title: Close-looped graft suturing improves mechanical properties of interference screw fixation in ACL reconstruction.
abstract: OBJECTIVE
  In anterior cruciate ligament reconstruction with looped soft-tissue grafts, an interference screw is frequently used for tibial fixation. This study compared three alternatives thought to improve the initial mechanical properties of direct bioabsorbable interference screw fixation: suturing the graft to close the loop, adding a supplementary staple, or increasing the oversize of the screw diameter relative to the bone tunnel from 1 to 2 mm.
  
  
  METHODS
  Twenty-eight porcine tibiae and porcine flexor digitorum profundus tendons were randomized into four testing groups: a base fixation using 10-mm-diameter screw with open-looped graft, base fixation supplemented by an extracortical staple, base fixation but closing the looped graft by suturing its ends, and base fixation but using an 11-mm screw. Graft and bone tunnel diameters were 9 mm in all specimens. Constructs were subjected to cyclic tensile load and finally pulled to failure to determine their structural properties.
  
  
  RESULTS
  The main mode of failure in all groups was pull-out of tendon strands after slippage past the screw. The sutured graft group displayed significantly lower residual displacement (mean value reduction: 47-67 %) and higher yield load (mean value increase: 38-54 %) than any alternative tested. No other statistical differences were found.
  
  
  CONCLUSIONS
  Suturing a soft-tissue graft to form a closed loop enhanced the initial mechanical properties of tibial fixation with a bioabsorbable interference screw in anterior cruciate ligament reconstructions using a porcine model, and thus, this may be an efficient means to help in reducing post-operative laxity and early clinical failure. No mechanical improvement was observed for an open-looped tendon graft by adding an extracortical staple to supplement the screw fixation or by increasing the oversize of the screw to tunnel diameter from 1 to 2 mm.
authors.affiliation: Laboratorio de Biomecánica, Departamento de Ingeniería Mecánica, Escuela de Ingenierías, Universidad de Malaga, C/Pedro Ortiz Ramos, s/n., 29071, Malaga, Spain.
authors.forename: María
authors.initials: M
authors.lastname: Prado
authors.forename: Belén
authors.initials: B
authors.lastname: Martín-Castilla
authors.forename: Alejandro
authors.initials: A
authors.lastname: Espejo-Reina
authors.forename: José Miguel
authors.initials: JM
authors.lastname: Serrano-Fernández
authors.forename: Ana
authors.initials: A
authors.lastname: Pérez-Blanca
authors.forename: Francisco
authors.initials: F
authors.lastname: Ezquerro
mesh_terms: D020341:Absorbable Implants; D000818:Animals; D059549:Anterior Cruciate Ligament Reconstruction / Q000379:methods*; D001696:Biomechanical Phenomena; D001863:Bone Screws; D023421:Models, Animal; D013536:Suture Techniques; D013552:Swine; D013710:Tendons / Q000637:transplantation*; D013977:Tibia / Q000601:surgery