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3D CT modeling demonstrates the anatomic feasibility of S1AI screw trajectory for spinopelvic fixation in neuromuscular scoliosis

  • Biomechanics
  • Published:
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Abstract

Purpose

In patients with neuromuscular scoliosis undergoing posterior spinal fusion, the S2 alar iliac (S2AI) screw trajectory is a safe and effective method of lumbopelvic fixation but can lead to implant prominence. Here we use 3D CT modeling to demonstrate the anatomic feasibility of the S1 alar iliac screw (S1AI) compared to the S2AI trajectory in patients with neuromuscular scoliosis.

Methods

This retrospective study used CT scans of 14 patients with spinal deformity to create 3D spinal reconstructions and model the insertional anatomy, max length, screw diameter, and potential for implant prominence between 28 S2AI and 28 S1AI screw trajectories.

Results

Patients had a mean age of 14.42 (range 8–21), coronal cobb angle of 85° (range 54–141), and pelvic obliquity of 28° (range 4–51). The maximum length and diameter of both screw trajectories were similar. S1AI screws were, on average, 6.3 ± 5 mm less prominent than S2AI screws relative to the iliac crests. S2AI screws were feasible in all patients, while in two patients, posterior elements of the lumbar spine would interfere with S1AI screw insertion.

Conclusion

In this cohort of patients with neuromuscular scoliosis, we demonstrate that the S1AI trajectory offers comparable screw length and diameter to an S2AI screw with less implant prominence. An S1AI screw, however, may not be feasible in some patients due to interference from the posterior elements of the lumbar spine.

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Data availability

Data is available for review upon request.

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Acknowledgments

We would like to acknowledge the Mighty Oak Medical and Orthopediatrics teams for their work in the 3D modeling and image processing of the CT scans. Neither Orthopediatrics nor Mighty Oak were involved in data analysis, interpretation or manuscript preparation. 

Funding

The author(s) received no financial support for the research, authorship, and/or publication of this article.

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Authors and Affiliations

  1. Department of Orthopaedic Surgery, Stanford University School of Medicine, 453 Quarry Rd, 3rd Floor, MC 5658, Palo Alto, CA, USA

    Xochitl M. Bryson, Nicole S. Pham, Ian Hollyer, Serena Hu, Lawrence A. Rinsky & John S. Vorhies

Authors
  1. Xochitl M. Bryson
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  2. Nicole S. Pham
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  3. Ian Hollyer
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  4. Serena Hu
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Contributions

All authors contributed to the study conception and design. Material preparation, data collection and analysis were performed by Xochitl Bryson, Nicole Segovia, Ian Hollyer, Serena Hu, Lawrence Rinsky, John Vorhies. The first draft of the manuscript was mainly written by Xochitl Bryson and Ian Hollyer and all authors assisted on previous versions of the manuscript. All authors read and approved the final manuscript. Xochitl Bryson: data collection, bulk of writing-original draft preparation, and approval of final version of manuscript, agree to be accountable for the work. Nicole Segovia: data collection, writing-original draft preparation, and approval of final version of manuscript, agree to be accountable for the work. Ian Hollyer: data collection, writing-original draft preparation, and approval of final version of manuscript, agree to be accountable for the work. Serena Hu: data collection, writing-original draft preparation, and approval of final version of manuscript, agree to be accountable for the work. Lawrence Rinsky: writing-original draft preparation, and approval of final version of manuscript, agree to be accountable for the work. John Vorhies: data collection, writing-original draft preparation, and approval of final version of manuscript, agree to be accountable for the work.

Corresponding author

Correspondence to John S. Vorhies.

Ethics declarations

Conflict of interest

Dr. John Vorhies receives grant funding from the Scoliosis Research Society (SRS), Pediatric Orthopaedic Surgery of North America (POSNA), and Stanford University. Dr. John Vorhies is an advisory board member for NSite medical and NView medical  and  has been an unpaid consultant for Ortho Pediatrics in the past, he a committee member of the SRS Program comittee Research Grant Committee as POSNA’s Program Comittee Industry Relations Committee and Research Committee, and a former member of the POSNA Evidence-Based Practice committee. The other authors report no conflict of interest concerning the materials or methods used in this study or the findings specified in this manuscript.

Ethical approval

This study was performed in line with the principles of the Declaration of Helsinki. Approval was granted by the Ethics Committee of Stanford University (IRB No. 65389).

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Bryson, X.M., Pham, N.S., Hollyer, I. et al. 3D CT modeling demonstrates the anatomic feasibility of S1AI screw trajectory for spinopelvic fixation in neuromuscular scoliosis. Spine Deform (2024). https://doi.org/10.1007/s43390-024-00840-z

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