title: Impact on the biomechanics of overground gait of using an 'Echelon' hydraulic ankle-foot device in unilateral trans-tibial and trans-femoral amputees.
abstract: BACKGROUND
  If a prosthetic foot creates resistance to forwards shank rotation as it deforms during loading, it will exert a braking effect on centre of mass progression. The present study determines whether the centre of mass braking effect exerted by an amputee's habitual rigid 'ankle' foot was reduced when they switched to using an 'Echelon' hydraulic ankle-foot device.
  
  
  METHODS
  Nineteen lower limb amputees (eight trans-femoral, eleven trans-tibial) walked overground using their habitual dynamic-response foot with rigid 'ankle' or 'Echelon' hydraulic ankle-foot device. Analysis determined changes in how the centre of mass was transferred onto and above the prosthetic-foot, freely chosen walking speed, and spatio-temporal parameters of gait.
  
  
  RESULTS
  When using the hydraulic device both groups had a smoother/more rapid progression of the centre of pressure beneath the prosthetic hindfoot (p≤0.001), and a smaller reduction in centre of mass velocity during prosthetic-stance (p<0.001). As a result freely chosen walking speed was higher in both groups when using the device (p≤0.005). In both groups stance and swing times and cadence were unaffected by foot condition whereas step length tended (p<0.07) to increase bilaterally when using the hydraulic device. Effect size differences between foot types were comparable across groups.
  
  
  CONCLUSIONS
  Use of a hydraulic ankle-foot device reduced the foot's braking effect for both amputee groups. Findings suggest that attenuation of the braking effect from the foot in early stance may be more important to prosthetic-foot function than its ability to return energy in late stance.
authors.affiliation: Division of Medical Engineering, School of Engineering, University of Bradford, Bradford BD7 1DP, UK.
authors.forename: Alan R
authors.initials: AR
authors.lastname: De Asha
authors.affiliation: Mobility & Specialised Rehabilitation Centre, Northern General Hospital, Sheffield S5 7AT, UK.
authors.forename: Ramesh
authors.initials: R
authors.lastname: Munjal
authors.affiliation: Disablement Services Centre, University Hospital of South Manchester, Manchester M20 1LB, UK.
authors.forename: Jai
authors.initials: J
authors.lastname: Kulkarni
authors.affiliation: Division of Medical Engineering, School of Engineering, University of Bradford, Bradford BD7 1DP, UK. Electronic address: J.Buckley@bradford.ac.uk.
authors.forename: John G
authors.initials: JG
authors.lastname: Buckley
mesh_terms: D000328:Adult; D000674:Amputees; D000842:Ankle / Q000503:physiopathology*; D000843:Ankle Joint / Q000503:physiopathology; D001186:Artificial Limbs; D001696:Biomechanical Phenomena; D005528:Foot / Q000503:physiopathology*; D005534:Foot Diseases / Q000503:physiopathology; D005684:Gait / Q000502:physiology; D006801:Humans; D008875:Middle Aged; D009127:Muscle Rigidity / Q000503:physiopathology; D011312:Pressure; D011474:Prosthesis Design; D013977:Tibia / Q000503:physiopathology; D016138:Walking / Q000502:physiology; D055815:Young Adult
keywords: Amputee; Gait; Prosthesis; Trans-femoral; Trans-tibial; Walking speed