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Construct Levels to Anchored Levels Ratio and Rod Diameter Are Associated With Implant-Related Complications in Traditional Growing Rods

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Abstract

Introduction

In addition to patient characteristics, consideration of length of construct to number of anchored levels ratio and rod diameter should be a part of preoperative planning to minimize implant-related complications (IRCs). IRCs including rod breakage, anchor dislodgement, and pullout are among the most common adverse events in traditional growing rods (TGRs). The current study hypothesized that anchor type and configuration are associated with IRC.

Methods

Patients with (1) age ≤10 years at surgery; (2) spine-based dual TGR; (3) minimum 2-year follow-up; and (4) available imaging. Cephalad and caudal foundations were grouped based on the number of instrumented levels and anchor type. All radiographs were reviewed. Based on the results, a “construct levels / anchored levels” (CL/AL) ratio was calculated, which is the number of levels spanned by instrumentation divided by the number of levels with bone-anchor fixation. Receiver operating characteristic curve was used to define the CL/AL threshold.

Results

274 patients divided into patients with complications (IRC+, n = 140) and without complications (IRC–, n = 134) groups. Mean follow-up was 6.3 years (2.1–18.0 years). No significant differences in age, gender, body mass index, ambulatory status, etiology, primary curve size, T1–S1 height, coronal and sagittal balance, and rod material were observed between the two groups. Comparative analysis showed that connector type, presence and location of crosslinks, number of levels instrumented, number and type of anchors, presence of pelvic fixation, and mirroring of cephalad and caudal foundations were not different. However, maximum kyphosis and rod diameter were significantly different. The CL/AL ratio threshold was 3.5. Multivariate analysis of kyphosis, rod diameter, and CL/AL ratio showed a significant association with IRC (p < .05).

Discussion and Conclusion

Although patient characteristics like kyphosis have been proven to be associated with instrumentation failure, it is a combination of characteristics that include rod diameter and CL/AL ratio that showed significant correlation with IRC. Validation of the CL/AL ratio is recommended.

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Author information

Authors and Affiliations

  1. San Diego Spine Foundation, 6190 Cornerstone Ct E 212, 92121, San Diego, CA, USA

    Pooria Hosseini MD, Stacie Nguyen MPH & Jeff Pawelek BS

  2. Department of Orthopedic Surgery, University of California, San Diego, 6190 Cornerstone Ct E 212, 92121, San Diego, CA, USA

    Behrooz A. Akbarnia MD

  3. Division of Spine Surgery, Department of Orthopedic Surgery, Harvard Medical School, 300 Longwood Ave., 02115, Boston, MA, USA

    John Emans MD

  4. Cincinnati Children’s Hospital Medical Center, Crawford Spine Center, 3333 Burnet Ave., MLC 2017, 45229, Cincinnati, OH, USA

    Peter F. Sturm MD

  5. Department of Orthopaedic Surgery, Johns Hopkins University, 21218, Baltimore, MD, USA

    Paul D. Sponseller MD

  6. Bloomberg Children’s Center, 1800 Orleans Street, 7359A, 21287, Baltimore, MD, USA

    Paul D. Sponseller MD

Authors
  1. Pooria Hosseini MD
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  2. Behrooz A. Akbarnia MD
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  3. Stacie Nguyen MPH
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  4. Jeff Pawelek BS
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  5. John Emans MD
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  6. Peter F. Sturm MD
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  7. Paul D. Sponseller MD
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Consortia

Growing Spine Study Group

Corresponding author

Correspondence to Behrooz A. Akbarnia MD.

Additional information

Author disclosures: PH (grants from Growing Spine Foundation, during the conduct of the study); BAA (grants from Growing Spine Foundation, during the conduct of the study; personal fees from NuVasive, personal fees from K2M, personal fees from DePuy Spine, outside the submitted work); SN (grants from Growing Spine Foundation, during the conduct of the study); JP (grants from Growing Spine Foundation, during the conduct of the study; other from San Diego Spine Foundation, outside the submitted work); JE (grants from Growing Spine Foundation, during the conduct of the study; personal fees from Medtronics, other from Johnson and Johnson, Synthes spine, outside the submitted work); PFS (grants from Growing Spine Foundation, during the conduct of the study; other from DePuy Spine, other from NuVasive, outside the submitted work); PDS (grants from Growing Spine Foundation, during the conduct of the study; grants and personal fees from DePuy Synthes Spine, personal fees from Globus, personal fees from JBJS, outside the submitted work); Growing Spine Study Group (grants from Growing Spine Foundation, during the conduct of the study; grants from NuVasive, outside the submitted work).

The Growing Spine Foundation (GSF) financially supports the Growing Spine Study Group, which provided the research data for this study. The GSF receives donations from the study group’s surgeon members, medical device industry, grateful patients and other donors.

FDA device/drug status: cleared.

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Hosseini, P., Akbarnia, B.A., Nguyen, S. et al. Construct Levels to Anchored Levels Ratio and Rod Diameter Are Associated With Implant-Related Complications in Traditional Growing Rods. Spine Deform 6, 320–326 (2018). https://doi.org/10.1016/j.jspd.2017.11.004

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  • DOI: https://doi.org/10.1016/j.jspd.2017.11.004

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