What happens to the unfused upper thoracic curve after posterior spinal fusion for adolescent idiopathic scoliosis?

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  • 1 Department of Neurosurgery, Rutgers University, Newark, New Jersey;
  • 2 Department of Orthopaedic Surgery and Neurosurgery, Shriners Hospitals for Children—Philadelphia, Pennsylvania;
  • 3 Department of Orthopaedic Surgery, Rady Children's Hospital, San Diego, California;
  • 4 Department of Orthopaedic Surgery, Nemours/Alfred I. duPont Hospital for Children, Wilmington, Delaware;
  • 5 Department of Orthopaedic Surgery, Johns Hopkins Hospital, Baltimore, Maryland; and
  • 6 Department of Orthopaedic Surgery, BC Children's Hospital, Vancouver, British Columbia, Canada
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OBJECTIVE

Spontaneous lumbar curve correction after selective thoracic fusion in surgery for adolescent idiopathic scoliosis (AIS) is well described. However, only a few articles have described the course of the uninstrumented upper thoracic (UT) curve after fusion, and the majority involve a hybrid construct. In this study, the authors sought to determine the outcomes and associated factors of uninstrumented UT curves in patients with AIS.

METHODS

The authors retrospectively reviewed a prospectively collected multicenter AIS registry for all consecutive patients with Lenke type 1–4 curves with a 2-year minimum follow-up. UT curves were considered uninstrumented if the upper instrumented vertebra (UIV) did not extend above 1 level from the lower end vertebra of the UT curve. The authors defined progression as > 5°, and divided patients into two cohorts: those with improvement in the UT curve (IMP) and those without improvement in the UT curve (NO IMP). Radiographic, demographic, and Scoliosis Research Society (SRS)–22 survey outcome measures were compared using univariate analysis, and significant factors were compared using a multivariate regression model.

RESULTS

The study included 450 patients (370 females and 80 males). The UT curve self-corrected in 86% of patients (n = 385), there was no change in 14% (n = 65), and no patients worsened. Preoperatively, patients were similar with respect to Lenke classification (p = 0.44), age (p = 0.31), sex (p = 0.85), and Risser score (p = 0.14). The UT curves in the IMP group self-corrected from 24.7° ± 6.5° to 12.6° ± 5.9°, whereas in the NO IMP group UT curves remained the same, from 20.3° ± 5.8° to 18.5° ± 5.7°. In a multivariate analysis, preoperative main thoracic (MT) curve size (p = 0.004) and MT curve correction (p = 0.001) remained significant predictors of UT curve improvement. Greater correction of the MT curve and larger initial MT curve size were associated with greater likelihood of UT curve improvement.

CONCLUSIONS

Spontaneous UT curve correction occurred in the majority (86%) of unfused UT curves after MT curve correction in Lenke 1–4 curve types. The magnitude of preoperative MT curve size and postoperative MT curve correction were independent predictors of spontaneous UT curve correction.

ABBREVIATIONS AIS = adolescent idiopathic scoliosis; CSVL = central sacral vertical line; IMP = improvement in the UT curve; MT = main thoracic; NO IMP = no improvement in the UT curve; PA = posteroanterior; PSF = posterior spinal fusion; SRS = Scoliosis Research Society; UIV = upper instrumented vertebra; UT = upper thoracic.

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Contributor Notes

Correspondence Steven W. Hwang: Shriners Hospitals for Children—Philadelphia, PA. stevenhwang@hotmail.com.

INCLUDE WHEN CITING Published online April 23, 2021; DOI: 10.3171/2020.10.PEDS20671.

Disclosures This study was supported in part by grants to the Setting Scoliosis Straight Foundation (SSSF) in support of Harms Study Group research from DePuy Synthes Spine, EOS imaging, K2M, Medtronic, NuVasive, and Zimmer Biomet.

Dr. Iqbal: consultant for DePuy Synthes, Stryker, NuVasive, and Zimmer Biomet. Dr. Samdani: royalties from NuVasive and Zimmer Biomet; consultant for DePuy Synthes Spine, Ethicon, Globus Medical, NuVasive, Stryker, Medical Device Business Services, Mirus, Orthofix, and Zimmer Biomet; and executive committee for SSSF and Pediatric Spine Study Group. Dr. Pahys: consultant for DePuy Synthes, NuVasive, and Zimmer Biomet. Dr. Newton: consultant for Stryker, Medtronic, and Pacira; patent holder with DePuy Synthes and Stryker; research support from DePuy Synthes Spine via SSSF, EOS imaging via SSSF, Stryker K2M via SSSF, Medtronic via SSSF, NuVasive via SSSF, and Zimmer Biomet via SSSF; royalties from DePuy Synthes Spine, Stryker, K2M, and Thieme Medical Publishers; and board or committee member of the Harms Study Group, International Pediatric Orthopedic Think Tank, SRS, and SSSF. Dr. Shah: research support from DePuy Synthes Spine via SSSF; K2M via SSSF, and NuVasive via SSSF; consultant for DePuy Synthes Spine, and Globus Medical; royalties from DePuy Synthes Spine, Stryker, and Springer; direct stock ownership in Electrocore and Innovative Surgical Designs; and board or committee member of AAOS, POSNA, SRS, and SSSF. Dr. Sponseller: research support from DePuy Synthes Spine; consultant for DePuy Synthes Spine; royalties from Globus Medical, DePuy Synthes Spine, and JBJS-A; editorial or governing board for JBJS; board or committee member of SRS; and other financial or material support from OrthoPediatrics. Dr. Miyanji: consultant for DePuy Synthes, OrthoPediatrics, Zimmer Biomet, and Stryker Spine; clinical or research support for the study described from SSSF; and royalties from Zimmer Biomet. Dr. Hwang: direct stock ownership in Auctus; consultant for NuVasive and Zimmer Biomet; and speakers bureau for NuVasive and Zimmer Biomet.

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