title: Effect of Different Preconditioning Protocols on Anterior Knee Laxity After ACL Reconstruction with Four Commonly Used Grafts.
abstract: BACKGROUND
  It is currently unknown if preconditioning an anterior cruciate ligament (ACL) graft prior to fixation is helpful in eliminating possible increases in anterior knee laxity. The purpose of this study was to measure cyclic increases in anterior tibial translation of four commonly used graft tissues subjected to four preconditioning protocols.
  
  
  METHODS
  A robotic system was used to apply 250 cycles of anteroposterior force (134 N of anterior force followed by 134 N of posterior force) to ten intact knees (ACL controls) and then to a single knee reconstructed, for separate tests, with bone-patellar tendon-bone, bone-Achilles tendon, hamstring tendon, and tibialis tendon grafts following (1) no preconditioning, (2) preconditioning on a tension board (89 N of initial force held for twenty minutes), (3) preconditioning in situ (89 N of force applied to the tibial end of the graft during twenty-five flexion-extension cycles), and (4) a combination of protocols 2 and 3.
  
  
  RESULTS
  Over the 250 cycles, all grafts were associated with a progressive increase in anterior tibial translation that was approximately an order of magnitude greater than that of the ACL, and preconditioning had no significant effect on this increase in translation. There were some significant differences in the progressive anterior tibial translation increase among the graft tissues within a given preconditioning protocol, but these differences were no greater than 1.1 mm. First-cycle and cycle-250 anterior tibial translation varied among the graft tissue types, possibly reflecting an initial "settling in" process. Regardless of the tissue type, ≥75% of the total increase in the anterior tibial translation occurred within the first 125 cycles.
  
  
  CONCLUSIONS
  Preconditioning had no significant effect on the progressive increase of anterior tibial translation from the first cycle to cycle 250 for any of the graft tissues tested.
  
  
  CONCLUSIONS
  On the basis of these results, current preconditioning methods appear to be ineffective in reducing progressive increases in anterior knee laxity from cyclic loading.
authors.affiliation: UCLA Rehabilitation Center, 1000 Veteran Avenue, Los Angeles, CA 90095.
authors.forename: Daniel V
authors.initials: DV
authors.lastname: Boguszewski
authors.affiliation: UCLA Rehabilitation Center, 1000 Veteran Avenue, Los Angeles, CA 90095.
authors.forename: Nirav B
authors.initials: NB
authors.lastname: Joshi
authors.affiliation: UCLA Orthopaedic Surgery, 1250 16th Street, Suite 3142, Santa Monica, CA 90404.
authors.forename: Dean
authors.initials: D
authors.lastname: Wang
authors.affiliation: UCLA Rehabilitation Center, 1000 Veteran Avenue, Los Angeles, CA 90095.
authors.forename: Keith L
authors.initials: KL
authors.lastname: Markolf
authors.affiliation: UCLA Orthopaedic Surgery, 76-143 CHS, 10833 Le Conte Avenue, Los Angeles, CA 90095.
authors.forename: Frank A
authors.initials: FA
authors.lastname: Petrigliano
authors.affiliation: UCLA Orthopaedic Surgery, 76-143 CHS, 10833 Le Conte Avenue, Los Angeles, CA 90095.
authors.forename: David R
authors.initials: DR
authors.lastname: McAllister
mesh_terms: D000293:Adolescent; D000328:Adult; D059549:Anterior Cruciate Ligament Reconstruction / Q000009:adverse effects / Q000379:methods*; D064594:Bone-Patellar Tendon-Bone Grafts; D002102:Cadaver; D004548:Elasticity; D006801:Humans; D007593:Joint Instability / Q000209:etiology / Q000503:physiopathology / Q000517:prevention & control*; D007719:Knee Joint; D008875:Middle Aged; D011300:Preoperative Care; D016059:Range of Motion, Articular; D013710:Tendons / Q000637:transplantation*; D053656:Tenodesis; D013718:Tensile Strength; D046509:Tissue Culture Techniques; D055815:Young Adult