title: Biomechanics of ramp descent in unilateral trans-tibial amputees: Comparison of a microprocessor controlled foot with conventional ankle-foot mechanisms.
abstract: BACKGROUND
  Walking down slopes and/or over uneven terrain is problematic for unilateral trans-tibial amputees. Accordingly, 'ankle' devices have been added to some dynamic-response feet. This study determined whether use of a microprocessor controlled passive-articulating hydraulic ankle-foot device improved the gait biomechanics of ramp descent in comparison to conventional ankle-foot mechanisms.
  
  
  METHODS
  Nine active unilateral trans-tibial amputees repeatedly walked down a 5° ramp, using a hydraulic ankle-foot with microprocessor active or inactive or using a comparable foot with rubber ball-joint (elastic) 'ankle' device. When inactive the hydraulic unit's resistances were those deemed to be optimum for level-ground walking, and when active, the plantar- and dorsi-flexion resistances switched to a ramp-descent mode. Residual limb kinematics, joints moments/powers and prosthetic foot power absorption/return were compared across ankle types using ANOVA.
  
  
  RESULTS
  Foot-flat was attained fastest with the elastic foot and second fastest with the active hydraulic foot (P<0.001). Prosthetic shank single-support mean rotation velocity (p =0.006), and the flexion (P<0.001) and negative work done at the residual knee (P=0.08) were reduced, and negative work done by the ankle-foot increased (P<0.001) when using the active hydraulic compared to the other two ankle types.
  
  
  CONCLUSIONS
  The greater negative 'ankle' work done when using the active hydraulic compared to other two ankle types, explains why there was a corresponding reduction in flexion and negative work at the residual knee. These findings suggest that use of a microprocessor controlled hydraulic foot will reduce the biomechanical compensations used to walk down slopes.
authors.affiliation: Division of Medical Engineering, School of Engineering, University of Bradford, Bradford, BD7 1DP, UK.
authors.forename: Vasily
authors.initials: V
authors.lastname: Struchkov
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 / Q000502:physiology*; D000843:Ankle Joint / Q000502:physiology; D001186:Artificial Limbs; D001696:Biomechanical Phenomena; D004867:Equipment Design; D005528:Foot / Q000502:physiology*; D005684:Gait / Q000502:physiology*; D006801:Humans; D007719:Knee Joint; D007866:Leg; D008297:Male; D008838:Microcomputers; D008875:Middle Aged; D011474:Prosthesis Design; D016059:Range of Motion, Articular; D013977:Tibia / Q000502:physiology*; D016138:Walking / Q000502:physiology
keywords: Ankle; Joint kinetics; Microprocessor; Prosthesis; Ramp descent; Trans-tibial amputee