On the pedicle subtraction osteotomy technique and its modifications during the past two decades: a complementary classi

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On the pedicle subtraction osteotomy technique and its modifications during the past two decades: a complementary classification to the Schwab’s spinal osteotomy classification Anouar Bourghli1   · Louis Boissière2 · Faisal Konbaz3 · Sami Al Eissa3 · Amro Al‑Habib4 · Bang‑Ping Qian5 · Yong Qiu5 · Kazunori Hayashi6 · Javier Pizones7 · Christopher Ames8 · Jean‑Marc Vital9 · Ibrahim Obeid2 Received: 27 May 2020 / Accepted: 30 October 2020 © Scoliosis Research Society 2020

Abstract Purpose  To propose a complementary classification to the Schwab’s osteotomy classification that would regroup together under a common umbrella different published pedicle subtraction osteotomy (PSO) variations that are commonly used, to have a common language and complete the spine surgeon’s armamentarium when dealing with rigid spinal deformities. Methods  The 2 general types corresponding to the grades 3 and 4 of the Schwab classification were separated into 6 gradual subtypes (grades 3A, 3B, 3C, 4A, 4B, 4C). The classification is based on the amount of resected pedicle, the inclusion or not of the disc above, and the location of the axis of rotation. Based on the proposed classification, a reliability study was performed using 18 cases that were classified by 8 readers with expertise in the management of adult deformities with the use of osteotomies. Results  Clinical cases were classified according to the 6 grades proposed in the classification. The intra-rater reliability for the classification was “almost perfect agreement” with a Fleiss kappa coefficient average of 0.92 (range 0.85–1.00). The inter-rater reliability was “almost perfect agreement” with a coefficient average of 0.90 for the 2 readings that were done at an interval of 2 weeks. Conclusion  The developed classification proved to be reliable and intuitive. It is an original way to display a catalog of different available PSO modifications including the original technique, in a logical and gradual order to help the surgeons in their decisions and show them that between a grade 2 osteotomy and a grade 5 osteotomy, many intermediate options are available. Further work with a treatment algorithm for clinical practice based on the current classification may be developed in the future. Keywords  Pedicle subtraction osteotomy · Modifications · Classification · Sagittal alignment · Adult spinal deformity

* Anouar Bourghli [email protected] 1

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Department of Spine Surgery, The Affiliated Drum Tower Hospital of Nanjing University Medical School, Nanjing, China



Orthopedic and Spinal Surgery Department, Kingdom Hospital, PO Box 84400, Riyadh 11671, Saudi Arabia

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Clinique du Dos, Elsan Jean Villar Private Hospital, Bordeaux, France

Department of Orthopedic Surgery, Osaka City University Graduate School of Medicine, Osaka, Japan

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Division of Orthopedics, Department of Surgery, King Abdulaziz Medical City, Ministry of National Guard Health Affairs, Riyadh, Saudi Arabia

Spine Unit, Department of Orthopedic Surgery, Hospital Universita