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Does vertebral level of Pedicle Subtraction Osteotomy correlate with degree of spino-
pelvic 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?
PurposePurpose
• Evaluate Evaluate radiographic changesradiographic changes of spinal and pelvic parameters of spinal and pelvic parameters induced by induced by PSO surgeryPSO surgery
• Define Define differencesdifferences regarding regarding spinal and pelvic parameters spinal and pelvic parameters related to level and degreerelated to level and degree of of osteotomy performed.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 AnalysisX-ray Analysis
Regional ParametersRegional Parameters• Lumbar LordosisLumbar Lordosis• Thoracic KyphosisThoracic Kyphosis• Thoraco-LumbarThoraco-Lumbar
Global AlignmentGlobal Alignment• SVASVA• T1 & T9 sagittal tiltT1 & T9 sagittal tilt• Global InclinationGlobal Inclination
Pelvic ParametersPelvic Parameters• Sacral SlopeSacral Slope• Pelvic TiltPelvic Tilt• Pelvic IncidencePelvic Incidence
SpineView® software …. >300 parametersSpineView® software …. >300 parameters
Analysis
2. PSO parametersVertebral level
Degree of resection
3. Correlation ?
1. Radiographic ChangesPre-op versus Post-op
t-test
PSO level vs focal correction
• No significant difference in focal correction by level
PSO Level
# of subjects
Focalcorrection
L1 6 24°
L2 15 24°
L3 29 25°
L4 20 22°
Change in Regional Curvatures
Mean ± 1SD
Lumbar
LordosisThoracic 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
Significant increase of sagittal curvaturesSignificant reduction of TL kyphosis
Change in Global Balance
SVAT1 sagittal
TiltT9 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
Significant SVA decreaseT1 Sagittal tilt “normalized”
SVA
Change in Pelvic Parameters
Pelvic Incidence
PelvicTilt
Sacral Slope
Pre 55 ± 13 31 ± 12 24 ± 12
Post 56 ± 13 23 ± 10 32 ± 10
∆ 0 ± 2 -8 ± 10 8 ± 10
p 0.517 0.000 0.000
Mean ± 1SD
No Change in PISignificant decrease of PT
PSO vs Change in Spinal parameters
• SVASVA (global sagittal balance) (global sagittal balance)– No correlation with PSO parameters
• Lumbar LordosisLumbar Lordosis – increases when PSO degree increases– Not with PSO vertebral level
• Thoracic KyphosisThoracic Kyphosis – increases when PSO degree increases
• +12°short fusion (<T10) => compensatory mechanism• + 5°long fusion (>T10)
CorrelationsCorrelation with PSO
degreeCorrelation with
PSO level
∆ SVA +0.217 -
∆ L1-S1 +0.655 ** -
∆ T4-T12 - 0.424 ** -
PSO vs Change in Pelvic parameters
• PT correctionPT correction increases when– PSO located on lower levels– PSO degree increases
CorrelationsCorrelation with PSO
degreeCorrelation with
PSO level
∆ Sacral Slope +0.471 ** +0.32 **
∆ Pelvic Tilt -0.436 ** -0.410 **
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