title: Geometric variable designs of cam/post mechanisms influence the kinematics of knee implants.
abstract: OBJECTIVE
  Reproducing the femoral rollback through specially designed mechanism in knee implants is required to achieve full knee function in total knee arthroplasty. Most contemporary implants use cam/post mechanism to replace the function of Posterior Cruciate Ligament. This study was aimed to determine the most appropriate cam and post designs to produce normal femoral rollback of the knee.
  
  
  METHODS
  Three different cams (triangle, ellipse, and circle) and three different posts (straight, convex, concave) geometries were considered in this study and were analysed using kinematic analyses. Femoral rollback did not occur until reaching 50° of knee flexion. Beyond this angle, two of the nine combinations demonstrate poor knee flexion and were eliminated from the study.
  
  
  RESULTS
  The combination of circle cam with concave post, straight post and convex post showed 15.6, 15.9 and 16.1 mm posterior translation of the femur, respectively. The use of ellipse cam with convex post and straight post demonstrated a 15.3 and 14.9 mm femoral rollback, whilst the combination of triangle cam with convex post and straight post showed 16.1 and 15.8 mm femoral rollback, respectively.
  
  
  CONCLUSIONS
  The present study demonstrates that the use of circle cam and convex post created the best femoral rollback effect which in turn produces the highest amount of knee flexion. The findings of the study suggest that if the design is applied for knee implants, superior knee flexion may be possible for future patients.
  
  
  METHODS
  IV.
authors.affiliation: Medical Devices & Technology Group (MEDITEG), Faculty of Biosciences and Medical Engineering, Universiti Teknologi Malaysia, 81310, Johor Bahru, Johor, Malaysia.
authors.forename: Ali
authors.initials: A
authors.lastname: Fallahiarezoodar
authors.forename: Mohammed Rafiq
authors.initials: MR
authors.lastname: Abdul Kadir
authors.forename: Mina
authors.initials: M
authors.lastname: Alizadeh
authors.forename: Sangeetha Vasudevaraj
authors.initials: SV
authors.lastname: Naveen
authors.forename: T
authors.initials: T
authors.lastname: Kamarul
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D019645:Arthroplasty, Replacement, Knee / Q000295:instrumentation*; D001696:Biomechanical Phenomena; D003198:Computer Simulation; D005260:Female; D005269:Femur / Q000503:physiopathology / Q000601:surgery*; D006801:Humans; D021621:Imaging, Three-Dimensional; D007719:Knee Joint / Q000503:physiopathology / Q000601:surgery*; D007720:Knee Prosthesis; D008297:Male; D011474:Prosthesis Design; D016059:Range of Motion, Articular; D013977:Tibia / Q000503:physiopathology / Q000601:surgery