title: Improved Weight-Bearing Symmetry for Transfemoral Amputees During Standing Up and Sitting Down With a Powered Knee-Ankle Prosthesis.
abstract: To test a new user-modulated control strategy that enables improved control of a powered knee-ankle prosthesis during sit-to-stand and stand-to-sit movements.
  
  
  
  Within-subject comparison study.
  
  
  
  Gait laboratory.
  
  
  
  Unilateral transfemoral amputees (N=7; 4 men, 3 women) capable of community ambulation.
  
  
  
  Subjects performed 10 repetitions of sit-to-stand and stand-to-sit with a powered knee-ankle prosthesis and with their prescribed passive prosthesis in a randomized order. With the powered prosthesis, knee and ankle power generation were controlled as a function of weight transferred onto the prosthesis.
  
  
  
  Vertical ground reaction force limb asymmetry and durations of movement were compared statistically (Wilcoxon signed-rank test, α=.05).
  
  
  
  For sit-to-stand, peak vertical ground reaction forces were significantly less asymmetric using the powered prosthesis (mean, 19.3%±11.8%) than the prescribed prosthesis (57.9%±13.5%; P=.018), where positive asymmetry values represented greater force through the intact limb. For stand-to-sit, peak vertical ground reaction forces were also significantly less asymmetric using the powered prosthesis (28.06%±11.6%) than the prescribed prosthesis (48.2%±16%; P=.028). Duration of movement was not significantly different between devices (sit-to-stand: P=.18; stand-to-sit: P=.063).
  
  
  
  Allowing transfemoral amputees more control over the timing and rate of knee and ankle power generation enabled users to stand up and sit down with their weight distributed more equally between their lower limbs. Increased weight bearing on the prosthetic limb may make such activities of daily living easier for transfemoral amputees.
authors.affiliation: Center for Bionic Medicine, Rehabilitation Institute of Chicago, Chicago, IL; Department of Physical Medicine and Rehabilitation, Northwestern University, Chicago, IL. Electronic address: annie-simon@northwestern.edu.
authors.forename: Ann M
authors.initials: AM
authors.lastname: Simon
authors.affiliation: Center for Bionic Medicine, Rehabilitation Institute of Chicago, Chicago, IL; Department of Physical Medicine and Rehabilitation, Northwestern University, Chicago, IL.
authors.forename: Nicholas P
authors.initials: NP
authors.lastname: Fey
authors.affiliation: Center for Bionic Medicine, Rehabilitation Institute of Chicago, Chicago, IL.
authors.forename: Kimberly A
authors.initials: KA
authors.lastname: Ingraham
authors.affiliation: Center for Bionic Medicine, Rehabilitation Institute of Chicago, Chicago, IL.
authors.forename: Suzanne B
authors.initials: SB
authors.lastname: Finucane
authors.affiliation: Center for Bionic Medicine, Rehabilitation Institute of Chicago, Chicago, IL.
authors.forename: Elizabeth G
authors.initials: EG
authors.lastname: Halsne
authors.affiliation: Center for Bionic Medicine, Rehabilitation Institute of Chicago, Chicago, IL; Department of Physical Medicine and Rehabilitation, Northwestern University, Chicago, IL; Department of Biomedical Engineering, Northwestern University, Evanston, IL.
authors.forename: Levi J
authors.initials: LJ
authors.lastname: Hargrove
mesh_terms: D000203:Activities of Daily Living; D000328:Adult; D000368:Aged; D000674:Amputees / Q000534:rehabilitation*; D001186:Artificial Limbs; D011211:Electric Power Supplies; D005260:Female; D005684:Gait; D006801:Humans; D035002:Lower Extremity; D008297:Male; D008875:Middle Aged; D009068:Movement / Q000502:physiology*; D026741:Physical Therapy Modalities; D011187:Posture; D016474:Weight-Bearing / Q000502:physiology*
keywords: Artificial limbs; Lower extremity; Prosthesis design; Rehabilitation; Weight-bearing