title: The Graft Bending Angle Can Affect Early Graft Healing After Anterior Cruciate Ligament Reconstruction: In Vivo Analysis With 2 Years' Follow-up.
abstract: BACKGROUND
  A high graft bending angle (GBA) after anterior cruciate ligament (ACL) reconstruction has been suggested to cause stress on the graft. Nevertheless, evidence about its effect on graft healing in vivo is limited.
  
  
  OBJECTIVE
  The signal intensity on magnetic resonance imaging (MRI) would be higher in the proximal region of the ACL graft, and higher signals would be correlated to a higher GBA.
  
  
  METHODS
  Descriptive laboratory study.
  
  
  METHODS
  Anatomic single-bundle ACL reconstruction was performed on 24 patients (mean age, 20 ± 4 years) using the transportal technique. A quadriceps tendon autograft with a bone plug was harvested. To evaluate graft healing, the signal/noise quotient (SNQ) was measured in 3 regions of interest (ROIs) of the proximal, midsubstance, and distal ACL graft using high-resolution MRI (0.45 × 0.45 × 0.70 mm), with decreased signals suggesting improved healing. Dynamic knee motion was examined during treadmill walking and running to assess the in vivo GBA. The GBA was calculated from the 3-dimensional angle between the graft and femoral tunnel vectors at each motion frame, based on tibiofemoral kinematics determined from dynamic stereo X-ray analysis. Graft healing and GBAs were assessed at 6 and 24 months postoperatively. Repeated-measures analysis of variance was used to compare the SNQ in the 3 ROIs at 2 time points. Pearson correlations were used to analyze the relationship between the SNQ and mean GBA during 0% to 15% of the gait cycle.
  
  
  RESULTS
  The SNQ of the ACL graft in the proximal region was significantly higher than in the midsubstance ( P = .022) and distal regions ( P < .001) at 6 months. The SNQ in the proximal region was highly correlated with the GBA during standing ( R = 0.64, P < .001), walking ( R = 0.65, P = .002), and running ( R = 0.54, P = .015) but not in the other regions. At 24 months, signals in the proximal and midsubstance regions decreased significantly compared with 6 months ( P < .001 and P = .008, respectively), with no difference across the graft area.
  
  
  CONCLUSIONS
  The signal intensity was highest in the proximal region and lowest in the distal region of the reconstructed graft at 6 months postoperatively. A steep GBA was significantly correlated with high signal intensities of the proximal graft in this early period. A steep GBA may negatively affect proximal graft healing after ACL reconstruction.
authors.affiliation: Department of Orthopaedic Surgery, University of Pittsburgh, Pittsburgh, Pennsylvania, USA.|Department of Orthopaedic Surgery, Kyushu University, Fukuoka, Japan.
authors.forename: Yasutaka
authors.initials: Y
authors.lastname: Tashiro
authors.affiliation: Department of Orthopaedic Surgery, University of Pittsburgh, Pittsburgh, Pennsylvania, USA.
authors.forename: Tom
authors.initials: T
authors.lastname: Gale
authors.affiliation: Department of Orthopaedic Surgery, University of Pittsburgh, Pittsburgh, Pennsylvania, USA.
authors.forename: Vani
authors.initials: V
authors.lastname: Sundaram
authors.affiliation: Department of Orthopaedic Surgery, University of Pittsburgh, Pittsburgh, Pennsylvania, USA.
authors.forename: Kanto
authors.initials: K
authors.lastname: Nagai
authors.affiliation: Department of Orthopaedic Surgery, University of Pittsburgh, Pittsburgh, Pennsylvania, USA.
authors.forename: James J
authors.initials: JJ
authors.lastname: Irrgang
authors.affiliation: Department of Orthopaedic Surgery, University of Pittsburgh, Pittsburgh, Pennsylvania, USA.
authors.forename: William
authors.initials: W
authors.lastname: Anderst
authors.affiliation: Department of Orthopaedic Surgery, Kyushu University, Fukuoka, Japan.
authors.forename: Yasuharu
authors.initials: Y
authors.lastname: Nakashima
authors.affiliation: Department of Orthopaedic Surgery, University of Pittsburgh, Pittsburgh, Pennsylvania, USA.|Department of Orthopaedic Surgery, University of Texas Health Science Center at Houston, Houston, Texas, USA.
authors.forename: Scott
authors.initials: S
authors.lastname: Tashman
authors.affiliation: Department of Orthopaedic Surgery, University of Pittsburgh, Pittsburgh, Pennsylvania, USA.
authors.forename: Freddie H
authors.initials: FH
authors.lastname: Fu
mesh_terms: D000293:Adolescent; D016118:Anterior Cruciate Ligament / Q000000981:diagnostic imaging* / Q000601:surgery; D059549:Anterior Cruciate Ligament Reconstruction / Q000379:methods*; D001696:Biomechanical Phenomena; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D013710:Tendons / Q000000981:diagnostic imaging; D014182:Transplantation, Autologous / Q000379:methods*; D014945:Wound Healing; D055815:Young Adult
keywords: MRI; anterior cruciate ligament; graft bending angle; graft healing; signal/noise quotient