Dissertation committee:
Νικολάου Βασίλειος, Επίκουρος Καθηγητής, Ιατρική, ΕΚΠΑ
Μπάμπης Γεώργιος, Καθηγητής, Ιατρική, ΕΚΠΑ
Παπαδόπουλος Ηλίας, Επίκουρος Καθηγητής, Ιατρική, ΕΚΠΑ
Κορρές Δημήτριος, Ομότιμος Καθηγητής, Ιατρική, ΕΚΠΑ
Χρονόπουλος Ευστάθιος, Αναπληρωτής Καθηγητής, Ιατρική, ΕΚΠΑ
Μαζαράκης Αντώνιος, Αναπληρωτής Καθηγητής, Ιατρική, ΕΚΠΑ
Πιάγκου Μαρία, Επίκουρη Καθηγήτρια, Ιατρική, ΕΚΠΑ
Summary:
According to the literature, a classification was needed and proposed for the assessment of the healing of fractures of the C2 vertebra in the anatomical position, based on measurements on the vertebrae of a European population, while measurements in other populations were recommended. In the present study, computed tomography (CT) measurements were performed on the odontoid process of the C2 vertebra of 115 Greek patients, as well as on the transverse foramens and pedicles of the C2 vertebra of 55 Greek patients. Additionally, a literature review was carried out concerning measurements on the C2 vertebra in different populations, in order to demonstrate the clinical significance of its anatomical parameters in cervical spine surgery.
The review of the literature depicted 26 studies which correlated the C2 lamina anatomy with the possibility of inserting a screw for the fixation of C2 fractures. From the studies in specific populations, eight concerned Asian populations, only two studies were conducted in non-Asians. It was demonstrated that it was generally possible to place a laminar screw of the standard diameter of 3.5 mm, with the exception of two studies. Preoperative CT was mainly proposed (eight studies), but preoperative CT with three-dimensional reconstruction was also recommended (five studies). In two out of the 16 studies which were performed only with CT, it was found that a significant number of patients could not receive a typical screw, so preoperative CT with a three-dimensional reconstruction was proposed. The generally high values in cadaveric measurements could be associated with high participation of the elderly population, with increased probability of degenerative spine disease, a fact which alters the anatomical parameters, according to the literature. Indeed, the five cadaveric studies have shown that the placement of the typical C2 laminar screw was generally feasible.
In seven out of the 39 studies which correlated the C2 pedicle anatomy with screw insertion, preoperative CT was recommended, in three studies preoperative CT adapted to the screw trajectory was proposed, in six studies CT with three-dimensional reconstruction was recommended, in one study preoperative CT angiography with three-dimensional reconstruction was proposed. From the studies involving specific populations, ten focused on Asian populations, only two on non-Asian populations. The five purely cadaveric studies showed that the anatomy of the C2 pedicle generally allowed the placement of a standard screw and in only one study a thorough preoperative assessment was recommended. On the contrary, 22 of the 24 purely CT studies recommended more strongly a thorough preoperative assessment. Also, in the literature there were five studies in which measurements on the odontoid process were performed in specific populations, three of which were Asian and two non-Asian. Only in two papers a specific preoperative imaging (CT) was recommended. Concerning the C2 transverse foramen, from the five studies found in the literature, three focused on Asian and two on non-Asian populations.
The results of the present study show that the average diameter of the C2 pedicle in this series of Greek patients is smaller than that found by other authors on Asian and Western populations. These findings are inconsistent with bibliographic data, according to which the C2 pedicles are smaller in Asians compared to Western populations. The anatomical differences between populations and the importance of thorough preoperative imaging are underlined, given that a significant number of studies that propose a simple CT are cadaveric, and therefore, as shown, may include falsely elevated values in the measurements. Also, there was a relative lack of studies on non-Asian populations. Further research could clarify whether the anatomy of the dens, pedicle and lamina of C2 allows screw fixation in a wider population range and possibly if different preoperative imaging protocols are recommended. Also, the present study demonstrated the superiority of the transverse diameter of the C2 transverse foramen of the particular Greek population in comparison with other populations. According to the literature, small diameter of transverse foramens may mean a hypoplastic vertebral artery, which may lead to ischemic events, while vertebral artery variations were more often detected in C2. Further research could clarify whether genetic factors affect the dimensions of transverse foramens in different populations and whether these dimensions are associated with a risk of ischemic events.
