title: Proximal tibial fracture following anterior cruciate ligament reconstruction surgery: a biomechanical analysis of the tibial tunnel as a stress riser.
abstract: OBJECTIVE
  This is the first biomechanical study to examine the potential stress riser effect of the tibial tunnel or tunnels after ACL reconstruction surgery. In keeping with literature, the primary hypothesis tested in this study was that the tibial tunnel acts as a stress riser for fracture propagation. Secondary hypotheses were that the stress riser effect increases with the size of the tunnel (8 vs. 10 mm), the orientation of the tunnel [standard (STT) vs. modified transtibial (MTT)], and with the number of tunnels (1 vs. 2).
  
  
  METHODS
  Tibial tunnels simulating both single bundle hamstring graft (8 mm) and bone-patellar tendon-bone graft (10 mm) either STT or MTT position, as well as tunnels simulating double bundle (DB) ACL reconstruction (7, 6 mm), were drilled in fourth-generation saw bones. These five experimental groups and a control group consisting of native saw bones without tunnels were loaded to failure on a Materials Testing System to simulate tibial plateau fracture.
  
  
  RESULTS
  There were no statistically significant differences in peak load to failure between any of the groups, including the control group. The fracture occurred through the tibial tunnel in 100 % of the MTT tunnels (8 and 10 mm) and 80 % of the DB tunnels specimens; however, the fractures never (0 %) occurred through the tibial tunnel of the standard tunnels (8 or 10 mm) (P = 0.032).
  
  
  CONCLUSIONS
  In the biomechanical model, the tibial tunnel does not appear to be a stress riser for fracture propagation, despite suggestions to the contrary in the literature. Use of a standard, more vertical tunnel decreases the risk of ACL graft compromise in the event of a fracture. This may help to inform surgical decision making on ACL reconstruction technique.
authors.affiliation: Department of Orthopaedic Surgery, McGill University, Montreal, QC, Canada.
authors.forename: Wassim
authors.initials: W
authors.lastname: Aldebeyan
authors.affiliation: Department of Orthopaedic Surgery, McGill University, Montreal, QC, Canada. antony.liddell@outlook.com.
authors.forename: Antony
authors.initials: A
authors.lastname: Liddell
authors.affiliation: Orthopaedic Research Laboratory, McGill University, Montreal, QC, Canada.
authors.forename: Thomas
authors.initials: T
authors.lastname: Steffen
authors.affiliation: Orthopaedic Research Laboratory, McGill University, Montreal, QC, Canada.
authors.forename: Lorne
authors.initials: L
authors.lastname: Beckman
authors.affiliation: Department of Orthopaedic Surgery, McGill University, Montreal, QC, Canada.
authors.forename: Paul A
authors.initials: PA
authors.lastname: Martineau
mesh_terms: D059549:Anterior Cruciate Ligament Reconstruction / Q000009:adverse effects* / Q000379:methods; D001696:Biomechanical Phenomena; D006801:Humans; D008953:Models, Anatomic; D013977:Tibia / Q000503:physiopathology / Q000601:surgery; D013978:Tibial Fractures / Q000209:etiology / Q000503:physiopathology*
keywords: Anterior cruciate ligament reconstruction; Biomechanical; Fracture; Stress riser