Does vertebral level of Pedicle Subtraction
Osteotomy correlate with degree of spinopelvic parameter correction?
Schwab Frank; Lafage Virginie; Patel Ashish; Hart Robert ;
Burton Douglas; Boachie-Adjei Oheneba; Shelokov Alexis;
Hostin Richard; Shaffrey Christopher; Gupta Munish;
Akbarnia Behrooz; Bess Shay
Context
• Pedicle subtraction osteotomy
– Correction of sagittal spinal
malalignment
• Impact of PSO level ?
– Caudal lumbar PSO results in
greater correction of SVA ?
Effect of PSO level on
immediate post-operative
spino-pelvic alignment?
Purpose
• Evaluate radiographic changes
of spinal and pelvic parameters
induced by PSO surgery
• Define differences regarding
spinal and pelvic parameters
related to level and degree of
osteotomy performed.
Clinical group
• Multi-center retrospective
study
– 70 patients
– 54 female, 16 male
– Lumbar PSO
• Full length x-rays
– Pre-op
– Post-op
– Spineview Analysis
SpineView®
X-ray Analysis
Regional Parameters
• Lumbar Lordosis
• Thoracic Kyphosis
• Thoraco-Lumbar
Global Alignment
• SVA
• T1 & T9 sagittal tilt
• Global Inclination
Pelvic Parameters
• Sacral Slope
• Pelvic Tilt
• Pelvic Incidence
SpineView® software …. >300 parameters
Analysis
1. Radiographic Changes
2. PSO parameters
Pre-op versus Post-op
t-test
Vertebral level
Degree of resection
3. Correlation
?
PSO level vs focal correction
PSO
Level
# of
subjects
Focal
correction
L1
6
24°
L2
15
24°
L3
29
25°
L4
20
22°
• No significant
difference in focal
correction by level
Change in Regional Curvatures
Lumbar
Lordosis
Thoracic
Kyphosis
Thoraco
Lumbar
Pre
22 ± 20
-30 ± 21
-10 ± 16
Post
47 ± 15
-38 ± 18
-6 ± 10
∆
26 ± 17
-8 ± 12
4 ± 12
p
0.000
0.001
0.026
Mean ± 1SD
Significant increase of sagittal curvatures
Significant reduction of TL kyphosis
Change in Global Balance
SVA
T1 sagittal
Tilt
T9 sagittal
Tilt
Pre
116 ± 82
3 ± 8
-8 ± 9
Post
31 ± 57
-4 ± 5
-11 ± 6
∆
-85 ± 57
-7 ± 6
-3 ± 6
p
0.000
0.000
0.000
Mean ± 1SD
SVA
Significant SVA decrease
T1 Sagittal tilt “normalized”
Change in Pelvic Parameters
Pelvic
Incidence
Pelvic
Tilt
Sacral
Slope
Pre
55 ± 13
31 ± 12
24 ± 12
Post
56 ± 13
23 ± 10
32 ± 10
0 ± 2
-8 ± 10
8 ± 10
0.517
0.000
0.000
∆
p
Mean ± 1SD
No Change in PI
Significant decrease of PT
PSO vs Change in Spinal parameters
Correlation with PSO
degree
Correlation with
PSO level
+0.217
-
∆ L1-S1
+0.655 **
-
∆ T4-T12
- 0.424 **
-
Correlations
∆ SVA
•
SVA (global sagittal balance)
– No correlation with PSO parameters
•
Lumbar Lordosis
– increases when PSO degree increases
– Not with PSO vertebral level
•
Thoracic Kyphosis
– increases when PSO degree increases
• +12°short fusion (<T10) => compensatory mechanism
• + 5°long fusion (>T10)
PSO vs Change in Pelvic parameters
Correlation with PSO
degree
Correlation with
PSO level
∆ Sacral Slope
+0.471 **
+0.32 **
∆ Pelvic Tilt
-0.436 **
-0.410 **
Correlations
• PT correction increases when
– PSO located on lower levels
– PSO degree increases
When selecting PSO level, desired PT
correction is an important consideration.
Conclusion
• PSO degree
– Affects regional curvatures
• Directly (Lumbar)
• Indirectly (Compensation)
• PSO level
– Impacts post-operative pelvic tilt
correction but not SVA