The Biomechanical Effects of Thoracic Spine Stapling

Shillington, Mark, Adam, Clayton J., Labrom, Robert D., & Askin, Geoffrey N. (2008) The Biomechanical Effects of Thoracic Spine Stapling. In Lenke, Lawrence G. & Hamzaoglu, Azmi (Eds.) 15th International Meeting on Advanced Spine Techniques, 8-11 July, 2008, Hong Kong.


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The use of anterior vertebral staples in the fusionless correction of scoliosis has received increased attention in recent literature. In 2007, Puttlitz measured the change in spinal range of motion (ROM) after staple insertion in a bovine model. They found a small but statistically significant decrease in ROM in axial rotation and lateral bending. The clinical significance of this is questionable as the differences were only a few degrees over three vertebral levels. A well designed biomechanical evaluation of the effects of staple insertion on spinal stability is needed. Four-pronged shape memory alloy staples were inserted into fourteen individual bovine thoracic motion segments. A displacement controlled six degree-of-freedom robotic facility tested control and staple constructs through a pre-determined ROM. Data was synchronised with robot position data and filtered using moving average methods. Stiffness was calculated in Nm/degree of rotation. Paired t-tests were used to compare results. Stiffness measurements in the control condition correlated with previously published measures. A significant decrease in stiffness (p<0.05) following staple insertion was found in flexion, extension, lateral bending away from the staple, and axial rotation away from the staple. Stiffness for axial rotation towards the stapled side was significantly greater than for away. A near significant increase in lateral bend stiffness away from the staple compared with towards was also seen. These results suggest that staple insertion consistently decreased stiffness in all directions of motion. This result could not be explained by changes in anatomy or tissue properties between specimens, as stapled motion segments were compared with their own intact state. Addition of the staple would intuitively be expected to increase motion segment stiffness, however we suggest that the staple prongs may cause sufficient disruption to the vertebral bodies and endplates to slightly reduce overall stiffness. Hence, growth modulation may be achieved through physical disruption of the endplate, rather than static mechanical stress. Further research is planned to investigate the effect of the staple on the cancellous bone and physis.

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ID Code: 17323
Item Type: Conference Item (Poster)
Refereed: Yes
Keywords: biomechanics, thoracic spine stapling, shape memory alloy, idiopathic scoliosis, growing spine
Divisions: Current > Schools > School of Chemistry, Physics & Mechanical Engineering
Past > QUT Faculties & Divisions > Faculty of Built Environment and Engineering
Current > Institutes > Institute of Health and Biomedical Innovation
Current > QUT Faculties and Divisions > Science & Engineering Faculty
Past > Schools > School of Engineering Systems
Copyright Owner: Copyright 2008 (The authors)
Deposited On: 04 Feb 2009 00:47
Last Modified: 05 May 2017 01:44

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