title: Knee kinetics and kinematics: What are the effects of TKA malconfigurations?
abstract: OBJECTIVE
  Total knee arthroplasty (TKA) is a very successful surgical procedure. However, implant failures and patient dissatisfaction still persist. Sometimes surgeons are not able to understand and explain these negative performances because the patient's medical images "look good", but the patient "feels bad". Apart from radiograph imaging and clinical outcome scores, conventionally used follow-up methods are mainly based on the analysis of knee kinematics. However, even if kinematics remains close to the "normal" range of motion, the patient may still complain about pain and functional limitations. To provide more insight into this paradox, a better quantitative understanding of TKA mechanics must be developed. For this purpose, improved techniques for clinical follow-up, combining kinetics and kinematics analysis, should be introduced to help surgeons to assess and understand TKA performance.
  
  
  METHODS
  An analysis on four TKA designs was performed, and the changes in kinematics and in kinetics induced by several implant configurations (simulating implant malalignment and different knee anatomy) were compared. More specifically, analysed tibio-femoral and patello-femoral contact forces and tibio-femoral kinematics were analysed during a squat task up to 120°.
  
  
  RESULTS
  The results from this study show that contact forces (with changes up to 67 %) are more heavily affected by malconfigurations than kinematics, for which maximum deviations are of the order of 5 mm or 5°, similar to the simulated surgical errors. The results present a similar trend for the different designs.
  
  
  CONCLUSIONS
  The results confirm the hypothesis that kinematics is not the only and also not the most relevant parameter to predict or explain knee function after TKA. In the future, techniques to analyse knee kinetics should be integrated in the clinical follow-up.
authors.affiliation: IRCCS Istituto Ortopedico Galeazzi, Via R. Galeazzi 4, 20161, Milan, Italy. silvia.pianigiani84@gmail.com.
authors.forename: Silvia
authors.initials: S
authors.lastname: Pianigiani
authors.affiliation: Biomechanics Section, KU Leuven, Celestijnenlaan 300C, 3001, Louvain, Belgium.
authors.forename: Luc
authors.initials: L
authors.lastname: Labey
authors.affiliation: IRCCS Istituto Ortopedico Galeazzi, Via R. Galeazzi 4, 20161, Milan, Italy.
authors.forename: Walter
authors.initials: W
authors.lastname: Pascale
authors.affiliation: BEAMS Department, Université Libre de Bruxelles, Avenue Roosevelt 50, 1050, Brussels, Belgium.
authors.forename: Bernardo
authors.initials: B
authors.lastname: Innocenti
mesh_terms: D000368:Aged; D019645:Arthroplasty, Replacement, Knee / Q000592:standards*; D001696:Biomechanical Phenomena; D017760:Bone Malalignment; D005269:Femur / Q000601:surgery; D006801:Humans; D007719:Knee Joint / Q000601:surgery; D007720:Knee Prosthesis; D011474:Prosthesis Design; D011859:Radiography; D016059:Range of Motion, Articular
keywords: Clinical follow-up; Knee contact forces; Knee kinematics; Malconfigurations; TKA performance