title: Biomechanical comparison of the bioabsorbable RetroScrew system, BioScrew XtraLok with stress equalization tensioner, and 35-mm Delta Screws for tibialis anterior graft-tibial tunnel fixation in porcine tibiae.
abstract: BACKGROUND
  Achieving effective soft tissue graft-tibial tunnel fixation remains problematic.
  
  
  OBJECTIVE
  No differences would exist for tibialis anterior graft-tibial tunnel fixation when comparing the RetroScrew System (20-mm retrograde screw, 17-mm antegrade screw), the 35-mm tapered Delta Screw (manual tensioning), and the 35-mm BioScrew XtraLok (applied using an instrumented tensioner).
  
  
  METHODS
  Controlled laboratory study.
  
  
  METHODS
  Porcine tibiae (apparent bone mineral density, 1.3 g/cm(2)) and human tendon allografts were divided into 3 matched groups of 6 specimens each before cyclic (500 cycles, 50-250 N, 1 Hz) and load-to-failure (20 mm/min) tests.
  
  
  RESULTS
  The BioScrew XtraLok (210.9 +/- 54.9 N/mm) and the 35-mm Delta Screw (224.3 +/- 43.7 N/mm) displayed superior stiffness to the RetroScrew System (114.1 +/- 23.3 N/mm) (P = .0004) during cyclic testing. The BioScrew XtraLok (1.0 +/- 0.2 mm) and the Delta Screw (0.9 +/- 0.2 mm) also displayed less displacement during cyclic testing than the RetroScrew System (1.8 +/- 0.5 mm) (P = .001). During load-to-failure testing, the BioScrew XtraLok withstood greater loads (1436.3 +/- 331.3 N) (P = .001) and displayed greater stiffness (323.6 +/- 56.8 N/mm) (P = .002) than the 35-mm Delta Screw (load, 1042.2 +/- 214.4 N; stiffness, 257.2 +/- 22.2 N/mm) and the RetroScrew System (load, 778.7 +/- 177.5 N; stiffness, 204.4 +/- 52.9 N/mm).
  
  
  CONCLUSIONS
  The BioScrew XtraLok with instrumented tensioning displayed superior fixation to the RetroScrew System and the 35-mm Delta Screw applied with manual tensioning.
  
  
  CONCLUSIONS
  The BioScrew XtraLok may provide superior soft tissue graft-tibial tunnel fixation. Further in vitro studies using human tissue and in vivo clinical studies are needed.
authors.affiliation: Division of Sports Medicine, Department of Orthopaedic Surgery, University of Louisville, 210 East Gray Street, Suite 1003, Louisville, KY 40202, USA.
authors.forename: Haw Chong
authors.initials: HC
authors.lastname: Chang
authors.forename: John
authors.initials: J
authors.lastname: Nyland
authors.forename: Akbar
authors.initials: A
authors.lastname: Nawab
authors.forename: Robert
authors.initials: R
authors.lastname: Burden
authors.forename: David N M
authors.initials: DN
authors.lastname: Caborn
mesh_terms: D020341:Absorbable Implants; D000328:Adult; D000818:Animals; D000070598:Anterior Cruciate Ligament Injuries; D001696:Biomechanical Phenomena; D001863:Bone Screws; D019544:Equipment Failure Analysis; D006801:Humans; D008422:Materials Testing; D013552:Swine; D013710:Tendons / Q000637:transplantation*; D013977:Tibia / Q000601:surgery; D014184:Transplantation, Homologous