title: In situ comparison of varying composite tibial tunnel interference screws used for ACL soft tissue graft fixation.
abstract: OBJECTIVE
  This mechanical study using an in vitro porcine model compared composite interference screw fixation of soft tissue ACL grafts in tibial tunnels.
  
  
  METHODS
  Forty-eight porcine profundus tendons and tibiae were divided into four groups of 12 closely matched specimens. Equivalent diameter grafts were assigned to each group. Tibial bone tunnels were drilled to 0.5mm greater than graft diameter. Grafts were fixed in tunnels using one 10 × 35 mm composite interference screw designed by four different manufacturers. Maximal insertion torque and perceived within group mechanical testing outcome predictions were recorded. Constructs were potted and loaded into a six degrees of freedom clamp that placed the servohydraulic device tensile loading vector in direct tunnel alignment. Constructs were pre-loaded to 25 N, pre-conditioned between 0 and 50 N for 10 cycles (0.5 Hz), submaximally tested between 50 and 250 N for 500 cycles (one hertz) and load to failure tested at 20mm/min.
  
  
  RESULTS
  Statistically significant differences were not observed between groups for displacement during submaximal cyclic loading, yield load, displacement at yield load, stiffness, ultimate load at failure and displacement at ultimate load. One composite screw group displayed a slightly greater proportion of specimens that required use of more than one screw during insertion.
  
  
  CONCLUSIONS
  Under highly controlled conditions groups displayed comparable fixation.
authors.affiliation: Division of Sports Medicine, Department of Orthopaedic Surgery, University of Louisville, 550 South Jackson Street, First Floor ACB, Louisville, KY 40202, United States; Athletic Training Program, Kosair Charities College of Health and Natural Sciences, Spalding University, 901 South 4th Street, Louisville, KY 40203-2188, United States. Electronic address: jnyland@spalding.edu.
authors.forename: John
authors.initials: J
authors.lastname: Nyland
authors.affiliation: Division of Sports Medicine, Department of Orthopaedic Surgery, University of Louisville, 550 South Jackson Street, First Floor ACB, Louisville, KY 40202, United States.
authors.forename: Ryan
authors.initials: R
authors.lastname: Krupp
authors.affiliation: Division of Sports Medicine, Department of Orthopaedic Surgery, University of Louisville, 550 South Jackson Street, First Floor ACB, Louisville, KY 40202, United States.
authors.forename: Joe
authors.initials: J
authors.lastname: Greene
authors.affiliation: Division of Sports Medicine, Department of Orthopaedic Surgery, University of Louisville, 550 South Jackson Street, First Floor ACB, Louisville, KY 40202, United States.
authors.forename: Richard
authors.initials: R
authors.lastname: Bowles
authors.affiliation: Division of Sports Medicine, Department of Orthopaedic Surgery, University of Louisville, 550 South Jackson Street, First Floor ACB, Louisville, KY 40202, United States.
authors.forename: Robert
authors.initials: R
authors.lastname: Burden
authors.affiliation: Division of Sports Medicine, Department of Orthopaedic Surgery, University of Louisville, 550 South Jackson Street, First Floor ACB, Louisville, KY 40202, United States.
authors.forename: David N M
authors.initials: DN
authors.lastname: Caborn
mesh_terms: D020341:Absorbable Implants; D000818:Animals; D016118:Anterior Cruciate Ligament / Q000503:physiopathology / Q000601:surgery*; D059549:Anterior Cruciate Ligament Reconstruction / Q000295:instrumentation*; D001696:Biomechanical Phenomena; D001863:Bone Screws; D004195:Disease Models, Animal; D007718:Knee Injuries / Q000503:physiopathology / Q000601:surgery*; D013552:Swine; D013710:Tendons / Q000637:transplantation*; D013977:Tibia / Q000601:surgery*
keywords: Bioresorbable; Fixation; Implantation; Interference screw; Soft tissue graft