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Session: Medical Instruments - Surgery II
Session starts: Friday 25 January, 13:00
Presentation starts: 14:00
Room: Lecture room 557

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Gerdine Meijer (University of Twente)
Martijn Wessels (University of Twente)
Edsko Hekman (University of Twente)
Jasper Homminga (University of Twente)
Bart Verkerke (University of Twente)

Abstract:
Scoliosis is a deformity of the spine and trunk, mainly characterized by a lateral deviation of the spinal column in combination with axial rotation of the vertebrae. In the current project, a new scoliosis correction implant was developed, which will apply small correction forces over a longer period of time [1]. Due to the visco-elastic properties and adaptation of the soft tissues of the spine, a complete correction is expected over time. Preclinical evaluation of new implants includes testing the efficacy in animal experiments. However, as scoliosis does not occur in animals, these tests study scoliosis induction rather than scoliosis correction. Methods for scoliosis correction in humans are thus tested by inducing scoliosis in animals. In this study, two previously developed finite element models were used [2], one of the healthy and one of the scoliotic spine (figure 1). The effects of a pure torsion moment (1.5 Nm) on the T8-vertebra of a healthy spine was compared to the effects of a correction moment at the same level (-1.5 Nm) on a scoliotic spine. The long-term correction and induction effects (including visco-elasticity and adaptation of soft tissues) on the 3D deformities were analyzed (table 1). Comparison of scoliosis correction and induction in our models showed that the mechanical effects of a torsion loading on a healthy spine differ from those on a scoliotic spine. Both showed effects in the axial rotation and lateral deformity, and no effects on the sagittal shape. However, the effects in the lateral plane were much higher in the scoliosis correction simulations than in the scoliosis induction simulations, which might be explained by the different functioning of the facet joints. Our study indicates that results from torsion-induced scoliosis in animals cannot be translated directly into scoliosis correction in humans or even in animals; from the results it is expected that the 3D correction in a real-world scoliosis procedure will be better than what was obtained in the scoliosis induction experiments in animals.