posterior margin of the foramen magnum and
appears as a broad, but thin ligament. Its lateral divisions, the oblique atlanto-occipital
ligaments, create with the vertebral artery sulcus an opening for the vertebral artery and
the suboccipital nerve.
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Fig. 2: Median sagittal section through the occipital bone and first three cervical
vertebrae.
References: www.wikipedia.org
Variants and asymptomatic deviations from the normal vertebral anatomy are often
confusing. This is the reason they have to be studied carefully to insure an adequate
differentiation from a pathological process.
If anomalous ossification occurs, a bony arch - named ponticulus posticus - bridges
the sulcus, encloses the foramen arcuate and through this, the vertebral artery and the
subocccipital nerve pass.
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Fig. 5: CT 3D reconstruction of cervical spine, lateral view - complete unilateral
ponticulus posticus (blue arrow)
References: - Cluj-Napoca/RO
Ponticulus posticus is a possible cause of posterior circulation ischemia, cervicogenic
headache, vertigo, neck pain, discopathy.
This condition had not been a matter of concern for physicians until its surgical
significance in the insertion of screws in the lateral mass of the atlas was reported.
Our interest for this anatomic variant was stimulated by its incidental appearance in
various lateral cervical spine examinations.
This study`s purpose was to determine occurrence, varieties, distribution by age and sex
of ponticulus posticus in a Radiology Ambulatory Care Service from Cluj-Napoca.
Images for this section:
Fig. 1: Atlas, first cervical vertebra - anatomy
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Fig. 2: Median sagittal section through the occipital bone and first three cervical
vertebrae.
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Fig. 3: Vertebral artery - lateral view
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Fig. 5: CT 3D reconstruction of cervical spine, lateral view - complete unilateral ponticulus
posticus (blue arrow)
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Methods and materials
Our present longitudinal, retrospective study was carried out over a period of a year 2012 - in the Radiology Department of the Integrated Ambulatory Service Care of the
Infectious Disease Clinic in Cluj - Napoca.
The protocol was approved by the institutional review board of our institution.
We included 462 patients, 276 women, 186 men, with ages between 4 and 90 years, who
underwent cervical spine radiographs for other symptoms than due to this variant. The
main symptoms in the adult population who referred to our service were chronic neck
pain and headache. Children mostly underwent lateral cervical spine radiographs after
traumatic events.
Only the radiographs of patients with clearly visible skull base and no history of
craniocervical operation were included in the study.
The radiographs were obtained by conventional X-ray equipment. The X-ray exposure
parameters were73 kV and 12 mA. Films were
processed automatically with a computed radiograph system and interpreted on a flat
screen.
Each radiograph was carefully inspected to look for the presence of a ponticulus posticus
and arcuate foramen.
The complete type was defined as a clear bony bridge between the superior articular
process and the posterior arch of the atlas, whereas the partial type included partial
posterior ponticuli, noted as distinct bony spicule extending from the superior articular
facet overhanging the dorsal arch.
Because we inspected only a neutral lateral radiograph, we were not able to determine
in all cases on which side ponticulus posticus occurs more often.
Besides the incidence and type of ponticulus posticus, its distribution by age and gender
was also analyzed.
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We could not specify that the prevalence of ponticuli in the patients we analyzed
would represent that of the normal Romanian population, because the studied patients
addressed our service for certain complaints, leaving the asymptomatic patients out of
the study.
Results
Ponticulus posticus was observed in 12.55% of the patients, with a slight female (53.44%)
predominance.
Incomplete bony outgrow was present in 51.72% of the cases. The prevalence of
incomplete ponticulus posticus was higher in female patients (63.33%).
When ossification was incomplete, the defect was mostly found at the anterior margin
(70%), although incomplete ossification may be found at any point in the arch.
The rest of 48.27% of the patients had a complete arch, with a male domination (57.14%).
Bilateral complete foramen was seen in 10.34% of the cases, 4 of them being female
and 2 being male patients.
The highest incidence was in the group between 40 and 49 years (30.76%). The youngest
patient who presented ponticulus posticus was 9 years old and the oldest patients in our
study was 78 years old.
There was a variation in size, configuration and position of the bony arch. Some of the
patients presented an incomplete and sometimes difficult to recognize arch, while other
patients had a thick and amorphous bony outgrow.
The sulcus of the vertebral artery also varied widely.
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Images for this section:
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Fig. 6: Lateral cervical radiograph - unilateral incomplete ponticulus posticus (blue arrow);
the bony projection grows from anterior to posterior
Fig. 10: Incidence of ponticulus posticus in our study
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Fig. 7: Lateral cervical radiograph - unilateral incomplete bony outgrow (blue arrow) from
the posterior margin
Fig. 11: Prevalence of Ponticulus Posticus as reported in literature
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Fig. 8: Lateral cervical radiograph - complete ponticulus posticus (blue arrow)
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Fig. 9: Lateral cervical radiograph - bilateral ponticuli (blue arrows)
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Conclusion
Some studies analyzed the presence of ponticulus posticus on anatomical specimens,
such as dry vertebrae (4), (12), (18), (19).
Other authors discovered this variant on cephalograms (13), (20), or lateral cervical spine
radiographs (6), (10), (16), like we did in our study.
In our study, the incidence of ponticulus posticus was 12.55%, whereas in other carried
studies it varied between 4.3% and 33.3%. (13,15)
The closest results regarding incidence were obtained by Pyo and Lowman, who found
an incidence of 12.67%. (20)
Our results revealed a higher incidence of an incomplete bony arch (51.72%), similar to
all carried studies. (1-20)
Pyo and Lowman (20) showed that in incomplete ponticuli, the defect was usually found
at the posterior margin. This goes contrary to our study which states the fact that the
defect was mostly found at the anterior margin (70%).
Regarding gender, the data indicate that the general distribution of the presence of the
bony bridge in the first cervical vertebra (53.44%) and the presence of an incomplete
bony arch (63.3%) is higher in female patients than in men. In comparison, the highest
incidence of complete ossification occurred in male patients (57.14%). The data can be
corroborated with the study carried out by Schilling J, Schilling A & Suazo G.I. (18)
Michael J Huang and John A Glaser (9) observed that the groove for the vertebral artery
on atlas varies in size and depth from a slight impression to a clear sulcus, which was
also observed in our study.
In our study, no clear relationship with age was found, since we found this variant in 5
cases of children, 2 of them having complete ossification. In their study, Lamberty and
Zivanovic observed ponticulus posticus in fetuses and children, making it even clearer
that this condition is not age-dependent. (4)
Therefore, it should not be considered as a calcification or ossification of the lateral
segment of the posterior atlanto-occipital ligament, but rather an ossification with
functional significance, developed in order to protect the passage of the vertebral artery
Page 22 of 25
in a region in which, by its sinuosity, is susceptible of being damaged or compressed as
a result of the craniocervical dynamics. (18)
Young et al have demonstrated that when examining a specimen with an arcuate foramen
through a standard dorsal approach, the broad ponticulus posticus can be easily mistaken
for a widened posterolateral aspect of the posterior arch of the atlas, when in reality
it is a foramen containing the vertebral artery. The placement of a lateral mass screw into
the atlas in this situation can predispose the vertebral artery to injury. (16)
It must especially alert the surgeon to avoid using the ponticulus posticus as a starting
point for a lateral mass screw, in order not to injure the vertebral artery, since the
placement of lateral mass screws into the atlas has become a popular means of treating
atlantoaxial instability. (16)
Ponticulus posticus is a relatively common finding in our patients and should be
mentioned by radiologists in their reports; the awareness of the presence of this variant
can improve later management of head and neck symptoms.
Limitations
In many cases, it was difficult to determine which side is affected more frequently, since
only a single lateral film was available.
Some studies certified that the plain cervical radiograph is not suitable for screening the
ponticuli, because in some cases it is not visible and bilateralness and completeness are
difficult to assess. (13)
Personal information
References
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