title: Reducing the "killer turn" in posterior cruciate ligament reconstruction by fixation level and smoothing the tibial aperture.
abstract: OBJECTIVE
  The aim of this study was to evaluate the influence of the operative technique on reducing the so called "killer turn" at the tibial bone tunnel exit in posterior cruciate ligament (PCL) reconstruction.
  
  
  METHODS
  We investigated the benefit of reducing the sharp edge of the tibial bone tunnel exit using a custom made rasp in combination with extracortical and aperture (interference screw) graft fixation. Grafts were fixed in a porcine tibia model. Ten reconstructions each (sharp and rounded edge) were cyclically loaded (2,000 times) between 50 and 150 N, and another 10 each were subjected to 2,000 cycles between 50 and 300 N force. The surviving PCL reconstructions were loaded to failure using a material testing machine.
  
  
  RESULTS
  Being subjected to the sharp edge of the posterior tibia, 5 of 10 extracortical and 8 of 10 aperture fixed grafts survived cyclic loading between 50 and 150 N. All extracortical fixed and 8 of 10 aperture fixed grafts failed before 2,000 cycles when loaded between 50 and 300 N. Structural properties of grafts fixed with interference screw were statistically significant higher when compared to extracortical fixation. After rounding the sharp edge of the tunnel, all grafts survived cycles between 50 and 150 N and 6 out of 10 extracortical and 8 of 10 aperture fixed grafts survived 2,000 cycles between 50 and 300 N.
  
  
  CONCLUSIONS
  The results of this study suggest that a rounded posterior aspect of the tunnel exit at the tibial tunnel exit leads to significant less graft damage when compared to the typical sharp edge of the bone tunnel exit ("killer turn"). Additionally, the results show that aperture fixation of soft tissue grafts in PCL reconstruction is superior when compared to an extracortical fixation site.
  
  
  CONCLUSIONS
  Aperture fixation and a rounded tibial bone tunnel exit seem to be a reasonable alternative in PCL reconstruction.
authors.affiliation: Department of Trauma, Hand, and Reconstructive Surgery, Westfalian Wilhelms University, Muenster, Germany. Andre.Weimann@ukmuenster.de
authors.forename: Andre
authors.initials: A
authors.lastname: Weimann
authors.forename: Alexandra
authors.initials: A
authors.lastname: Wolfert
authors.forename: Thore
authors.initials: T
authors.lastname: Zantop
authors.forename: Anne-Kathleen
authors.initials: AK
authors.lastname: Eggers
authors.forename: Michael
authors.initials: M
authors.lastname: Raschke
authors.forename: Wolf
authors.initials: W
authors.lastname: Petersen
mesh_terms: D000818:Animals; D066298:In Vitro Techniques; D019637:Orthopedic Procedures / Q000379:methods*; D016119:Posterior Cruciate Ligament / Q000601:surgery*; D019651:Plastic Surgery Procedures / Q000379:methods*; D013314:Stress, Mechanical; D034421:Sus scrofa; D013977:Tibia / Q000601:surgery*