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