title: Effect of femoral socket position on graft impingement after anterior cruciate ligament reconstruction.
abstract: BACKGROUND
  Despite improved biomechanical stability and kinematics with anatomic anterior cruciate ligament (ACL) reconstruction, concerns regarding notch impingement of the graft have persisted, particularly with increasingly anterior tibial tunnel position. The potentially mitigating effect of anatomic femoral socket position, however, has not been evaluated.
  
  
  OBJECTIVE
  Placement of the femoral socket in the central or posterolateral bundle footprint reduces the risk and magnitude of graft impingement after ACL reconstruction compared with placement in the anteromedial bundle footprint.
  
  
  METHODS
  Controlled laboratory study.
  
  
  METHODS
  This study employed computer-assisted navigation in a cadaveric model to evaluate the effect of tibial and femoral tunnel position on ACL graft impingement. Sixteen cadaveric knees were tested using the Praxim ACL Surgetics Navigation System, with the tibial tunnel positioned in the footprint of the anteromedial bundle and the femoral socket placed in the (1) anteromedial bundle footprint, (2) center of footprint, or (3) posterolateral bundle footprint. The amount of maximum impingement, angle of initial impingement, and location of graft impingement were documented through a full arc of knee motion.
  
  
  RESULTS
  Impingement occurred with all 3 femoral socket positions, but the mean angle of impingement with the anteromedial femoral position (42.8° ± 26.4°) was significantly greater (P < .003) than the mean angles of impingement with the central femoral position (19.4° ± 19.2°) and the posterolateral bundle femoral position (16.7° ± 13.3°).
  
  
  CONCLUSIONS
  Although notch impingement was seen in all femoral socket locations with an anteromedial tibial socket position, femoral socket position in a central or posterolateral bundle location may reduce the risk and magnitude of graft impingement after ACL reconstruction. Additional studies are necessary to determine the influence of these different constructs on graft isometry and knee kinematics.
  
  
  CONCLUSIONS
  Anatomic femoral socket position in the center of the native ACL footprint may reduce the risk and magnitude of notch impingement compared with an anteromedial bundle position with ACL reconstruction.
authors.affiliation: Hospital for Special Surgery, New York, New York, USA.
authors.forename: Travis G
authors.initials: TG
authors.lastname: Maak
authors.forename: Asheesh
authors.initials: A
authors.lastname: Bedi
authors.forename: Bradley S
authors.initials: BS
authors.lastname: Raphael
authors.forename: Musa
authors.initials: M
authors.lastname: Citak
authors.forename: Eduardo M
authors.initials: EM
authors.lastname: Suero
authors.forename: Thomas
authors.initials: T
authors.lastname: Wickiewicz
authors.forename: Andrew D
authors.initials: AD
authors.lastname: Pearle
mesh_terms: D000328:Adult; D000368:Aged; D016118:Anterior Cruciate Ligament / Q000502:physiology*; D000070598:Anterior Cruciate Ligament Injuries; D006801:Humans; D007718:Knee Injuries / Q000601:surgery*; D007719:Knee Joint / Q000502:physiology*; D008875:Middle Aged; D011183:Postoperative Complications / Q000209:etiology*