## 3 Results
In the L5/S1 motor segment, the maximum value was 51\(\times\) mm (right side, section I) and the minimum value was 47.3 mm (left side, section II). In the case of surface area, the highest value of this indicator was found in section I and this amounted to 173.9 mm\({}^{2}\) (right side); the minimum value was observed on the right side and this was 156.4 mm\({}^{2}\) (section II). For the L5/S1 motor segment, the maximum value was 158.9 mm\({}^{2}\), which was found in section III (right side). In turn, the minimum value was 140.3 mm\({}^{2}\) (left side, II section). Table S1 presents the results for the L4/5 motor segment, taking into account the gender criterion. Referring to the data related to the perimeter and surface area, differences in the average values of the mentioned parameters can be noticed. In women, in each analyzed cross-section, both the circumference and the surface area had a higher value. The site did not matter in this case. Table S2 presents the results for the L5/S1 motor segment, taking into account the gender criterion. In the male population, the mean circumference values were higher. For cross-sectional areas, higher values were noted in the female population. Tables S3 and S4 present the results for the motor segments L4/5 and L5/S1, taking into account the age criterion. In the case of the L4/5 motor segment, age turned out to be a factor that influenced the value of the circumference. In the younger population, the circumference values for individual sections were higher. In the context of surface areas, such a relationship was observed for sections II and III. With regard to the motor segment L5/S1, it can be stated that the values of surface areas were higher in the younger population (excluding section I). The situation was similar in the context of circumference. In the older population, the mean circumference was only higher in section I (left side). Based on these results, it can be concluded that age and gender may be factors that affect the value of dimensions related to surface area and circumference. In the subsequent part of this study, correlations between dimensions in individual sections will be shown. Tables S5-S7 present the [PERSON]'s correlation coefficients for the measurement results (in mm) according to the L4/5 and L5/S1 motor section for sections I-III. In all cross-sections, significant positive correlations (\(p>0.5\)) were found between the right and left sides between individual measurements in segment L4/5 and L5/S1, except for MaxX in cross-section II in L5/S1 (0.2). The surface area correlated significantly and positively with the circumference in all cross-sections in the L4/5 and L5/S1 segments. This means that the larger the surface area, the higher the perimeter. Such a relationship is a prognostic indicator helpful in the process of diagnosing a patient with spinal canal stenosis. Based on this correlation, it can be concluded that the bony shape of the canals at individual levels was similar in the study population; greater irregularity would result in a lack of correlation between the surface area and the circumference. However, no such correlation with MinX was demonstrated. MaxX and MaxY positively correlated with the area in the L4/5 segment on the right and left. In the L5/S1 segment, MaxX and MaxY positively correlated with the surface area on the right side, while, on the left side, the values of the coefficient amounted to a maximum of 0.6, and there was no significant correlation between MaxX/Area in sections I and III. In Tables S8-S13, the influence of gender on the correlation between individual measurements is analyzed. Table S8 presents the results of the correlation between the L4/5 and L5/S1 segments (Section 1) in the female population. The obtained data indicate the occurrence of correlations between measurements. It has been shown that the surface area (on the right side) correlates, among others, with the circumference. The same relationship is observed for the circumference and area on the left side.