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| S. number | Parameters of lateral mass of axis vertebrae (pedicle, SAF, IAF, FT, and angles) |
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| 1 | Pedicle length (PL) | Length was measured from anterior most point of the pedicle axis to the posterior point of pedicle axis projection EF = PL (Figure 1(a)). |
| 2 | Pedicle width (PW) | It was taken from internal surface of pedicle to its external surface at the level of transverse foramen ef = PW (Figure 1(a)). |
| 3 | Pedicle height (PH) | It was measured from its superior surface to inferior surface with in the foramen transversarium E′F′ = PH (Figure 1(a)). |
| 4-5 | Superior articular facet length (SAFL) and width (SAFW) | It is the maximum anteroposterior and transverse diameter of articular surface of superior facet. (IJ = SAFL) (KL = SAFW) (Figure 1(b)). |
| 6 | External height (SAFHE) | It was taken from upper midpoint on the superior articular surface to the lower midpoint on the inferior surface. ST = SAFHE (Figure 2(a)). |
| 7 | Internal height (SAFHI) | It was taken from midpoint of articular surface to the nearest point on the inferior surface. st = SAFHI (Figure 2(b)). |
| 8 | Depth of vertebral artery | It was taken as the difference between external and internal height. |
| 9-10 | Inferior articular facet length (IAFL) and width (IAFW) | It is the maximum anteroposterior and transverse diameter of articular surface of Inferior facet. (ij = IAFL) (kl = IAFW) (Figure 1(c)). |
| 11–13 | Foramen transversarium length (FTL), width (FTW), and depth (FTD) | It is the maximum anteroposterior, transverse, and superoinferior diameter. (MN = FTL) (mn = FTW) (OP = FTD) (Figures 3(a) and 3(b)). |
| 14 | Pedicle superior angle (PSA) | It was measured as the angle between the pedicle axis and a line drawn perpendicular to the body of the axis read as PSA (Figure 4). |
| 15 | Pedicle median angle (PMA) | It was measured as the angle between the pedicle axis and line passing through the midline of the vertebral body and the spinous process and read as PMA (Figure 5). |
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