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 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)