title: Posterior stabilized versus cruciate retaining total knee arthroplasty designs: conformity affects the performance reliability of the design over the patient population.
abstract: Commercially available fixed bearing knee prostheses are mainly divided into two groups: posterior stabilized (PS) versus cruciate retaining (CR). Despite the widespread comparative studies, the debate continues regarding the superiority of one type over the other. This study used a combined finite element (FE) simulation and principal component analysis (PCA) to evaluate "reliability" and "sensitivity" of two PS designs versus two CR designs over a patient population. Four fixed bearing implants were chosen: PFC (DePuy), PFC Sigma (DePuy), NexGen (Zimmer) and Genesis II (Smith & Nephew). Using PCA, a large probabilistic knee joint motion and loading database was generated based on the available experimental data from literature. The probabilistic knee joint data were applied to each implant in a FE simulation to calculate the potential envelopes of kinematics (i.e. anterior-posterior [AP] displacement and internal-external [IE] rotation) and contact mechanics. The performance envelopes were considered as an indicator of performance reliability. For each implant, PCA was used to highlight how much the implant performance was influenced by changes in each input parameter (sensitivity). Results showed that (1) conformity directly affected the reliability of the knee implant over a patient population such that lesser conformity designs (PS or CR), had higher kinematic variability and were more influenced by AP force and IE torque, (2) contact reliability did not differ noticeably among different designs and (3) CR or PS designs affected the relative rank of critical factors that influenced the reliability of each design. Such investigations enlighten the underlying biomechanics of various implant designs and can be utilized to estimate the potential performance of an implant design over a patient population.
authors.affiliation: State Key Laboratory for Manufacturing System Engineering, School of Mechanical Engineering, Xi'an Jiaotong University, Xi'an, China. Electronic address: mostafavizadeh@yahoo.com.
authors.forename: Marzieh M
authors.initials: MM
authors.lastname: Ardestani
authors.affiliation: Medical and Biological Engineering, School of Engineering, University of Hull, Hull, UK.
authors.forename: Mehran
authors.initials: M
authors.lastname: Moazen
authors.affiliation: Biomedical Engineering Department, Amirkabir University of Technology, Tehran, Iran.
authors.forename: Ehsan
authors.initials: E
authors.lastname: Maniei
authors.affiliation: State Key Laboratory for Manufacturing System Engineering, School of Mechanical Engineering, Xi'an Jiaotong University, Xi'an, China; Institute of Medical and Biological Engineering, School of Mechanical Engineering, University of Leeds, UK.
authors.forename: Zhongmin
authors.initials: Z
authors.lastname: Jin
mesh_terms: D019645:Arthroplasty, Replacement, Knee / Q000295:instrumentation* / Q000379:methods; D001696:Biomechanical Phenomena; D003198:Computer Simulation; D016208:Databases, Factual; D005260:Female; D020342:Finite Element Analysis; D006801:Humans; D007719:Knee Joint / Q000503:physiopathology / Q000601:surgery; D007720:Knee Prosthesis; D008297:Male; D025341:Principal Component Analysis; D011336:Probability; D011474:Prosthesis Design; D011475:Prosthesis Failure; D016059:Range of Motion, Articular; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
keywords: Finite element simulation; Inter-patient variability; Principal component analysis; Sensitivity; Stanmore knee simulator; Total knee arthroplasty