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The impact of lumbar alignment targets on mechanical complications after adult lumbar scoliosis surgery



The purpose of this study was to determine the discriminatory ability of age-adjusted alignment offset and the global alignment and proportion (GAP) score parameters to predict postoperative mechanical complications.


Surgical patients from the Adult Symptomatic Lumbar Scoliosis cohort were reviewed at 2 year follow up. Age-adjusted alignment offsets and GAP parameters were calculated for each patient. A series of nonlinear logistic regression models were fit, and the odds of mechanical complications were calculated. The discriminatory ability of the GAP score, GAP score parameters, and age-adjusted alignment offsets were determined plotting receiver operative characteristic (ROC) with the C statistic (AUC).


A total of 165 patients were included. A total of 49 mechanical complications occurred in 41 patients (21 proximal junctional kyphosis and 28 pseudoarthrosis). The GAP score had no discriminatory ability in this cohort. Relative lumbar lordosis 15 degrees greater than ideal lumbar lordosis was associated with greater mechanical complications. A lumbar distribution index of 90% was associated with fewer mechanical complications compared to a lumbar distribution index of 65%. Age-adjusted offset alignment targets had no discriminatory ability to predict mechanical complications.


Radiographic alignment targets using either age-adjusted alignment target offset or GAP score parameters had minimal ability to predict mechanical complications in isolation. Mechanical complications following adult spinal deformity surgery are complex, and patient factors play a critical role.

Clinical trial registeration This study was registered at (number NCT00854828) in March 2009.

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Data sharing request should be sent to KHB.

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Funding was from the National Institute of Arthritis and Musculoskeletal and Skin Diseases of the U.S. National Institutes of Health (R01AR055176) and the Scoliosis Research Society.

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Authors and Affiliations



Drs. Dial, Hills, and Kelly involved in study conception and design, data analysis and interpretation, manuscript drafting. Drs. Shaffrey, Schwab, Smith, and Bridwell took part in data acquisition and interpretation of results. Drs. Bess, Lazaro, Bruni, Lafage, and Mr. Lafage involved in interpretation of results. All authors reviewed the results and approved the final version of the manuscript.

Corresponding author

Correspondence to Michael P. Kelly.

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Conflict of interest

Drs. Dial, Hills, Bridwell, Sardi, Lazaro, R Lafage, and Kelly report no conflicts of interest. Dr. Bess reports the following conflicts: royalties: Pioneer Spine; consulting: Allosource, DePuy, EOS, K2M, Medtronic, Misonix; scientific advisory board/other office: North American Spine Society, Scoliosis Research Society; research support (investigator salary, staff/materials): Allosource, Biomet Spine, DePuy, EOS, K2M, Medtronic, NuVasive, OrthoFix. Dr. V Lafage reports the following conflicts: stock ownership: Nemaris; consulting: Globus Medical; speaking and/or teaching arrangements: DePuy, K2M; scientific advisory board/other office: International Spine Study Group, Scoliosis Research Society; research support (investigator salary, staff/materials): Depuy, Medtronic, Nuvasive, Stryker. Dr. Shaffrey reports the following conflicts: royalties: Medtronic, Nuvasive, Zimmer Biomet; stock ownership: Nvasive; consulting: Biomet Spine, Medtronic, Nuvasive, Stryker; speaking and/or teaching arrangements: Medtronic, Nuvasive; board of directors: Spine Deformity; scientific advisory board/other office: AANS, Cervical Spine Research Society, Spine; research support (investigator salary, staff/materials): DePuy, Globus Medical, Medtronic, Neurosurgery RRC. Dr. Smith reports the following conflicts: royalties: Zimmer Biomet; consulting: Nuvasive, K2M, Allosource, Cerapedics; scientific advisory board/other office: Cervical Spine Research Society, Neurosurgery, Operative Neurosurgery. Dr. Schwab reports the following conflicts: grant: DePuy Synthes, SRS; royalties: K2M, MSD; stock ownership: Nemaris; speaking and/or teaching arrangements: Zimmer Biomet, NuVasive, K2M, MSD, Medicrea; board of directors: Nemaris.

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All patients provided informed consent to participate.

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Washington University IRB approval 201102183.

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Dial, B.L., Hills, J.M., Smith, J.S. et al. The impact of lumbar alignment targets on mechanical complications after adult lumbar scoliosis surgery. Eur Spine J 31, 1573–1582 (2022).

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  • Adult spinal deformity
  • Spinal alignment
  • Global alignment and proportion
  • Age-adjusted