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The anatomical and biomechanical consequences of anterior vertebral stapling for the fusionless correction of scoliosis

Shillington, Mark, Adam, Clayton J., Labrom, Robert D., & Askin, Geoffrey N. (2009) The anatomical and biomechanical consequences of anterior vertebral stapling for the fusionless correction of scoliosis. In Annual Scientific Meeting of the Spine Society of Australia, April 17-19, 2009, Brisbane, Australia. (Unpublished)

Abstract

Fusionless scoliosis surgery is an emerging treatment for idiopathic scoliosis as it offers theoretical advantages over current forms of treatment. Anterior vertebral stapling using a nitinol staple is one such treatment. Despite increasing interest in this technique, little is known about the effects on the spine following insertion, or the mechanism of action of the staple. The aims of this study were threefold; (1) to measure changes in the bending stiffness of a single motion segment following staple insertion, (2) to describe the forces that occur within the staple during spinal movement, and (3) to describe the anatomical changes that occur following staple insertion. Results suggest that staple insertion consistently decreased stiffness in all directions of motion. An explanation for the finding may be found in the outcomes of the strain gauge testing and micro-CT scan. The strain gauge testing showed that once inserted, the staple tips applied a baseline compressive force to the surrounding trabecular bone and vertebral end-plate. This finding would be consistent with the current belief that the clinical effect of the staples is via unilateral compression of the physis. Interestingly however, as each specimen progressed through the five cycles of each test, the baseline load on the staple tips gradually decreased, implying that the force at the staple tip-bone interface was decreasing. We believe that this was likely occurring as a result of structural damage to the trabecular bone and vertebral end-plate by the staple effectively causing ‘loosening’ of the staple. This hypothesis is further supported by the findings of the micro-CT scan. The pictures depict significant trabecular bone and physeal injury around the staple blades. These results suggest that the current hypothesis that stapling modulates growth through physeal compression may be incorrect, but rather the effect occurs through mechanical disruption of the vertebral growth plate.

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ID Code: 25967
Item Type: Conference Paper
Keywords: biomechanics, staples, shape memory alloy, scoliosis, fusionless scoliosis correction
Subjects: Australian and New Zealand Standard Research Classification > ENGINEERING (090000) > BIOMEDICAL ENGINEERING (090300) > Biomechanical Engineering (090302)
Divisions: Past > QUT Faculties & Divisions > Faculty of Built Environment and Engineering
Current > Institutes > Institute of Health and Biomedical Innovation
Past > Schools > School of Engineering Systems
Copyright Owner: Copyright 2009 please consult the authors
Deposited On: 30 Jun 2009 15:49
Last Modified: 11 Aug 2011 01:23

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