=====Pelvis=====
The pelvis (plural pelves or pelvises) is either the lower part of the trunk, between the abdomen and the thighs (sometimes also called pelvic region of the trunk), or the skeleton embedded in it (sometimes also called bony pelvis, or pelvic skeleton).

The pelvic region of the trunk includes:

The bony pelvis

The [[pelvic cavity]] 

The pelvic floor, below the pelvic cavity, and the perineum, below the pelvic floor.

The pelvic skeleton is formed in the area of the back, by the sacrum and the coccyx and anteriorly and to the left and right sides, by a pair of hip bones. The two hip bones connect the spine with the lower limbs. They are attached to the sacrum posteriorly, connected to each other anteriorly, and joined with the two femurs at the hip joints.

The pelvis is characterized by an important anatomic landmark, the [[pelvic incidence]] (PI). 

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Hresko et al. proposed a classification system dividing high grade [[spondylolisthesis]] cases into unbalanced and balanced pelvic groups based on the orientation, i.e. radiographic parameters, of the [[pelvis]]. Balanced pelvises had higher SS and lower pelvic tilt, whereas unbalanced pelvises incompletely compensate with lower SS and pelvic retroversion, resulting in a higher pelvic tilt (PT)
((Hresko MT, Labelle H, Roussouly P, Berthonnaud E. Classification of high-grade spondylolistheses based on pelvic version and spine balance: possible rationale for reduction. Spine 2007;32:2208-13.))