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J Neurol Surg A Cent Eur Neurosurg 2025; 86(02): 128-134
DOI: 10.1055/a-2206-2578
Original Article

A New Concept for Cervical Expansion Screws Using Shape Memory Alloy: A Feasibility Study

Ronny Grunert
1   Department of Neurosurgery, University Leipzig, Leipzig, Germany
2   Fraunhofer Institute for Machine Tools and Forming Technology, Zittau, Germany
,
Dirk Winkler
1   Department of Neurosurgery, University Leipzig, Leipzig, Germany
,
Nikolas Knoop
1   Department of Neurosurgery, University Leipzig, Leipzig, Germany
,
Martin Weidling
3   Department Orthopedics, Trauma Surgery and Plastic Surgery, University Leipzig, Leipzig, Germany
,
Cornelia Matzke
1   Department of Neurosurgery, University Leipzig, Leipzig, Germany
,
Sebastian Scholz
2   Fraunhofer Institute for Machine Tools and Forming Technology, Zittau, Germany
,
Juergen Meixensberger
1   Department of Neurosurgery, University Leipzig, Leipzig, Germany
,
Felix Arlt
1   Department of Neurosurgery, University Leipzig, Leipzig, Germany
› Author Affiliations Funding Our project with the funding code 03ZZ1026C could only be realized with the support of the Federal Ministry of Education and Research.
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Abstract

Background In general, sufficient anchoring of screws in the bone material ensures the intended primary stability.

Methods Shape memory materials offer the option of using temperature-associated deformation energy in a targeted manner to compensate the special situation of osteoporotic bones or the potential lack of anchoring. An expansion screw was developed for these purposes. Using finite element analysis (FEA), the variability of screw configuration and actuator was assessed from shape memory. In particular, the dimensioning of the screw slot, the actuator length, and the actuator diameter as well as the angle of attack in relation to the intended force development were considered.

Results As a result of the FEA, a special configuration of expansion screw and shape memory element could be found. Accordingly, with an optimal screw diameter of 4 mm, an actuator diameter of 0.8 mm, a screw slot of 7.8 mm in length, and an angle of attack of 25 degrees, the best compromise between individual components and high efficiency in favor of maximum strength can be predicted.

Conclusion Shape memory material offers the possibility of using completely new forms of power development. By skillfully modifying the mechanical and shape memory elements, their interaction results in a calculated development of force in favor of a high primary stability of the screw material used. Activation by means of body temperature is a very elegant way of initializing the intended locking and screw strength.

Keywords

screw implant - shape memory alloy - finite element analysis

Data Availability Statement

The data that support the findings of this study are available from the corresponding author, upon request.


Ethics Approval

Ethical approval was not required. The feasibility of shape memory screws was demonstrated with FE analysis and production. Until now, there was no application on body donors or patients.


Author Contributions

R.G. and M.W. developed the technical concept of the shape memory screw. D.W., N.K., C.M., J.M., and F.A. were responsible for the development of different design variations from the clinical point of view. M.W. created the CAD model and performed the finite element analysis. R.G., M.W., and S.S. evaluated different production technologies.


Consent to Publish

The authors confirm that the work described has not been published before.




Publication History

Received: 13 July 2023

Accepted: 06 November 2023

Accepted Manuscript online:
08 November 2023

Article published online:
21 November 2024

© 2024. Thieme. All rights reserved.

Georg Thieme Verlag KG
Rüdigerstraße 14, 70469 Stuttgart, Germany

 

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