title: Stress distribution is deviated around the aperture of the femoral tunnel in the anatomic anterior cruciate ligament reconstruction.
abstract: OBJECTIVE
  Final tunnel location in the anterior cruciate ligament (ACL) reconstruction is unpredictable due to tunnel widening and/or transposition. The mechanical stress around the tunnel aperture seems to be a major factor but is not fully investigated. The purpose of this study was to measure the stress from the ACL graft around the tunnel aperture when the ACL graft tension reaches its peak.
  
  
  METHODS
  Six cadaveric knees were used. Single-bundle ACL reconstruction was performed using a hamstrings graft. Both femoral and tibial tunnels were created at the centre of the original ACL footprint. A 7-mm-internal-diameter aluminium cylinder with pressure sensors was placed in the femoral tunnel. Hamstrings graft with a microtension sensor was inserted. After fixation, passive extension-flexion was performed while monitoring the tunnel aperture pressure and the graft tension simultaneously. The pressure on the femoral tunnel aperture when the ACL graft tension reach its peak was compared between four directions.
  
  
  RESULTS
  The ACL graft tension peaked (67 ± 49 N) at full extension (-5.8 ± 4.1°). Pressure at the femoral tunnel aperture was different between different directions (p < 0.01). Distal part had significantly larger pressure (1.7 ± 1.3 MPa) than the other directions (p < 0.01). Second largest pressure was carried in the anterior part (0.6 ± 0.5 MPa), followed by proximal and posterior parts (0.4 ± 0.3, 0.2 ± 0.2 MPa respectively).
  
  
  CONCLUSIONS
  The stress distribution at the femoral tunnel aperture is not equal in different directions, while the distal part dominantly bears the stress from the ACL graft. Surgeons should pay close attention to the distal edge of the femoral tunnel which should be inside the anatomic ACL footprint eventually.
authors.affiliation: Department of Orthopaedic Surgery, Kobe Kaisei Hospital, 11-15, Shinohara-Kitamachi, 3-chome, Nada-ku, Kobe, 657-0068, Japan. you.1.hoshino@gmail.com.
authors.forename: Yuichi
authors.identifier: http://orcid.org/0000-0001-6142-8973
authors.initials: Y
authors.lastname: Hoshino
authors.affiliation: Department of Orthopaedic Surgery, Graduate School of Medicine, Kobe University, Kobe, Japan.
authors.forename: Ryosuke
authors.initials: R
authors.lastname: Kuroda
authors.affiliation: Department of Orthopaedic Surgery, Graduate School of Medicine, Kobe University, Kobe, Japan.
authors.forename: Yuichiro
authors.initials: Y
authors.lastname: Nishizawa
authors.affiliation: Department of Orthopaedic Surgery, Graduate School of Medicine, Kobe University, Kobe, Japan.
authors.forename: Naoki
authors.initials: N
authors.lastname: Nakano
authors.affiliation: Department of Orthopaedic Surgery, Graduate School of Medicine, Kobe University, Kobe, Japan.
authors.forename: Kanto
authors.initials: K
authors.lastname: Nagai
authors.affiliation: Department of Orthopaedic Surgery, Graduate School of Medicine, Kobe University, Kobe, Japan.
authors.forename: Daisuke
authors.initials: D
authors.lastname: Araki
authors.affiliation: Department of Orthopaedic Surgery, Kobe Kaisei Hospital, 11-15, Shinohara-Kitamachi, 3-chome, Nada-ku, Kobe, 657-0068, Japan.
authors.forename: Shinya
authors.initials: S
authors.lastname: Oka
authors.affiliation: Department of Human and Artificial Intelligent Systems, Graduate School of Engineering, University of Fukui, Fukui, Japan.
authors.forename: Shogo
authors.initials: S
authors.lastname: Kawaguchi
authors.affiliation: Department of Human and Artificial Intelligent Systems, Graduate School of Engineering, University of Fukui, Fukui, Japan.
authors.forename: Kouki
authors.initials: K
authors.lastname: Nagamune
authors.affiliation: Department of Orthopaedic Surgery, Graduate School of Medicine, Kobe University, Kobe, Japan.
authors.forename: Masahiro
authors.initials: M
authors.lastname: Kurosaka
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D059549:Anterior Cruciate Ligament Reconstruction; D001696:Biomechanical Phenomena; D005260:Female; D005269:Femur / Q000601:surgery*; D000070633:Hamstring Muscles / Q000637:transplantation; D006801:Humans; D007719:Knee Joint / Q000601:surgery*; D008297:Male; D013314:Stress, Mechanical
keywords: Anatomic ACL reconstruction; Anterior cruciate ligament; Femoral tunnel; Graft tension; Hamstrings graft; Stress distribution