title: Effects of bone block position and orientation within the tibial tunnel for posterior cruciate ligament graft reconstructions: a cyclic loading study of bone-patellar tendon-bone allografts.
abstract: BACKGROUND
  Posterior laxity occurring after posterior cruciate ligament reconstruction with a tibial tunnel could be related to thinning and permanent elongation of the graft as it is cyclically loaded in vivo.
  
  
  OBJECTIVE
  The orientation and position of the bone block within the tibial tunnel will have a significant effect on thinning and elongation of the graft after cyclic loading.
  
  
  METHODS
  Controlled laboratory study.
  
  
  METHODS
  In test series 1 (27 fresh-frozen graft pairs), all bone blocks were positioned flush with the posterior opening of the tibial tunnel; 1 graft was oriented with the bone block facing posteriorly, whereas its pair was tested with the bone block facing anteriorly. In test series 2 (20 graft pairs), all grafts were oriented with the bone block facing posteriorly; 1 graft had the bone block positioned flush with the posterior tunnel opening, whereas its pair was tested with the bone block recessed 1 cm from the posterior opening.
  
  
  RESULTS
  In series 1, 3 of 27 grafts with posterior bone block orientations failed at the tunnel edge before 2000 cycles of testing could be completed; all specimens with anterior bone block placements survived the testing intact. In series 2, 3 of 20 grafts with recessed bone blocks failed at the tunnel edge, whereas all those with flush bone blocks survived.
  
  
  CONCLUSIONS
  The best position for the bone block of a bone-patellar tendon-bone graft was flush with the posterior tunnel opening with the bone block facing anteriorly in the tibial tunnel.
authors.affiliation: Biomechanics Research Section, David Geffen School of Medicine at UCLA, University of California, Los Angeles, Los Angeles, California 90095-6902, USA.
authors.forename: Keith
authors.initials: K
authors.lastname: Markolf
authors.forename: Mark
authors.initials: M
authors.lastname: Davies
authors.forename: Bojan
authors.initials: B
authors.lastname: Zoric
authors.forename: David
authors.initials: D
authors.lastname: McAllister
mesh_terms: D000328:Adult; D001642:Bicycling; D002102:Cadaver; D006801:Humans; D008297:Male; D008875:Middle Aged; D019637:Orthopedic Procedures / Q000379:methods*; D010329:Patella / Q000601:surgery; D016119:Posterior Cruciate Ligament / Q000293:injuries* / Q000601:surgery*; D011475:Prosthesis Failure; D019651:Plastic Surgery Procedures / Q000379:methods*; D013710:Tendons / Q000637:transplantation*; D013977:Tibia / Q000601:surgery; D016474:Weight-Bearing