title: Mobile-bearing total knee arthroplasty: More rotation is evident during more demanding tasks.
abstract: BACKGROUND
  Some reports showed few but significant more axial femorotibial rotation in favor of mobile-bearing (MB) versus fixed-bearing (FB) total knee arthroplasty (TKA), mostly during knee bend fluoroscopic studies. The goal of the current study was to submit MB and FB groups of TKA patients to a turning activity, in which additional rotation was to be expected.
  
  
  METHODS
  Two consecutive cohorts of patients after TKA (10 FB and 11 MB knees in a total of 18 patients) were assessed using motion analysis five year postoperatively, while performing gait and sit-to-walk (STW) movements with and without turning steps.
  
  
  RESULTS
  Mean range of rotation in the FB group increased from 9.7° during gait, to 11.7° during STW straight, and to 14.3° during STW turning. Mean range of rotation in the MB group increased from 13.4° during gait to 21.0° during STW straight, and stayed at 21.1° during STW turning.
  
  
  CONCLUSIONS
  Too many uncontrolled variables in the current study hinder a meaningful discrimination of MB from FB TKA rotation. However, the study does illustrate how more demanding task loads could be helpful in exploring the geometric constraints of TKA variants.
  
  
  METHODS
  Level III, therapeutic study.
authors.affiliation: Department of Orthopedic Surgery, Diakonessen Hospital, Bosboomstraat 1, 3582 KE Utrecht, The Netherlands. Electronic address: aw_zurcher@hotmail.com.
authors.forename: Arthur W
authors.initials: AW
authors.lastname: Zürcher
authors.affiliation: Department of Rehabilitation Medicine, VU University Medical Center, Amsterdam, The Netherlands.
authors.forename: Kim
authors.initials: K
authors.lastname: van Hutten
authors.affiliation: Department of Rehabilitation Medicine and Research Institute MOVE, VU University Medical Center, Amsterdam, The Netherlands.
authors.forename: Jaap
authors.initials: J
authors.lastname: Harlaar
authors.affiliation: Department of Epidemiology and Biostatistics, EMGO Institute of Health and Care Research, VU University Medical Center, Amsterdam, The Netherlands.
authors.forename: Caroline B
authors.initials: CB
authors.lastname: Terwee
authors.affiliation: Department of Orthopedic Surgery, AVE Orthopaedic Clinics, Huizen, The Netherlands.
authors.forename: G H
authors.initials: GH
authors.lastname: Rob Albers
authors.affiliation: Department of Orthopedic Surgery, Slotervaart Hospital and VU University Medical Center, Amsterdam, The Netherlands.
authors.forename: Ruud G
authors.initials: RG
authors.lastname: Pöll
mesh_terms: D000328:Adult; D019645:Arthroplasty, Replacement, Knee / Q000295:instrumentation*; D015331:Cohort Studies; D005260:Female; D005684:Gait / Q000502:physiology*; D006801:Humans; D007720:Knee Prosthesis; D008297:Male; D008875:Middle Aged; D020370:Osteoarthritis, Knee / Q000503:physiopathology / Q000601:surgery*; D016059:Range of Motion, Articular / Q000502:physiology*; D012399:Rotation; D016474:Weight-Bearing / Q000502:physiology*; D055815:Young Adult
keywords: Mobile-bearing; Rotation; Sit-to-walk; TKA