The pedicle screws are used for the posterior spine fixation to treat various spine disorders or trauma. However, inaccurate placement is relatively common even when placement is performed under fluoroscopic control [
5], and it can cause severe vascular and neurological complications [
10]. However, in clinical practice, for safe and accurate screw placement, the screw dimensions as well as the proper position of the screw are essential. Optimum diameter of the pedicle screw is necessary to maximize the rigidity of the construct, as larger diameter screws may break the pedicle, while screws with narrower diameter do not offer sufficient resistance to pull out [
11]. Regarding the screw length, short screws reduce the rigidity of the construct, while long screws may penetrate the anterior wall of the vertebral body and injure vital structures. Biomechanical studies have shown that the pull-out strength of a pedicle screw at 85% insertion depth is similar to the pullout strength at 100% insertion depth [
12]. Another important parameter for proper screw position is the knowledge of PAA for each vertebra, in order to prevent medial or lateral pedicle wall breach [
13]. Therefore, a profound knowledge of the morphometric characteristics of the vertebrae is needed [
14].
Some morphometric measurements of the vertebrae and pedicles significantly differ among different ethnic groups and preoperative software-based morphometric data should be collected for preoperative planning [
9,
15‐
19]. Vertebral morphometric measurements of the Greek population shared some similarities and differences with other ethnic groups. There is only one study in the literature regarding the pedicle dimensions in the Greek population. Christodoulou et al. [
9] studied 12 human cadaveric spines (5 women and 7 men) with a mean age of 69.6 years (range 62 to 84 years) at the time of death. The authors measured the transverse and sagittal outside pedicle isthmus widths, the internal transverse diameter, and cortex width of pedicles with electronic calipers. In our study, the widest outer cortical pedicle width was at L5 with a mean of 17.08 mm (SD ± 1.97 mm) at left pedicle in males. This is in accordance with the results of Christodoulou et al. [
9] who found that the widest transverse diameter was at the same level of L5 with a mean of 11.3 mm (range 7.55–15.46 mm). Zindrick et al. [
20], who conducted one of the largest morphometric measurements of the pedicles by CT in Western populations, found the same level with a mean of 18.0 mm (range 9.1–29.0 mm), similar to our measurements. Regarding the widest inner cancellous pedicle width, in this study, it was at the L5 vertebra with a mean of 11.3 mm (SD ± 2.68 mm) at the right pedicle in males. However, Christodoulou et al. [
9] found the widest inner at L4 level with a mean of 8.26 mm (range 7.10–9.23 mm). In this report, as far as the largest outer pedicle height is concern, it was found at T11 left pedicle in males with a mean of 18.82 (SD ± 1.37 mm). This finding is also in accordance with the results of Christodoulou et al. [
9] who found the largest height at the same level with a mean of 17.23 mm (range 14.84–19.57 mm) and also with the results of Zindrick et al. [
20] with a mean value of 17.4 mm (range 12.5–24.1 mm). The narrowest inner pedicle width was observed at T9 and T10 vertebrae in our study, with a mean from 2.83 mm (SD ± 0.97 mm) to 4.00 mm (SD ± 1.43 mm) for male and female population, respectively. However, Christodoulou et al. [
9] stated that a 5-mm-diameter screw may safely be inserted at the levels of T9 vertebra. Zindrick et al. [
20] also found that the mean inner pedicle width at T9 and T10 was larger with 6.1 mm (range 3.7–9.0 mm) at T9 and 6.3 mm (range 3.1–8.5 mm) at T10 vertebra. In clinical practice, the diameter of pedicle screws for thoracolumbar levels range from 4 mm to 7 mm, with 1.0 mm clearance. [
12]. Based on the analysis of the present study, in the Greek population, the pedicles of T9 and T10 vertebrae may hardly accommodate a 4.0-mm pedicle screw, due to the narrow inner cancellous pedicle width. Studies have shown that pedicles between T4 and T8 should be measured on CT scans before an operation, because they might not be suitable for fixation with screw due to their narrow width [
14,
16]. Based on the results of this study, T9 and T10 must also be included in the CT scan preoperative, especially for the Greek population. Regarding the PAA of the pedicles in this study, the largest PAA was at L5 with a mean of 26.23° (SD ± 2.65°), at the left pedicle in males, while the smallest was found at T9 with a mean of 9° (SD ± 3.67°), at the left pedicle in females. Zindrick et al. [
20] also stated that the largest angle was seen at L5 with the mean pedicle of 29.8° (range 19.0–44.0°); however, the shallowest was at T1, with the mean PAA at T9 vertebra 7.6° (range 0.0–10.5°). The longest PTLP in our study was 55.31 mm (SD ± 4.52 mm) at L4, at the left pedicle in males and the shortest at T9, at the right pedicle in females, with a mean of 39.44 mm (SD ± 3 mm). However, Zindrick et al. [
20] found the longest PTLP (through pedicle axis) at L2 and L3 that was 51.9 mm (ranges 45.0–58.0 and 42.0–62.0 mm, respectively), Olsewski et al. [
21] at L4, and Vaccaro et al. [
22] at T12.
As far as the differences between both sexes are concerned, Christodoulou et al. [
9] concluded that regarding the internal diameter in the lumbar spine, there was a difference between males and females especially at L3 levels (
p < 0.05), and almost in all levels regarding the cortex width. In our report, the more pronounced statistically significant difference (
p < 0.0001) between the two sexes was the PTLP at all vertebral levels from T9 to L5. In this study, the L5 vertebra was found to have the largest AVBH, PAA, and the width of pedicles in both sexes. AVBH was found to be smaller compared to the PVBH at T9–L3 vertebral bodies, almost equal at L4 level and greater only at L5 vertebral. This observation may be due to the normal physiological lordosis present in the thoracolumbar region.
Although this study provides important information about the morphometry of vertebrae in the Greek population, it has some limitations. The current findings were obtained from patients visiting a single hospital, and possible differences in the morphometric parameters might exist between Greek people from different geographic regions (i.e., South, West, Central Greece). The male patients were almost four times more than the female ones (79 men and 21 women). Another limitation was the variety of slice thickness at the CT scans (range from 5 mm to 0.5 mm) and at the axial CT scan, which provides only a two-dimensional view of the three-dimensional shape of the pedicles. It is however recommended that the preoperative CT imaging be implemented with thinner slices as possible for a more accurate assessment of the morphometric characteristics of the vertebrae.