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Artificial Intelligence Based Hierarchical Clustering of Patient Types and Intervention Categories in Adult Spinal Deformity Surgery

Towards a New Classification Scheme that Predicts Quality and Value

Ames, Christopher P. MD; Smith, Justin S. MD, PhD; Pellisé, Ferran MD; Kelly, Michael MD§; Alanay, Ahmet MD; Acaroğlu, Emre MD||; Pérez-Grueso, Francisco Javier Sánchez MD∗∗; Kleinstück, Frank MD††; Obeid, Ibrahim MD‡‡; Vila-Casademunt, Alba MSc§§; Shaffrey, Christopher I. Jr§§; Burton, Douglas MD¶¶; Lafage, Virginie PhD||||; Schwab, Frank MD||||; Shaffrey, Christopher I. Sr MD; Bess, Shay MD∗∗∗; Serra-Burriel, Miquel PhD†††; European Spine Study Group, International Spine Study Group

doi: 10.1097/BRS.0000000000002974

Study Design. Retrospective review of prospectively-collected, multicenter adult spinal deformity (ASD) databases.

Objective. To apply artificial intelligence (AI)-based hierarchical clustering as a step toward a classification scheme that optimizes overall quality, value, and safety for ASD surgery.

Summary of Background Data. Prior ASD classifications have focused on radiographic parameters associated with patient reported outcomes. Recent work suggests there are many other impactful preoperative data points. However, the ability to segregate patient patterns manually based on hundreds of data points is beyond practical application for surgeons. Unsupervised machine-based clustering of patient types alongside surgical options may simplify analysis of ASD patient types, procedures, and outcomes.

Methods. Two prospective cohorts were queried for surgical ASD patients with baseline, 1-year, and 2-year SRS-22/Oswestry Disability Index/SF-36v2 data. Two dendrograms were fitted, one with surgical features and one with patient characteristics. Both were built with Ward distances and optimized with the gap method. For each possible n patient cluster by m surgery, normalized 2-year improvement and major complication rates were computed.

Results. Five hundred-seventy patients were included. Three optimal patient types were identified: young with coronal plane deformity (YC, n = 195), older with prior spine surgeries (ORev, n = 157), and older without prior spine surgeries (OPrim, n = 218). Osteotomy type, instrumentation and interbody fusion were combined to define four surgical clusters. The intersection of patient-based and surgery-based clusters yielded 12 subgroups, with major complication rates ranging from 0% to 51.8% and 2-year normalized improvement ranging from −0.1% for SF36v2 MCS in cluster [1,3] to 100.2% for SRS self-image score in cluster [2,1].

Conclusion. Unsupervised hierarchical clustering can identify data patterns that may augment preoperative decision-making through construction of a 2-year risk–benefit grid. In addition to creating a novel AI-based ASD classification, pattern identification may facilitate treatment optimization by educating surgeons on which treatment patterns yield optimal improvement with lowest risk.

Level of Evidence: 4

Artificial intelligence-based unsupervised hierarchical clustering may augment preoperative decision-making for adult spinal deformity through construction of a novel 2-year risk–benefit classification grid. In addition, pattern identification may facilitate treatment optimization by educating surgeons on which treatment patterns yield optimal improvement with lowest risk.

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

Department of Neurosurgery, University of Virginia Medical Center, Charlottesville, Virginia

Spine Surgery Unit, Hospital Vall d’Hebron, Barcelona, Spain

§Department of Orthopaedic Surgery, Washington University, St Louis, Missouri

Department of Orthopedics and Traumatology, Acibadem University, Istanbul, Turkey

||Ankara Spine Center, Ankara, Turkey

∗∗Spine Surgery Unit, Hospital Universitario La Paz, Madrid, Spain

††Spine Center Division, Department of Orthopedics and Neurosurgery, Schulthess Klinik, Zurich, Switzerland

‡‡Spine Surgery Unit, Bordeaux University Hospital, Bordeaux, France

§§Vall d’Hebron Institute of Research, Barcelona, Spain

¶¶Department of Orthopaedic Surgery, University of Kansas Medical Center, Kansas City, Kansas

||||Department of Orthopaedic Surgery, Hospital for Special Surgery, New York, New York

∗∗∗Denver International Spine Center, Presbyterian St. Luke's/Rocky Mountain Hospital for Children, Denver, Colorado

†††Center for Research in Health and Economics, Universitat Pompeu Fabra, Barcelona, Spain.

Address correspondence and reprint requests to Miquel Serra-Burriel, PhD, Center for Research in Health Economics, Department of Economics and Business, Universitat Pompeu Fabra, Office 23.111 Merce Rodoreda Building (Ciutadella Campus), Ramon Trias Fargas, 25-27, Barcelona 08005, Spain; E-mail:

Received 16 July, 2018

Revised 12 November, 2018

Accepted 13 December, 2018

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

The International Spine Study Group Foundation receives funding support from DePuy Synthes, K2M, Nuvasive, Orthofix, and Zimmer Biomet. The European Spine Study Group receives funding support from DePuy Synthes and Medtronic. Additional support was provided through Project PI16/01283, funded by Instituto de Salud Carlos III and co-funded by European Union (ERDF/ESF).

Relevant financial activities outside the submitted work: board membership, consultancy, grants, stocks, royalties, payment for lecture.

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