The age of the European patient cohort ranged from 41 to 92 years, with an average of 63.9 years ± 17.98 years (mean ± standard deviation, SD) when CT was performed.
Outer and Inner Pedicle Diameters
We analyzed the data to determine whether sex-specific differences could be observed.
The absolute minimum value was observed at thoracic vertebra four (T4), with an OPD of 5.6 mm (± 1.2 mm). The first maximum value for the OPD was located at thoracic vertebra T1 with value 8.7 mm (± 3 mm), and the second maximum was at T11 with an equal value of 8.7 mm (± 1.7 mm) on average. The maximum IPD occurs at T11 with a value of 5.1 mm (± 1.4 mm) and the minimum occurs at T4 with a value of 2.7mm (± 0.9 mm).
With an average Diff of 3,3 mm (± 0,7 mm) for males and Diff of 3,4 mm (± 0,9 mm) for females, p = 0,19 statistically significant results could not be detected.
Diagram 2 graphically demonstrates when the IPD is subtracted from the OPD, resulting in differences in the outer and inner diameters (Diff) of each pedicle. This value was calculated to approximate how much cortical bone is in each pedicle. In this diagram, we can observe an absolute maximum at T1 with a value of 4,3 mm (± 0,8 mm), an absolute minimum at T4 with a value of 2,9 mm (± 0,7 mm) and then a steady growth of the curve toward T11 where another local maximum is found with a value of 3,7 mm (± 0,8 mm). At T12, the difference between the outer and inner circumferences and thus the amount of cortical bone decreased again. Although this is only a curve that was derived and not directly measured, it is displayed and highlights T4 once again.
To gain some understanding of how the Diff (ri)/(le) corticalis thickness was located and distributed in each pedicle, Diagram 2 shows the cortical thickness of the right and left pedicles across the thoracic spine.
Lateral and medial walls
The average thickness of the lateral walls of the pedicle was 1.57 mm (± 0.52 mm). The absolute minimum cortical thickness was located at T4. The medial corticalis thickness is, on average, greater at 1,72 mm (± 0,42 mm). The smallest medial corticalis was located at T4, at 1.53 mm (± 0.33 mm). The smallest lateral corticalis was also located at T4, at 1,31 mm (± 0,31 mm). The lateral cortical bone was significantly thinner than the medial cortical bone (p < 0,001). An overview of the values for medial and lateral wall thickness can be seen in Table 1.
Angle measurements of potential pedicle screws
The PSA, as shown in Table 2, for the male population was 17.4° (± 4.6° SD), and it was 14.9° (± 3.9° SD) for the female patients. Significant differences were observed (p < 0,001). In contrast, no significant sex-specific differences (p = 0,21) were detected for PAA. Here, the male average PAA was 14.1° (± 7.3°), and the female average was 13.5° (± 5.5°).
Finally, measurements of the PAL, representing the lengths of the screws used in surgery, showed significant sex-specific differences. The male population had an average PAL of 43.6 mm (± 6.4 mm), whereas the females had an average PAL of 39.6 mm (+- 6.5 mm) (p < 0.001). The PAL increased throughout the thoracic spine, with the smallest increase occurring at T1 (31.8 mm (± 3.5 mm)) and the greatest increase occurring at T12 (47.4 mm (± 4.8 mm)). The PAL is shown in Table 3.
The average outer pedicle width (OPW) shown in Table 4 was 6.87 mm (± 1.65 mm) for males and 5.89 mm (± 1.52 mm) for females, with a significant difference between the two (p < 0.001).
Similarly, the pedicle height (PH) shown in Table 5 was significantly greater for male patients (12.86 ± 2.46 mm) than for female patients (11.77 ± 2.46 mm), with a p value < 0.001.
A summarized overview of the sex-specific differences in the thoracic spine is provided in Table 6.