Development and validation of risk stratification models for adult spinal deformity surgery

Ferran PelliséSpine Surgery Unit, Vall d’Hebron Hospital, Barcelona, Spain;

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Miquel Serra-BurrielCenter for Research in Health and Economics, Universitat Pompeu Fabra, Barcelona, Spain;

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Justin S. SmithDepartment of Neurosurgery, University of Virginia Medical Center, Charlottesville, Virginia;

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Sleiman HaddadSpine Surgery Unit, Vall d’Hebron Hospital, Barcelona, Spain;

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Michael P. KellyDepartment of Orthopaedic Surgery, Washington University, St. Louis, Missouri;

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Alba Vila-CasademuntSpine Research Unit, Vall d’Hebron Institute of Research (VHIR), Barcelona, Spain;

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Francisco Javier Sánchez Pérez-GruesoSpine Surgery Unit, Hospital Universitario La Paz, Madrid, Spain;

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Shay BessDenver International Spine Center, Presbyterian St. Luke’s/Rocky Mountain Hospital for Children, Denver, Colorado;

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Jeffrey L. GumNorton Leatherman Spine Center, Louisville, Kentucky;

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Douglas C. BurtonDepartment of Orthopedic Surgery, University of Kansas Medical Center, Kansas City, Kansas;

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Emre AcaroğluAnkara ARTES Spine Center, Ankara, Turkey;

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Frank KleinstückSpine Center Division, Department of Orthopedics and Neurosurgery, Schulthess Klinik, Zürich, Switzerland;

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Virginie LafageDepartment of Orthopedic Surgery, Hospital for Special Surgery, New York, New York;

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Ibrahim ObeidSpine Surgery Unit, Bordeaux University Hospital, Bordeaux, France;

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Frank SchwabDepartment of Orthopedic Surgery, Hospital for Special Surgery, New York, New York;

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Christopher I. ShaffreyDepartment of Neurosurgery, University of Virginia Medical Center, Charlottesville, Virginia;

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Ahmet AlanayDepartment of Orthopedics and Traumatology, Acıbadem University, Istanbul, Turkey; and

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Christopher AmesDepartment of Neurosurgery, University of California, San Francisco, California

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the International Spine Study Group
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the European Spine Study Group
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OBJECTIVE

Adult spinal deformity (ASD) surgery has a high rate of major complications (MCs). Public information about adverse outcomes is currently limited to registry average estimates. The object of this study was to assess the incidence of adverse events after ASD surgery, and to develop and validate a prognostic tool for the time-to-event risk of MC, hospital readmission (RA), and unplanned reoperation (RO).

METHODS

Two models per outcome, created with a random survival forest algorithm, were trained in an 80% random split and tested in the remaining 20%. Two independent prospective multicenter ASD databases, originating from the European continent and the United States, were queried, merged, and analyzed. ASD patients surgically treated by 57 surgeons at 23 sites in 5 countries in the period from 2008 to 2016 were included in the analysis.

RESULTS

The final sample consisted of 1612 ASD patients: mean (standard deviation) age 56.7 (17.4) years, 76.6% women, 10.4 (4.3) fused vertebral levels, 55.1% of patients with pelvic fixation, 2047.9 observation-years. Kaplan-Meier estimates showed that 12.1% of patients had at least one MC at 10 days after surgery; 21.5%, at 90 days; and 36%, at 2 years. Discrimination, measured as the concordance statistic, was up to 71.7% (95% CI 68%–75%) in the development sample for the postoperative complications model. Surgical invasiveness, age, magnitude of deformity, and frailty were the strongest predictors of MCs. Individual cumulative risk estimates at 2 years ranged from 3.9% to 74.1% for MCs, from 3.17% to 44.2% for RAs, and from 2.67% to 51.9% for ROs.

CONCLUSIONS

The creation of accurate prognostic models for the occurrence and timing of MCs, RAs, and ROs following ASD surgery is possible. The presented variability in patient risk profiles alongside the discrimination and calibration of the models highlights the potential benefits of obtaining time-to-event risk estimates for patients and clinicians.

ABBREVIATIONS

ACS NSQIP = American College of Surgeons National Surgical Quality Improvement Program; ASD = adult spinal deformity; EBL = estimated blood loss; LIV = lowest instrumented vertebra; MC = major complication; ODI = Oswestry Disability Index; OOB = out of bag; PROM = patient-reported outcome measure; RA = readmission; RO = reoperation; SF-36 = SF-36v2 Health Survey; SRS-22r = Scoliosis Research Society 22-item patient outcome questionnaire.

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