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Posterior Global Malalignment After Osteotomy for Sagittal Plane Deformity: It Happens and Here is Why

Blondel, Benjamin MD*,†; Schwab, Frank MD*; Bess, Shay MD; Ames, Christopher MD§; Mummaneni, Praveen V.§; Hart, Robert MD; Smith, Justin S. MD, PhD[BULLET OPERATOR]; Shaffrey, Christopher I. MD[BULLET OPERATOR]; Burton, Douglas MD**; Boachie-Adjei, Oheneba MD††; Lafage, Virginie PhD*

Spine:
doi: 10.1097/BRS.0b013e3182872415
Deformity
Abstract

Study Design. Multicenter, retrospective analysis of 183 consecutive patients undergoing lumbar osteotomy.

Objective. To evaluate cause and impact of posterior postoperative alignment.

Summary of Background Data. Sagittal malalignment in the setting of adult spinal deformity (ASD) has shown significant correlation with pain and disability. Surgical treatment often entails correction of deformity by pedicle subtraction osteotomies (PSO). Key radiographical spinopelvic objectives to reach improvement in clinical outcomes have been previously reported. Although anterior alignment is a cause of poor outcomes, the impact and cause of posterior spinal alignment by PSO has not been reported.

Methods. The patient inclusion criteria were age, more than 18 years, with a diagnosis of sagittal plane deformity (C7 plumbline offset >5 cm, a pelvic tilt >20°, or a lumbar lordosis to pelvic incidence mismatch of ≥10°) requiring a surgical procedure involving a lumbar posterior osteotomy and a long fusion. Patients were divided into 3 groups based on postoperative sagittal vertical axis (SVA): neutral alignment (0 < SVA < 50 mm), anterior alignment (SVA > 50 mm), and posterior alignment (SVA < 0 mm). All patients underwent pre- and postoperative full-length sagittal spine radiography. Differences between groups were evaluated using ANOVA and χ2 analysis.

Results. Seventy-six patients were postoperatively classified in the anterior group: 59 in the neutral group and 48 in the posterior group. These groups were comparable preoperatively in terms of surgical status (revision vs. primary surgery) and regional alignment (lumbar lordosis and thoracic kyphosis). The patients with posterior alignment were younger and had a significantly lower pelvic incidence (53° vs. 62°), preoperative pelvic tilt (30 vs. 36°), SVA (94 vs. 185 mm) and cervical lordosis (16° vs. 25°) than patients in the anterior alignment group. No significant differences were found in terms surgical procedure. Patients in the posterior alignment group demonstrated a significantly greater change in SVA and pelvic tilt correction (P < 0.05) but with a lower gain in thoracic kyphosis (5 vs. 12°) and reduction of cervical lordosis (4° vs. 22°).

Conclusion. A significantly lower pelvic incidence and lack of restoration of thoracic kyphosis may lead to sagittal overcorrection with a posterior alignment. Although the clinical significance of posterior malalignment is still unclear, this study showed a compensatory loss of cervical lordosis in these patients. Particular attention must be paid to preoperative planning before sagittal realignment procedures. Further study will be necessary to evaluate long-term clinical outcomes of these patients.

In Brief

Clinical and radiographical analysis of 183 patients with adult spinal deformity who underwent pedicle subtraction osteotomies was performed to identify surgical strategies leading to posterior sagittal alignment. Patients with posterior alignment, were younger, had a significantly lower pelvic incidence, preoperative pelvic tilt, and preoperative sagittal vertical axis than other patient groups.

Author Information

*Spine Division, NYU Hospital for Joint Diseases, New York, NY

Université Aix-Marseille, Marseille, France

Department of Orthopedic Surgery, Rocky Mountain Hospital for Children, Denver, CO

§Department of Neurosurgery, University of California San Francisco, San Francisco, CA

Department of Orthopedic Surgery, Oregon Health and Sciences University, Portland, OR

[BULLET OPERATOR]Department of Neurological Surgery, University of Virginia, Charlottesville, VA

**Department of Orthopedic Surgery, University of Kansas Medical Center, Kansas City, KS; and

††Department of Orthopedic Surgery, Hospital for Special Surgery, New York, NY.

Address correspondence and reprint requests to Virginie Lafage, PhD, Spine Division, Hospital for Joint Diseases, New York University, New York, NY; E-mail: virginie.lafage@gmail.com

Acknowledgment date: January 19, 2012. First revision date: May 6, 2012. Second revision date: November 26, 2012. Acceptance date: December 13, 2012.

The manuscript submitted does not contain information about medical device(s)/drug(s).

Deputy Spine grant funds were received in support of this work.

Relevant financial activities outside the submitted work: board membership, consultancy, royalties, stock/stock options, payment for lectures, payment for development of educational presentations, patents, support for travel, and expert testimony.

© 2013 Lippincott Williams & Wilkins, Inc.