title: Initial and 6 weeks postoperative structural properties of soft tissue anterior cruciate ligament reconstructions with cross-pin or interference screw fixation: an in vivo study in sheep.
abstract: OBJECTIVE
  The purpose of this study was to evaluate the detrimental effects of interference screw fixation on soft tissue anterior cruciate ligament (ACL) reconstruction after 6 weeks and compare them with a cross-pin technique.
  
  
  METHODS
  In an intra-articular model, ovine soft tissue grafts were fixed with two 3.3-mm biodegradable pins or with interference screws. Maximum load, yield load, and stiffness of the femur-graft-tibia complex were evaluated immediately after surgery and 6 weeks postoperatively.
  
  
  RESULTS
  For knees with interference screw fixation, strength deteriorated by 81% and stiffness deteriorated by 67%. For knees with double cross-pin fixation, strength deteriorated by 48% and stiffness improved by 52%. These differences were statistically significant. At the time of surgery, all grafts failed by slippage of the graft past the screw or by cross-pin failure. At 6 weeks postoperatively, the grafts of both groups failed at the tibial or femoral tunnel entrance.
  
  
  CONCLUSIONS
  After 6 weeks, the biomechanical characteristics of grafts that were fixed with cross-pins were superior to those of grafts after interference screw fixation.
  
  
  CONCLUSIONS
  Because of significantly inferior biomechanical stability after interference screw fixation, a less aggressive program of rehabilitation might be recommended.
authors.affiliation: Department of Trauma, Hand, and Reconstructive Surgery, Westfälische Wilhelms-University Münster, Münster, Germany.
authors.forename: Thore
authors.initials: T
authors.lastname: Zantop
authors.forename: Andre
authors.initials: A
authors.lastname: Weimann
authors.forename: Kerstin
authors.initials: K
authors.lastname: Wolle
authors.forename: Volker
authors.initials: V
authors.lastname: Musahl
authors.forename: Martin
authors.initials: M
authors.lastname: Langer
authors.forename: Wolf
authors.initials: W
authors.lastname: Petersen
mesh_terms: D000125:Achilles Tendon / Q000637:transplantation; D000818:Animals; D016118:Anterior Cruciate Ligament / Q000601:surgery*; D001858:Bone Nails; D001863:Bone Screws; D005260:Female; D023421:Models, Animal; D019651:Plastic Surgery Procedures / Q000379:methods*; D012756:Sheep; D014182:Transplantation, Autologous