title: Variations in morphological characteristics of prostheses for total knee arthroplasty leading to kinematic differences.
abstract: OBJECTIVE
  The aim of this study is to compare kinematics during weight-bearing deep knee-bending motion in patients after bilateral total knee arthroplasty (TKA) of two types: 1) a conventional ScorpioFlex prosthesis and 2) a contemporary redesigned non-restrictive-geometry (NRG) prosthesis installed by the same surgeon.
  
  
  METHODS
  We enrolled 15 patients who underwent conventional ScorpioFlex posterior-stabilised TKA in one knee and contemporary NRG TKA on the contralateral side (the same surgeon). During fluoroscopic examination, each patient performed weight-bearing deep knee bending. Motions among all components were analysed using a two- to three-dimensional registration technique.
  
  
  RESULTS
  The mean maximum flexion was 108° (SD 8) and 120° (SD 9) after ScorpioFlex and NRG TKAs, respectively; there were statistically significant differences between the groups. From extension to maximal flexion, the medial condyle translated by 4.8mm (SD 1.2) and 5.4mm (SD 2.4) posteriorly after ScorpioFlex TKA and NRG TKA, respectively. The lateral femoral condyle moved 8.4mm (SD 1.5) and 12.2mm (SD 2.1) posteriorly after ScorpioFlex TKA and NRG TKA, respectively. There were no significant differences in medial condyle translation between the groups except for the lateral condyle. The total amount of tibial axial rotation during extension to flexion was 5.1° (SD 1.8) after ScorpioFlex and 13.2° (SD 3.4) after NRG TKAs; there were statistically significant differences between the groups.
  
  
  CONCLUSIONS
  NRG resulted in much better maximum flexion, lateral condyle movement and tibial internal rotation than did ScorpioFlex TKAs. The observed kinematic differences are most likely caused by variations in the morphological characteristics of the two implants.
authors.affiliation: Orthopaedic Department, West China Hospital, Sichuan University, 37 Guo-xue Lane, Wu-hou District, Chengdu, China.
authors.forename: Xiaojun
authors.initials: X
authors.lastname: Shi
authors.affiliation: Orthopaedic Department, West China Hospital, Sichuan University, 37 Guo-xue Lane, Wu-hou District, Chengdu, China.
authors.forename: Zongke
authors.initials: Z
authors.lastname: Zhou
authors.affiliation: Orthopaedic Department, West China Hospital, Sichuan University, 37 Guo-xue Lane, Wu-hou District, Chengdu, China.
authors.forename: Bin
authors.initials: B
authors.lastname: Shen
authors.affiliation: Orthopaedic Department, West China Hospital, Sichuan University, 37 Guo-xue Lane, Wu-hou District, Chengdu, China.
authors.forename: Jing
authors.initials: J
authors.lastname: Yang
authors.affiliation: Orthopaedic Department, West China Hospital, Sichuan University, 37 Guo-xue Lane, Wu-hou District, Chengdu, China.
authors.forename: Pengde
authors.initials: P
authors.lastname: Kang
authors.affiliation: Orthopaedic Department, West China Hospital, Sichuan University, 37 Guo-xue Lane, Wu-hou District, Chengdu, China. Electronic address: peifuxing@yeah.net.
authors.forename: Fuxing
authors.initials: F
authors.lastname: Pei
mesh_terms: D000368:Aged; D019645:Arthroplasty, Replacement, Knee / Q000295:instrumentation* / Q000379:methods; D001696:Biomechanical Phenomena / Q000502:physiology*; D005260:Female; D006801:Humans; D007719:Knee Joint / Q000503:physiopathology* / Q000601:surgery; D007720:Knee Prosthesis; D008297:Male; D008875:Middle Aged; D020370:Osteoarthritis, Knee / Q000503:physiopathology / Q000601:surgery*; D011446:Prospective Studies; D011474:Prosthesis Design; D016059:Range of Motion, Articular / Q000502:physiology*; D016474:Weight-Bearing / Q000502:physiology
keywords: Fixed bearing; Fluoroscopic analysis; Kinematics; Total knee arthroplasty