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3D printed guided positioning of extreme pedicle screws to aid in vertebral derotation : A feasibility cadaver study to improve scoliosis surgery

Suurd, Diederik P.D. (2017) 3D printed guided positioning of extreme pedicle screws to aid in vertebral derotation : A feasibility cadaver study to improve scoliosis surgery.

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Abstract:Objective: In scoliosis correction derotation of the vertebrae is challenging, resulting in non-ideal rotational alignment of the vertebrae. Nowadays, unconventional pedicle screw trajectories can be planned with the advent of 3D printed guiding techniques. We studied preplanned extreme screw positions to aid in vertebral rotation and the use of drill guides. Methods: The study is a feasibility study in a human cadaver. Volumes of the vertebrae are reconstructed. The volumes are used for planning and manufacturing of the drill guide. Six sections of three vertebrae represented the test situation where cephalad en caudal vertebrae were fixed. The middle vertebra was instrumented with an extreme screw on one side. Pre-bent CoCr rods were used to gain more vertebral rotation. Thereby, forces acting on the screw-rod construct were measured with a torque wrench during instrumentation and calculated using a FEM simulation. After instrumentation, a CT scan was used to analyze drill guide accuracy and the translational and rotational movement of the middle vertebra. Results: In total 24 screws were inserted with the drill guide; 5 extreme pedicle screw trajectories and 19 conventional pedicle screw trajectories. 11 conventional screws were correctly placed. 8 screws had incorrect placement. 4 out of 5 of the extreme pedicle screws were pulled out during the rotational maneuver. One extreme pedicle screw was not pulled out. However, derotation of the instrumented vertebra was not observed. Discussion: Extreme pedicle screw placement is feasible. However, extreme screw trajectories are not optimal which led to high pull-out ratio. Planning of extreme pedicle screws needs to be improved for higher success percentage. Further research is needed with improved extreme pedicle screw placement to aid in vertebral derotation.
Item Type:Essay (Master)
Clients:
UMC Utrecht, Utrecht, Nederland
Faculty:TNW: Science and Technology
Subject:44 medicine
Programme:Technical Medicine MSc (60033)
Link to this item:http://purl.utwente.nl/essays/73842
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