title: The Shank-to-Vertical-Angle as a parameter to evaluate tuning of Ankle-Foot Orthoses.
abstract: The effectiveness of an Ankle-Foot Orthosis footwear combination (AFO-FC) may be partly dependent on the alignment of the ground reaction force with respect to lower limb joint rotation centers, reflected by joint angles and moments. Adjusting (i.e. tuning) the AFO-FC's properties could affect this alignment, which may be guided by monitoring the Shank-to-Vertical-Angle. This study aimed to investigate whether the Shank-to-Vertical-Angle during walking responds to variations in heel height and footplate stiffness, and if this would reflect changes in joint angles and net moments in healthy adults. Ten subjects walked on an instrumented treadmill and performed six trials while walking with bilateral rigid Ankle-Foot Orthoses. The AFO-FC heel height was increased, aiming to impose a Shank-to-Vertical-Angle of 5°, 11° and 20°, and combined with a flexible or stiff footplate. For each trial, the Shank-to-Vertical-Angle, joint flexion-extension angles and net joint moments of the right leg at midstance were averaged over 25 gait cycles. The Shank-to-Vertical-Angle significantly increased with increasing heel height (p<0.001), resulting in an increase in knee flexion angle and internal knee extensor moment (p<0.001). The stiff footplate reduced the effect of heel height on the internal knee extensor moment (p=0.030), while the internal ankle plantar flexion moment increased (p=0.035). Effects of heel height and footplate stiffness on the hip joint were limited. Our results support the potential to use the Shank-to-Vertical-Angle as a parameter to evaluate AFO-FC tuning, as it is responsive to changes in heel height and reflects concomitant changes in the lower limb angles and moments.
authors.affiliation: Department of Rehabilitation Medicine, MOVE Research Institute Amsterdam, VU University Medical Center, Amsterdam, The Netherlands. Electronic address: y.kerkum@vumc.nl.
authors.forename: Yvette L
authors.initials: YL
authors.lastname: Kerkum
authors.affiliation: MOVE Research Institute Amsterdam, Faculty of Human Movement Sciences, VU University, Amsterdam, The Netherlands; Heliomare Rehabilitation, Research and Development, Wijk aan Zee, The Netherlands.
authors.forename: Han
authors.initials: H
authors.lastname: Houdijk
authors.affiliation: Department of Rehabilitation Medicine, MOVE Research Institute Amsterdam, VU University Medical Center, Amsterdam, The Netherlands; Department of Rehabilitation, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands.
authors.forename: Merel-Anne
authors.initials: MA
authors.lastname: Brehm
authors.affiliation: Department of Rehabilitation Medicine, MOVE Research Institute Amsterdam, VU University Medical Center, Amsterdam, The Netherlands.
authors.forename: Annemieke I
authors.initials: AI
authors.lastname: Buizer
authors.affiliation: MOVE Research Institute Amsterdam, Faculty of Human Movement Sciences, VU University, Amsterdam, The Netherlands.
authors.forename: Manon L C
authors.initials: ML
authors.lastname: Kessels
authors.affiliation: MOVE Research Institute Amsterdam, Faculty of Human Movement Sciences, VU University, Amsterdam, The Netherlands.
authors.forename: Arjan
authors.initials: A
authors.lastname: Sterk
authors.affiliation: Department of Rehabilitation Medicine, MOVE Research Institute Amsterdam, VU University Medical Center, Amsterdam, The Netherlands.
authors.forename: Josien C
authors.initials: JC
authors.lastname: van den Noort
authors.affiliation: Department of Rehabilitation Medicine, MOVE Research Institute Amsterdam, VU University Medical Center, Amsterdam, The Netherlands.
authors.forename: Jaap
authors.initials: J
authors.lastname: Harlaar
mesh_terms: D000328:Adult; D000843:Ankle Joint / Q000502:physiology*; D001696:Biomechanical Phenomena; D004867:Equipment Design; D005260:Female; D061826:Foot Orthoses; D064368:Healthy Volunteers; D006365:Heel / Q000502:physiology*; D006801:Humans; D007719:Knee Joint / Q000502:physiology*; D008297:Male; D011897:Random Allocation; D012775:Shoes; D016138:Walking / Q000502:physiology*
keywords: Ankle-Foot Orthosis-Footwear Combination; Biomechanics; Footplate; Gait; Heel-sole differential