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Correction objectives have higher impact than screw pattern and density on the optimal 3D correction of thoracic AIS: a biomechanical study

Luigi La Barbera, A. Noelle Larson and Carl-Éric Aubin

Article (2021)

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Cite this document: La Barbera, L., Larson, A. N. & Aubin, C.-É. (2021). Correction objectives have higher impact than screw pattern and density on the optimal 3D correction of thoracic AIS: a biomechanical study. Spine Deformity, 9(3), p. 655-664. doi:10.1007/s43390-020-00275-2
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Abstract

Study design Assessment of screw pattern, implant density (ID), and optimization of 3D correction through computer-based biomechanical models. Objective To investigate how screw pattern and ID affect intraoperative 3D correction of thoracic curves in adolescent idiopathic scoliosis, and how different correction objectives impact the optimal screw pattern. Summary of background data Screw pattern, ID, correction objectives and surgical strategies for posterior fusion of AIS are highly variable among experienced surgeons. The “optimal” instrumentation remains not well defined. Methods 10 patient-specific multibody models of representative adolescent idiopathic scoliosis Lenke 1A cases were built and used to compare alternative virtual correction surgeries. Five screw patterns and IDs (average: 1.6 screws/instrumented level, range: 1.2–2) were simulated, considering concave rod rotation, en bloc derotation, and compression/distraction as primary correction maneuvers. 3D correction descriptors were quantified in the coronal, sagittal and transverse planes. An objective function weighting the contribution of intraoperative 3D correction and mobility allowed rating of the outcomes of the virtual surgeries. Based on surgeon-dependent correction objectives, the optimal result among the simulated constructs was identified. Results Low-density (ID ≤ 1.4) constructs provided equivalent 3D correction compared to higher (ID ≥ 1.8) densities (average differences ranging between 2° and 3°). The optimal screw pattern varied from case to case, falling within the low-density screw category in 14% of considered scenarios, 73% in the mid-density (1.4 < ID < 1.8) and 13% in the high-density. The optimal screw pattern was unique in five cases; multiple optima were found in other cases depending on the considered correction objectives. Conclusions Low-density screw patterns provided equivalent intraoperative 3D correction to higher-density patterns. Simulated surgeon’s choice of correction objectives had the greatest impact on the selection of the optimal construct for 3D correction, while screw density and ID had a limited impact.

Uncontrolled Keywords

Adolescent idiopathic scoliosis (AIS), Correction objectives Screw pattern, Implant density, Multibody model, Optimization, Patient-specific biomechanical modeling

Open Access document in PolyPublie
Subjects: 1900 Génie biomédical > 1901 Technologie biomédicale
2100 Génie mécanique > 2100 Génie mécanique
Department: Département de génie mécanique
Research Center: Autre
Funders: CRSNG/NSERC - Medtronic Industrial Research Chair in Spine Biomechanics, Canada Research Chair in Orthopedic Engineering, TransMedTech Institute Postdoctoral Fellowship - Canada First Research Excellence Fund, Politecnico di Milano LLB
Date Deposited: 25 Mar 2022 13:29
Last Modified: 26 Mar 2022 01:20
PolyPublie URL: https://publications.polymtl.ca/9267/
Document issued by the official publisher
Journal Title: Spine Deformity (vol. 9, no. 3)
Publisher: Springer Nature
Official URL: https://doi.org/10.1007/s43390-020-00275-2

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