Enhancing spinal bone anchor pull-out resistance with an L-shaped anchor

Journal article (2024)

Authors

E.P. de Kater Medical Instruments & Bio-Inspired Technology - Mechanical, Maritime and Materials Engineering
M.N. Blom Student
T.C. van Doorn Student
Q.H. Tieu Student
D.J. Jager EMSD EEMCS Project technicians
A. Sakes Medical Instruments & Bio-Inspired Technology - Mechanical, Maritime and Materials Engineering
P. Breedveld Medical Instruments & Bio-Inspired Technology - Mechanical, Maritime and Materials Engineering
Research Group
Medical Instruments & Bio-Inspired Technology (Mechanical, Maritime and Materials Engineering) (TU Delft)
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Published Date

2024

Language

English

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Faculty

Mechanical, Maritime and Materials Engineering

Department

Biomechanical Engineering

Research Group

Medical Instruments & Bio-Inspired Technology

Abstract

The success rate of spinal fusion surgery is mainly determined by the fixation strength of the spinal bone anchors. This study explores the use of an L-shaped spinal bone anchor that is intended to establish a macro-shape lock with the posterior cortical layer of the vertebral body, thereby increasing the pull-out resistance of the anchor. The performance of this L-shaped anchor was evaluated in lumbar vertebra phantoms (L1-L5) across four distinct perpendicular orientations (lateral, medial, superior, and inferior). During the pull-out experiments, the pull-out force, and the displacement of the anchor with respect to the vertebra was measured which allowed the determination of the maximal pull-out force (mean: 123 N ± 25 N) and the initial pull-out force, the initial force required to start motion of the anchor (mean: 23 N ± 16 N). Notably, the maximum pull-out force was observed when the anchor engaged the cortical bone layer. The results demonstrate the potential benefits of utilising a spinal bone anchor featuring a macro-shape lock with the cortical bone layer to increase the pull-out force. Combining the macro shape-lock fixation method with the conventional pedicle screw shows the potential to significantly enhance the fixation strength of spinal bone anchors.