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The Effect of Rod Diameter on Correction of Adolescent Idiopathic Scoliosis at Two Years Follow-Up

Prince, Daniel E. MD, MPH*; Matsumoto, Hiroko MA; Chan, Charles M. MD; Gomez, Jaime A. MD; Hyman, Joshua E. MD†,§; Roye, David P. Jr MD†,§; Vitale, Michael G. MD, MPH†,§

Journal of Pediatric Orthopaedics: January 2014 - Volume 34 - Issue 1 - p 22–28
doi: 10.1097/BPO.0b013e318288b3c1

Study Design: The review of multicenter national pediatric scoliosis database.

Objective: The purpose of this study was to compare the radiographic outcomes of patients who underwent scoliosis surgery utilizing different rod diameter constructs by the posterior approach.

Background: Little attention has specifically been focused on the effect of rod diameter on correction of spinal deformity after posterior spinal instrumentation and fusion in children with adolescent idiopathic scoliosis (AIS).

Methods: The review of national database comprised of 1125 patients, of which 352 patients had a minimum follow-up of 2 years. Of these, 163 patients received 5.5 mm and 189 patients received 6.35 mm diameter rods for posterior spinal instrumentation.

Results: The 6.35 mm rods were used more often for patients who were male, taller, heavier, with larger coronal curves, and more flexible curves. Larger diameter rods were also more likely to be stainless steel, implanted with an increased number of implants per level, and an increased number of pedicle screws used on the concavity of the curve. Univariate analysis of coronal curve showed a significant difference between 5.5 and 6.35 mm rods in correction (67.0% vs. 57.3%) at 2 years. Multivariate analysis revealed that the most significant factors affecting coronal curve correction at 2 years were rod diameter, the patient’s preoperative coronal major curve and flexibility, and the implant density. In the sagittal plane, preoperative sagittal curve and rod diameter are the predictors of sagittal correction at 2 years.

Conclusions: The study did not support our hypothesis that larger rods would be associated with a greater correction of frontal and sagittal plane in patients with AIS. In addition to rod diameter, implant density and the inherent flexibility and deformity of the patient were found to be influential factors contributing for the correction and maintenance of coronal and sagittal curves in AIS.

*Sinai Hospital of Baltimore, Baltimore, MD

Division of Pediatric Orthopaedic Surgery, Department of Orthopaedic Surgery

Department of Orthopaedic Surgery, Columbia University

§New York-Presbyterian Morgan Stanley Children's Hospital, Columbia University Medical Center, New York, NY

Supported by Spinal Deformity Study Group (SDSG). SDSG registry was utilized to obtain the raw data. The SDSG is supported by Medtronic Spine. However, no payment was received from any commercial entity to directly support this study.

H.M. has research support from SRS, POSNA, CWSDRF and CPIRF. J.E.H. has research support from POSNA and CPIRF. J.E.H. is a member of the board of directors of SICOT and AACPDM. D.P.R. Jr. is a consultant for Stryker but receives no financial reimbursement other than travel expenses. He has research support from SRS, POSNA, CPIRF, and CWSDRF. D.P.R. is a member of the board of directors of SICOT. Furthermore, D.P.R., M.G.V. have received travel support from the SDSG and CWSDSG in the past. M.G.V. receives royalty from Biomet and a consultant for Stryker and Bioment. He receives research support from SRS, POSNA and CWSDRF. He is a member of the board of directors for CWSDSG and POSNA. The Division of Pediatric Orthopaedics at Columbia University has received support from OMeGA, Biomet, Stryker and OREF for the fellowship program. The other authors have no conflict of interest to declare.

Reprints: Hiroko Matsumoto, MA, Division of Pediatric Orthopaedic Surgery, Department of Orthopaedic Surgery, Columbia University, 3959 Broadway 800 North, New York, NY 10032. E-mail:

© 2014 by Lippincott Williams & Wilkins