title: ACL substitution may improve kinematics of PCL-retaining total knee arthroplasty.
abstract: OBJECTIVE
  One of the key factors responsible for altered kinematics and joint stability following contemporary total knee arthroplasty (TKA) is resection of the anterior cruciate ligament (ACL). However, ACL retention can present several technical challenges, and in some cases may not be viable due to an absent or nonfunctional ACL. Therefore, the goal of this research was to investigate whether substitution of the ACL through an anterior post mechanism could improve kinematic deficits of contemporary posterior cruciate ligament (PCL) retaining implants.
  
  
  METHODS
  Kinematic analysis of different implant types was done using KneeSIM, a previously established dynamic simulation tool. Walking, stair-ascent, chair-sit, and deep knee bend were simulated for an ACL-substituting (PCL-retaining) design, a bi-cruciate-retaining and ACL-sacrificing (PCL-retaining) implant, as well as the native knee. The motion of the femoral condyles relative to the tibia was recorded for kinematic comparisons.
  
  
  RESULTS
  The ACL-substituting and ACL-retaining implants provided similar kinematic improvements over the ACL-sacrificing implant, by reducing posterior femoral shift in extension and preventing paradoxical anterior sliding. During all simulated activities, the ACL-sacrificing implant showed between 7 and 8 mm of posterior shift in extension in contrast to the ACL-retaining implant and the ACL-substituting design, which showed overall kinematic trends similar to the native knee.
  
  
  CONCLUSIONS
  The absence of ACL function has been linked to abnormal kinematics and joint stability in patients with contemporary TKA. ACL-substituting implants could be a valuable treatment option capable of overcoming the limitations of contemporary TKA, particularly when retaining the native ACL is not feasible or is challenging.
authors.affiliation: Department of Orthopaedic Surgery, Technology Implementation Research Center, Massachusetts General Hospital, 55 Fruit St, GRJ-1223, Boston, MA, 02114, USA.|Institute for Biomechanics, ETH Zurich, Hönggerbergring 64, 8093, Zurich, Switzerland.
authors.forename: Thomas
authors.initials: T
authors.lastname: Zumbrunn
authors.affiliation: Department of Orthopaedic Surgery, Technology Implementation Research Center, Massachusetts General Hospital, 55 Fruit St, GRJ-1223, Boston, MA, 02114, USA.
authors.forename: Michael P
authors.initials: MP
authors.lastname: Duffy
authors.affiliation: Department of Orthopaedic Surgery, Technology Implementation Research Center, Massachusetts General Hospital, 55 Fruit St, GRJ-1223, Boston, MA, 02114, USA.
authors.forename: Harry E
authors.initials: HE
authors.lastname: Rubash
authors.affiliation: Department of Orthopaedic Surgery, Technology Implementation Research Center, Massachusetts General Hospital, 55 Fruit St, GRJ-1223, Boston, MA, 02114, USA.
authors.forename: Henrik
authors.initials: H
authors.lastname: Malchau
authors.affiliation: Department of Orthopaedic Surgery, Technology Implementation Research Center, Massachusetts General Hospital, 55 Fruit St, GRJ-1223, Boston, MA, 02114, USA.
authors.forename: Orhun K
authors.initials: OK
authors.lastname: Muratoglu
authors.affiliation: Department of Orthopaedic Surgery, Technology Implementation Research Center, Massachusetts General Hospital, 55 Fruit St, GRJ-1223, Boston, MA, 02114, USA. kmangudivaradarajan@mgh.harvard.edu.
authors.forename: Kartik Mangudi
authors.initials: KM
authors.lastname: Varadarajan
mesh_terms: D016118:Anterior Cruciate Ligament / Q000601:surgery*; D019645:Arthroplasty, Replacement, Knee / Q000379:methods*; D001696:Biomechanical Phenomena; D003198:Computer Simulation; D006801:Humans; D007593:Joint Instability / Q000209:etiology / Q000517:prevention & control*; D007719:Knee Joint / Q000503:physiopathology / Q000601:surgery*; D008953:Models, Anatomic; D016119:Posterior Cruciate Ligament / Q000601:surgery*; D011183:Postoperative Complications / Q000517:prevention & control*; D016059:Range of Motion, Articular; D016896:Treatment Outcome
keywords: ACL substitution; Dynamic simulation; Kinematics; Total knee arthroplasty