Relationship between body mass index and sagittal vertical axis change as well as health-related quality of life in 564 patients after deformity surgery

Nitin Agarwal; Federico Angriman; Ezequiel Goldschmidt; James Zhou; Adam S Kanter; David O Okonkwo; Peter G Passias; Themistocles Protopsaltis; Virginie Lafage; Renaud Lafage; Frank Schwab; Shay Bess; Christopher Ames; Justin S Smith; Christopher I Shaffrey; Douglas Burton; D Kojo Hamilton; International Spine Study Group

doi:10.3171/2019.4.SPINE18485

Relationship between body mass index and sagittal vertical axis change as well as health-related quality of life in 564 patients after deformity surgery

J Neurosurg Spine. 2019 Aug 9;31(5):697-702. doi: 10.3171/2019.4.SPINE18485.

Authors

Nitin Agarwal¹, Federico Angriman², Ezequiel Goldschmidt¹, James Zhou¹, Adam S Kanter¹, David O Okonkwo¹, Peter G Passias³, Themistocles Protopsaltis⁴, Virginie Lafage⁵, Renaud Lafage⁵, Frank Schwab⁵, Shay Bess⁴, Christopher Ames⁶, Justin S Smith⁷, Christopher I Shaffrey⁷, Douglas Burton⁸, D Kojo Hamilton¹; International Spine Study Group

Affiliations

¹ 1Department of Neurological Surgery, University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania.
² 2Department of Internal Medicine, Hospital Italiano de Buenos Aires, Buenos Aires, Argentina.
³ 3New York Spine Institute, New York, New York.
⁴ 4Department of Orthopaedic Surgery, New York University, New York, New York.
⁵ 5Spine Service, Hospital for Special Surgery, New York, New York.
⁶ 6Department of Neurosurgery, University of California, San Francisco, California.
⁷ 7Department of Neurosurgery, University of Virginia, Charlottesville, Virginia; and.
⁸ 8Department of Orthopedic Surgery, University of Kansas Medical Center, Kansas City, Kansas.

PMID: 31398699
DOI: 10.3171/2019.4.SPINE18485

Abstract

Objective: Obesity, a condition that is increasing in prevalence in the United States, has previously been associated with poorer outcomes following deformity surgery, including higher rates of perioperative complications such as deep and superficial infections. To date, however, no study has examined the relationship between preoperative BMI and outcomes of deformity surgery as measured by spine parameters such as the sagittal vertical axis (SVA), as well as health-related quality of life (HRQoL) measures such as the Oswestry Disability Index (ODI) and Scoliosis Research Society-22 patient questionnaire (SRS-22). To this end, the authors sought to clarify the relationship between BMI and postoperative change in SVA as well as HRQoL outcomes.

Methods: The authors performed a retrospective review of a prospectively managed multicenter adult spinal deformity database collected and maintained by the International Spine Study Group (ISSG) between 2009 and 2014. The primary independent variable considered was preoperative BMI. The primary outcome was the change in SVA at 1 year after deformity surgery. Postoperative ODI and SRS-22 outcome measures were evaluated as secondary outcomes. Generalized linear models were used to model the primary and secondary outcomes at 1 year as a function of BMI at baseline, while adjusting for potential measured confounders.

Results: Increasing BMI (compared to BMI < 18) was not associated with change of SVA at 1 year postsurgery. However, BMIs in the obese range of 30 to 34.9 kg/m2, compared to BMI < 18 at baseline, were associated with poorer outcomes as measured by the SRS-22 score (estimated change -0.47, 95% CI -0.93 to -0.01, p = 0.04). While BMIs > 30 appeared to be associated with poorer outcomes as determined by the ODI, this correlation did not reach statistical significance.

Conclusions: Baseline BMI did not affect the achievable SVA at 1 year postsurgery. Further studies should evaluate whether even in the absence of a change in SVA, baseline BMIs in the obese range are associated with worsened HRQoL outcomes after spinal surgery.

Keywords: Oswestry Disability Index; Scoliosis Research Society–22 patient questionnaire; body mass index; deformity; sagittal vertical axis.