Abstract
Background
Clinically significant proximal junctional kyphosis (PJK) occurs in 20% of children with scoliosis treated with posterior distraction-based growth-friendly surgery. In an effort to identify modifiable risk factors, it has been theorized biomechanically that low radius of curvature (ROC) implants (i.e., more curved rods) may increase post-operative thoracic kyphosis, and thus may pose a higher risk of developing PJK. We sought to test the hypothesis that early onset scoliosis (EOS) patients treated with low ROC distraction-based implants will have a greater risk of developing clinically significant PJK as compared to those treated with high ROC (straighter) implants.
Methods
We conducted a retrospective review of prospectively collected data obtained from a multi-centre EOS database on children treated with rib-based distraction with a minimum 2-year follow-up. Variables of interest included: implant ROC at index (220 mm or 500 mm), participant age, pre-operative scoliosis, pre-operative kyphosis, and scoliosis etiology. PJK was defined as clinically significant if revision surgery with a superior extension of the upper instrumented vertebrae was performed.
Results
In 148 participants with scoliosis, there was a higher risk of clinically significant PJK with low ROC (more curved) rods (OR: 2.6 (95% CI 1.09–5.99), χ2 (1, n = 148) = 4.8, p = 0.03). Participants had a mean pre-operative age of 5.3 years (4.6y 220 mm vs 6.2y 500 mm, p = 0.002). A logistic regression model was created with age as a confounding variable, but it was determined to be not significant (p = 0.6). Scoliosis etiologies included 52 neuromuscular, 52 congenital, 27 idiopathic, 17 syndromic with no significant differences in PJK risk between etiologies (p = 0.07). Overall, participants had pre-op scoliosis of 69° (67° 220 mm vs 72° 500 mm, p = 0.2), and kyphosis of 48° (45° 220 mm vs 51° 500 mm, p = 0.1). The change in thoracic kyphosis pre-operatively to final follow-up (mean 4.0 ± 0.2 years) was higher in participants treated with 220 mm implants compared to 500 mm implants (220 mm: 7.5 ± 2.6° vs 500 mm: − 4.0 ± 3.0°, p = 0.004).
Conclusions
Use of low ROC (more curved) posterior distraction implants is associated with a significantly greater increase in thoracic kyphosis which likely led to a higher risk of developing clinically significant PJK in participants with EOS.
Level of evidence
Level III – retrospective comparative study.
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Data availability
Registry data is available to member institutions. Measurements and analysis done at the IWK Health Centre are on a password-protected server. Access may be arranged through an application to the REB.
Code availability
Statistical analysis was performed using Statistical Package for the Social Sciences (SPSS), version 19 (IBM Corp, Armonk, NY) and GraphPad Prism version 8.0 for Macintosh (GraphPad Software, La Jolla, California, USA).
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Acknowledgement
Pediatric Spine Study Group Collaborators: Noriaki Kawakami, Kenneth Cheung, Kenny Kwan, Jason Cheung, John Emans, Lawrence Karlin, Brian Snyder, Firoz Miyanji, Jaime Gomez, Lindsay Andras, David Skaggs, Sumeet Garg, Benjamin Roye, Michael Vitale, Lisa Saiman, Patrick Cahill, Jack Flynn, Oscar Mayer, Matthew Oetgen, Josh Murphy, Peter Sturm, Stefan Parent, Ron El-Hawary, Paul Sponseller, Jeffrey Sawyer, A Noelle Larson, Robert Murphy, G Ying Li, Suken Shah, Richard Anderson, Laurel Blakemore, Douglas Brockmeyer, John Smith, Behrooz Akbarnia, Burt Yaszay, Michael Glotzbecker, Christina Hardesty, George Thompson, Gregory Redding, Klane White, Purnendu Gupta, Steven Hwang, Josh Pahys, Amer Samdani, Charles Johnston, Amy McIntosh, James Sanders, Scott Luhmann, Gokhan Demirkiran, Kenny Kwan, Grant Hogue, Kevin Smit, Jason Anari, Jason Howard, Timothy Oswald, Judson Karlen, Ryan Fitzgerald, Selina Poon, Michelle Welborn, Jaysson Brooks, Stephanie Ihnow, Susan Nelson, Laura Bellaire, Chris Bonfield, Hazem Sebaie, Oheneba Boachie-Adjei, Raphael Vialle, Sanchez Marquez, Javier Pizones, Adrian Gardner, Ilkka Helenius, Craig Birch, Daniel Hedequist, Timothy Hresko, Jacob Schulz, Kenneth Illingworth, Mark Erickson, John Thometz, John Anderson, Nigel Price, Richard Schwend, Nicholas Fletcher, Jonathan Martin, Robert Lark, Tenner Guillaume, Daniel Miller, Walter Truong, Norman Ramirez-Lluch, Abdullah Saad Abdulfattah Abdullah, Luis Rodriguez, Frances Farley, Peter Gabos, Stuart Mackenzie, John Heflin, Greg Mundis, Peter Newton, Erin MacKintosh, Kim Hammerberg, Michal Szczodry, John Vorhies, Haemish Crawford, Josh Holt, Stuart Weinstein, William Lavelle, Jeffrey Martus, Brian Kelly.
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EP, MAA, JH, PSSG, and RE-H designed or performed data acquisition, analysis, or interpretation; drafted or critically revised the work; approved it; and are accountable for it.
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Ellen Parker has nothing to disclose. Mohammed Al Anazi has nothing to disclose. Jennifer Hurry has nothing to disclose. Pediatric Spine Study Group reports grants from the Pediatric Orthopaedic Society of North America, grants from the Food and Drug Administration, grants from NuVasive, grants from DePuy Synthes Spine, grants from Children’s Spine Foundation, and grants from Growing Spine Foundation. Ron El-Hawary reports personal fees from Depuy Synthes Spine, personal fees from Medtronic Spine, grants from Depuy Synthes Spine, grants from Medtronic Spine, grants from Zimmer Biomet, personal fees from Orthopediatrics, other from Pediatric Spine Foundation, other from Scoliosis Research Society, outside the submitted work.
Ethical approval
This work is a sub-study of the Pediatric Spine Study Group Registry which was approved by the Research Ethics Board at the IWK Health Centre (#1002256) in accordance with the ethical standards outlined in the Tri-Council Policy Statement and the 1964 Declaration of Helsinki and its later amendments.
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All research participants or their legal guardians provided written consent to be a part of the registry and have the data collected to be used in ongoing research on scoliosis.
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Parker, E., Al Anazi, M., Hurry, J.K. et al. Low radius of curvature growth-friendly rib-based implants increase the risk of developing clinically significant proximal junctional kyphosis. Spine Deform 11, 733–738 (2023). https://doi.org/10.1007/s43390-023-00645-6
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DOI: https://doi.org/10.1007/s43390-023-00645-6