Table 1 Descriptive statistics: mean value ± standard deviation [min−/max-values]

Vertical distance symphysis-sacrococcygeal joint (in mm)

40.1 ± 18.5

[12.6–70.7]

35.3 ± 19.6

[11–73.8]

36.8 ± 22.2

[3.6–71.1]

25.4 ± 13.9

[8.3–46.1]

Horizontal distance symphysis-midpoint sacrococcygeal joint (in mm)

4.8 ± 3

[0–10.4]

4.1 ± 3.1

[0–10.4]

5.3 ± 4.1

[0–13.5]

3.8 ± 1.4

[1.7–6.1]

Vertical distance symphysis-tip of the coccyx (in mm)

13.5 ± 16.1

[− 16.2–33.3]

11.9 ± 15

[− 12.6–33.8]

8.2 ± 19.1

[− 23.4–34.2]

1 ± 16.3

[− 29.2–20.5]

Vertical distance symphysis-lower end of the sacroiliac joint (in mm)

83.9 ± 19.1

[63–123.3]

80.7 ± 15.9

[63.9–117]

79.2 ± 17.4

[59.4–98.6]

68.1 ± 15.7

[49.8–100.8]

Ratio vertical/horizontal diameter pelvic foramen

0.6 ± 0.1

[0.48–0.92]

0.6 ± 0.1

[0.45–0.75]

0.6 ± 0.1

[0.46–0.75]

0.5 ± 0.1

[0.4–0.72]

Ratio vertical/horizontal diameter obturator foramen right

1.0 ± 0.2

[0.54–1.41]

1.0 ± 0.2

[0.69–1.31]

1.0 ± 0.2

[0.74–1.49]

1.2 ± 0.1

[0.96–1.39]

Ratio vertical/horizontal diameter obturator foramen left

1.1 ± 0.3

[0.71–1.56]

1.1 ± 0.2

[0.84–1.36]

1.1 ± 0.2

[0.78–1.63]

1.2 ± 0.2

[0.77–1.54]