title: Change in collateral ligament length and tibiofemoral movement following joint line variation in TKA.
abstract: OBJECTIVE
  The primary intent of total knee arthroplasty is the restoration of normal knee kinematics, with ligamentous constraint being a key influential factor. Displacement of the joint line may lead to alterations in ligament attachment sites relative to knee flexion axis and variance of ligamentous constraints on tibiofemoral movement. This study aimed to investigate collaterals strains and tibiofemoral kinematics with different joint line levels.
  
  
  METHODS
  A previously validated knee model was employed to analyse the change in length of the collateral ligaments and tibiofemoral motion during knee flexion. The models shifted the joint line by 3 and 5 mm both proximally and distally from the anatomical level. The data were captured from full extension to flexion 135°.
  
  
  RESULTS
  The elevated joint line revealed a relative increase in distance between ligament attachments for both collateral ligaments in comparison with the anatomical model. Also, tibiofemoral movement decreased with an elevation in the joint line. Conversely, lowering the joint line led to a significant decrease in distance between ligament attachments, but greater tibiofemoral motion.
  
  
  CONCLUSIONS
  Elevation of the joint line would strengthen the capacity of collateral ligaments for knee motion constraint, whereas a distally shifted joint line might have the advantage of improving tibiofemoral movement by slackening the collaterals. It implies that surgeons can appropriately change the joint line position in accordance with patient's requirement or collateral tensions. A lowered joint line level may improve knee kinematics, whereas joint line elevation could be useful to maintain knee stability.
  
  
  METHODS
  V.
authors.affiliation: Technology Translation Center for Medical Device, Chung Yuan Christian University, Chungli City, Taiwan.
authors.forename: Kun-Jhih
authors.initials: KJ
authors.lastname: Lin
authors.affiliation: Technology Translation Center for Medical Device, Chung Yuan Christian University, Chungli City, Taiwan.|Department of Physical Therapy and Assistive Technology, National Yang-Ming University, Taipei, Taiwan.
authors.forename: Hung-Wen
authors.initials: HW
authors.lastname: Wei
authors.affiliation: Biomechanics Research Laboratory, Department of Biomedical Research, Mackay Memorial Hospital, New Taipei City, Taiwan.
authors.forename: Chang-Hung
authors.initials: CH
authors.lastname: Huang
authors.affiliation: United Orthopedic Corporation, Taipei, Taiwan.
authors.forename: Yu-Liang
authors.initials: YL
authors.lastname: Liu
authors.affiliation: Orthopaedic Device Research Center, National Yang-Ming University, Taipei, Taiwan.
authors.forename: Wen-Chuan
authors.initials: WC
authors.lastname: Chen
authors.affiliation: Orthopaedic Biomechanics Laboratory, Institute of Biomedical Engineering, National Yang-Ming University, No. 155, Sec. 2, Li-Nung St., Shih-Pai, Taipei, 11221, Taiwan.
authors.forename: Colin Joseph
authors.initials: CJ
authors.lastname: McClean
authors.affiliation: Orthopaedic Biomechanics Laboratory, Institute of Biomedical Engineering, National Yang-Ming University, No. 155, Sec. 2, Li-Nung St., Shih-Pai, Taipei, 11221, Taiwan. ckcheng2009@gmail.com.
authors.forename: Cheng-Kung
authors.initials: CK
authors.lastname: Cheng
mesh_terms: D019645:Arthroplasty, Replacement, Knee; D001696:Biomechanical Phenomena; D017885:Collateral Ligaments / Q000601:surgery*; D006801:Humans; D007719:Knee Joint / Q000601:surgery; D008953:Models, Anatomic; D009068:Movement / Q000502:physiology*; D018482:Muscle, Skeletal / Q000601:surgery; D016059:Range of Motion, Articular / Q000502:physiology*
keywords: Collateral ligament; Joint line; Knee kinematics; Length change; Total knee arthroplasty