Table 2 Formulas to determine the displacement type
From: A computer aided measurement method for unstable pelvic fractures based on standardized radiographs
Type | Plane | Formulas and parameters | Direction | Related axes |
|---|---|---|---|---|
Translational | Outlet | |Y’C-YS|-|YC-YS| > 0 | Cephlad | Y |
|Y’C-YS|-|YC-YS| < 0 | Caudad | Y | ||
Inlet | |Y’H-YS|-|YH-YS| > 0 | Anterior | Z | |
|Y’H-YS|-|YH-YS| < 0 | Posterior | Z | ||
|X’H-XS|-|XH-XS| > 0 | Lateral | X | ||
|X’H-XS|-|XH-XS| < 0 | Medial | X | ||
Rotational | Sagittal | |YA-YB|-|Y’A-Y’B| < −2 | Flexion | X |
−2 ≤ |YA-YB|-|Y’A-Y’B| ≤ 2 | Neutral | X | ||
|YA-YB|-|Y’A-Y’B| > 2 | Extension | X | ||
Inlet | |XG-XH|-|X’G-X’H| < −2 | External rotation | Y | |
−2 ≤ |XG-XH|-|X’G-X’H| ≤ 2 | Neutral | Y | ||
|XG-XH|-|X’G-X’H| > 2 | Internal rotation | Y | ||
Outlet | |XE-XD|-|X’E-X’D| < −2 | Valgus | Z | |
−2 ≤ |XE-XD|-|X’E-X’D| ≤ 2 | Neutral | Z | ||
|XE-XD|-|X’E-X’D| > 2 | Varus | Z |