Pelvic Angles: How to perform

Last updated on July 6 2022

Description 

The pelvic parameters are important in the analysis of deformities and to choose the appropriate treatment. The pelvic parameters are composed of pelvic tilt (PT), pelvic incidence (PI) and sacral slope (SS). To measure these values a lateral view is needed.

PI determines the relative position of the sacral plate in relation to the femoral heads. A lower value of PI is approximately 35°, the higher is around 85° and the average is 51.9°. This angle is an algebraic sum of two angles: PT + SS.

Pelvic tilt measures the position of the pelvis; low values indicate anteversion, more common in standing position, and high values indicate retroversion, more common in sitting position.

The sacral slope parameter measures the angle of the sacral in relation to the ground. Depending on the position of the sacral, forces can act on the discs and facets.

Measurements

The measurements made by the procedure are displayed in the image:

• Pelvic Incidence (PI): the angle between the line along with the S1 end plate and the reference horizontal line;
• Pelvic Tilt (PT): the angle between the reference vertical line that crosses the femoral heads’ midpoint (MP) and the line that goes from MP to S1 end plate’s midpoint;
• Sacral Slope (SS): the angle between the line along with the S1 end plate and the reference horizontal line. 

Auxiliary references  

To show this procedure, PeekMed® needs additional references:

• Femoral heads midpoint (MP): the midpoint between the left and right femoral heads;
• Center of the S1 end plate: the midpoint between the anterior and posterior edges of the superior end plate of S1.