Controlling horizontal deceleration during gait termination in transfemoral amputees: Measurements and simulations. (bibtex)
by Helco G. van Keeken, Aline H. Vrieling, At L. Hof, Klaas Postema, Bert Otten
Abstract:
In this study we investigated how leading limb angles combined with active ankle moments of a sound ankle or passive stiffness of a prosthetic ankle, influence the center of mass (CoM) velocity during the single limb support phase in gait termination. Also, we studied how the trailing limb velocity influences the CoM velocity during this phase. We analyzed force plate data from a group of experienced transfermoral (TF) amputee subjects using a prosthetic limb, and the outcome from a two-dimensional mathematical forward dynamics model. We found that when leading with the sound limb, the subjects came almost to a full stop in the single limb support phase, without the use of the prosthetic limb. When leading with the prosthetic limb, the CoM deceleration was less in a relatively short single limb support phase, with a fast forward swing of the trailing sound limb. Slowing down the heavier trailing sound limb, compared to the prosthetic limb, results in a relatively larger braking force at the end of the swing phase. The simulations showed that only narrow ranges of leading limb angle and ankle moments could be used to achieve the same CoM velocities with the mathematical model as the average start and end velocities of the prosthetic limb user. We conclude that users of prosthetic limbs have a narrow range of options for the dynamics variables to achieve a target CoM velocity. The lack of active control in the passive prosthetic ankle prevents the TF amputee subjects from producing sufficient braking force when terminating gait with the prosthetic limb leading, forcing the subjects to use both limbs as a functional unit, in which the sound limb is mostly responsible for the gait termination.
Reference:
Controlling horizontal deceleration during gait termination in transfemoral amputees: Measurements and simulations. (Helco G. van Keeken, Aline H. Vrieling, At L. Hof, Klaas Postema, Bert Otten), In Med Eng Phys, 2012.
Bibtex Entry:
@ARTICLE{2012,
  author = {{van Keeken}, Helco G. and Vrieling, Aline H. and Hof, At L. and
	Postema, Klaas and Otten, Bert},
  title = {Controlling horizontal deceleration during gait termination in transfemoral
	amputees: Measurements and simulations.},
  journal = {Med Eng Phys},
  year = {2012},
  month = {Aug},
  __markedentry = {[hvk:]},
  abstract = {In this study we investigated how leading limb angles combined with
	active ankle moments of a sound ankle or passive stiffness of a prosthetic
	ankle, influence the center of mass (CoM) velocity during the single
	limb support phase in gait termination. Also, we studied how the
	trailing limb velocity influences the CoM velocity during this phase.
	We analyzed force plate data from a group of experienced transfermoral
	(TF) amputee subjects using a prosthetic limb, and the outcome from
	a two-dimensional mathematical forward dynamics model. We found that
	when leading with the sound limb, the subjects came almost to a full
	stop in the single limb support phase, without the use of the prosthetic
	limb. When leading with the prosthetic limb, the CoM deceleration
	was less in a relatively short single limb support phase, with a
	fast forward swing of the trailing sound limb. Slowing down the heavier
	trailing sound limb, compared to the prosthetic limb, results in
	a relatively larger braking force at the end of the swing phase.
	The simulations showed that only narrow ranges of leading limb angle
	and ankle moments could be used to achieve the same CoM velocities
	with the mathematical model as the average start and end velocities
	of the prosthetic limb user. We conclude that users of prosthetic
	limbs have a narrow range of options for the dynamics variables to
	achieve a target CoM velocity. The lack of active control in the
	passive prosthetic ankle prevents the TF amputee subjects from producing
	sufficient braking force when terminating gait with the prosthetic
	limb leading, forcing the subjects to use both limbs as a functional
	unit, in which the sound limb is mostly responsible for the gait
	termination.},
  doi = {10.1016/j.medengphy.2012.07.002},
  institution = {Center for Human Movement Sciences, University Medical Center Groningen,
	University of Groningen, Groningen, The Netherlands.},
  language = {eng},
  medline-pst = {aheadofprint},
  owner = {hvk},
  pii = {S1350-4533(12)00182-8},
  pmid = {22901854},
  timestamp = {2012.08.21},
  url = {http://dx.doi.org/10.1016/j.medengphy.2012.07.002}
}
 
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