A biomechanical investigation of dual growing rods used for fusionless scoliosis correction

Quick, M. E., Grant, C. A., Adam, C. J., Askin, G. N., Labrom, R. D. and Pearcy, M. J. (2015) A biomechanical investigation of dual growing rods used for fusionless scoliosis correction. Clinical Biomechanics, 30 1: 33-39. doi:10.1016/j.clinbiomech.2014.11.008

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Author Quick, M. E.
Grant, C. A.
Adam, C. J.
Askin, G. N.
Labrom, R. D.
Pearcy, M. J.
Title A biomechanical investigation of dual growing rods used for fusionless scoliosis correction
Journal name Clinical Biomechanics   Check publisher's open access policy
ISSN 1879-1271
Publication date 2015-01-01
Year available 2014
Sub-type Article (original research)
DOI 10.1016/j.clinbiomech.2014.11.008
Open Access Status Not Open Access
Volume 30
Issue 1
Start page 33
End page 39
Total pages 7
Place of publication Kidlington, Oxford United Kingdom
Publisher Pergamon Press
Collection year 2016
Language eng
Formatted abstract

The use of dual growing rods is a fusionless surgical approach to the treatment of early onset scoliosis which aims to harness potential growth and correct spinal deformity. The purpose of this study was to compare the in-vitro biomechanical response of two different dual rod designs under axial rotation loading.


Six porcine spines were dissected into seven level thoracolumbar multi-segment units. Each specimen was mounted and tested in a biaxial Instron machine, undergoing nondestructive left and right axial rotation to peak moments of 4 Nm at a constant rotation rate of 8 deg. s−1. A motion tracking system (Optotrak) measured 3D displacements of individual vertebrae. Each spine was tested in an un-instrumented state first and then with appropriately sized semi-constrained and ‘rigid’ growing rods in alternating sequence. The range of motion, neutral zone size and stiffness were calculated from the moment–rotation curves and intervertebral range of motion was calculated from Optotrak data.


Irrespective of test sequence, rigid rods showed a significant reduction of total rotation across all instrumented levels (with increased stiffness) whilst semi-constrained rods exhibited similar rotational behavior to the un-instrumented spines (P < 0.05). An 11.1% and 8.0% increase in stiffness for left and right axial rotation respectively and 14.9% reduction in total range of motion were recorded with dual rigid rods compared with semi-constrained rods.


Based on these findings, the Semi-constrained growing rods were shown to not increase axial rotation stiffness compared with un-instrumented spines. This is thought to provide a more physiological environment for the growing spine compared to dual rigid rod constructs.
Keyword Scoliosis
Fusionless correction
Growing rod
In vitro
Range of motion
Q-Index Code C1
Q-Index Status Provisional Code
Institutional Status UQ

Document type: Journal Article
Sub-type: Article (original research)
Collections: Mater Research Institute-UQ (MRI-UQ)
Official 2016 Collection
School of Medicine Publications
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Created: Thu, 31 Mar 2016, 15:14:15 EST by Kristen Gibbons on behalf of School of Medicine