title: A novel implant-free tibial pull-press-fixation for ACL reconstruction.
abstract: BACKGROUND
  Extracortical fixation techniques in anterior cruciate ligament reconstruction bear the risk of tunnel enlargement, while close-to-aperture fixations often show lower failure loads. The purpose for this study was to investigate the biomechanical benefits of a novel implant-free combination of an extra-cortical and close-to-aperture fixation.
  
  
  METHODS
  Quadrupled human cadaveric semitendinosus tendons were fixed to 30 porcine tibiae with either a cannulated interference screw (I), an implant-free post-fixation (S), or a novel pull-press fixation (P). Specimens were cyclically loaded 20 times between 20 and 60 N followed by 500 cycles with 60-200 N, followed by a load-to-failure test with 1 mm/s.
  
  
  RESULTS
  The mean elongation of the tendons in the P-group during the 500 cycles between 60 and 200 N was significantly lower (5.69 ± 2.16 mm) compared to 9.20 ± 3.21 mm in S-group and 9.37 ± 3.1 mm in the I-group (p < 0.05). The mean maximum load-to-failure was significantly higher in the P-group (728.2 ± 76.4 N) compared to 476.4 ± 68.8 N in the S-group and 625.9 ± 82.5 N in the I-group (p < 0.05). Stiffness of the constructs in the P-group was significantly higher (121.7 ± 44.9 N/mm) compared to 46.2 ± 17.7 N/mm in the S- and 72.8 ± 29.8 N/mm in the I-group (p < 0.03).
  
  
  CONCLUSIONS
  This study indicates superior biomechanical properties of a novel implant-free tibial pull-press fixation to conventional implant-free and close-to-aperture interference screw fixations in terms of cyclic elongation and maximum load-to-failure.
  
  
  METHODS
  Not applicable, basic science study.
authors.affiliation: Trauma Department, Hannover Medical School (MHH), Carl-Neuberg-Str. 1, 30625, Hannover, Germany. kwisda.sebastian@mh-hannover.de.
authors.forename: Sebastian
authors.initials: S
authors.lastname: Kwisda
authors.affiliation: Orthopaedic Surgery Department, Hannover Medical School (MHH), Anna-von-Borries-Straße 1-7, 30625, Hannover, Germany.
authors.forename: Antonios
authors.initials: A
authors.lastname: Dratzidis
authors.affiliation: Orthopaedic Surgery Department, Hannover Medical School (MHH), Anna-von-Borries-Straße 1-7, 30625, Hannover, Germany.
authors.forename: Max
authors.initials: M
authors.lastname: Ettinger
authors.affiliation: Trauma Department, Hannover Medical School (MHH), Carl-Neuberg-Str. 1, 30625, Hannover, Germany.
authors.forename: Mohamed
authors.initials: M
authors.lastname: Omar
authors.affiliation: Laboratory for Biomaterials and Biomechanics (LBB), Orthopaedic Surgery Department, Hannover Medical School (MHH), Anna-von-Borries-Str. 1-7, 30625, Hannover, Germany.
authors.forename: Christof
authors.initials: C
authors.lastname: Hurschler
authors.affiliation: Trauma Department, Hannover Medical School (MHH), Carl-Neuberg-Str. 1, 30625, Hannover, Germany.
authors.forename: Maximilian
authors.initials: M
authors.lastname: Petri
authors.affiliation: Trauma Department, Hannover Medical School (MHH), Carl-Neuberg-Str. 1, 30625, Hannover, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Krettek
authors.affiliation: Klinikum Schaumburg, Kreiskrankenhaus Stadthagen, Am Krankenhaus 1, 31655, Stadthagen, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Jagodzinski
mesh_terms: D000818:Animals; D059549:Anterior Cruciate Ligament Reconstruction / Q000295:instrumentation / Q000379:methods; D001696:Biomechanical Phenomena; D001863:Bone Screws; D006801:Humans; D013552:Swine; D013710:Tendons / Q000502:physiology / Q000601:surgery
keywords: ACL reconstruction; Hamstring tendons; Implant-free reconstruction; Pull-press fixation