title: Performance of conventional and X2® prosthetic knees during slope descent.
abstract: BACKGROUND
  Individuals with transfemoral amputation often have difficulty descending sloped surfaces due to increased lower extremity range of motion and torque requirements. The X2®, a new microprocessor-controlled prosthetic knee, claims to improve gait over sloped terrain. The aim of this study was to evaluate how experienced prosthesis users descended a sloped surface using the X2®, compared to a conventional knee, either mechanical (MECH) or microprocessor (MP).
  
  
  METHODS
  Descent technique and biomechanics were assessed in 21 service members with unilateral transfemoral amputation as they descended an instrumented 10° slope at a self-selected walking velocity.
  
  
  RESULTS
  Use of the X2® in the MECH group resulted in greater hill assessment scores (8.5 to 11.0, P=0.026), due primarily to decreased reliance on handrail use. The use of the X2® in the MP group increased prosthetic knee flexion to a median of 6.4° at initial contact (P=0.002) and 73.7° in swing (P=0.005), contributing to longer prosthetic limb steps (P=0.024) and increased self-selected velocity (P=0.041). Additionally, the use of the X2® in the MP group increased prosthetic limb impact peaks (11.6N/kg, P=0.004), improving impact peak symmetry to -1.3% (P=0.004).
  
  
  CONCLUSIONS
  Decreased reliance on handrail use as MECH users descended in the X2® indicate improved function and perhaps greater confidence in the device. Additional biomechanical improvements for existing MP users suggest potential longer-term benefits with regard to intact limb health and overuse injuries.
authors.affiliation: Department of Rehabilitation, Walter Reed National Military Medical Center, Bethesda, MD 20889, USA; DOD-VA Extremity Trauma and Amputation Center of Excellence, San Antonio, TX, USA.
authors.forename: Elizabeth M
authors.initials: EM
authors.lastname: Bell
authors.affiliation: Department of Rehabilitation, Walter Reed National Military Medical Center, Bethesda, MD 20889, USA; DOD-VA Extremity Trauma and Amputation Center of Excellence, San Antonio, TX, USA.
authors.forename: Alison L
authors.initials: AL
authors.lastname: Pruziner
authors.affiliation: Center for the Intrepid, San Antonio Military Medical Center, JBSA Fort Sam Houston, San Antonio, TX 78234, USA.
authors.forename: Jason M
authors.initials: JM
authors.lastname: Wilken
authors.affiliation: Department of Rehabilitation, Walter Reed National Military Medical Center, Bethesda, MD 20889, USA; DOD-VA Extremity Trauma and Amputation Center of Excellence, San Antonio, TX, USA. Electronic address: erik.j.wolf6.civ@mail.mil.
authors.forename: Erik J
authors.initials: EJ
authors.lastname: Wolf
mesh_terms: D000293:Adolescent; D000328:Adult; D000673:Amputation, Traumatic / Q000534:rehabilitation*; D001696:Biomechanical Phenomena; D005684:Gait / Q000502:physiology*; D006801:Humans; D007720:Knee Prosthesis; D035002:Lower Extremity / Q000503:physiopathology; D008838:Microcomputers; D008889:Military Personnel; D011474:Prosthesis Design; D016059:Range of Motion, Articular; D016138:Walking / Q000502:physiology*; D055815:Young Adult
keywords: Ambulation; Biomechanics; Gait analysis; Slope descent; Transfemoral amputation