title: Effect of tunnel position and graft size in single-bundle anterior cruciate ligament reconstruction: an evaluation of time-zero knee stability.
abstract: OBJECTIVE
  To determine whether (1) increased graft size with anatomic anterior cruciate ligament reconstruction (ACLR) would confer proportionally increased time-zero biomechanical stability and (2) larger grafts would compensate for the inferior time-zero biomechanical kinematics of nonanatomic, single-bundle ACLR.
  
  
  METHODS
  Ten cadaveric knees were allocated for single-bundle ACLR in an anatomic, center-center or nonanatomic, posterolateral-to-anteromedial footprint position with hamstring autograft. Medial arthrotomy defined the native anterior cruciate ligament (ACL) tibial and femoral footprints. ACLR was performed with a 6-mm semitendinosus graft in 6-mm tunnels and repeated with a 9-mm semitendinosus and gracilis graft in 9-mm tunnels for each knee. Lachman and instrumented pivot-shift examinations assessed knee stability in the ACL-intact, ACL-deficient, and ACLR conditions. Medial and lateral meniscectomies after ACL transection created reproducible pivot shifts. Significance was defined as P < .05.
  
  
  RESULTS
  ACLR in the center-center or posterolateral-to-anteromedial position significantly reduced anterior tibial translation compared with the ACL- and meniscus-deficient conditions (P < .001). Larger graft size, however, did not significantly improve time-zero biomechanical stability compared with a smaller graft in the same position for either reconstruction (P = .41 to .74). A center-center ACLR controlled tibial translation significantly better than a nonanatomic graft position regardless of graft size (P < .001). A smaller graft in the anatomic position controlled tibial translation significantly better than a larger graft in a nonanatomic position (P < .001).
  
  
  CONCLUSIONS
  This study showed that increasing graft size did not improve the time-zero biomechanical stability of the knee after ACLR. Increased graft size did not compensate for the biomechanical instability documented with the nonanatomic tunnel position. Restoration of native footprint anatomy in ACLR is of paramount importance regardless of graft size and source.
  
  
  CONCLUSIONS
  A larger graft size does not ameliorate the inferior time-zero biomechanics associated with nonanatomic tunnel preparation during single-bundle ACLR.
authors.affiliation: Computer-Assisted Surgery Laboratory and Sports Medicine and Shoulder Surgery Service, Hospital for Special Surgery, New York, New York, USA.
authors.forename: Asheesh
authors.initials: A
authors.lastname: Bedi
authors.forename: Travis
authors.initials: T
authors.lastname: Maak
authors.forename: Volker
authors.initials: V
authors.lastname: Musahl
authors.forename: Padhraig
authors.initials: P
authors.lastname: O'Loughlin
authors.forename: Dan
authors.initials: D
authors.lastname: Choi
authors.forename: Musa
authors.initials: M
authors.lastname: Citak
authors.forename: Andrew D
authors.initials: AD
authors.lastname: Pearle
mesh_terms: D059549:Anterior Cruciate Ligament Reconstruction / Q000379:methods*; D001696:Biomechanical Phenomena; D006801:Humans; D007593:Joint Instability / Q000209:etiology / Q000517:prevention & control*; D007719:Knee Joint / Q000502:physiology / Q000503:physiopathology* / Q000601:surgery; D009929:Organ Size; D011183:Postoperative Complications / Q000517:prevention & control*; D013710:Tendons / Q000033:anatomy & histology / Q000637:transplantation*; D013997:Time Factors