title: Asymmetric leg loading during sit-to-stand, walking and quiet standing in patients after unilateral total hip replacement surgery.
abstract: BACKGROUND
  Asymmetric limb loading persists well after unilateral total hip replacement surgery and represents a risk of the development of osteoarthritis in the non-operated leg. Here we studied bilateral limb loading in hip arthroplasty patients for a variety of everyday activities.
  
  
  METHODS
  Twenty-seven patients and 27 healthy age-matched control subjects participated in the study. They were asked to stand up from a chair, to stand quietly, to perform isometric maximal voluntary contractions and to walk along a 10 m path at a natural and fast speed. Two force platforms measured vertical forces under each foot during quiet standing and sit-to-stand maneuver. Temporal variables of gait were measured using footswitches.
  
  
  RESULTS
  In all tasks patients tended to preferentially load the non-operated limb, though the amount of asymmetry depended on the task being most prominent during standing up (inter-limb weight bearing difference exceeded 20%, independent of speed or visual conditions). In contrast, when performing maximal voluntary contractions, or during walking and quiet standing, the inter-limb difference in the maximal force production, stance/swing phase durations or weight bearing was typically less than 10%.
  
  
  CONCLUSIONS
  The results suggest that the amount of asymmetry might not be necessarily the same for different tasks. Asymmetric leg loading in patients can be critical during sit-to-stand maneuver in comparison with quiet standing and walking, and visual information seems to play only a minor role in the control of the weight-bearing ability. The proposed asymmetry indices might be clinically significant for development of post-surgical rehabilitation.
authors.affiliation: Laboratory of Neurobiology of Motor Control, Institute for Information Transmission Problems, Russian Academy of Science, Bolshoy Karetny 19, Moscow 127994, Russia. VeraTalis@yahoo.com
authors.forename: V L
authors.initials: VL
authors.lastname: Talis
authors.forename: A A
authors.initials: AA
authors.lastname: Grishin
authors.forename: I A
authors.initials: IA
authors.lastname: Solopova
authors.forename: T L
authors.initials: TL
authors.lastname: Oskanyan
authors.forename: V E
authors.initials: VE
authors.lastname: Belenky
authors.forename: Y P
authors.initials: YP
authors.lastname: Ivanenko
mesh_terms: D000328:Adult; D000368:Aged; D019644:Arthroplasty, Replacement, Hip / Q000534:rehabilitation*; D016022:Case-Control Studies; D005080:Exercise Test; D005260:Female; D005528:Foot / Q000503:physiopathology; D006801:Humans; D007537:Isometric Contraction; D007699:Kinesthesis; D007866:Leg / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D009068:Movement; D053580:Muscle Strength; D004856:Postural Balance; D011187:Posture; D013647:Task Performance and Analysis; D014160:Transducers, Pressure; D016138:Walking; D016474:Weight-Bearing