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How Much is Too Much? Higher Degrees of Curve Correction Correlate with Worsened Sagittal Balance: Paper #16

Vitale, Michael G. MD, MPH; Jameel, Omar F. MD; Sucato, Daniel J. MD, MS; Richards, Stephens B. MD; Emans, John B. MD; Erickson, Mark A. MD; Sanders, James O. MD; Lenke, Lawrence G. MD

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United States

Summary: Modern day techniques of correction of spinal deformity allow dramatic correction in both the frontal and axial plane, but concerns have mounted about unintended hypo‐kyphosing effects and negative sagittal balance. This study reviews sagittal considerations in patients with adolescent idiopathic scoliosis (AIS) and demonstrates an association between worsened sagittal balance and >50% correction of the main coronal curve.

Introduction: Current methods of segmental fixation for the treatment of AIS allow higher degrees of frontal and axial plane curve correction, but can have unintended negative effects on sagittal balance.

Methods: Review of a large prospectively‐collected multicenter dataset was performed to identify patients with AIS with neutral or negative sagittal balance at baseline, identifying 732 patients with 2 year postoperative follow up. Socioclinical variables and radiographic measures were reviewed to determine the association between major curve correction and sagittal balance.

Results: For the entire group, sagittal balance averaged ‐32.2 mm preoperatively and ‐29.6 mm postoperatively (p=0.89). However, 235 of 732 patients (32.1%) had a worsening of >10 mm in the negative direction at 2 years.

Patients with >50% major curve correction had significantly worse negative sagittal balance at 2 years than those who had <50% curve correction (‐30.9 mm vs. ‐23.3mm, p<0.01). These two groups had equal sagittal balance at baseline (‐31.2mm vs. ‐31.9mm, p=0.76).

The relationship between postoperative sagittal balance and frontal plane correction was highly significant in Lenke type 1 (p=0.01) and 6 (p=0.05) curves, present but not significant in type 2 (p=0.14) and 3 (p=0.23) curves and not present in type 4 and 5 curves. Additionally among Lenke type 1 curves this relationship was especially strong in 1A curves (p=0.02), and present but not significant in Lenke type 1B (p=0.12) and 1C (p=0.20) curves. Finally this relationship was also marked for thoracic modifier “N” curves (p=0.01) and “+” curves (p=0.05) but not for”‐” curves (p=0.8).

Conclusion: Roughly one‐third of patients treated with modern day instrumentation techniques experience a significant worsening of preexisting negative sagittal balance at 2 years postoperatively. The effect of posterior spinal instrumentation on the sagittal plane must be carefully considered when surgeons are planning and executing correction of multidimensional spinal deformity.

The FDA has not cleared the drug and/or medical device for the use described in this presentation (i.e., the drug or medical device is being discussed for an ‘off label’ use).

© 2010 Lippincott Williams & Wilkins, Inc.

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