title: An In Vitro Robotic Assessment of the Anterolateral Ligament, Part 2: Anterolateral Ligament Reconstruction Combined With Anterior Cruciate Ligament Reconstruction.
abstract: BACKGROUND
  Recent biomechanical studies have demonstrated that an extra-articular lateral knee structure, most recently referred to as the anterolateral ligament (ALL), contributes to overall rotational stability of the knee. However, the effect of anatomic ALL reconstruction (ALLR) in the setting of anterior cruciate ligament (ACL) reconstruction (ACLR) has not been biomechanically investigated or validated.
  
  
  OBJECTIVE
  The purpose of this study was to investigate the biomechanical function of anatomic ALLR in the setting of a combined ACL and ALL injury. More specifically, this investigation focused on the effect of ALLR on resultant rotatory stability when performed in combination with concomitant ACLR. It was hypothesized that ALLR would significantly reduce internal rotation and axial plane translation laxity during a simulated pivot-shift test compared with isolated ACLR.
  
  
  METHODS
  Controlled laboratory study.
  
  
  METHODS
  Ten fresh-frozen cadaveric knees were evaluated with a 6 degrees of freedom robotic system. Knee kinematics were evaluated with simulated clinical examinations including a simulated pivot-shift test consisting of coupled 10-N·m valgus and 5-N·m internal rotation torques, a 5-N·m internal rotation torque, and an 88-N anterior tibial load. Kinematic differences between ACLR with an intact ALL, ACLR with ALLR, and ACLR with a deficient ALL were compared with the intact state. Single-bundle ACLR tunnels and ALLR tunnels were placed anatomically according to previous quantitative anatomic attachment descriptions.
  
  
  RESULTS
  Combined anatomic ALLR and ACLR significantly improved the rotatory stability of the knee compared with isolated ACLR in the face of a concurrent ALL deficiency. During a simulated pivot-shift test, ALLR significantly reduced internal rotation and axial plane tibial translation when compared with ACLR with an ALL deficiency. Isolated ACLR for the treatment of a combined ACL and ALL injury was not able to restore stability of the knee, resulting in a significant increase in residual internal rotation laxity. ALLR did not affect anterior tibial translation; no significant differences were observed between the varying ALL conditions with ACLR except between ACLR with an intact ALL and ACLR with a deficient ALL at 0° of flexion.
  
  
  CONCLUSIONS
  In the face of a combined ACL and ALL deficiency, concurrent ACLR and ALLR significantly improved the rotatory stability of the knee compared with solely reconstructing the ACL.
  
  
  CONCLUSIONS
  Significant increases in residual internal rotation and laxity during the pivot-shift test may exist in both acute and chronic settings of an ACL deficiency and in patients treated with isolated ACLR for a combined ACL and ALL deficiency. For this subset of patients, surgical treatment of the ALL, in addition to ACLR, should be considered to restore knee stability.
authors.affiliation: Steadman Philippon Research Institute, Vail, Colorado, USA.
authors.forename: Marco
authors.initials: M
authors.lastname: Nitri
authors.affiliation: Steadman Philippon Research Institute, Vail, Colorado, USA.
authors.forename: Matthew T
authors.initials: MT
authors.lastname: Rasmussen
authors.affiliation: Steadman Philippon Research Institute, Vail, Colorado, USA.
authors.forename: Brady T
authors.initials: BT
authors.lastname: Williams
authors.affiliation: Steadman Philippon Research Institute, Vail, Colorado, USA.
authors.forename: Samuel G
authors.initials: SG
authors.lastname: Moulton
authors.affiliation: Steadman Philippon Research Institute, Vail, Colorado, USA.
authors.forename: Raphael Serra
authors.initials: RS
authors.lastname: Cruz
authors.affiliation: Steadman Philippon Research Institute, Vail, Colorado, USA.
authors.forename: Grant J
authors.initials: GJ
authors.lastname: Dornan
authors.affiliation: Steadman Philippon Research Institute, Vail, Colorado, USA.
authors.forename: Mary T
authors.initials: MT
authors.lastname: Goldsmith
authors.affiliation: Steadman Philippon Research Institute, Vail, Colorado, USA The Steadman Clinic, Vail, Colorado, USA drlaprade@sprivail.org.
authors.forename: Robert F
authors.initials: RF
authors.lastname: LaPrade
mesh_terms: D000328:Adult; D016118:Anterior Cruciate Ligament / Q000502:physiology / Q000601:surgery; D000070598:Anterior Cruciate Ligament Injuries; D059549:Anterior Cruciate Ligament Reconstruction / Q000379:methods*; D001696:Biomechanical Phenomena / Q000502:physiology; D002102:Cadaver; D006801:Humans; D007593:Joint Instability / Q000601:surgery; D007719:Knee Joint / Q000502:physiology / Q000601:surgery; D008023:Ligaments, Articular / Q000293:injuries / Q000502:physiology / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D010808:Physical Examination / Q000379:methods; D016059:Range of Motion, Articular / Q000502:physiology; D065287:Robotic Surgical Procedures; D012399:Rotation; D013977:Tibia / Q000601:surgery; D019415:Torque
keywords: anterior cruciate ligament; anterolateral ligament; pivot shift; reconstruction; robotics; rotational instability