Pelvic Incidence Overview

Questions and Answers

What is the normative range for PI (Pelvic Incidence)?

30°-80° (20°-100° can still be considered normal)

How is PI (Pelvic Incidence) measured?

Draw a line from the center of where the femoral heads overlap to the middle of the S1 endplate. Then draw a line starting at the middle of the S1 endplate that is perpendicular to the S1 endplate. PI is the angle that these two lines form.

What is the formula that relates PT (pelvic tilt), PI (pelvic incidence), and SS (sacral slope)?

PI = PT + SS

What is the normative range for LL (lumbar lordosis)?

30°-80° (20°-100° can still be considered normal) Signup and view all the answers

How is LL (lumbar lordosis) measured?

Cobb angle between the superior L1 endplate and superior S1 endplate. Signup and view all the answers

How is proximal LL (lumbar lordosis) measured?

Cobb angle between superior L1 endplate & superior L4 endplate. Signup and view all the answers

How is distal LL (lumbar lordosis) measured?

Cobb angle between superior L4 endplate and superior S1 endplate. Signup and view all the answers

What is the relationship between PI (pelvic incidence) and LL (lumbar lordosis)?

PI and LL should theoretically match. PI determines LL target. Signup and view all the answers

What is the normative range for PI-LL (pelvic incidence-lumbar lordosis)?

20° Signup and view all the answers

What is the normative range for TK (thoracic kyphosis)?

20°-50° Signup and view all the answers

How is TK (thoracic kyphosis) measured?

Angle between the superior endplate of T4 and the inferior endplate of T12. Signup and view all the answers

What is the normative range for PT (pelvic tilt)?

30° Signup and view all the answers

How is PT (pelvic tilt) measured?

Draw a line from the center of where the femoral heads overlap to the middle of the S1 endplate. Then draw a vertical reference line (ideally from the center of where the femoral heads overlap). The pelvic tilt is the angle between these lines. Signup and view all the answers

What does PT (pelvic tilt) measure?

Pelvic retroversion. Signup and view all the answers

What is the normative range for SVA (sagittal vertical axis)?

9.5 cm Signup and view all the answers

How is SVA (sagittal vertical axis) measured?

Horizontal offset distance between C7 plumb line and posterior point of sacral endplate. Signup and view all the answers

What is the normative range for TL (thoracolumbar junction)?

TBD Signup and view all the answers

Study Notes

Pelvic Incidence (PI)

Normative range for PI is 30°-80°, but values from 20°-100° can still be considered normal.
PI is measured by drawing a line from the center of the overlapping femoral heads to the middle of the S1 endplate and a perpendicular line from the middle of the S1 endplate; the angle formed is the PI.
The relationship formula is PI = PT + SS, linking pelvic tilt (PT) and sacral slope (SS) with PI.

Lumbar Lordosis (LL)

Normative range for LL is 30°-80°, and 20°-100° can also be viewed as normal.
LL is measured using the Cobb angle between the superior endplate of L1 and the superior endplate of S1.
Proximal LL measures the Cobb angle between the superior endplates of L1 and L4, while distal LL is the Cobb angle between the superior endplate of L4 and S1.
PI and LL should ideally match; PI adjusts the LL target at which alignment is aimed.

Pelvic Incidence-Lumbar Lordosis Relationship

The normative range for the difference between PI and LL (PI-LL) is 20°.

Thoracic Kyphosis (TK)

Normative range for TK is 20°-50°.
TK is measured as the angle between the superior endplate of T4 and the inferior endplate of T12.

Pelvic Tilt (PT)

The normative range for PT is around 30°.
Measurement involves a line from the center of the overlapping femoral heads to the middle of the S1 endplate, and a vertical reference line; the angle between these lines represents the pelvic tilt.
PT primarily measures pelvic retroversion.

Sagittal Vertical Axis (SVA)

The normative range for SVA is approximately 9.5 cm.
SVA is measured as the horizontal offset distance from the C7 plumb line to the posterior point of the sacral endplate.

Thoracolumbar Junction (TL)

Normative range for TL is not provided; further information may be required.

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Description

This quiz covers important concepts related to Pelvic Incidence (PI), including its normative range and measurement techniques. Test your knowledge on the definitions and the methodology used in evaluating PI. Perfect for students in the health sciences or orthopedic fields.