title: Measuring the effect of femoral malrotation on knee joint biomechanics for total knee arthroplasty using computational simulation.
abstract: OBJECTIVE
  Malrotation of the femoral component can result in post-operative complications in total knee arthroplasty (TKA), including patellar maltracking. Therefore, we used computational simulation to investigate the influence of femoral malrotation on contact stresses on the polyethylene (PE) insert and on the patellar button as well as on the forces on the collateral ligaments.
  
  
  METHODS
  Validated finite element (FE) models, for internal and external malrotations from 0° to 10° with regard to the neutral position, were developed to evaluate the effect of malrotation on the femoral component in TKA. Femoral malrotation in TKA on the knee joint was simulated in walking stance-phase gait and squat loading conditions.
  
  
  RESULTS
  Contact stress on the medial side of the PE insert increased with internal femoral malrotation and decreased with external femoral malrotation in both stance-phase gait and squat loading conditions. There was an opposite trend in the lateral side of the PE insert case. Contact stress on the patellar button increased with internal femoral malrotation and decreased with external femoral malrotation in both stance-phase gait and squat loading conditions. In particular, contact stress on the patellar button increased by 98% with internal malrotation of 10° in the squat loading condition. The force on the medial collateral ligament (MCL) and the lateral collateral ligament (LCL) increased with internal and external femoral malrotations, respectively.
  
  
  CONCLUSIONS
  These findings provide support for orthopaedic surgeons to determine a more accurate femoral component alignment in order to reduce post-operative PE problems.Cite this article: K-T. Kang, Y-G. Koh, J. Son, O-R. Kwon, C. Baek, S. H. Jung, K. K. Park. Measuring the effect of femoral malrotation on knee joint biomechanics for total knee arthroplasty using computational simulation. Bone Joint Res 2016;5:552-559. DOI: 10.1302/2046-3758.511.BJR-2016-0107.R1.
authors.affiliation: Department of Mechanical Engineering, Yonsei University, Seoul, Republic of Korea.
authors.forename: K-T
authors.initials: KT
authors.lastname: Kang
authors.affiliation: Joint Reconstruction Center, Department of Orthopaedic Surgery, Yonsei Sarang Hospital, Seoul, Republic of Korea.
authors.forename: Y-G
authors.initials: YG
authors.lastname: Koh
authors.affiliation: Department of Mechanical Engineering, Yonsei University, Seoul, Republic of Korea.
authors.forename: J
authors.initials: J
authors.lastname: Son
authors.affiliation: Joint Reconstruction Center, Department of Orthopaedic Surgery, Yonsei Sarang Hospital, Seoul, Republic of Korea.
authors.forename: O-R
authors.initials: OR
authors.lastname: Kwon
authors.affiliation: Department of Mechanical and Control Engineering, The Cyber University of Korea, Seoul, Republic of Korea.
authors.forename: C
authors.initials: C
authors.lastname: Baek
authors.affiliation: Department of Orthopedic Surgery, Yonsei University College of Medicine, Seoul, Republic of Korea.
authors.forename: S H
authors.initials: SH
authors.lastname: Jung
authors.affiliation: Department of Orthopedic Surgery, Yonsei University College of Medicine, Seoul, Republic of Korea oskkpark@gmail.com.
authors.forename: K K
authors.initials: KK
authors.lastname: Park
keywords: Finite element analysis; Malrotation; Total knee arthroplasty