title: Eliminating impingement optimizes patellar biomechanics in high knee flexion.
abstract: BACKGROUND
  We investigated the impact of eliminating the impingement between extensor mechanism and tibial insert on patellar tracking and patellar ligament tension in high knee flexion.
  
  
  METHODS
  Six cadaveric specimens were tested on an Oxford-type testing rig. The Genesis II knee system was implanted into each specimen knee with the traditional tibial insert and high-flex insert successively. Compared to traditional insert, the high-flex insert was characterized with a chambered anterior post and a chambered anterior lip which eliminates patella-post and patellar ligament-anterior lip impingements. The patella was tracked with an NDI Optotrak Certus system. The patellar ligament tension was measured using a NKB S-type tension transducer.
  
  
  RESULTS
  There was a decrease of resultant patellar translation relative to the femur with statistically significant (P<0.05) at 90 degrees to 150 degrees of knee flexion and a decrease of patellar ligament tension with statistical significance (P<0.05) at 100 degrees, 120 degrees, 130 degrees, and 140 degrees of flexion using high-flex insert compared to traditional insert.
  
  
  CONCLUSIONS
  Eliminating the impingement between extensor mechanism and implant in high knee flexion altered patellar tracking and reduced patellar ligament tension, which would facilitate high knee flexion.
authors.affiliation: Department of Orthopaedic Surgery, Beijing Jishuitan Hospital, Fourth Clinical College of Peking University, Beijing 100035, China.
authors.forename: Qi-heng
authors.initials: QH
authors.lastname: Tang
authors.forename: Yi-xin
authors.initials: YX
authors.lastname: Zhou
authors.forename: Jing
authors.initials: J
authors.lastname: Tang
authors.forename: Hong-yi
authors.initials: HY
authors.lastname: Shao
authors.forename: Guang-zhi
authors.initials: GZ
authors.lastname: Wang
mesh_terms: D001696:Biomechanical Phenomena; D006801:Humans; D066298:In Vitro Techniques; D007719:Knee Joint / Q000502:physiology*; D008023:Ligaments, Articular / Q000502:physiology*; D017847:Patellar Ligament / Q000502:physiology; D016059:Range of Motion, Articular / Q000502:physiology