Chapter 14 - Adult Spinal Deformity

Question 1

Key sagittal plane measurements

Answer 1

C7 Sagittal vertebral axis: horizontal distance between the C7 plumb line and the posterior superior aspect of S1 (normal is <5cm)

T1 pelvic angle: the angle drawn from the center of T1 to the center of the femoral heads, then to the midpoint of the S1 end plate. (surgical goal <14deg)

Question 2

Pelvic Incidence:

Answer 2

angle between a line drawn from the center of the femoral heads to the center os the S1 superior endplate and a line perpendicular to the midpoint of the S1 end plate

PI = SS+ PT

PI DOES NOT change with pelvic positioning

Question 3

Pelvic Tilt:

Answer 3

Angle between a vertical line drawn straight up from the center of the femoral head and a line drawn between the center of the femoral heads and the center of the S1 superior endplate (normal is <20)

Varies with pelvic positioning

increasing pelvic tilt is compensatory for sagittal plane imbalance

Question 4

Sacral Slope

Answer 4

angle between the horizontal and a line drawn flush with the S1 superior end plate.

Varies with pelvic positioning

Question 5

Normal cervical lordosis

Answer 5

40degrees

Question 6

Cervical Sagittal vertebral axis

Answer 6

horizontal distance between the C2 plumb line and the posterior superior margin of C7 (normal <40mm)

Question 7

Types of osteotomies: Posterior column osteotomy

Answer 7

resects the facet joints, ligamentum flavum, other posterior elements. Ponte osteotomy when performed at an unfused segment, smith pete osteotomy when performed at a fused level

TEN DEGREES of correction per segment

Question 8

Types of osteotomies: Pedicle subtraction osteotomy

Answer 8

posterior elements removed, pedicles, and vertebral body wedge

25-35 degrees of correction per segment