On the pedicle subtraction osteotomy technique and its modifications during the past two decades: a complementary classification to the Schwab’s spinal osteotomy classification

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.

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Funding

No funds were received for the current study.

Author information

Affiliations

Authors

Contributions

AB, FK, SA, AA, BPQ, YQ, KH, JP: none. LB: Consultant Spineart, Medicrea. CA: Consultant Depuy Synthes, Medtronic, Stryker, Medicrea, K2M and Zimmer Biomet, receipt of royalties from Stryker, Zimmer Biomet, Depuy Synthes, Nuvasive, K2M, Medicrea, Research support from Titan Spine, Depuy Synthes, and ISSG. JMV: Consultant Depuy Synthes, LDR. IO: Consultant Alphatec spine, Depuy Synthes and Medtronic, receives research support from Depuy Synthes, receipt of royalties from Alphatec, Clariance and Spineart. AB: conception, drafting, final approval, and agreement to be accountable for all aspects of the work. LB: conception, critical revision, final approval, and agreement to be accountable for all aspects of the work approval. FK: conception, drafting, final approval, and agreement to be accountable for all aspects of the work. SAE: interpretation of data, critical revision, final approval, and agreement to be accountable for all aspects of the work. AA-H: interpretation of data, critical revision, final approval, and agreement to be accountable for all aspects of the work. B-PQ: interpretation of data, critical revision, final approval, and agreement to be accountable for all aspects of the work. YQ: design, critical revision, final approval, and agreement to be accountable for all aspects of the work. KH interpretation of data, critical revision, final approval, and agreement to be accountable for all aspects of the work. JP: interpretation of data, critical revision, final approval, and agreement to be accountable for all aspects of the work. CA: design, critical revision, final approval, and agreement to be accountable for all aspects of the work. J-MV: design, critical revision, final approval, and agreement to be accountable for all aspects of the work. IO: design, critical revision, final approval, and agreement to be accountable for all aspects of the work.

Corresponding author

Correspondence to Anouar Bourghli.

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Bourghli, A., Boissière, L., Konbaz, F. et al. On the pedicle subtraction osteotomy technique and its modifications during the past two decades: a complementary classification to the Schwab’s spinal osteotomy classification. Spine Deform (2020). https://doi.org/10.1007/s43390-020-00247-6

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Keywords

  • Pedicle subtraction osteotomy
  • Modifications
  • Classification
  • Sagittal alignment
  • Adult spinal deformity