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A novel, hydroxyapatite-based screw-like device for anterior cruciate ligament (ACL) reconstructions

: Schumacher, Thomas C.; Tushtev, Kamen; Wagner, Ulrich; Becker, Caroline; Große Holthaus, Marzellus; Hein, Sebastian B.; Haack, Janne; Heiss, Christian; Engelhardt, Markus; Khassawna, Thaqif el; Rezwan, Kurosch

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The knee 24 (2017), No.5, pp.933-939
ISSN: 1873-5800
ISSN: 0968-0160
Bundesministerium für Bildung und Forschung BMBF
Journal Article, Electronic Publication
Fraunhofer IFAM ()
anterior cruciate ligament; hydroxyapatite; interference screw; all-ceramic; pull-out strength

Background: Rupture of the anterior cruciate ligament (ACL) is one of the most common injuries of the knee. Common techniques for ACL reconstruction require a graft fixation using interference screws. Nowadays, these interference screws are normally made of titanium or polymer/ceramic composites. The main challenge of application of a fixation device made entirely of bioactive ceramic is in relation to the low strength of such materials. The purpose of this study was to evaluate a novel geometry for a fixation device made of pure hydroxyapatite for ACL reconstructions that can overcome some problems of the titanium and the polymer/ceramic screws.
Methods: Finite Element Analysis was used for optimization of the stress distribution in conventional interference screw geometry. For experimental evaluation of the new fixation device, ex vivo tests were performed.
Results: The innovative screw-like fixation device is characterized by multiple threads with a large thread pitch. The novel design enabled the insertion of the screw into the bone without the application of an external torque or a screwdriver. In turn, it also allowed for the use of low-strength and high-bioactivity materials, like hydroxyapatite. Ex vivo tests showed that the novel screw can sustain pull-out forces up to 476 N, which is comparable to that of the commercially available BioComposite™ interference screws (Arthrex Inc., Germany), as a reference.
Conclusions: In summary, the novel screw design is a promising strategy to develop all-ceramic fixation devices for ACL reconstructions, which may eliminate some drawbacks of the current interference screws.