title: Comparison of anterior cruciate ligament tunnel position and graft obliquity with transtibial and anteromedial portal femoral tunnel reaming techniques using high-resolution magnetic resonance imaging.
abstract: OBJECTIVE
  Using 3-dimensional high-resolution magnetic resonance imaging (MRI), we sought to compare femoral and tibial tunnel position and resultant graft obliquity with single-bundle anterior cruciate ligament (ACL) reconstruction using transtibial (TT) or anteromedial (AM) portal femoral tunnel reaming techniques.
  
  
  METHODS
  Thirty patients were prospectively enrolled after primary, autogenous bone-patellar tendon-bone ACL reconstruction by 2 groups of high-volume, fellowship-trained sports medicine surgeons. With the TT technique, an external starting point was used to maximize graft obliquity and femoral footprint capture. By use of high-resolution MRI and imaging analysis software, bilateral 3-dimensional knee models were created, mirrored, and superimposed. Differences between centroids for each femoral and tibial insertion, as well as corresponding ACL/graft obliquity, were evaluated with paired t tests and 2-sided Mann-Whitney nonparametric tests, with P < .05 defined as significant.
  
  
  RESULTS
  No significant differences were observed between groups in position of reconstructed femoral footprints. However, on the tibial side, AM centroids averaged 0.8 ± 1.9 mm anterior to native ACL centroids, whereas the TT group centered 5.23 ± 2.4 mm posterior to native ACL centroids (P < .001). Sagittal obliquity was closely restored with the AM technique (mean, 52.2° v. 53.5° for native ACL) but was significantly more vertical (mean, 66.9°) (P = .0001) for the TT group.
  
  
  CONCLUSIONS
  In this clinical series, AM portal femoral tunnel reaming more accurately restored native ACL anatomy than the TT technique. Although both techniques can capture the native femoral footprint with similar accuracy, the TT technique requires significantly greater posterior placement of the tibial tunnel, resulting in decreased sagittal graft obliquity. When a tibial tunnel is drilled without the need to accommodate subsequent femoral tunnel reaming, more accurate tibial tunnel position and resultant sagittal graft obliquity are achieved.
  
  
  METHODS
  Level III, retrospective comparative study.
authors.affiliation: Sports Medicine and Shoulder Service, Hospital for Special Surgery, New York, New York, USA.
authors.forename: Andrea L
authors.initials: AL
authors.lastname: Bowers
authors.forename: Asheesh
authors.initials: A
authors.lastname: Bedi
authors.forename: Joseph D
authors.initials: JD
authors.lastname: Lipman
authors.forename: Hollis G
authors.initials: HG
authors.lastname: Potter
authors.forename: Scott A
authors.initials: SA
authors.lastname: Rodeo
authors.forename: Andrew D
authors.initials: AD
authors.lastname: Pearle
authors.forename: Russell F
authors.initials: RF
authors.lastname: Warren
authors.forename: David W
authors.initials: DW
authors.lastname: Altchek
mesh_terms: D016118:Anterior Cruciate Ligament / Q000033:anatomy & histology* / Q000601:surgery; D000070598:Anterior Cruciate Ligament Injuries; D059549:Anterior Cruciate Ligament Reconstruction / Q000379:methods*; D006801:Humans; D007718:Knee Injuries / Q000601:surgery*; D007719:Knee Joint / Q000033:anatomy & histology* / Q000601:surgery; D008279:Magnetic Resonance Imaging; D012189:Retrospective Studies; D013710:Tendons / Q000637:transplantation*; D016896:Treatment Outcome