title: A comparison of three adjustable cortical button ACL fixation devices.
abstract: OBJECTIVE
  Adjustable cortical fixation has gained popularity recently for ACL reconstruction; however, one concern with these types of devices is the potential for laxity occurring post-operatively. An indicator of clinical laxity is cyclic displacement during bench-top mechanical testing. The hypothesis was that the cyclic displacement and maximum strength of different adjustable buttons currently on the market would vary depending on their mechanism of fixation.
  
  
  METHODS
  Three devices were studied: Biomet's ToggleLoc with ZipLoop Technology (ZL), Arthrex's TightRope RT (TR), and DePuy Mitek's RIGIDLOOP Adjustable (RLA). Each was tested in isolation on a servohydraulic test machine. The implants were pre-conditioned from 5 to 67 N for 10 cycles and then tested from 50 to 250 N for 1000 cycles at 1 Hz. Following cyclic loading, a load to failure test was conducted at a rate of 20 mm/min. Total displacement was calculated from the 1st to the 1000th cycle, and ultimate strength and failure mode were recorded.
  
  
  RESULTS
  Results showed that the RLA had significantly lower displacement versus both the TR (p = 0.012) and the ZL (p < 0.001). The TR also showed significantly lower displacement than the ZL (p < 0.001). The RLA and the ZL were both significantly stronger than the TR (p < 0.001).
  
  
  CONCLUSIONS
  Both the RLA and TR showed clinically acceptable amounts of cyclic displacement and maximum strength. The clinical relevance of this study is that cyclic displacement results from bench-top tests may correlate with post-operative laxity, which ideally should be kept to a minimum.
authors.affiliation: DePuy Synthes Mitek Sports Medicine, 325 Paramount Drive, Raynham, MA, 02767, USA.
authors.forename: Meghan
authors.initials: M
authors.lastname: Pasquali
authors.affiliation: Foundry Orthopedics and Sports Medicine, 285 Promenade Street, Providence, RI, 02908, USA.
authors.forename: Matthew J
authors.initials: MJ
authors.lastname: Plante
authors.affiliation: Foundry Orthopedics and Sports Medicine, 285 Promenade Street, Providence, RI, 02908, USA.
authors.forename: Keith O
authors.initials: KO
authors.lastname: Monchik
authors.affiliation: DePuy Synthes Mitek Sports Medicine, 325 Paramount Drive, Raynham, MA, 02767, USA. dspencin@its.jnj.com.
authors.forename: David B
authors.identifier: http://orcid.org/0000-0003-4893-3953
authors.initials: DB
authors.lastname: Spenciner
mesh_terms: D016118:Anterior Cruciate Ligament / Q000601:surgery; D059549:Anterior Cruciate Ligament Reconstruction / Q000295:instrumentation*; D001696:Biomechanical Phenomena; D005269:Femur / Q000601:surgery; D006801:Humans; D016268:Internal Fixators / Q000706:statistics & numerical data*
keywords: ACL reconstruction; Adjustable cortical button; Cortical fixation; Cyclic displacement; Laxity