title: Vacuum level effects on gait characteristics for unilateral transtibial amputees with elevated vacuum suspension.
abstract: BACKGROUND
  The elevated vacuum suspension system has demonstrated unique health benefits for amputees, but the effect of vacuum pressure values on gait characteristics is still unclear. The purpose of this study was to investigate the effects of elevated vacuum levels on temporal parameters, kinematics and kinetics for unilateral transtibial amputees.
  
  
  METHODS
  Three-dimensional gait analysis was conducted in 9 unilateral transtibial amputees walking at a controlled speed with five vacuum levels ranging from 0 to 20inHg, and also in 9 able-bodied subjects walking at self-preferred speed. Repeated ANOVA and Dunnett's t-test were performed to determine the effect of vacuum level and limb for within subject and between groups.
  
  
  RESULTS
  The effect of vacuum level significantly affected peak hip external rotation and external knee adduction moment. Maximum braking and propulsive ground reaction forces generally increased for the residual limb and decreased for the intact limb with increasing vacuum. Additionally, the intact limb experienced an increased loading due to gait asymmetry for several variables.
  
  
  CONCLUSIONS
  There was no systematic vacuum level effect on gait. Higher vacuum levels, such as 15 and 20inHg, were more comfortable and provided some relief to the intact limb, but may also increase the risk of osteoarthritis of the residual limb due to the increased peak external hip and knee adduction moments. Very low vacuum should be avoided because of the negative effects on gait symmetry. A moderate vacuum level at 15inHg is suggested for unilateral transtibial amputees with elevated vacuum suspension.
authors.affiliation: School of Medical Imaging, Xuzhou Medical University, Xuzhou, China; Department of Mechanical Engineering, University of Utah, Salt Lake City, UT, USA. Electronic address: h_xu@xzmc.edu.cn.
authors.forename: Hang
authors.initials: H
authors.lastname: Xu
authors.affiliation: Department of Mechanical Engineering, University of Utah, Salt Lake City, UT, USA. Electronic address: kaseygreenland@gmail.com.
authors.forename: Kasey
authors.initials: K
authors.lastname: Greenland
authors.affiliation: Department of Mechanical Engineering, University of Utah, Salt Lake City, UT, USA. Electronic address: donbloswick@me.com.
authors.forename: Donald
authors.initials: D
authors.lastname: Bloswick
authors.affiliation: School of Medical Imaging, Xuzhou Medical University, Xuzhou, China; Department of Biomedical Imaging and Radiological Sciences, National Yang-Ming University, Taipei, Taiwan. Electronic address: zhaojie@xzmc.edu.cn.
authors.forename: Jie
authors.initials: J
authors.lastname: Zhao
authors.affiliation: Department of Mechanical Engineering, University of Utah, Salt Lake City, UT, USA. Electronic address: a.merryweather@utah.edu.
authors.forename: Andrew
authors.initials: A
authors.lastname: Merryweather
mesh_terms: D000672:Amputation Stumps; D000674:Amputees; D001186:Artificial Limbs; D001696:Biomechanical Phenomena; D005684:Gait / Q000502:physiology*; D006615:Hip / Q000502:physiology; D006801:Humans; D007700:Kinetics; D007717:Knee / Q000502:physiology; D035002:Lower Extremity / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D011474:Prosthesis Design; D012399:Rotation; D014618:Vacuum
keywords: Amputees; Biomechanics; Comfort; Gait; Prosthesis; Vacuum level